The plate is cut, here is the brawn in action before I did glue up today. Paint tomorrow.
Got some drips on the paint job Are you planning on doing some vacuum forming?
love it. what is it?
Not drips, bad glue up, more of a glue weld-up.
Vacuum hold down system.
Gah! You have your Nomad on a folding table?
Its sitting directly on top of a piece of .75" x 22" x 22" MDF with 4 layers of fake dynamat. Perfect to kill the noise, and excellent for portability in the garage.
Oh snap, first test with quiet vacuum work holding 100% success. video processing/uploading now.
I was more concerned with the table rocking.
Can not wait to see this in action. Great project. I am working on a large bed low profile vice for my hold down solution, but this looks pretty cool.
Nice. How did you decide how much accumulator you needed? What is the leak rate with the setup shown in the video? I.E. how long does it take for the pressure to rise 1 psi?
I like the accumulator approach. It lets you run a smaller pump as long as the leak rate isn’t too high. Nice job.
It always makes me shake my head when someone comes up with something innovative and posts a contribution and then it gets picked on for irrelevant details. Thanks for all your work and for taking the time to share it! This is a nice contribution to the community.
If you get a chance to check the leak rate with various materials and setups I would appreciate the info. Also, if you could show some close up shots of the seals and any info regarding materials used.
Thanks again and great job.
I just guessed on the accumulator volume. 2" PVC x 100" (4 @ 25").
I have zero leaks in the system right now when using a small gasket between the platen and a piece of candlestone as in the video.
I do leak when I use a MDF spoil board. So much so that it will not hold a true vacuum. Even MDF sealed with 2 coats of poly leaks some. More tests in this area will need to be done for sure.
The system has a vacuum controller in it that is currently adjusted to about 22 in Hg and will auto cycle the pump to maintain that level of vacuum in the system. As long as I don’t have any leaks that are massive (like a MDF spoil) I should maintain vacuum clamping with relatively minimal pump running time.
The key now will be in the design of the spoil/holder boards. I will probably look to make these purely out of HDPE or starboard or some similar non-porous material.
Thanks for the feedback. I’ve done a lot of testing in the past for sealed enclosures. One thing I learned is that everything leaks… its just a matter of how much. It sounds like your system, with the right interface to the seals leaks slowly enough that it doesn’t cause the pump to come on during a typical job. That’s great.
For larger parts you won’t need much vacuum anyway to hold it firmly, especially for the Nomad, since it doesn’t ever take much of a cut anyway. I’d guess you could get by with a few psi for a larger part which would keep the pump from cycling much even with MDF.
Thanks again for stimulating thought here. Keep posting your innovations. These posts are very motivating to me as well as to others, I’m sure.
You are correct, everything leaks. Mostly it is around the mating of the work piece to the vice itself. Making sure I get a good seal between the vice and plenum is critical (I use a rubber seal here), and good smooth top surface on the vice. I have found a small thin layer of bees wax on the vice top makes a great super thin seal.
I like the notion of your ganged PVC accumulator… silent work-holding is golden! I concur that your rig is a nice innovative setup!! I missed this original post as I started monkeying seriously with Shapeoko in late May.
How does your Z-axis behave under vacuum and wondering if there’s an introduction of offsets (if you have this characterized) over time as things equalize?
@jimidi as far as Z goes, the stock gets pulled flatter to the base as it gets milled thinner (at least with a stiffer stock like candlestone) and I do see that the pressures increase over the duration of the cut.
So, to make this work in the garage with a good old AC vac pump, I needed to build an exhaust system for the pump, so half a garden hose did the trick.
No fumes or oil in the air .
Next up was to make more holes in the cover for the hose.
And here is a close up of one of the custom holding fixtures (HDPE) that sits on top of plenum. This one is for doing 7.5" x 3.75" plates.