Vaccum clamp

[osdhillon]

Hi,
I am looking for info on vaccum clamp. My router table size is 4'X8'. I just finished building 4 X 4' router out of MDF and aluminum. I came out nice and the first cut (a simple circle) just came perfect. Now I am in process of building one out of metal. My gantry and Z-axis design is done and the base and bed design is awaiting for the info on the vaccum table.

Can anybody help please. How can I build a vaccum table? What basic parts do I need and which blower should I use (Or should I build one).

In my machine shop I have a CNC bench mill and a 9X20 lathe. Your input is valuable and appreciated.

I will be posting the pics of the mill conversion and the MDF router, once I moved to a new location. MY 2 car garage is just too full (how can I upload a picture)

Thanks,
Onkar

[Chris D]

I know this is a "No no", but it works well. My table is two sheets of plywood (1/2" thick) sandwiched over some 1/2" x 1/2" spacers and a perimeter frame. This creates a torsion box type of structure that is hollow and allows for air flow.

I started out trying to get my Gast vacuum pump (rotary vane) to draw a vacuum - but it simple did not have enough CFM to keep up with leakage through the pores of the wood. Stumped and on a tight budget, I went to the local home center and bought the cheapest shop vac they had - about $25.00. I bored a hole in one end of the table to accept the hose, turned it on and it works great.

On the tables surface, I milled 1/4" wide by 1/4" deep grooves in the surface creating a series of 2" square pads. I picked up some O-Ring chord stock from Mcmaster.com, and I put that in the grooves to help seal the part against the machine table. I also drilled four 1/4" holes around one of the squares to allow for the air to evacuate from the cavity between the work and the machine table.

I know the Vacuum will burn up some day as it isn't getting enough air to cool it. However, it doesnt seem to run any hotter connected to the machine than if it is just sucking air through and open hose.

So, if you are on a tight budget and don't mind the noise of a shop vac (the one I got isn't as loud as some of the others I have even though it was cheap), pick on up and give it a try. Remember that the larger the workpiece, the greater the clamping force so you really don't need a super duper high powered vacuum pump.

Hope this helps a bit

Chris

[skippy]

I've never seen an american vacuum cleaner so I don't know if they're the same as the ones here or not but pretty well all the vacuum cleaners produced here or should I say sold here in the last five years have a motor bypass system so that if the hose blocks the motor won't overheat and burn out. These are perfect as a high flow vac source such as what you're talking about here (cheap too).

[Chris D]

I have no idea if it is or isn't - I don't even remember looking at the information on the box. I just saw a small shop vac for twenty some dollars and I saw the word "Quiet" somewhere on the package graphics. That was enough for me to buy it and it is working great for the purpose.

Even though I am a tool junkie, I don't think I could justify anything else in the form of vacuum pumps for this application.

Chris

[mxtras]

I completely agree with Chris D - and not just because he's a "Chip Sweeper" like me!

Having been around experimental, prototype and production equipment that uses vacuum for hold-down for the past 19 years, I would recommend that you spend your money elsewhere - just use a shop vac for your vacuum source. If you have volume issues, get a bigger shop vac or two and manifold them together with PVC pipe. You will be glad you kept your money in your pocket.

I have had the same Shop-Vac in place on an industrial panel router for almost four years without a minute's trouble and it is still going strong. As Chris D mentioned - you will have enough air flow from small leaks and through the porosity of the MDF to provide adequate cooling I believe, not to mention that a shop vac is not a sealed "pump" - it is a blower and is pretty durable. The high pressure pumps (water ring, oil ring or roots stlye pumps) require cooling as you might know due to the higher pressure. But that's another topic.

As far as the table design - again, I agree with Chris D. I suggest that you use two sheets of MDF. I suggest that you mount the bottom one (1/2"or 3/4") to the router frame in semi-permanent fashion. Then rout channels or grooves in it to distribute the air flow (in the top surface). Skim cut the top surface of this bottom sheet clean with a large diameter cutter to make it flat with your XY plane. Then place a sacrificial piece (1/8" or 1/4" or ?) on top. You can tape around the edges with plastic packing tape or whatever to seal the edges. You can also use a heavy paint to seal the unused surfaces to further prevent losses.

