Over the past few months I have been working on a new vacuum table to hold some of my work in place. I have been through a lot of trial and error and have come a long way, but still have a long way to go. I have been reading just about everything I could find about vacuum systems and homemade vacuum tables. So I thought I would start a new thread to share some ideals and gain ideals from others. I am going to go through the photos that I have taken of my table so far and post a few of them and my experiences I have had been through so far on my quest to make a vacuum table. Feel free to weight in and share any ideals you may have. Also if you have a homemade vacuum system please share it with us, I would love to see how others tackle some of the challenges in making a vacuum system.

I'd be interested. I've made a couple. One worked but it is just some pvc connected to particleboard with plumbing fixtures. All on or all off.

I'm working on a vac-table, suction area will be about 36 sq in, it will be made from a 1" thick slab of 6061, ~5" x ~15". I'm planning to use some 1/4" EPDM foam cord for the seal, and will be dealing with non-porous surfaces.

One of the "unknowns" for me is determining the depth of the channel that the EPDM cord will sit in. If I remember right, it will compress 25% at ~10 PSI. The cord's diameter tolerance isn't great, so just using a 75% of .250" slot for the seal may not work. I'll test the channel depth on a piece of scrap before I mill the "big slab".

I built a venturi vac (thread in this forum), and am building a second one for a "how to" for this forum (got pictures of construction this time)- I'll finish that up when I get around to it... :D

I bought a vac-clamp (from www.vac-clamp.com). My design is losely based on the vac-clamp product, in aluminum. No grid structure for resizing of the seal as in the vac-clamp, I'll be dealing with the same size plate every time.

I'll gate the air to the venturi vac with a solenoid-actuated valve.

I've seen pressure switches, but haven't yet looked for economical "vacuum switches", something to tell me when the vacuum level is appropriate (a "yes" when the piece is properly sucked down). Initial thought is to take a vacuum gauge, rip off the front of it, and wire in an optical sensor pair to read the needle position. It'd be cheap, and somewhat adjustable, too!

I used this switch when I built mine. I managed to find a different source, and got it for about $15, but I don't remember where. http://www.joewoodworker.com/catalog/product_info.php?cPath=60_36&products_id=58

Square D makes vacuum switches. Like pressure switches on an air compressor but in reverse.

Thanks, Guys!

I had a "duh" moment- how else would one know to shut off a vacuum? :D

I checked the 1" alu slab, very true.

The 1" alu slab has a brushed finish, which I think will be advantageous as a vac-table. I'll cut "veins" into the table top within the gasketed area, I suppose you could call the brushed finish "capillaries".

No new work on this table as yet...

Thanks,
Paul

Any pictures?

No pics as yet... I picked up an Asco 4-way valve (120v AC) and a Whitman vacuum switch off Ebay, arrived the other day. I had to loosen the switch and move it a hair to get the switch to actuate on a vacuum. I need to test the coil on the valve, but I'll probably be driving it with a Sharp S101S02 solid state relay (good for 1.5A at 125v AC, the solenoid is only 17 watts). I wonder how these SSR's will handle this solenoid... :D

I think vacuum tables are the way to go. I just don't know enough about them to build one yet.

Im glad to see all the interest, maybe together we can come up with some pretty good ideals.
I have some pics I will try to post when I get the image size changed.

I am in the process of outfitting a large machine with a vacuum table. Actually what I will be doing is 'tiling' a 5' by 10' surface with eighteen separate vacuum surfaces each 19" by 19". So far I have not progressed any further than a model of the vacuum tiles shown upside down in the picture. The four corner holes match up with an existing 4" by 4" array of holes tapped in the machine table and the tile will be bolted down with an O-ring gasket around the perimeter so the machine table forms the bottom of the vacuum cavity. Two indents can be seen where the perimeter wall loops in and this is where venturi vacuum generators will be fitted. Each tile will have its own controlled air supply. The aim is to install these tiles on the table, face and machine the top surface grooves for gaskets with full vacuum applied so that in use the surface is as true as possible and mark each tile with its location. It will then be possible to remove the tiles for non-vacuum work and replace them in the same location and go back to the same accuracy. My goal is flat to plus/minus 0.002" over the whole surface for engraving on large areas of thin material.

I'm normally a reader and not a poster but I do have a little experience with home made vacuum tables that I don't mind sharing. I'm not exactly sure where I saw the original design that mine is fashioned from but it seems to work really well! It's made from 1 inch 6061. It's base is 6" x 3.5". It's working surface is 5" x 3.5". It has 9 horizontal (Y) channels and 9 Vertical (X) channels. Each channel is 1/8 x 1/8 with chamfered edges. The gasket material is 1/8 x 5/32 leaving 1/32 above table level. There is a single 1/8 hole in the center of the table that provides vacuum to all channels. I don't have any details about the vacuum pressures. I just use a small vac/compressor without any problems. I use it for small engraving jobs or when I need to fly cut several pieces of stock when I work on multiple projects of the same piece.

This link will show you a page with one Quicktime movie at the top showing my first design in action. Click on the photo and see a page showing 8 short Quicktime movies of how I made the vacuum table. Click Here (http://www.alphalineinc.com/ALcncmovies.html)

What is the max depth of cut you can take with that table? I'm trying to get a feel for how much force you can put on these in relation to the surface area.

What is the max depth of cut you can take with that table? I'm trying to get a feel for how much force you can put on these in relation to the surface area.

It depends on how much vacuum you can pull. One atmosphere of pressure at sea level is 14.7 psi so if you can pull a perfect vacuum your work is held down by 14.7 lbs for every square inch or 2117 lbs for every square foot.

A perfect vacuum is not possible; good vacuum pumps with no leaks in your system can come very close so you can get a clamping force of over 14 lbs per square inch. Everything goes down from here; venturi vacuum generators using compressed air might get you 12 lbs per square inch, Roots blower type pumps will get to 5-3/4 or so and a regular vacuum cleaner might get to 2 lbs per square inch, maybe more.

All of the above was for a more or less leak free system or very small leaks. If you have porous material you have large leaks and the vacuum you get depends very much on how fast your pump can remove the air that has leaked through. In this case a regular vacuum cleaner may be the fairly good because it can move a large (ish) air volume and keep ahead of significant leaks. It is possible to get venturi vacuum generators that can move a lot of volume and still get to a clamping effect of 5 lbs per square inch or maybe more. But you will need an air compressor the size of a small car if you are working with large areas so this is not really practical. Proper vacuum pumps if they are large enough can keep ahead of leaks of course but then you are looking at big dollars. Roots blowers can handle fairly large volumes of leakage and still get to the 5 lbs per square inch region but they are also expensive.

I've got a welch vacuum pump capable of 10cfm and it will pull 29.5HG, or as close as is practical to a perfect vacuum. I've got an 11"x9" table in the mail. I'm hoping I'll be able to do profiling with 1/4" endmills at 15ipm with a .08" doc.

Here are some photos of the table itself. There is nothing really special about it, its just 2 pieces of 3/4" birch plywood bolted together with some vacuum seal between to hold in the vacuum. I modeled it after a few tables I seen on here and my table top on my CNC at work.

The way the table works is the vacuum comes in throught an opening one the bottom piece then follows the channels(also in the bottom piece). It then has holes in the top piece that allow the vacuum to flow through. On the top piece I have a grid of 1 3/8" squares that I can run vacuum seal between to mask off an area for a form. Then I cover the other exposed holes leaving the ones under the form open. I also have several inserts in the top piece were I can just bolt down forms with 1/4" bolts and screw the piece to be machined down to the form and not use the vacuum at all. I am currently in the process of sealing the top and bottom pieces to help hold in vacuum, make it more durable, and also so it won't stain as easily. I will try to post some photos when it is finished.

