vacuum table & small parts

[dttworld]

For one application I'll be cutting small parts out of sheets of 1/4" ABS plastic. These parts could be as small as 2" x 2". I'm thinking a vacuum table can't hold down small parts due to insufficient surface area. Is this generally true? My plan would be to add tabs to the parts and cut them out by hand later.

thx

[knight_toolworks]

the plastic will want to lift up as that's plastics nature. I just cut some with a 1 f straight bit from onsrud and it stayed in place. a 1/8" straight bit may keep the parts in place with vacuum. Otherwise I would use bray's methods with double sided tape.

[knight_toolworks]

I forgot I was cutting these parts that were around 18x12 or so with a 1/2" endmill. I had a real problem cutting through and not having the pieces or the sheet lift up. that was when I want to a straight bit and the problem was solved.

[pappybaynes]

Get in touch with the folks at All-Star Adhesives http://allstaradhesives.com/ - I made a special 4'x8' board with a full gasket for my machine...cut vacuum channels in the underside and place it on my sacrificial top....I was cutting 4" coasters out of 1/4" bamboo 4x8 sheets - 242 of them to a sheet - I designed a cut file to cut the gasket material out in the spaces between each coaster and had drilled a hole down to the vacuum channel on the underside...I had no problem with hold-down - did approximately 110 sheets without replacing the gasket material - give them a call, John Murphy has been working with this stuff for years.

[dttworld]

I forgot I was cutting these parts that were around 18x12 or so with a 1/2" endmill. I had a real problem cutting through and not having the pieces or the sheet lift up. that was when I want to a straight bit and the problem was solved.

I need to start buying another set of bits for the CNC router. The 2 and 4 flute tooling I have for my CNC mill may not be optimal for the ShopBot setup.

[dttworld]

Get in touch with the folks at All-Star Adhesives http://allstaradhesives.com/ - I made a special 4'x8' board with a full gasket for my machine...

How much money was the 4'x8' gasket in your photo?

[knight_toolworks]

Get in touch with the folks at All-Star Adhesives http://allstaradhesives.com/ - I made a special 4'x8' board with a full gasket for my machine...cut vacuum channels in the underside and place it on my sacrificial top....I was cutting 4" coasters out of 1/4" bamboo 4x8 sheets - 242 of them to a sheet - I designed a cut file to cut the gasket material out in the spaces between each coaster and had drilled a hole down to the vacuum channel on the underside...I had no problem with hold-down - did approximately 110 sheets without replacing the gasket material - give them a call, John Murphy has been working with this stuff for years.

for that my regular table is more then plenty. using a 5/32" downcut none but maybe on the corners would come loose. I cut 3" lids out of 1/2" euro ply with just my normal vacuum table and only one corner comes loose so I put tabs on it. 128 per 1/2 sheet of 5x5
but plastic is a whole other ball game it tends to lift up and you can't always use the sawdust to hold the parts in place like you can do with wood.

[myxpykalix]

For really sharp and long lasting bits go to www.centuriontools.com Also, although i have no experience with them you might want to google "vacumn pucks" or vacumn holddowns"

This article features a shopbot
http://www.solutionsforwood.com/_docs/profiles/TP-Vacuum-hold-down-strength-CNC.pdf

google is your friend...:D

[myxpykalix]

here is more info:
http://blog.cnccookbook.com/2012/02/18/fixturing-with-vacuum-tables-vacuum-chucks-and-vacuum-clamping-systems/

[pappybaynes]

How much money was the 4'x8' gasket in your photo?

I will have to check with the accounting - my good wife!

[Brady Watson]

For one application I'll be cutting small parts out of sheets of 1/4" ABS plastic. These parts could be as small as 2" x 2"

Vacuum Film (http://talkshopbot.com/forum/showthread.php?t=11481) is what you need. It outperforms AllStar when machining small parts. I cut several hundred thousand of 1.5" tall letters with this method.

-B

[dttworld]

Vacuum Film (http://talkshopbot.com/forum/showthread.php?t=11481) is what you need. It outperforms AllStar when machining small parts. I cut several hundred thousand of 1.5" tall letters with this method.

-B

Great. Another technique to try out. I can get those materials in my first order from HarborSales.net. In the link someone mentioned possibly using a pressure foot. I just saw this item in the ShopBot accessories link and wonder if it will also be effective for cutting small parts.

[Brady Watson]

Yes - the pressure foot does work very well - However there are some limitations. Read up on it via the WidgetWorks site to see if it is a match for what you want to do.

-B