Let us know what you end up with!

[Chris D]

For your table, you have a spoil board on the top of the "Base board". You cut your grooves in the base board which allows air to flow around. You face off this board to quailify it to the machine's axis - great idea.

You then attach the spoil board on top of the base board - makes sense so far to me. Sealing the edges with tape is a great idea and painting if need is also a great idea.

However, I missed something - do you make a couple of holes in the spoil board to allow air to pass through it?

Also, have you ever had the need to use any rubber material as a seal between your work material and the spoil board?

Thanks!

Chris

Originally Posted by mxtras I completely agree with Chris D - and not just because he's a "Chip Sweeper" like me! Having been around experimental, prototype and production equipment that uses vacuum for hold-down for the past 19 years, I would recommend that you spend your money elsewhere - just use a shop vac for your vacuum source. If you have volume issues, get a bigger shop vac or two and manifold them together with PVC pipe. You will be glad you kept your money in your pocket. I have had the same Shop-Vac in place on an industrial panel router for almost four years without a minute's trouble and it is still going strong. As Chris D mentioned - you will have enough air flow from small leaks and through the porosity of the MDF to provide adequate cooling I believe, not to mention that a shop vac is not a sealed "pump" - it is a blower and is pretty durable. The high pressure pumps (water ring, oil ring or roots stlye pumps) require cooling as you might know due to the higher pressure. But that's another topic. As far as the table design - again, I agree with Chris D. I suggest that you use two sheets of MDF. I suggest that you mount the bottom one (1/2"or 3/4") to the router frame in semi-permanent fashion. Then rout channels or grooves in it to distribute the air flow (in the top surface). Skim cut the top surface of this bottom sheet clean with a large diameter cutter to make it flat with your XY plane. Then place a sacrificial piece (1/8" or 1/4" or ?) on top. You can tape around the edges with plastic packing tape or whatever to seal the edges. You can also use a heavy paint to seal the unused surfaces to further prevent losses. Let us know what you end up with!

[mxtras]

Chris D -

I don't usually use anything on the edges other than plastic tape. I will typically screw down the waste board with drywall screws (recessed) then tape around the perimeter and skim cut the deck leaving two fences to help locate a panel accurately. I use up to 1" UHMW and cut parts no smaller than about 6" square. The MDF breathes well enough to where I can position a panel or plate, cover (or turn off in my case) the un-used regions of the table and go fo it. I 'lightly' tape down thin plastic to seal unused sections.

In the past, I was asked to cut several thousand samples that were 4" square with rounded corners from large sheets. To make a long story short - I tried using thinner MDF to facilitate hold-down without success in this case. I have had success using 1/2" MDF without holes to hold smaller sizes before, but not in this quantity. The solution was to perforate the top board in an array that matched the part program array, then cut a row of parts and as the machine would advance to the next row, I would cover the row it just finished. Does that make sense?

I guess it depends on what you are cutting and how small the parts are. I may be giving the impression that all I have cut are large, flat parts, but that is not the case. I usually will look at the job and modify the table to suit the requirements - that's one of the advantages of using MDF - it is relatively cheap so you can hack it up - use it as a fixture. I will frequently screw fixtures in place using drywall screws and machine things like mold parts from 1" thick 6061 aluminum.

And yes - I have used double sided carpet tape to hold parts to the table surface - either to create a seal or to completely hold the part - not for aggressive machining obviously. I also have blocked the material in place with MDF screwed to the table.

Of course - the disadvantage of MDF is moisture absorbtion. It tends to swell on the edges faster than in the center, and temperature and humidity changes will cause it to move around. This is why I will skim the top board - sometimes twice in one day if necessary - depends on the parts, material, etc. Cutting the factory surface also allows MDF to breathe a bit better.

What type of materials do you guys typically cut on your vacuum tables? (what parts do you make?)

[Chris D]

Okay, I wasn't sure if the MDF would be porus enough to allow for clamping without first drilling some holes. I have not tried it yet but probably will on my next table. I also like your idea as it makes for a thinner table - mine is pretty thick and like on most routers - z axis is limitted.