Rob, I'm guessing that part of the problem your having is trying to get a perfect seal over such a large area. The venturi vacuum system is not very tolerant of leaks. When I ever get around to building one, I was thinking of using a few valves to break the table into seperate, smaller zones that would be easier to manage. Especially with larger parts, where it might be difficult to get an initial seal. Looks good, though. Very well done. :)

Thanks Gerry,
I think building seperate vacuum zones is the way to go, I didn't even think about it untill a couple of days after I finished cutting mine. If I ever make another one I think I will make it with 2 seperate zones. I may just make a new bottom piece for mine with two zones, I should still be able to use the same top piece. I think I have mine fairly good enough to hold down most of the things I will be cutting. I screwed a vacuum gage into some of the holes on top, and I am getting about 10 - 12 Hg( or at least I think it is Hg). At work on my old pump I used to get about 8 - 15 Hg. Then they bought a new one and im getting bout 24-27. When I first started I was planning on using a regular shop vac, like I seen many others use. I built a large test setup to try it out, and the test pieces would not budge. Then after I build the real thing I couldn't get it to hold well enough. I tried a couple different shop vacs but still no luck. Thats when I decided to build a pump like on joewoodworker.com. Your right you need a near perfect seal to get enought vacuum. One of the ideals in my original plan was to use LDF spoil boards and cut large pieces of plywood, etc. I now know that is pretty much out of the question unless I find a more powerfull vacuum source. I had been in contact with a local industrial supply and they had several small industrial pumps for sale for $400 each. They seemed to be in fairly good condiction, but they are all 440 volts. The guy spoke of another pump that he may be about to get and sell me. That one is 220 volts, but I have yet to see it and have't herd from him in over a week. I have also read of alot of people using Fein shop type vacs. But about 50% of the people that have them say they have enough vacuum to hold plywood through a spoil board and about 50% say they don't. So im still kinda sceptical. And that would be alot of money to pay for something that may not work. What kind of pumps are the rest of you guys using.

Our router at work uses a vacuum pods, with a good sized pump. We tried to set up a spoilboard using LDF, but it didn't work very well. I talked to someone I know the other day that has a router with twin 5x5 tables, with spoilboards. Each table has it's own 25HP pump :eek: and each pump is bigger than your router. Jmo, but I don't think the spoilbard method would work too well. I could be wrong, though.

If you can't get it to work, I'd go with 3 or 4 zones. I was also thinking of making some double sided pods that you could just stick anywhere you want. You could make a couple different sizes, and use the push in quick disconnect fitttings to swap them out quickly. Just some ideas.

At work they have a 50 hp pump hooked to two other machines, one is usually always running either 5x5 or 4x8 sheets of plywood. And even with all that vacuum they still have parts to move sometimes. I think the pod system would be a great ideal for smaller pumps. Especially with the quick disconnect system, you could make several different size pods for different sized work. You could ever make different shapes of pods like circles or other shapes if you wanted to.

Have a look at the vacuum piping on the machines you are referring to with the 50 hp pump. I had a machine for a while with a big pump but all the vacuum lines were very small; some as small as 3/8" ID. This is a ridiculous design because these small lines choke the flow when you have leakage such as occurs with plywood to a some extent and with a spoil board setup to a large extent. The pump is generating a good vacuum at its end but when there is leakage and air flowing through the system the vacuum at the table or pod end is much less.

It is similar to the line drop in compressed air systems but much worse. With compressed air when there is a large flow it is not unusual to drop 1 psi per foot of tube but it is always possible to crank the pressure up at the compressor end to get the required pressure at the delivery end (within limts).

Working with vacuum it is not possible to crank the vacuum down beyond 1 atmosphere, 14.7 psi, so line loss cannot be overcome with brute force and it is necessary to size vacuum lines much larger.

The pipes coming into the machines are pretty massive, I would say they are about 4 or 5 inch diameter, but I would have to check. It splits into two when it gets to the machines, one goes into an older RYE machine, I think the imput for that is around 3 or 4 inches and the other goes into a new Onsrud router, im not sure of its input size. I think one of there problems is the pump is getting worn out, they were down for about an hour last week due to pump problems. The company is talking about getting a new 60 hp pump, but I think they would be better off getting to smaller pumps (one for each machine.). Not only because now when they have to skim down a form, the other has to stop and wait, But mainly because where I work plywood frames are like gold, its the biggest seller. I think buying one big pump would be like putting all your eggs in one basket, if it breaks down you lose both machines. And it would be hard to ever run plywood on my machine because its only a 4x8 model with 4 tools in a row(2 routers and 2 drills). Tool 1 can't reach all the way over to ther right side and tool 4 can't reach all the way over to the left side. Which means it would be hard for me to use all the tools I would need for some of the frames we do.

That system sounds like it is set up much better than I have seen with a 1-1/2 line from the pump to the machine and then 3/8 coiled hoses to different locations on the machine.

Your comments on the lack of good sense in getting a single big pump rather than multiple smaller ones are very pertinent. I expect it is more likely hell will freeze over than that management will actually listen to somebody running the machines. After all their bean counter can prove they will save money getting one big pump.

That system sounds like it is set up much better than I have seen with a 1-1/2 line from the pump to the machine and then 3/8 coiled hoses to different locations on the machine.

Your comments on the lack of good sense in getting a single big pump rather than multiple smaller ones are very pertinent. I expect it is more likely hell will freeze over than that management will actually listen to somebody running the machines. After all their bean counter can prove they will save money getting one big pump.


Your right about that, me telling them what I think would almost be like me talking to a brick wall. I figure they will wait untill the pump they have now is bairly usible before they buy a new one. Thats what they did with mine, I was using a small 10hp pump before, They were taking of getting me a new one, but they waited till mine finely died before they bought the new 25 hp one. Leaving me down for about 3 weeks.

I forgot to mention that one of my favorate features about the table came from the way most of the professional tables are built. The top piece is cut so that when the machine is homed to 0,0 the center of the bit sits perfectly over the corner of the table and the rest of the top piece is cut the size of the cutting area. So if the part fits on the top part of the table, the machine can cut it. I built it this way so that when I draw a part in my CAD or CAM program I know exactly where it will be one the table. I also have the drawing of the from mounting bolt holes and vacuum channels that I can bring up so I could draw a part and it would sit exactly where I need it, if I need it between the form mounting bolts if I wanted to bolt the form down.

I briefly read the posts and to be quite frank you guys amaze me! This is innovation at its best! I do not want to spoil any of the collaborative efforts occuring but this is great stuff. I will only contribute some reference information for everyones consideration;
1.) Referencing the spoil board comments, they can work very well if constructed properly. Key considerations - construction material - mdf will work but a better method may be a melamine or plastic based product. Leave all areas that will not be used to hold the product unmachined (and some of the area that will be used to machine the product unmachined as support islands, machining the melamine off on the inside area of the seal trough except for the islands as noted)You may want to seal the edges with tape, paint, etc. You may also need to cut additional vacuum channels within the area where the vacuum is applied, starting at the hole(s) where the vacuum will be applied and radiating in a pattern of your chosing towards the extremities of the application area. As for your seal trough, this can be done from simple to elaborate. Some people only uses double sided adhesive seal, if your application is nto very intensive you can get by with this. Others want more presicion and a higher quality seal. Here is one example - If your control has "scaling" capability, and you have a pheriphery cut around the exterior you can simply scale the pheriphery cut to say 90% and your code for you spoil seal trough is already done! I believe the best seal material in spoil board applications is round, this however is NOT the case when it comes to vacuum pods. Two slightly different animals. To achieve optimum results with the round seal, some people have custom ball nose cutters ground soley to cut their trough. These cutters allow you to cut about 80% of the crosssection of the circle, only leaving about 20% or the seal exposed above the spoil level. http://www.allstaradhesives.com/ <---great seal site!
2.) Referrencing the pictures I believe from the original poster...this design is solid. I would only recommend if possible to reduce the "island" size and within each island machine vacuum troughs ( the pattern would ressemble a (+) sign if viewed from the aerial view) on each island. You can use a standard ball nose cutter with appr. a 1-2mm (.04-.08in) depth.
3.) Very accurate assesment was made about geography, it does matter! If you are in Denver your vacuum pump, regardless of design, will work harder and not last as long. Keep that in mind.
4.) This is what you can do with a good vacuum set up. I can take you to numerous places which throw one 1/2-3/4" piece of MDF directly on their solid sealed phenolic table. They surface both sides of the MDF to true it. This is now their spoilboard. They then take whatever they intend to cut (ussually a 4' x 8' sheet) and place directly on top of the spoilboard. If they are nesting, they then cut a complete cabinet out of the top sheet (sometimes in less than a minute with feeds exceeding 700 ipm) This is without any seal on the "wafer" or intermediatte spoilboard! There are special considerations when running multiple small parts. I define a small part as one in which the total surface efacement presented to the spoil is less that 35" square inches. There are also considerations when you are cutting high quantity parts out of one sheet. You must then overcome the vacuum loss by the tool swath, if you need to cut completely through. "Tabbing" or leaving some connection with the part and the base sheet is a common method used to overcome this consideration.

