Vacuum Table questions

[Nick12]

Thats not good. another question: If I have a 4 x 8 Spoilboard laid on my CNC table and underneath it I have a 2 x 8 area gasket ed off am I loosing vacuum from the area that is not gasket ed off. Do I need to cut my board in half and put it directly over the zoned off area and seal all the edges of it?

[gfacer2]

Well your current board is probably fine because its not pulling anything through but otherwise yes, the vacuum will spread out within the spoilboard and go past your intended area. The gaskets in the plenum will help but still assume at least 8-12" outwards from that will have some air leakage as it spreads out. I cover up my un used areas with coroplast or offcuts but if you are doing a regular job then I'd make a custom sheet that covers your unused area or cut and seal the spoilboard to match the job. The former is what you can do if you need the table for other things and the later if the machine just needs to do one thing well.

[Nick12]

Great, Thanks for the help. Is it possible to filter or reach people on here that live or work close to me. I found a dealer for Trupan ultra light but they want me to buy 40 sheets at a time which would be ok if I could find other CNC guys who would like to purchase it from me for there tables. I run my own business so it wouldn't be much for me to stock it and sell it.

Thanks

[gfacer2]

I'd take the opposite approach. Ask them for a buyers name and get a couple of sheets off them (unless they can just bring it in by the skid with no local buyers). I really don't think Trupan is needed but I'm biased because I've never used it. Good luck.

[ger21]

Although we have two, I'm running basically the same pump as you, and have always just used regular MDF.
My guess is that with Trupan, you may end up with less vacuum, as you'll have more leakage through the Trupan?

[Nick12]

Gerry. I am using Regular MDF right now and I am not getting enough vacuum through it. My gauge is reading 17HG with and without boards covering it up. I believe the regular MDF is to dense to allow flow through. Based on the conversation I have had on here with gfacer2 I need to switch to a light or ultra light board. I am not a CNC wizard by any means but I have to believe that I should be experiencing some pressure change when the spoil board is open vs covered up. I think your right Trupan might be way to light. But I have spoke to distributors and not all of them can get Trupan but they told me that if I could find Trupan Ultra Light then that would be the best on the market for spoilboards.

[Nick12]

gfacer2. I asked them if I could just get them from a buyer and they said probably not because the buyers buy it by the truckload and go through it very quickly for production of furniture

[gfacer2]

I do know some people prefer straight mdf as ultralight can compress a bit (I personally don't think it's as dimensional stable as mdf).

but as the brand of mdf I tried was horrible (no flow) I went back to an ultralight to get up and running.

So experimenting is needed but then you'll settle into one that works. You might call some cabinet shops and just ask them.

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[Nick12]

was the difference you seen from the regular MDF to the ultra light a HUGE difference or just a better? Also I am cutting 3/4" HDPE so I dont know if there are other requirements for hold down force on this stuff then regular wood

[gfacer2]

was the difference you seen from the regular MDF to the ultra light a HUGE difference or just a better? Also I am cutting 3/4" HDPE so I dont know if there are other requirements for hold down force on this stuff then regular wood

Yes huge for me. Unusable even for a day. Basically as you described maybe 2hg drop with open 5x8 table vs all valves closed (just relief valve).

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[Nick12]

I was using Duct tape to seal my edges. What is absolutely the best way to seal the edges?

[Nick12]

Yes huge for me. Unusable even for a day. Basically as you described maybe 2hg drop with open 5x8 table vs all valves closed (just relief valve).

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Thanks for your help. I will be purchasing a light board tomorrow. I will get back on here and let you know how things go later. Thanks again

[ger21]

Make sure you are using a standard, "cheap" grade of MDF, rather than the premium, or "super-refined" grades.

[Nick12]

The stuff I am using now is cheap grade stuff and I am not getting any flow through.

[ger21]

I can put the palm of my hand on our spoilboard and feel the vacuum pulling through.

[Nick12]

Yes I also feel the vacuum pulling through my current MDF board when I put my palm on it. But its still not pulling through enough. I am getting 17 HG on my table with or without the spoilboard being covered up. I found some Trupan Ultralight (32 Density). I am going to pick it up now. and I am also going to change the size of my piping from 1" to 2" and see if that helps at all. I will keep everyone posted. Thanks for all your help.

[Nick12]

Ok, I swapped out my piping from 1" to 2". I have my dedicated zone hooked straight to my vacuum (Not through the 6 zone manifold) I bought a Trupan Ultra light board (32 lb/ft3). I cut it it half so that I am only covering up my dedicated zone and if all leaks (and I mean all leaks) are sealed I am pulling 20-21HG with boards on and with boards off I am pulling around 15 HG. So I definitely see major improvement there. I am going to take the other half of Trupan and put it on top and see if that will help with having to secure every single leak. So far so good. My 10 HP Becker rotary vane vac is rated for 24 HG so I am happy getting 21 HG. Its also a 2003 model so some loss should be expected due to wear and tear. I will post back on here when I get new results.

[ger21]

If that pump has seen a lot of use, you should check the vanes, as they may need replacement. I'm getting ready to replace ours (2007). The vanes are about $1300 a set.

[Nick12]

Thanks for the advice. I actually bought the vac last year and right before I did the seller put new vanes in it. Its rated at 24 HG but I am getting 23 HG right at the vac with nothing attached to it. So I am down 1 HG probably based on the age and use of it. Not a big deal. I will be looking to buy a newer vac in the future but for now this one will work. I am looking at 15-20 HP Busch Minks and Dekker VMax. These Vacs pull up to 29 HG and CFM of over 300. Brand New they are between $10,000 and $25,000 depending on which one I go with.

[gfacer2]

You skimmed the trupan on both sides right?

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