Carpet tape is a great hold down clamp - use it all the time, and not just on the router.

I have a secondary clamping system on my table too. I mentioned that I milled 1/4" x 1/4" grooves over the surface creating a pattern of 2" squares. I can place a cleat in these grooves to work as a stop - which also aligns the part to the machine as the grooves were machined on the machine. The secondary clamping comes in from the opposite edge of the board. On the opposited side of the stop, I put another cleat in a groove about 2 to 4" away. Between this stop and the part, I use a wedge to force the part against my work stop cleat. The wedges are very easy to make on the table saw and look like sliding parallels (adjustable parallels) - works great most of the time.

I too will make wooden fixtures and screw them down to the table - had to do this for making the encoder wheels for the MPGs I made.

As for what I machine on my router, just about anything that fits on it. I have been making parts for furniture etc. but also parts for the machine and the shop. While it is only a router, I have been doing some aluminum milling on it from time to time.

Chris

Originally Posted by mxtras Chris D - I don't usually use anything on the edges other than plastic tape. I will typically screw down the waste board with drywall screws (recessed) then tape around the perimeter and skim cut the deck leaving two fences to help locate a panel accurately. I use up to 1" UHMW and cut parts no smaller than about 6" square. The MDF breathes well enough to where I can position a panel or plate, cover (or turn off in my case) the un-used regions of the table and go fo it. I 'lightly' tape down thin plastic to seal unused sections. In the past, I was asked to cut several thousand samples that were 4" square with rounded corners from large sheets. To make a long story short - I tried using thinner MDF to facilitate hold-down without success in this case. I have had success using 1/2" MDF without holes to hold smaller sizes before, but not in this quantity. The solution was to perforate the top board in an array that matched the part program array, then cut a row of parts and as the machine would advance to the next row, I would cover the row it just finished. Does that make sense? I guess it depends on what you are cutting and how small the parts are. I may be giving the impression that all I have cut are large, flat parts, but that is not the case. I usually will look at the job and modify the table to suit the requirements - that's one of the advantages of using MDF - it is relatively cheap so you can hack it up - use it as a fixture. I will frequently screw fixtures in place using drywall screws and machine things like mold parts from 1" thick 6061 aluminum. And yes - I have used double sided carpet tape to hold parts to the table surface - either to create a seal or to completely hold the part - not for aggressive machining obviously. I also have blocked the material in place with MDF screwed to the table. Of course - the disadvantage of MDF is moisture absorbtion. It tends to swell on the edges faster than in the center, and temperature and humidity changes will cause it to move around. This is why I will skim the top board - sometimes twice in one day if necessary - depends on the parts, material, etc. Cutting the factory surface also allows MDF to breathe a bit better. What type of materials do you guys typically cut on your vacuum tables? (what parts do you make?)

[strat]

i have a post with a pic on it somewhere around here but what i did was route the 2x2 squares and drilled a hole to the center and from the edge to center i had an old compressor around that sucks and blows so put a quick disconnect air connector in the MDF and sealed it all up with plastidip .... its a rubber for dipping tool handles in but gave my cut area a nice rubbery no slip feel and holds all the air in the wood
i use neoprene foam in the slots works fine for me

[ynneb]

WWW.vac-clamp.com

I did a review on it here http://www.cnczone.com/reviews/showp...cat/all/page/1

Sorry there was much more detail in my original review but somehow it got butchered down to nothing. I dont know why I bothered doing the review.
I hoep this helps anyway

[osdhillon]

Chris , Great Idea!

But I have another issue. My router will be able to machine aluminum also. So MDF is not going to work with the coolant. Few months ago, i saw a thread on somebody building a excellent router table with extrusions for the table. Does any body have any info on that thread.

The table should also accomodate the 'T-Sots' for clamping along with the vaccum clamp.

Any ideas on building a proffesional one. My budget for the table is about $ 1500.

thanks
Onkar

[ger21]

Here's Benny's review of the Vac-Clamp. http://www.cnczone.com/forums/showthread.php?t=7643