I hope this was not to lengthy or off topic! This is a great thread, I intend to recommend it to people! If you want to discuss any of this email me at ntek1@aol.com or visit my website at www.cnccustomservices.com and email me from there!

MarkT

Thanks Mark, your post was very informative. I thought I would take a moment and post a few photos of the stand for my homemade vacuum pump. I will try to post some of the finished pump in a few days. Right now I have the tanks off of it because I just painted them. I know its not the best job in the world but it serves it purpose.

Here is the finished vacuum pump.

It might not be the best job in the world, but does it need to be? If it works and is safe, then it sounds like you're at least half way there.

Oh, and btw, it actually looks quite neat.

I finely got my table put back together again after sealing it. I had all the channels and the bottom of the top piece sealed before, So I didn't think that sealing every thing else would make that big of a difference. I guess I was wrong because I now have nearly double the vacuum I had before. I checked the vacuum pressure in different areas of the table with a vacuum gauge and the vacuum ranges from 17 to 19. I think I couple probably increase the vacuum a little bit more if i had a better seal between the hose coming into the table and the table itself, right now I am just using a piece of rubber inner tube for a gasket and can hear the vacuum being lost. I also just inserted the gauge with a few turns and could hear a small amount of vacuum loss there also. I have included a few photos of the test. I could not get to board in the photo to move at all. I could literally pick up the CNC with the board and it would not move. Right now I am more then happy with the setup.

Hey Rob. Which kit or kits did you buy from joewoodworkers.com to build your system? I just picked up a similar pump like yours off ebay and need to start ordering some parts but not exactly sure what I need to get.

Thanks,
Carl

Hey Carl, I believe I got this kit http://www.joewoodworker.com/catalog/product_info.php?products_id=610 , But was not 100% sure, so I wrote Joe and ask him. I will let you know as soon as he writes back.

That would be great. I took a closer look at your photos and I can see you also have the 3-way MAC valve along with the filter so you might have gotten this kit as well. http://www.joewoodworker.com/catalog/product_info.php?products_id=1149

Im glad you pointed that out, I didn't get that kit but I did get the Pressure Release Upgrade, I forgot about that. I bought the filter by itself.

One thing I thought about doing was wireing it up like he did here http://www.joewoodworker.com/veneering/vacuumclamping.htm , but instead of using the footpedal, use some kind of push button switch. I think that would be pretty cool. It would be more like the professionally built tables. It would also be easier to clamp and unclamp material, especially if you could wire 2 swiches, one on each side of the machine.

Yeah I agree. I don't think the foot pedal switch is the ideal thing to use on a CNC router. Just another cable lying on the ground to trip over.

Yeah I agree. I don't think the foot pedal switch is the ideal thing to use on a CNC router.

Most commercial machines use foot switches. Lets you position the piece and hold it while turning the vacuum on /off.

Foot switches can be a very handy thing the trip hazard can be minimized by limited line feed cable to what you need

I don't think I would want a foot pedal on my machine, I know I would hit it by mistake. Even if it were the covered kind, I used to work on a airclamp that had one and hit it alot by accdent.

You can get a foot pedal with a shield so that will not happen also seen them wired with a switch that will open circuit and close after use

Joe just emailed me back and said he checked, and the kit I linked to above was the kit I ordered.

Ok, thanks Rob. :)

Today I finely got a chance to make my first test cut with the vacuum setup. It worked great. The test part isn't really anything, I just drew a part that would be about the average size of a typical part I would cut. I also added servial curves to make sure I tested it fully. I made the form from 3/4 birch plywood and weather stripping. If I were making it for a real part I would probably use vacuum seal instead of weather stripping and seal the plywood. I have included a few pics of the test cut. I will also post a video of it when I figure out how to edit it down to the best parts. If someone would like to help me with that please let me know, right now it is over 40mb in size.

http://www.cnczone.com/gallery/data/500/medium/100_6186.JPG

http://www.cnczone.com/gallery/data/500/medium/100_6191.JPG

http://www.cnczone.com/gallery/data/500/medium/100_6192.JPG

http://www.cnczone.com/gallery/data/500/medium/100_6197.JPG

http://www.cnczone.com/gallery/data/500/medium/100_6196.JPG

These posts have been really helpful. I once built a vaccuum press for laminating styrofoam to phenolic sheets, but have never tried making a hold-down. Here is my experience...I hope it saves someone a lot of grief....

If you use MDF board to distribute the vaccuum via a grid of grooves, it is vital that you seal all the MDF surfaces because MDF is really porous, especially any cut faces and edges. My vacuum laminating system was 10ft by 5ft with a 3/4" MDF grooved base and a 1/32" PVC coversheet to go over the workpiece. The PVC was sealed to the base with EPDM seals and MDF battens. I bought a 0.1 HP medical vaccum pump. It was bitterly disappointing, on turning it on for the first time, to discover that I got no vacuum at all. I couldn't find any leaks anywhere so went out and hired a bigger pump.

Same result. When I took the hired pump back to the vaccum equipment people I mentioned my woes, and they told me about the porosity of MDF. The problem was solved my giving the MDF two coats of white glue diluted 1:4 with water followed by a coat of gloss paint. This made an incredible difference and the small pump could easily achieve 12psi and cycled (via a vac switch) typically for 20 secs every 5 minutes. Seal that MDF!

Martin

Cutting grooves in MDF to distribute the vacuum is a bit redundant.

Cutting grooves in MDF to distribute the vacuum is a bit redundant.


Not necessarily. You can draw vacuum through MDF with a huge pump. Or you can cut grooves, and seal the MDF and use a low volume (cheap) pump. MDF being used because of the low cost.

Not necessarily. You can draw vacuum through MDF with a huge pump. Or you can cut grooves, and seal the MDF and use a low volume (cheap) pump. MDF being used because of the low cost.

Dear ger21 and Geof,

My set-up was for a vacuum press, not a hold-down.

Yes, it does seem that MDF is sufficiently porous to distribute a vacuum within itself, but if you have to seal the MDF to stop the vacuum escaping to the outside world ( which was the case with my "coversheet" vacuum press, you can't use the MDF itself as a means of distribution.

I put grooves in my "bed" because I had seen an article in Fine Woodworking (about 14 years ago) which showed a showed a vacuum bag set up which went (from lower surface up)

bag
grooved sheet
spoil sheet
sandwich to be laminated
top spoil sheet
bag

I think that the purpose of the grooved sheet was to void air out of the bag faster and to do so more evenly in order to stop the sandwich workpiece from being skewed before even vacuum pressure was obtained. Anyway, I just copied the idea.

