Need Help with vacum table


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    Default Need Help with vacum table

    Need help design of vacum hold down table. This will hold a 4x8 sheet and looking to put vacum in the middle. What type of wood, how thick or would you use inserts?
    I will have a manafold down the side with 6 up tubes and T valves.

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    Default help

    need help here



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    Default Vacuum table

    Todd I've done many vacuum fixtures in aerospace. message me with your needs for cheap advice. Brian

    Been doing this too long


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    Gold Member cabnet636's Avatar
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    Default try

    shopbots forum search vacuum tables theres a lot of info there

    jim



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    Default Help

    I need to be universal with this table. This table I want to be able to clamp on the outside and vacuum on the inside for smaller pieces and would like to put detailed vacuum on the datum corner for small pieces. I do not have a project for this machine but I have a friend that has a machine shop and he has talked about sending me work. If someone stops in and needs something done I don't want to tell them I have no way of holding it.
    Thanks,



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    Default

    Is that an ezrouter plasma table? Are you trying to convert it to a wood router? Or are you thinking of routing aluminum.



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    Default combo

    This is a combo table 5x10, with 5hp spindle. I have already made the grid removeable in one piece and doing the same for the vacuum table. have had this table since first week of Feb. and only cut one sheet of steel. Long story, got damaged in shipment, took them 3 weeks to show up, 1 guy to repair other for training. Took both all day to repair and neither really knew the software, got no training. my hand torch was to fit the holder but to find out only the miller will fit. So there were no guard so I made guard, all the screws, nut, and bolts were falling out,ect. But the torch kept crashing so they sent me new updates and have not put them in yet.
    But I hope I never see them or talk to them again.



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    Default

    Have fun with that machine. I have one and it has been a nightmare.



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    Gold Member cabnet636's Avatar
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    Default vacuum

    you'll find more on this in commercial router section of cnc zone, here are some pics, check them out and ask questions. this is my table.

    there are some people who ask about ez router on the commercial end but no one responds there.

    http://www.cnczone.com/forums/showthread.php?t=60467

    there are vacuum setups done on several threads here
    camaster, remain cnc and excitech

    http://www.cnczone.com/forums/forumdisplay.php?f=215

    jim
    www.mcgrewwoodwork.com

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    Default Nick

    Any pointers or what problems have you had?
    Thanks



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    Gold Member cabnet636's Avatar
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    Default

    this machine came with table built. i have ordered a new sheet of phenolic to replace it and i have a new router ordered and i will be building my table for it,

    the big delima is the use and amount of vacuum needed, i have had to learn a lot in this area and am not totally there yet!!

    it comes down to affordability on the motor, i have used the two fein turbo 3
    method and it works, i also have a fpz regen and all three will do the trick on plwwood. i do know io will be shopping for a becker or busch pump at the iwf show in atlanta in august!!

    back later gotta travel top work

    jim



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    Default still working on table

    Picture of board support. As I complete each stage I will try to post pictures.

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    Default

    Have you decided on a design for the top? I think I still have one that uses 1 inch squares for a 4x8 table.



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    Default decide

    What I have done is left about 1 and 1/8 inch depth for a 3/4 bottom board that will have the plumming in it and the air way then a 1/2 on top so we can fly cut for accuracy and put pin holes for air. Still would like to put something in the datum corner for a more postive hold for small parts.



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    Gold Member cabnet636's Avatar
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    Default todd

    you can create zones in any configuration you want, i am building a new table with a 2x2 x2 on the close end and 3 2x4 on the other zones making 5 zones over a 4x8 table. you could use a fein turbo 3 which pulls 7.5" and 110 cfms for the small zones and another for the other three. i have done this and it does work. what type of material are you planning to cut? vacuum can be an expensive road. i do know its not like a air hockey table and small holes restrict vacuum not in crease it. more later



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    Default

    You are going to need 1" for a top unless you are talking about metal.



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    Default why

    why would the top need to be 1 inch if total of the two is 1 and 1/8 inch thick?
    I am new to the vacuum world.
    The top board will be the replaceable board and trying to keep the cost down.
    Thanks



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    Gold Member cabnet636's Avatar
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    Default cool

    thought you'd like to see this'

    and if your serious you can get phenolic in fla for 500.00- per sheet, the thickness is needed to keep table flat during vacuum

    jim

    http://www.talkshopbot.com/forum/mes...tml?1216870902

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    Last edited by cabnet636; 07-24-2008 at 04:50 AM.


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    Default just for the sake of it

    bill glenn wrote this for some of us who were learning vacuum.




