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Discussion in 'CNC Mills/Routers' started by Florian Bauereisen, Feb 27, 2016.
only 2 screws to hold down even bent sheet material and vaccum dust removal in one
Florian Bauereisen published a new build:
Read more about this build...
Nice design. Will be following this thread to see how it performs. Please keep us updated.
Thanks for sharing.
I second the great idea! Looking forward to seeing how the acrylic version turns out!
Great for working with engraving and cutouts, making sure the work piece is flat against table.
How is it working out with, say detail engraving where the work turns the surface into rough terrain for the 'sled' ? Didn't look to see if the edges are rounded to slide up/down ... maybe use HDPE as it tends to be slippery ?
it is intendet only for holding down thin materials i.e. thin plywood. Quite often these are bend and you simply cannot screw/nail it down enough to stay flat while routing. I simply got sick of snapped bits from the ply vibrating. The holddown works great for this purpose so far.
Atm it is oly made of ply as it is a work in progress/ proto. I intend the final version to be made of acrylic... for beeing able to light it using LED rings...
And yes there is a "ring" on the lower surface to spread the pressure evenly around the bit.
I think this is visible in one of the drawings..
Indeed those thinner material are always far from perfectly flat. Even 1/2" ply tends to "curl" ...
I just cut a Croquignole game out of a 32"x48" piece of "good" grade 1/2" ply with myOX I wished I had a vacuum table ... or something. Your concept would of been perfect, especially as the cutout is being done ... the plywood "sprung" up since I had not allowed for tabs ... got lots of HDPE bottle caps and such ready to melt and shape. So I'll take a closer look at your prototype and see if I take the plunge.
Thank you for a great contribution. You should probably make it a "Resource" so it doesn't get buried in a discussion.
Any updates on this?
I have been playing around with a similar setup to this to cut 3.175 mm thick material. My build is a bit different, but the same basic idea and so I think the same principles apply. Here are some usage notes so far:
(1) Weak springs will not hold parts in place perfectly. With weaker springs, I would still notice some edges of the part where the part had shifted and so the spindle had cut some out.
(2) Strong springs work much better at clamping. But strong springs provide a lot of pushback like you are plunging into a hard material even when you are cutting into a soft one.
(3) If there is flex in your x-axis, the strong springs will exercise it. And you can easily get into situations where it is hard to precisely set z-axis settings because when the z-axis screw turns the system flexes instead of plunging.
(4) So be ready to have your spoilboard really act as a spoilboard. Because you will be unlikely to get a perfect z-axis cut even with a touch plate and a lot of futzing.
(5) It works best if you cut down to an onion skin and then cut the last layer away afterwards.
(6) My vacuum doesn't suck up all of the swarf material. But the OP looks like they have a more airtight system so it may work better. The vacuum at least keeps it all contained for later cleanup with a secondary vacuum.
(7) The lower ring has to be absolutely flat on the table. Otherwise the linear guides can bind and that can be very bad. I found that the best way to do this was to loosen the assembly, lower the z-axis so that the ring was just touching the table, then hold the ring flat as you tighten things up again.
(8) The lower ring takes up a fair amount of space and it can never touch anything taller than the workpiece. No clamps can be within 40 mm or so of it (depending on how big the ring is). Even screwheads that sit above the plane of the workpiece can cause troubles.
(9) This setup works best when you have large workpieces that you clamp at the corners or which overhang the table and are clamped well outside of the work area. A 6" x 6" piece clamped on the edges gives you maybe a 2"x2" safe working area. A 24"x24" piece clamped at the corners gives you a working area consisting of the whole workpiece except for a couple of inches from each corner.
This is an essential upgrade if you want to cut a lot of small pieces and have a machine that can handle the extra stresses while being large enough to get a usable workspace. I really hope to see more of the OP's build progress because this is such a useful upgrade.
no updates so far as
a) it works just fine
b) i`m buisy milling and updating this or even fiddling around is just happening on the backburner...
about the above;
1) i have pretty weak springs and it works like a dream
2,3,4,5) i always cut through for 1/10 mm no onion skin leftovers but than i have a 160 kg mill which has virtually no flex
6) my vacuum works just fine , but than i have a sorta 90% thin tube glued to the hold-down ring for better suction.
7) my ring is fixed in position, and moves along with the spindle.. the idea is to make different lower assemblies for different aplications... Only the thin sheet needs holddown, so my setup porvides only say 4-5mm of travel. I set my bits so that bit and ring touch my workpiece at the same time...
no binding on mine...
8) i run my ring regulary over the workpice´s edges, no trouble there, as i use (mentioned above) very little force down. I do not use screws anymore but rather use 2 max 3 nails to keep material from shifting ...
Will take some pics or vid soon... once i get my camera back which i forgot in my buddies car...