For what it is worth, can I point out that my medical vac pump has one tenth of a horse power motor and was used to laminate workpieces of 4 by 8 feet panels which were 4 1/2" thick with a really small pump run duty cycle. If you use a 50 horsepower motor, why bother to build a press/hold-down gadget at all, you can probably rely on motor brute force alone. (only joking!)

Best wishes

Martin

For what it is worth, can I point out that my medical vac pump has one tenth of a horse power motor and was used to laminate workpieces of 4 by 8 feet panels which were 4 1/2" thick with a really small pump run duty cycle. If you use a 50 horsepower motor, why bother to build a press/hold-down gadget at all, you can probably rely on motor brute force alone. (only joking!)

Best wishes

Martin

Yes but all your little pump was doing was removing a teeny bit of air from the inside. Mother Nature with the help of a column of air several miles high was doing all the work. :)

Yes but all your little pump was doing was removing a teeny bit of air from the inside. Mother Nature with the help of a column of air several miles high was doing all the work. :)

Dear Geof,

Thank god for Mother!

Best wishes

Martin

Dear ger21 and Geof,

My set-up was for a vacuum press, not a hold-down.

I thought he was talking about the hold down. I have a vacuum bag press myself. The grooves keep the air from getting trapped.

Agreement???

Surely not!

Martin

I thought he was talking about the hold down. I have a vacuum bag press myself. The grooves keep the air from getting trapped.

For what it is worth there was an article in "fine woodworking" issue #66,oct 1987entitled "vacuum jigs,holding the work with thin air" by J.L.Kassner It is worth a read...mjh

I still don't get it. Don't you lose all of your vacuum as soon as you put a hole in the work? As you cut more and more into the work, don't you have to increase the vacuum pump to compensate? I thought you had to use a sacrificial board underneath attached to the work with some kind of tape to keep the vacuum.

I still don't get it. Don't you lose all of your vacuum as soon as you put a hole in the work? As you cut more and more into the work, don't you have to increase the vacuum pump to compensate? I thought you had to use a sacrificial board underneath attached to the work with some kind of tape to keep the vacuum.

That's exactly what Rob's doing. Look at the pics in post #44.

You're right, you can't cut through into the vacuum area, or the part will come loose. But you shouldn't have a problem cutting most of the way through, unless the material is very porous.

Exactly what Gerry said, If you did want a few holes to go all the way through you could just seal off around the hole or pocket, so the vacuum would not leak out. Now if you had a form that you wanted to use for more than one part, say a generic form, and you didn't want to mess it up by drilling holes into the form or if your pocket was so big you would loose a lot of vacuum area, you could do as Gerry said and not go all the way through, Just go almost all the way but leave enought to hold the vacuum in, then finish it up by hand. Unless its porous as Gerry said, because you would then loose all the vacuum anyway. Hope this helps.

For what it is worth there was an article in "fine woodworking" issue #66,oct 1987entitled "vacuum jigs,holding the work with thin air" by J.L.Kassner It is worth a read...mjh

Dear Mike,

I have now dug out my stash of Fine Woodworking mags. It was more like twenty years ago, not fourteen. The article that originally inspired me was in FW Number 56, Jan/Feb 1986, page 70, Vacuum Veneering by Greg Elder. There have been quite a few articles and tips in FW about vacuum presses and hold-downs and a mass of other good stuff besides. It is well worth a look.

Regards

Martin

You guys might also want to look at Shop Notes #40

I do the odd vacuum veneering jobs here and there and use an old refrigerator compressor It will pull 20" + inches of Hg with ease

Dear Mike,

I have now dug out my stash of Fine Woodworking mags. It was more like twenty years ago, not fourteen. The article that originally inspired me was in FW Number 56, Jan/Feb 1986, page 70, Vacuum Veneering by Greg Elder. There have been quite a few articles and tips in FW about vacuum presses and hold-downs and a mass of other good stuff besides. It is well worth a look.

Regards

Martin

Martin ..FYI I just came across a complete index of FWW at http://www.cs.rochester.edu/u/roche/rec.wood.misc/fww.index. Just go into "edit" and "find" the word "vacuum " and it lists every article ever done on it...mjh

How about vacuum pucks that move depending on the cut? Expensive?

Im not sure about the expense, but vacuum pucks can be a great way to hold work if you don't want to build a full size table, You can even make them where they have a vacuum on each side so they hold there self in place. You can also put a quick coupling on them so they are easily interchangeable.

Martin ..FYI I just came across a complete index of FWW at http://www.cs.rochester.edu/u/roche/rec.wood.misc/fww.index. Just go into "edit" and "find" the word "vacuum " and it lists every article ever done on it...mjh

Dear Mike,

Thank-you.

Fine Woodworking (Taunton Press) publish an index to articles and topics at least once a year in the magazine. I think that almost everything is available on CD as well, but ,having a paper subscription, I have never checked it out.

As a source of "can do" woodworking shop tips it is beyond compare.

Best wishes,


Martin

An update on my post #23, The company I work for did buy a bigger 100hp pump(all four of us in the department advised them to get 2 smaller ones instead of the bigger one) . The plan being to rebuild the older one and use it as long as possible then if it isn't fixable any longer put both machines on the 100hp pump.

Not necessarily. You can draw vacuum through MDF with a huge pump. Or you can cut grooves, and seal the MDF and use a low volume (cheap) pump. MDF being used because of the low cost.

Are you inferring pulling a vacuum in the torsion [bed] box as a whole and that the vacuum will penetrate the top of the bed [assuming the MDF is porus}holding work in place while it is being machined ?

I would have thought MDF is not very porus, if at all . pulling a vacuum on the Torsion box [bed ] would in my opinion result in it's destruction

Dear Mike,

Thank-you.

Fine Woodworking (Taunton Press) publish an index to articles and topics at least once a year in the magazine. I think that almost everything is available on CD as well, but ,having a paper subscription, I have never checked it out.

As a source of "can do" woodworking shop tips it is beyond compare.

Best wishes,


Martin

Actually the index I quoted is not total it lists all articles from Jan 1975 ,the inception of FWW to march 1995.... As you mentioned a wealth of woodworking info...mjh

Are you inferring pulling a vacuum in the torsion [bed] box as a whole and that the vacuum will penetrate the top of the bed [assuming the MDF is porus}holding work in place while it is being machined ?

I would have thought MDF is not very porus, if at all . pulling a vacuum on the Torsion box [bed ] would in my opinion result in it's destruction

No commercial machines use a sacrificial sheet of MDF, known as a spoil board, and suck down sheets right through it. You need a BIG pump, though. That's what Rob's talking about when he mentioned a 100HP vacuum pump.

I would have thought MDF is not very porus, if at all .

Dear Mike,


MDF is porous, See posts #45 and #48 above.

Yes, you can implode most X axis beds of MDF Jgro/ joe200che type machines, but first you need to apply a partial vacuum to the inside of the "torsion box".

Without an extremely powerful vac. pump,( that means one that can void large quantities of air) you are unlikely to be able to achieve even a small level of vacuum if the MDF is unsealed.

If you give the MDF a couple of coats of PVA (white glue) diluted with water,

you have a good chance of imploding it with a really small pump.


If you can seal the inside of the X-axis torsion box bed, and use that as a means of putting vacuum onto the workpiece, without destroying the bed, I would say that you are some way down the road to finding The Holy Grail.

Keep questing..