    There is much confusion about what kind of vacuum pumps are needed for different applications regarding hold-down on CNC Routers. Many of us think that more horsepower automatically results in better hold-down and opt for more HP and of course more electric bills. I will try to give an unbiased view on how it works and what works best from a (kuntryboys) way of saying it. I have used everything from reverse blowers from Grainger that will work on 220 single phase to 25 HP regenerative blowers to Positive displacement pumps such as Becker, Busch, or others. I have built CNC routers for 13 years and just lately feel like I understand it enough to really help someone else understand it. For most people including myself, we may think that a pump holds down parts because it "sucks the part down with air". When we understand what really holds the part it will help us understand more about holding down parts. Piab is a company that makes small vacuum cups, small pumps, etc. Several years ago I read a book they had and it explains very well how it works and it was very interesting. Basically without getting too deep into science this is it:

    On what is called a standard day which is 59 degrees F at sea level air weighs about 15 lbs per square inch. Think of it as a column of air 1 inch square that goes all the way toward outer space until there is no air molecules. If you live in the mountains say at 2000 ft in elevation then your column of air is going to weigh less because there is not as much of it to weigh. If any of you are airplane pilots then you already know that the hotter the temperature the farther apart the air molecules are and the longer it takes to get off the ground and the slower you will fly. The same is true with vacuum. It will not hold down with as much force the hotter it is and the higher in elevation you are. But remember this column of air is fluid so it will try to replace any vacuumed areas. THIS IS VERY IMPORTANT. Air only weighs 15 lbs per square inch maximum. It cannot be made to weigh more with any size vacuum pump because the most you can vacuum out of anything is whats there. (15 LBS. MAX) if you have a 10" square you are trying to hold down the maximum you can hold down with is (10" x 10"=100 square inches) = 150 lbs of force. This is only with a pump that will pull 28-29 inches of vacuum. This can be accomplished with a positive displacement pump such as Busch, Becker, or others that can pull this kind of vacuum. Regenerative blowers on the other hand cannot pull this kind of vacuum but are more on the order of 10-12 inches which would make its hold down force per square inch be more around 6 or 7 lbs per inch. If you were holding the same 10 inch sq piece of material it would be held down with more like 60 or 70 lbs.

    Positive displacement pumps would probably be the ultimate but we have to remember that they do not put out the same volume as a regen blower. They put out much less per given HP because they are doing more work so you must find a balance. They also require more HP to get the job done. So if you use residential electricity you may find that you want to go with a 5-7.5 HP positive displacement pump such as Busch, Becker, etc and make sure you don't have leakages etc. I will mention some tips there later. If these pumps are too high new there are several companies that sell rebuilt ones with a guarantee. If you have plenty of electricity you may want a high volume regen blower such as Fuji, FPZ, etc of 20 or 25HP and when you have that kind of volume you don't have to be as bothered by leakage. On a 4 x 8 table I feel that 10 HP regen and below is a little bit marginal. Of course there are huge vacuums that will pull huge volume and high vacuum but most of us are trying to do CNC on a budget and could live off some peoples electric bills. Positive displacement pumps generally cost nearly 2-3 times the price of a regen blower.

    I have a customer who has 2 of our machines. I was surprised to learn that he is running both tables with 7 1/2 HP rebuilt Busch pump that pulls 28-29 inches and has decent volume. He paid about 3300.00 for the pump. He is careful with his leakage. Heres how he does it:
    Our low-cost vac tables are MDF 1 1/2" thick with a grid sytem cut into the table with 4 zones on a 4 x 8. Each zone is 24" x 49" with a 2" PVC pipe running to each zone that has a PVC cut off/on for each zone. He mills a sheet of 3/4 LDF or MDF on one side. He then adhere this to his grid table being careful to only put the wood glue on the grid itself so as to not seal up the bottom of the sacrifice board. This keeps the sacrifice board from becoming sealed. Then he mills the top of the sacrifice board. He also then seals up the edge of the sacrifice board to not let air escape through the edges. When you cut your parts be careful to set your z so that it doesn't go unnecisarily deep into the sacrifice board. When the sacrifice board gets uneven and is affecting the vacuum you can then remill the board just enough to clean it up. When you get down to the grid again simply do the same with another board and start over. This works very well. (Thanks to Greg Westberry for the enlightenment on how he does his vacuum system and some help on the above info as well)

    I have also found that if you have limited electricity available such as only 220 single phase and don't want a phase converted setup that a Dayton 10 HP blower working in reverse works fairly well because it has such a huge volume but uses a lot of electricity to start and you have to build a different vacuum box to handle the volume.

    Hope this helps a little in making your decisions. I will try later to give some tips on how to cut parts with low volume or no vacuum at all.

    Bill Glenn
    Camaster CNC



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    Default pump

    I have a copelend 4cyl 20hp self contained unit that I got from a scrap yard and I thought I might be able to use the intake side and a small vacuum tank of some sort since there is not enough volume.
    What do you think?
    Electric is no problem, 480 3ph
    Thanks,



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