Techno Vacuum Table Help

[ericscottf]

I'll reply more tomorrow... But something to think about tonight... Doesn't this Lead you to conclude that there's nothing wrong with your table, and the issue is a leak between your material and your gasketing?

[Dave's_Not_Here]

Gasketing is new.

I have wondered if a different supplier, other than Allstar, which is highly recommended, might be in order. . . or a different durometer.
Not sure what to think anymore, other than 2x4's - plywood with holes and no gasket - and a Shop Vac did one hell of a job for $50..

[ericscottf]

Dave,

You've brought up several things, I'll respond to all of them and then ask some more questions. I don't see how this problem is somehow endemic to the techno system, and feel that it should work, so if you want to keep working on this, I think we can make it do what you need.

1) We don't supply all star gasket, we use a different manufacturer, but all star should be fine. I don't think a different rubber will make a difference for you.
2) Most people are happy with the original techno vacuum system. Most of those people used a Becker VTLF250 pump (or the newer VTLF2.250 that we even supply to this day). This is a higher vacuum lower flow system than what you have now - the becker will pull to over 25inhg when properly sealed. Even through MDF. We provided blowers when customers needed to pull through open cell materials like open cell foam, where high pressure, low flow pumps would give up due to the flow. Ordinarily, I'd say that a blower is the wrong pump for holding down acrylic, but since you're using an entire 4x8 sheet that you want to hold down, it should be fine - indeed, even a vacuum cleaner should be able to do that kind of work (until it burns out).

Now, on to questions for you:
1) Are you certain that there are no gaps in your gasketing? I don't mean large gaps, I mean any gaps. You need to install the gasketing "Fat", and have any joints push into each other. That means not stretching the gasket when you install it (push down, don't stretch to insert), and when two pieces meet each other, there needs to be a small bulge, not a small gap. Even a 1/16" gap is to be avoided.
See this picture here:
https://www.joewoodworker.com/veneer...g-tape-top.jpg
That's what you want yours to look like, or even less of a gap - gasketing forced, interfering slightly, piece to piece.

2) Why do you think there is a difference between your new plugs and the discs, when you are using them to seal the table? How do the discs work, and why are they different from the plugs?

3) Can you confirm that when you put a sheet on the table and it drops to 5inhg, you're putting a sheet of non porus material right on top of the gasketing and not on a spoilboard like MDF or something else?

4) What happens if you put down your sheet and open one ball valve at a time? Maybe one table strip is leakier than another and is the culprit for the issue you're seeing? Imagine if the table weren't flat and your sheet, spanning several table extrusions, had a dip in it and wasn't meeting the surface well enough to seal?

5) More to the point on 4: Did you flycut the material before cutting the grooves in? This is an important step in making a vacuum table - it must be flat, and between the material used and the original techno extrusion, unless you flycut and touch every part of the table with the cutter, it won't be.

6) Lastly, feel free to send me pictures of your original $50 plywood/shop vac setup, so we can talk about what is different between that and the system you have now - perhaps we can identify the change between the two that is causing your current system to not perform to your needs.

Regards,
Eric

[ericscottf]

Dave,

What ever came of this? Let me know if you want to continue trying to figure out what's going on, if you've solved the issue, if you're doing other things for now, or if you've given up.

Eric

[Dave's_Not_Here]

Dave,

You've brought up several things, I'll respond to all of them and then ask some more questions. I don't see how this problem is somehow endemic to the techno system, and feel that it should work, so if you want to keep working on this, I think we can make it do what you need.

1) We don't supply all star gasket, we use a different manufacturer, but all star should be fine. I don't think a different rubber will make a difference for you.
I see a lot of people using the round profile and a harder density than I seem to be using.
2) Most people are happy with the original techno vacuum system. Most of those people used a Becker VTLF250 pump (or the newer VTLF2.250 that we even supply to this day). This is a higher vacuum lower flow system than what you have now - the becker will pull to over 25inhg when properly sealed. Even through MDF. We provided blowers when customers needed to pull through open cell materials like open cell foam, where high pressure, low flow pumps would give up due to the flow. Ordinarily, I'd say that a blower is the wrong pump for holding down acrylic, but since you're using an entire 4x8 sheet that you want to hold down, it should be fine - indeed, even a vacuum cleaner should be able to do that kind of work (until it burns out).
My shop vac did great for many, many hours and still cleans the shop and blows out the leaves.