Best wishes

Martin

Martin,
I have been having exactly the problems you describe and had worked out that the mdf is the problem. Amazed at how much vacuum I'm loosing.
You say 2 coats of a ratio of 4:1 pva. Is that 4 parts pva or 4 parts water?
You also said you paint over it. I would have thought the paint alone would seal it.
In your post above you only mention pva. Assume using both is best but wondering with your experimenting what will suffice.
Paul

Martin,
I have been having exactly the problems you describe and had worked out that the mdf is the problem.
Paul

Dear Paul,

The PVA:water ratio is not at all critical. For sealing MDF, I generally use about 1 part PVA to 4 parts water. For the vacuum press, I used two coats of this mix. I then put on one coat of gloss paint. Why? you may ask.

Well, I had been tearing my hair out for ten days trying to work out where the leakage was coming from and when the vacuum pump man said that MDF was porous, I thought I'd take a "belt and braces" approach to making the problem go away. Besides, cut edges of MDF soak up oil based paint like a sponge, and PVA is a good primer, in my experience.

My guess is that two coats of pva/water would work by itself, but I do not know for sure.

Good luck

Best wishes

Martin

Besides, cut edges of MDF soak up oil based paint like a sponge, and PVA is a good primer, in my experience.

Martin

Now I understand. The PVA makes a good primer for edges.
Thanks for that Martin.
Paul

just a general Q
If I wanted to create a vacuum bed for an 8 x 4 router table (I'm thinking of using the same design as Posted in #12 (back on the first page) If instead of one hole I added several hole every 6-9 inches,

[how do I know how far to place them appart??]

these holes could be sealed off using grub screws and then linked these hole to several channals which in turn could be turned on / off to suite the job.......How big a vacuum would I need to create?

someone mentioned a fridge compressor - off what size fridge??

Could this vacuum be created using the suction side of a standard Compressor?

Is there a formula that will tell you if you are cutting 1/2" steel 5mm deep you require X-lots of vacuum?

or can it be worked out that if the cutter generates 15lb of force then tripple this for a hold down force ??

arn't I just full of questions - it's like having you 8yr old neice stay for a week why?, but Why !

I dont know if this pump would produce enough vacumn for a vacumn table but I put it for sale in the classifieds.

http://www.cnczone.com/classifieds/showproduct.php/product/957/cat/14/date/1136483929

I have placed a Question in the clasified section but will post here for contineuity also...

what' the details on the Decal of the pump shown in the Photo ?

Also...what would the cost of the pump only to SYDNEY, Australia, post code 2324. (surface mail is OK) as I have several motors here and can make the trolley etc.

thanks for your time

just an update on progress........ I'm currently working on a vacuume hold down system using a fridge compressor (it appears they can VAC down to 50" mercury) this is about 25psi. and using a compressor off a double fridge/freezer I'm told they have about a 20CFM flow on the inlet.

thing is looking at the size I have it is difficult to imagine 20CMF... (if I had to guess on it's size I would have said 2 maybe 5CFM at MAX..

just an update on progress........ I'm currently working on a vacuume hold down system using a fridge compressor (it appears they can VAC down to 50" mercury) this is about 25psi. and using a compressor off a double fridge/freezer I'm told they have about a 20CFM flow on the inlet.

thing is looking at the size I have it is difficult to imagine 20CMF... (if I had to guess on it's size I would have said 2 maybe 5CFM at MAX..

They will have to be a bit magic to VAC down to 50" mercury. One atmosphere is about 30 inches of mercury and a piston type pump will pull down close to this or around 14 psi.

yer I know 27.4 is 1 atmospher (14.7Psi) I thought 50 was too high but that is what the bloke said

I will measure and report back...

I have been taking some night classes for CNC at the local community college. I though their vacuum setup was kinda neat so I thought I would share it. They use a regular vacuum pump and it hooks up to the machine normally, but instead of having a top on the the vacuum table, they just use a sacrifical board for the top. Thus cutting out the need to make individual vacuum jigs. Then when they want to make something new they just dry run it to get the outline of the part on the sacrifical board. Then they just put weather stripping inside the outline, and hand bore a couple of holes in it. And tape up any open holes from previous projects. This would not be a good solution for companies that need large production runs of hundreds of different types of parts. But it works out pretty good for what they use it for.

Here are a few pics of the vacuum setup at college, That I mentioned in my last post.
http://www.cnczone.com/gallery/data/500/medium/100_6679.jpg


http://www.cnczone.com/gallery/data/500/medium/100_6680.jpg


http://www.cnczone.com/gallery/data/500/medium/100_6681.jpg

Here are a few pics of the vacuum setup at college, That I mentioned in my last post.
http://www.cnczone.com/gallery/data/500/medium/100_6679.jpg


http://www.cnczone.com/gallery/data/500/medium/100_6680.jpg


http://www.cnczone.com/gallery/data/500/medium/100_6681.jpg


Dear CNCRob,

Thank you for the pictures. They are worth many thousands of words. Can you let us know what the compressor motor rating is in HP?

Thanks

Martin

Sure Martin, I go back Monday night, I will try to check it out then.

I found out something interesting the other day. After I left work one of the CNC's had a fire. It was bad enough to go right through the vacuum table. So they took the top of it off. The design is almost the same as mine. The only difference was it has 6 zones and instead of using channels in the bottom piece it has a bunch of little squares that keeps the top piece from sucking down to the bottom piece. I have always thought it was made this way but was never queit sure. My machine(at work) on the other hand uses vacuum hoses to get vacuum to all the vacuum holes. Im sure alot of big CNC companies use the two piece methode, but it was still kinda neat to see it.

Dear CNCRob,

Thank you for the pictures. They are worth many thousands of words. Can you let us know what the compressor motor rating is in HP?

Thanks

Martin

I looked tonight but I couldn't find the rating, I searched the entire thing over about 4 times. I beleive I found where it was suppose to list it, but the tag had been removed. Sorry I couldn't have been of better help.

Dear CNCRob,

Never mind. Thanks for trying anyway.

Best wishes

Martin

I have been doing some research and it seems that most guys want to sell a 20CM/min oil lube vacuume pump or a 1.5Kw side channel 200CM/min blower VACuume pump for an 8 x 4 Ft table theyt are also suggesting 1" plumbing and definately not the 1/4" copper I was going to run.

I think if I run a resovior (sp) of 80-120Lts. I should be able to draw down the material fast enough for a 12Cm/min oil lube pump to give me 100Kpa and cost is under $1,000USD including tank filter valve and plumbing

EDIT...choice of plumbing will be 25mm (1") thick wall white PVC pipe - I'll be using plumbers glue for my joints (thus NO LEAKS .....Hay that's the plan).

On a side note untill I can get the CASH for this system I'm currently playing with a fridge compressor .... Will post as I know

Great thread guys. Thanks.
I have just started working on a vacuum for my machine as well. I had been looking at the pumps on Ebay. Not too bad at all. Then I remembered. I had a small AC unit that gave up it's freon years ago. Still worked, but wouldn't cool.
I tore it apart and used the original switches. Disconnected the motor. The compressor pulls a great vacuum. I will hook up my AC guages to it to see just what it does.
One thing about using a comprressor like this or out of a fridge, make sure you cut the lines above the compressor at its highest point. Then the mineral oil won't leak out when its running.
My router is a little production machine and is dedicaated to specific parts. The way I have it now, I would have to remove the table to do another type part.
I plan on making several small vac tables. Some job specific. others that can do multiple duty. My machine is about 23" by 36" cutting area, but my parts are about 12" by 20". I plan on making each vac table using the pvc pegboard on top of a torsion box type rig.
For my dedicted tables, I'll cover the top with lexan and cut the parts out. I make blanks that fit in the relief that are then dadoed and slotted.
I just got the pump working today. Will post some photo's when I can.

