I have a need to cut .040 styrene plastic on my cnc router and divised this simple but effective vacuum hold down fixture, works well. Bob.
https://www.youtube.com/watch?v=g4kAmXegcXI
Printable View
I have a need to cut .040 styrene plastic on my cnc router and divised this simple but effective vacuum hold down fixture, works well. Bob.
https://www.youtube.com/watch?v=g4kAmXegcXI
Or could he have just taped it down? I would have liked to have seen trying to pick it up without the vacuum turned on.
I expect he would be able to pick it up exactly the same way WITHOUT the vacuum cleaner on, as the packing tap would hold down the plastic very well!
A 6 & a 1/2 minute video about nothing.. after tapping the plastic down of course he's not going to lift it off the vacuum box. unless his whole point wasn't so much to demonstrate that it held it on but held it flat against the wooden top keeping the plastic sheet flat so he could route what ever design he needed in th eplastic. In that case then he probably has achieved his goal
Well, Peter Sanders, If just taping it would have done the job, I wouldn't need a vacuum fixture. 5 minjutes into the video when I turn on the shop vac. look closely and you can see the plastic move down about 1/8th of an inch, holding it solidly against the fixture. Taping around the frame has nothing to do with holding the plastic down directly, as the reason is to make a seal, so the there will be no leakage of air, so that the vacuum will hold the plastic down. I suggest you critics out there, try your design first, before you knock someone's design. There can be no movement up and down when cutting allowing the blade to exit the plastic without lifting it, as the blade will try to lift the plastic if not held down, and also the vacuum will keep it from racking from side to side, so obviously you haven't tried to cut thin plastic with great accuracy, so your expectations are wrong. Bob.
That's more in lines with what I thought the vacuum fixture was for. it was probably the block of wood glued to the plastic in an effort to demonstrate how the vacuum was working that caused the stir. Large aircraft manufactures use vacuum tables to hold huge sheets of aluminum down for milling
Yes, you are correct. The 2x4 was just so that I could get a hold of it to show that there was no movement off of the fixture, hence the blade would not stick to the plastic and lift it. Bob.
Yes, you are correct. The 2x4 was just so that I could get a hold of it to show that there was no movement off of the fixture, hence the blade would not stick to the plastic and lift it. Bob.
I've built a very similar vacuum table originally for vacuum forming plastic sheet, but soon realized how useful it would be for holding down thin plywood for cutting out intricate parts. I use inch square wood for the outside sandwiched between 18mm mdf with a few bits of the 1" glued in the middle to prevent sagging . I then made a adapter to fit the vacuum hose and drill the holes in a about 3/4" apart. Any hole that hit the supports I just re drill at a angle.
Using thick mdf allows for skimming the surface should it get marked.
If the work is not as big as the table I use thin plastic sheet to cover the unused hole (plastic bag).
If the cutouts cover a few holes they will stay in place while the the remaining cutting takes place but the cutting order is important outside last. bits of plastic bag can be placed over exposed holes but be careful they don't get caught in cutter.
One important point is that most vacs need air to pass through them for cooling and have cutouts to prevent overheating. I use a Dyson which has a bypass valve if the vacuum gets to much.
And most important don't forget to switch on vac before starting cutting.
John
I will keep all of your pointers in mind, thanks for the hints, Bob.
<!-- BEGIN /var/www/html/homemadetools/protected/modules/zeus/views/tool/postUpdate.php -->
Thanks machiningfool! We've added your Vacuum Hold Down Fixture to our Workholding category,
as well as to your builder page: machiningfool's Homemade Tools. Your receipt:
<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="http://www.homemadetools.net/homemade-vacuum-hold-down-fixture"> <img src="/uploads/207528/homemade-vacuum-hold-down-fixture.jpeg"/> </a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="http://www.homemadetools.net/homemade-vacuum-hold-down-fixture">Vacuum Hold Down Fixture</a> <span> by <a href="http://www.homemadetools.net/builder/machiningfool">machiningfool</a></span> </div> <div class="tags">tags: <a href='http://www.homemadetools.net/tag/holding'>holding</a>, <a href='http://www.homemadetools.net/tag/vacuum'>vacuum</a>, <a href='http://www.homemadetools.net/tag/fixture'>fixture</a> </div> </div> </div> </div>
<!-- END /var/www/html/homemadetools/protected/modules/zeus/views/tool/postUpdate.php -->
Bob
I think you did a very nice job and holding anything soft and possible of deforming or smashing with pressure requires a better way and you nailed it. Nice job and thanks for sharing
Nelson
Thank you very much. It does work as designed and I am surprised at the holding force. Bob.
Now I want to see it working or more so how you actually use it!!
Ralph
Ralph, if you have read all of the posts by me regarding the vacuum hold down, your questions will be answered. How I use it is, I cut a piece of plastic to fit the entire fixture and turn on the vacuum. It pulls 2 lbs. per square inch, so, 8" by 32" =256 sq. in. and 512 lbs. total pressure, enough to hold the plastic rigidly for cutting. I use a drag knife in my router and the cutter cuts almost through the plastic and I remove the parts by bending the plastic. The plastic is about .040 inches thick. Thanks for your interest. Bob.Quote:
Originally Posted by Ralphxyz
Thanks Bob, " the cutter cuts almost through the plastic " was what I was wondering about and would like to see in action.
I was picturing cutting all the way through and losing the vacuum as you moved along but almost through should retain the seal.
Ralph
Yes, that is where I thought you were going. No it doesn't cut through, for that reason. Bob. No vacuum this time.Quote:
Originally Posted by Ralphxyz
link to Youtube https://www.youtube.com/watch?v=00YJxl51CE4
Bob, Nice job on the vacuum table.
Most commercial CNC routers use a vacuum table. Your's is a good example of how to build one for a home use environment. thanks for posting.