Now, on to questions for you:
1) Are you certain that there are no gaps in your gasketing? I don't mean large gaps, I mean any gaps. You need to install the gasketing "Fat", and have any joints push into each other. That means not stretching the gasket when you install it (push down, don't stretch to insert), and when two pieces meet each other, there needs to be a small bulge, not a small gap. Even a 1/16" gap is to be avoided.
See this picture here:
https://www.joewoodworker.com/veneer...g-tape-top.jpg
That's what you want yours to look like, or even less of a gap - gasketing forced, interfering slightly, piece to piece.
I have known Joe for a number of years. Bought my Vacuum Veneering setup from him and covered for him while he was in the hospital. My gaskets are tight.

2) Why do you think there is a difference between your new plugs and the discs, when you are using them to seal the table? How do the discs work, and why are they different from the plugs?
The discs lay flat on the area surrounding the hole. The plugs only make contact around the rim of the hole. Any discrepancy in the hole and/or plug diameter will not seal well.

3) Can you confirm that when you put a sheet on the table and it drops to 5inhg, you're putting a sheet of non porus material right on top of the gasketing and not on a spoilboard like MDF or something else?
3/4" Marine Grade Plywood (MDO) right on top of the gaskets.

4) What happens if you put down your sheet and open one ball valve at a time? Maybe one table strip is leakier than another and is the culprit for the issue you're seeing? Imagine if the table weren't flat and your sheet, spanning several table extrusions, had a dip in it and wasn't meeting the surface well enough to seal?
Haven't tried that yet.

5) More to the point on 4: Did you flycut the material before cutting the grooves in? This is an important step in making a vacuum table - it must be flat, and between the material used and the original techno extrusion, unless you flycut and touch every part of the table with the cutter, it won't be.
Fly cut with Amana's $260 RC-2252 CNC Insert Solid Carbide Spoilboard Surfacing cutter.

6) Lastly, feel free to send me pictures of your original $50 plywood/shop vac setup, so we can talk about what is different between that and the system you have now - perhaps we can identify the change between the two that is causing your current system to not perform to your needs.
I will have to see if I saved any. . .

Regards,
Eric

...

[Dave's_Not_Here]

Dave,

What ever came of this? Let me know if you want to continue trying to figure out what's going on, if you've solved the issue, if you're doing other things for now, or if you've given up.

Eric

Haven't decided what I am going to do. NATO Rounds and Tannerite come to mind.

[ericscottf]

Dave,

I'm sorry you're having trouble with this. I'm happy to keep working on it with you if you wish.

I doubt your gasketing is the problem, however, if you think so, there's plenty to be tried - you can get it from us (we sell the square stuff, not from all star), or the round stuff from many places. So long as the gasketing doesn't have gaps in it, and it's proud of the table surface enough to seal the material, it should work.

When you seal the table with the discs, are you using gasketing under them? If so, the good seal you're seeing there should demonstrate that the gasketing is working in that case.

I also recommend trying one extrusion at a time by shutting all but one ball valve and checking the vacuum gauge on each

It's this simple: if the vacuum is completely obstructed on the table side (no leaks, solid material like plastic on top), your gauge should show nearly the same value as with all the ball valves closed. If it isn't showing the same, then air is getting in somewhere. Enough volume of air to have an effect on the pressure (which takes more in a blower than a pump).

If you want to keep at this, email me or post

Eric

[Dave's_Not_Here]

No gasket under the discs.

[ericscottf]

What are the discs made of?

[Dave's_Not_Here]

Laser cut flat acrylic.

[ericscottf]

I'm missing something here then. Help me understand what's going on.

I'm under the impression that you've experienced the following:
Closed off all ball valves - 10inhg on the gauge.
Opened up all ball valves, placed sheets of acrylic covering the table, butted up against each other, on top of well laid gasketing - 5inhg on the gauge.
Opened up all ball valves, plugged all vent holes in the table with tapered silicone plugs - 8inhg on the gauge
Opened up all ball valves, plain acrylic discs on top of the vent holes of the table, and NO gasketing - 10inhg on the gauge.

Is this correct? Because that last one doesn't make any sense to me. How could that possibly seal at all, and what's more, better than a comparable acrylic sheet that spans the entire table w/ gasketing?

[Dave's_Not_Here]

It is correct.
I have 190 - .375 inch deep x .5" diameter holes, milled into the PVC with an endmill.
I have 190 - .25" diameter holes drilled through the middle of the 190 - .375" x .5" milled holes.
I put 190 - .0625" x .495" diameter discs over the 190 - .25" holes; bypassing all the gaskets.
I opened all the ball valves.
I turned on the blower and pulled the reading I posted.

Welcome to my world.

I am going to be.

[ericscottf]

Was there going to be more to your post?

Eric

[Dave's_Not_Here]

Was there going to be more to your post?

Eric

No. I was tired and going to bed. Typo.