Thought someone might be interested in how I built my vacuum table plate.
I had been using MDF as the machine table surface. I really didn't like the stuff. I had noticed some minor swelling since first installing it. I chose to use some stuff called Seaboard or Star board. This is used in place of plywood for marine applications. Real nice sturdy stuff.
I mounted it and then used a 1/2" end mill to spiral cut to leveling the surface to the router. This particular brand has a texture. It rarely ever snows here, but it did in my shop yesterday. :rolleyes:
I let the machine drill holes for threaded inserts. These are brass and lead and are a press fit. Works very well and if you hit them, it won't hurt a cutter.
I will be using all brass screws in the future. I don't know how many bits I've dulled up using hardened steel. (chair)

I had some 1/4" aluminum plate around and decided to use it for my dedicated vacuum table. I will make a few more of these for different applications. This will really allow me to produce my product and play with other stuff, without loosing any original settings.
I built it using 3/4" aluminum tube and automotive Goop as a sealer. I put two braces torsion box style inside the box. I thought I had taken a photo of that, but evidently it didn't take.
These will keep the plate from bowing when under full vacuum.
I am using an old air condition unit for my vacuum. I tested it with my automotive AC guages and it pulls so close to 30 hg, that I can't tell exactly what it is. Probably about 29.5 hg. Probably only 20 to 25 feet above sea level here. It works great. Cheap too. I still need to install a water separator inline to act as a filter. I just used standard 1/4" air hose fittings and disconnects. This machine has no problem at all cutting aluminum. Very pleased with it. Hope this helps to inspire or assist some of Y'all. :)

what patten of holes / slotts did you use in the top plate of your vacuum table? sorry I was not able to tell from the photos

In pic 4 and 5, I am getting ready to setup to cut a sheet of lexan for nesting. The beauty of this is I can flip this table over and drill holes in the other side for more standard duty. A 1/6" sheet of lexan would seal the bottom side. Had I not drilled my sub table for inserts, it may have held this plate down to the sub table with just the vacuum.
Haven't tested that, but kinda too late anyway. I already have the inserts.
Check out these links.

Link 1. (http://www.toolpost.co.uk/system/index.html)

Link 2. (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7630607088)

Link 3. (http://www.systauto.com/vacuum/index.html)

Thats a very nice job Lee.

Before I wasn't planning on using a foot pedal to turn the vacuum pressure on and off. I was planning on installing dual on and off buttons on the front and back of the machine( just like my machine at work). Now after thinking a lot about it I am considering the foot pedal. I like how much simpler it would be and I also like that instead of having vacuum buttons in just two permanite locations I can move a foot pedal anywhere around the machine. And I also like that (as mentioned in a eariler post) I can keep both hands free to hold down the part; to help stubborn parts suck down. I was looking at joewoodworker.com and I noticed that he now offers pneumatic foot valves. I beleive before he used an electric foot pedal with an electric valve (if im not mistaken). I was wondering which type would work best. The electric one or the pneumatic? To me it seems like the pneumatic one would last longer. Any ideals? Thanks- Robbie

As I don't have a lot of experiance on either I would GUESS each has it's own problems electric ones would have problems with chafing wires and Pneumatic ones with leaks and kinked hoses but all under consideration I would again GUESS keeping like sysytems together (air with air etc...) Pneumatic foot valves would be more robust cheeper and longer lasting
JM2C

Salty

Here are a couple of photos of the burnt table top that I wrote about in post #82. I aquired it because I was thinking about cutting it down and using it on my machine. But I am so happy with the way mine has been working I don't think I will. I am not in the pic with all the people in it cutting it, I was behind the camera.

http://www.cnczone.com/gallery/data/500/medium/burnt_cnc_table_top1.jpg


http://www.cnczone.com/gallery/data/500/medium/burnt_cnc_table_top2.jpg


http://www.cnczone.com/gallery/data/500/medium/fire_hole2.jpg


http://www.cnczone.com/gallery/data/500/medium/fire_hole3.jpg


http://www.cnczone.com/gallery/data/500/medium/cutting_the_table.jpg

I was wondering if anyone know if they make a air valve like this one ( http://www.lowes.com/lowes/lkn?action=productDetail&productId=221029-1126-IFA114&lpage=none ). with some kind of mount attached to it. Some kind of plate where you could screw or bolt the valve in place. If there is such a valve; anyone know where to buy it at. Thanks in advance- Robbie

have you thought about drilling a large hoe in some angle plate and attaching the valve thru the plate with a thin nut?

sir could you please send a link with your movies the one you posted seams to not work, iam in need of help building a vacuum table, thanks much

john

sir could you please send a link with your movies the one you posted seams to not work, iam in need of help building a vacuum table, thanks much

john


John, I'm not sure if It is me that your request is directed at. Please could you advise

Thanks for the help Salty72. Seems like the angle plate ideal maybe the way to go.

just remember that the thread is tappered so keep the angle plate thin and you might be better off using a washer and this way the attached fitting will seat properly (approx 2/3 along the thread) and the edge of the fitting will push on the washer to secure the valve

AS you will probably know the air tight seal is gained from the threads and not the end faces so don't forget the thread tape ..

I went to Lowes the other day, and bought some supplies to try some different ideals to mount the valve. Last night I went down to my machine to try some of them out. I starting thinking about which would be the best option. I then came up with an ideal I thought would be quicker and easier then all the rest I had thought of. It seems to have worked out great. The solution I came up with was just to drill 4 holes in a piece of plywood I already had mounted under my machine( two at the top of the valve and two at the bottom. I just inserted two short pieces of wire in the holes, one piece of wire in the top two holes and one in the bottom two holes, wrapping it around the valve into the plywood and twisting it at the back. When I put the hose clamps on I turned 1 one way and 1 the other, that way they keep the valve from twisting. There is not much pressure used to open and close the valve so I think it will work out pretty well. I wanted something less permanent because I am still thinking about getting a foot pedal valve later on. Right now Im in such a small area i usely have stuff laying where the foot pedal would go. Maybe when I ever get my workshop built I can get one. Who knows I may still use it the way it is now. I will try to take some pics of the setup to better show what I was tring to explain.

Here are a few pics of what I was talking about above. I have included a few differen't angles to try to show it better. It was kinda hard to take pics of something that small without it blurring.

http://www.cnczone.com/gallery/data/500/medium/valve2.JPG


http://www.cnczone.com/gallery/data/500/medium/valve_and_estop.jpg


http://www.cnczone.com/gallery/data/500/medium/valve1.JPG

Large commercial routers,5x10 require 15 to 20Hp vacuum pumps.Is it possible to make say 4 zones and the software could sense where the router is and turn on a relay to a valve switching the vacuum to the area the spindle is cutting?You could get away with less Hp.
Larry

Large commercial routers,5x10 require 15 to 20Hp vacuum pumps.Is it possible to make say 4 zones and the software could sense where the router is and turn on a relay to a valve switching the vacuum to the area the spindle is cutting?You could get away with less Hp.
Larry


I have read of routers that have air clamps that hold the part inplace on all four sides. When the router gets close to a clamp on one side, the control will automaticly raise the clamp on that side untill the cutter passes. Then after it passes the clamp will lower itself again. In theory, it don't seem like changing vacuum zones would be much different. One thing that might prevent it from working would be to get dust and chips under one of the zones that wasn't sucked down then when it came time for it to change to that zone it may cause problems. Maybe someone else can answer this a little better then me.

... When the router gets close to a clamp on one side, the control will automaticly raise the clamp on that side untill the cutter passes. Then after it passes the clamp will lower itself again.....

Or if the clamp does not do its thing, actually it was a stop that did not lower on my friends machine, all hell breaks loose.

On some machine using pucks the zone activation is used, mostly to allow for reloading the machine in one zone while it is working in the other. But they still have a big pump because pucks need a good vacuum.

