If you do a lot of one-off parts on your CNC machine you’ll know setup is the worst part of the process. Usually you’re using scrap material, you have to figure out how you’re going to clamp it, make sure the the piece is big enough to use, etc etc. Wouldn’t it be nice to just throw the material on the bed and start machining? Well, with a vacuum table as nice as this, you pretty much can!
[Jack Black] has an awesome CNC machine. As he’s been expanding his prototyping abilities, he decided he needed a better way of securing work pieces for machining, so he machined a two-piece aluminum vacuum table.
It features four separate vacuum pockets which can be used individually or all at once. The top surface is a grid pattern with square channels. Using little rubber plugs or screws you can block the channels you aren’t using to maximize the vacuum force on your part.
When securing a part, another gasket is required between the work-piece and the table — but as you can see video below, once in place, it’s not moving anywhere.
If you need a vacuum table for your laser cutter there is a much simpler version available to make — it’s just not gonna cut it on a CNC machine.
A friend uses a vacuum table for his CNC work. He was concerned because the work showed a scallop on the edge. It was almost microscope but clearly there. Interestingly it was on both sides of material being cut and the period was 60 hz. After checking all the software, the CNC machine, and everything else the culprit was found.
The vacuum pump was on a lower shelf. The vibration from it was causing the head or material to jiggle just enough to cause the scallop.
Interesting, thanks for letting us know!
If you drill a hole through your piece you will lose the vacuum….
No work holding solves all issues, this one solves many issues were other strategies are unsuitable or lack luster. Drilling can be done as a secondary operation on a drill press if the holes are simply spot faced or center drilled. Gaskets can also be placed around large hole (through pocket) locations. Or it simply isn’t the right tool for the hypothetical project.
I use a vacuum table like this for my PCB milling. The vacuum force holds after the pcb has been drilled, you can even mill board isolation channels before the workpiece would slip. It’s surprising how powerful that force is.
And video is blocked on copyright grounds. People! Don’t use copyrighted music in your videos!
Yup -_-
Project page says:
> Please see my video for all information on this project.
Hahaha. Well forget it.
Odd. Works for me (Slovenia).
UMG – Universal Music Group.
Learn to use the correct browser with the correct plugins. Firefox with Proxtube did the job. You have to watch the video on youtube though.
If you make a video for general consumption you should not expect the viewers to have to install things to work around the issue.
nice idea but IMHO he is missing a large problem with vacuum tables and CNC machines that is lateral pressure. Yes he can hold stuff down but both pressure from the cutting surface and vibrations cause material to move and the problem becomes worse when you add cutting oil into the picture.
anyway cool build but i’ll stick with vices and bed clamps
They’re not that much worse than mag bases, just reduce the feeds and they’re good enough.
This type of “clamp” is certainly more geometry dependent than many others but given enough surface area and a proper vacuum pump, parts that are suctioned down are held quite securely.
You do have to use a proper vacuum pump, however.
Friction on the bed (which is usually all that’s holding down your stock when you’re machining sheets) is directly proportional to the amount of force holding the material down. While vacuum clamping is unsuitable for small pieces, due to the fact that it’s reliant on having a good amount of surface area for the atmosphere to press on, it’s perfectly acceptable for moderate to large sheets. Even with just a 10×10″ square and an imperfect vacuum, that’s well over half a ton of hold-down force.
While this still isn’t all that much for high-feed machining (where clamping forces of several tons isn’t uncommon), this is perfectly acceptable for plenty of jobs.It’s just another potentially useful workholding option, nothing more, nothing less.
All of this is overkill. Professional CNC wood routers that I have witnessed, simply pull a vacuum on a sheet of MDF used as the bed. Some have a custom pattern to pilot a basic hole pattern (one tiny hole on an inch grid) or simply pulling the vacuum straight through a virgin sheet.
That’s because they’re running vacuum pumps in the 10hp range, which are huge and expensive. This can work with a $100 AC purging pump.
I’ve never actually understood the usage of a vacuum table for a CNC. Almost every time I have used a CNC mill, I have had some features that go through all the material (like the outline, holes or whatever), which means a vacuum table is pretty much worthless for me, since I would destroy it every time I mill. I see very few operations on sheets where you don’t cut all the way through on at least one place.
Engraving thin sheet stock e.g. for equipment faceplates is a killer app. Low side loads, and difficult to keep flat with traditional clamping methods.
You can also make a custom fixture from scratch material which channels vacuum to “zones” under the workpiece, letting you drill and cut without breaking the hold-down. Kinda labor-intensive for a one-off, but not uncommon for production. Horst Witte even offer an innovative rubber mat with individual suction cups which can be pierced without breaching the whole table:
http://www.metronom.com.au/vacuum_workholding/vac-mat.html
Custom per-job vacuum tooling gaskets could be an interesting application for 3D printed compressible filament.
I’ve considered trying a variant of this for PCB milling but then reality sets in. If I don’t clamp and secure the work at all, relying on the vacuum to keep it in place, what happens should the vacuum fail? Some of the parts we construct take a considerable time to finish, and it’s not practical to babysit the process. Could make a lot of scrap relying on just the vacuum method.