Well it's been awhile since I posted on the Zone but the house has been keeping me busy and haven't had much free time. Haven't even been doing any work with the CNC router, but I finally got some time to finish my vacuum pump stand. Thanks again Robbie for the Cad files of you stand. :D

http://www.cnczone.com/gallery/data/500/medium/vacuumpump1.JPG
http://www.cnczone.com/gallery/data/500/medium/vacuumpump5.JPG

I picked up some 3/4" thick HDPE sheet which I will use to make a removable vacuum table for the cnc router. Hopefully I will find some more projects to do with the router especially with winter coming. Yes I said the "W" word. HEHE :D:D


Hey Robbie. You mentioned earlier you were thinking about using a foot pedal to switch your vacuum clamp on and off. Did you see the one they sell now at joewoodworker.com? Not a bad little unit but I think for the price the lever valves work just fine.
http://www.joewoodworker.com/catalog/images/footpedal.jpg


Carl :D:D

WOW! Your stand turned out great Carl. Maybe I should have painted mine a solid color, that looks awesome. Again great work on the stand! - Robbie

Thanks Robbie.

I used particle board for my stand because it was much cheaper then a good quality plywood such as Russian ply but in hindsight I probably should have used the plywood since particle board is not the strongest stuff and breaks easy. When I was tightening the pipe straps to secure the pvc tanks some cracks developed in the particle board and particle board doesn't give the nicest finish when painting. A learning experience but it's done now and I am quite happy with it. I was quite pleased that I didn't have one leak to fix the first time around. :D I was surprised at how low the vacuum force actually felt like when I put my finger tip at the end of the hose. I thought it would be so strong that you couldn't remove your finger but it wasn't that way at all even at 21"hg. I guess it is different when the vacuum is spread over a larger area?

Carl

I've been vacuum clamping for about 15 years on a manual overhead router using a small 3 to 4 cubic mtr per hour rotary vane vac pump. I always use close grained hardwood for the base (most mdf leaks too much) the smallest item I can hold safely is about 4 inch diameter. Neopreen round strip let into groove is the best sealing stuff I have found but flat self adhesive is good too. you can easily tell when the piece to be machined is ready, which is almost instantly you turn on the vacuum and you just leave the vacuum running whilst you machine. they are designed for this, shop vacs and hoovers arn't they will ovrheat.
I have also just had the good fortune to buy a virtually brand new vac blower off ebay worth about £1500 gb pounds new for £80 which I am going to use on my cnc. I have been doing some tests and the smallest area this can hold is about 8 x 8 inches but it will hold a lot of this size from the one pump and small leaks are not a problem.
Hope this helps a bit feel free to ask

Cheers
Colin

Thanks Robbie.

I used particle board for my stand because it was much cheaper then a good quality plywood such as Russian ply but in hindsight I probably should have used the plywood since particle board is not the strongest stuff and breaks easy. When I was tightening the pipe straps to secure the pvc tanks some cracks developed in the particle board and particle board doesn't give the nicest finish when painting. A learning experience but it's done now and I am quite happy with it. I was quite pleased that I didn't have one leak to fix the first time around. :D I was surprised at how low the vacuum force actually felt like when I put my finger tip at the end of the hose. I thought it would be so strong that you couldn't remove your finger but it wasn't that way at all even at 21"hg. I guess it is different when the vacuum is spread over a larger area?

Carl


Wow no leaks on your tanks the first time around, I wish I could have said that. I had to use that calking ideal on the plans with mine. The key to making it work properly is to have as few leaks as possible. Thats what caused me all the pains in the beginning. I thought my plywood was dense enough. I thought I would be able to hold a good vacuum without having to seal it. I was planning on sealing it eventually anyway, just not for a while. I tried my vacuum out and it wasn't holding hardly any vacuum. I didn't think it was leaking straight through the plywood. Any how I sealed all the edges on the plywood table and it made all the difference in the world. It also made the table look better and made it more durible. I don't think you will have too much to worry about using the HDPE sheet for your table. It should seal pretty well. Your right about it having more vacuum over a larger area. Here are a few pictures of things I have cut using nothing but the vacuum to hold it down.

http://www.cnczone.com/gallery/data/500/medium/Kayla_s_Room.jpg


http://www.cnczone.com/gallery/data/500/medium/I_love_you_heart_2.jpg


http://www.cnczone.com/gallery/data/500/medium/The_Fosters.jpg


http://www.cnczone.com/gallery/data/500/medium/The_Velasquez.jpg


http://www.cnczone.com/gallery/data/500/medium/Gone_Fishing_Sign.jpg


http://www.cnczone.com/gallery/data/500/medium/The_Perrins_sign.jpg


http://www.cnczone.com/gallery/data/500/medium/The_Haris_s_Sign.jpg


http://www.cnczone.com/gallery/data/500/medium/Lighthouse.jpg


http://www.cnczone.com/gallery/data/500/medium/100_6197.JPG

That's just the tip of the ice burg of the things I have used the vacuum table to hold while machining. Keep in mind the signs are 3/4" mdf. Which leaks vacuum straight through the work. It still held in place great. I have been using the same vacuum fixture for most of the work I have been doing lately, Its about worn out but keeps on going.

http://www.cnczone.com/gallery/data/500/medium/Multi_Purpose_Vacuum_Fixture.jpg

That pic was taking a while back. It looks even worse now( I will try to get a recent photo of it). It still works though

And heres one last photo of a sign being machined.


http://www.cnczone.com/gallery/data/500/medium/cutting_sign.jpg


After using my vacuum table for the past while, It makes me wonder how I ever lived with out it.

I finally got some time to make my first vacuum jig and I'm amazed how strong the vacuum really is. I used 3/4" HDPE sheet and cut all the grooves on the cnc router. Already got a second jig drawn out and I just need to get some time to cut it. It's going to have two zones that will be controlled seperately. Still working on the design for the main vacuum table which will also be made from HDPE. Just need to figure out how many zones I will have in it and how to best cut them. I was thinking of how you did your table Robbie and I might cut the bottom of the HDPE with the vacuum channels and bolt the whole sheet to a piece of aluminum plate or more HDPE sheet to seal it.

I have just posted a video on our website www.vac-clamp.com (http://www.vac-clamp.com) showing a sign being machined using our vacuum hold downs, and face plugs.

The video quite large (2Mb), but I would like to know if it makes sense to everyone, or should I reshoot the thing.

Look in the Video Gallery drop down menu or Click Here (http://www.vac-clamp.com/vc%20cnc.htm) for the link to the CNC application page
Errol

I machine only plastic components in work, and we use a lot of vacuum fixtures when we are not able to use a vice.

Beezer, i would use a different material to HDPE as its quite soft and isnt as stable. We use Delrin and Cast Nylon as they are pretty solid and relatively inexpensive.

We also have a CNC router, which has a wooden bed with a grid of slots in. On top of this we use MDF for fixtures with a neoprene/rubber vac seal between the mdf sheet and bed and then around the area of the part to be machined. A few grooves/slots about 0.5 - 1 mm deep are machined to help suck part down to fixture.With a normal pistol drill we drill a few holes through the MDF.

I've been working on a fixture out of aluminum. It uses a .025 thick gas permeable paper between it and the parts to be cut. The problem I'm having is the paper I have is 2'x3' and my fixture is 4'x4'. I found the paper at Datron and can't seem to find anything else like it anywhere.

The fixture is 4 24"x24" parts mounted in a square. Right now each square has 2400 3/32" holes in it. I may have to enlarge the holes to get better flow thru though. I was pulling 3psi of vacuum with no parts or paper on the prototype 12"x12" I made.

If anyone has any suggestions for some permeable paper I would appreciate it. I will post some pics of it when it's finally built. I have to wait to use our VF5 to make the fixtures.

Hi cl707programer
You might want to have a look at what is being used in the Nested Based CNC area. They use MDF as a spoil-board, and draw a vacuum through that.
Make sure you seal the edges of the spoil-board and make sure that you have a powerful vacuum pump.
Vac-Clamp

creating a vacuum thru a sheet of MDF is the best method, but it does take a RAELLY BIG Vac pump, and most of these motors as I have fond out are 3Ph especially if the MDF sheet is to be used as a spoilboard (10-20mm thick)

one thing I tried was 2mm sheet of MDF sanded both sides with 60grit paper -this removes the gloss coating and allows better suction.
I then painting the edges of the MDF with a PVA glue and used plastercene (like playdough) to form the seal around the edge of the material to be cut.

This worked really well untill the tool cut into the PVA glue and I lost VACUUM, - guess this goes back to you need a REALLY BIG Vac Pump so it can overcome losses

Has anyone tried to modify a dust extractor to creat a rotory vain vac pump, - Reason I think this might work is that if you aren't goining to "suck" any particular matter up, you should be able to place the vains very close to the wall of the housing to increase it efficiency, and over a 12"x12" area even a partial vacuum of 7psi is a huge amount of pressure

Go to your local car wrecker and pick up an old carburetted V6 or V8 engine; you need one that has a separate intake manifold to each cylinder bank. Or has a manifold that can be blanked off to isolate half the cylinders.

Run the engine on one cylinder bank and just attach your vacuum tube to the other unused manifold feeding the other cylinder bank.

A carburetted engine can easily pull a manifold vacuum down in the 20 inches of mercury region and if you getting a honking great V8 it will pull a lot of volume.

And you don't need three phase electricity to run it.

What about using a turbine to generate the high flow High Pressure required to suck thru MDF ???

Hi All,
Did anyone answer the thread of using the intake of an air compressor pump? Or would this screw things up?
Joeski

Hi All,
Did anyone answer the thread of using the intake of an air compressor pump? Or would this screw things up?
Joeski

I think it was greolt has a thread 'An Aussie Adventure in Vacuum Pumps' or a name like that and he describes converting a compressor to a vacuum pump.

here is the link

http://www.cnczone.com/forums/showthread.php?t=34537&highlight=An+Aussie+Adventure

what sort of stuff have Ppl cut (held down) using this method

http://www.dream-models.com/eco/vacuumpump.html

how much leakage do you think you will be able to get away with (what CFM are the pumps)

Thats what Im looking to do but over my 4'x8 table.
Do you happen to have a dxf file of the cut boards?
What are you using to hook the vacuum up to the table?
got any underneath pics?
Your post is a great help... it seems like the simplest design.
Thanks
Andre


Here are some photos of the table itself. There is nothing really special about it, its just 2 pieces of 3/4" birch plywood bolted together with some vacuum seal between to hold in the vacuum. I modeled it after a few tables I seen on here and my table top on my CNC at work.

Thats what Im looking to do but over my 4'x8 table.
Do you happen to have a dxf file of the cut boards?
What are you using to hook the vacuum up to the table?
got any underneath pics?
Your post is a great help... it seems like the simplest design.
Thanks
Andre

Hi Andre,
Sorry for taking so long to answer this question. I didn't even notice it untill now. To hook the vacuum to the table I just used a 90 degree elbow my dad had laying around. I beleive he said it is something used in electrical work. I'll have to ask him to make sure though. I have also included the photos of the bottom. I will look for the dxf drawings I used and post them here when I find them. I hope this helps- Robbie

Hey Guys,
I have already built a vacuum bag for veneering and also fixture construction, but am now looking to build a vacuum table. I have a commercial refrigeration vac pump that is rotary vane type, I am not sure of the cfm, but if necessary I can acquire another to double up - although I don't believe this to be necessary with the right construction. At the moment I only plan to machine hardwoods. If the fixture presents itself as suitable I will possibly use it for metalwork in the future.

My initial brain storm was to cut a platen out of composite (.500 - .750" think) (prob nylon or an acrylic type.) with .250w x .125d slots spaced .500 apart. I think four independantly valved zones would be ideal and then use a sealed spoil board and employ the drilled hole method as mentioned by CNCRob.

Thank you,


J

How come you router guys don’t do this the way the aerospace folks vacuum down a wing section? Just lay down some particle board on your bases (the same size as your base), then deck the surface so it’s nice and flat. Make sure your vacuums on though. Then just place your work piece on the top of the particle board but place thin sheets of sheet metal of some type on the un-used areas of the new table surface to maintain a decent vacuum? And if you still have small voids here and there, lay down some masking tape in the exposed areas. It works pretty darn good holding down metal & aluminum, I don’t see any reason why it wouldn’t hold down a block or piece of wood!

know nothing about pumps...anyone know what size pump I should get for a 4x8 sized table (im cutting mdf & pvc board).
Also who has the best deal on pumps...and which ones!

Thanks All!
Andre

Does anyone have a dxf of a vacuum table top that I can modify and cut from mdf?
or does anyone know the best size squares to cut into the board?
Thanks for your help
Andre

Does anyone have a dxf of a vacuum table top that I can modify and cut from mdf?
or does anyone know the best size squares to cut into the board?
Thanks for your help
Andre

Here are the dxf's for my vacuum table top the one called vacuum channels is the vacuum channels them self and the one called bolt down fixture holes is for the holes I made so I could bolt down some of my fixtures if I wanted to. Hope they help

Here is the dxf for the vacuum channels under the table top that allow the vacuum through all the holes in the top itself. I did make the pocket around the main vacuum entrance (the big hole on the drawing) a little bigger then the one in the dxf

Thanks for your help.

I am not sure if this is the right forum for this question.
I bought a couple of V-Clamps for hand routing (sorry not CNC..yet). I moved the rubber to line up with the size piece that I wanted, but one of them works well and the other not at all. They were both working properly when I first got them, but now one does not want to hold.

Any suggestions would be appreciated

I am not sure if this is the right forum for this question.
I bought a couple of V-Clamps for hand routing (sorry not CNC..yet). I moved the rubber to line up with the size piece that I wanted, but one of them works well and the other not at all. They were both working properly when I first got them, but now one does not want to hold.

Any suggestions would be appreciated

Difficult to say without a picture. It doesnt take much to loose a vacume if the pump is small.
Dirt under gasket.
Nick in gasket.
If it is one of those round rubber jobs it can be difficult to get a seal where the end meets the side when it completes the loop. You may be streaching the rubber gasket so it leaves a gap there.
Paul

Hello Philthy,
A couple of thing to try.
I am making the assumption that the only thing that has changed is that the seal has been moved or cut to allow you to hold a smaller piece.

First one, which might seem obvious, have you included the vacuum port in the area sealed with the gasket?

You need to make sure that the ends of the seal are touching, and that where they meet the cut is clean. You also need to make sure that you cut the seal to size, and don't try to make the end of the seal butt up to the side of the seal rubber.

Remember the vacuum pump/generator is built into the clamp, so they are not large devices. They will tolerate slightly porous materials but an outright leak will mean the clamps will not function properly.

PaulC's suggestion of a stretched seal may also be worth looking at too.

Errol at V-Clamp (http://www.vac-clamp.com)

Thanx for the help. Redid the rubber bit and now all is good.

I have to pass this on for what it is worth.

I have now got the hang of this little sucker and I have to say I use it more than I thought I would. No need to run it at 80 psi to 120 psi as the manufacturer recommends because 60 psi gives me more than enough hold and uses a lot less air.
I can use a large chamfering bit without any movement, and the best bit is no clamps in the way.

Phil

just caught your article , I have some pics of the one i made up now. In Vacuum Jigs . ( AMMACH ) works great. Cheap

Just built a vac table for cutting and drilling 6mm Ali parts. All Vac equipment, hoses, presure vessel(vacuum in this case) from trips to the scrapyard. I am mighty impressed with the clamping force to say the least and I am just thinking up more and more uses for vac by the minute.
Good thread guys!
http://i261.photobucket.com/albums/ii62/zoeper/14062008002.jpg
http://i261.photobucket.com/albums/ii62/zoeper/14062008.jpg