[Shane1234]

We have been machining alot of uhmw & delrin at our work lately, and I have some questions about cnc routers w/vacuum tables, hoping to free up our cnc vmc's for the stainless steel work.

Anyways, couple questions i have are concerning a northwood cnc router w/vacuum table, 5x10 foot. When cutting thru your material, what stops you from routing into your table? Will the vacuum table be able to secure the parts during the full profile cut, even if they are light and small (6 inch diameter sprocket with 4 inch ID hole, 1 inch thick uhmw plastic)? The boss is concerned about these things before even considering purchasing a cnc router. He also is worried that once you fully cut the profile, what stops the part from jerking against the tool and ruining itself, due to its lack of weight and size....... I have never operated a cnc router, but I have no doubts that I can adapt to one easily enough.

i have been looking at this northwood cnc router, model 105NT, w/40hp vacuum table..... Overland Tool: Power Tools, Wood Working Equipment, Dust Collection Machines, Fasteners, Service and more ...

please give me some insight to the cnc router world.......

[MCPservice]

When cutting thru your material, what stops you from routing into your table? Now this is from a Multicam prospective, their machine have to take a measurement on top of your material and your max depth, which is taken on the MDF, and it calculates the thickness of your material and will not allow you to cut deeply into your MDF. It is a safety to keep you from plowing into your MDF or your table.

Will the vacuum table be able to secure the parts during the full profile cut, even if they are light and small (6 inch diameter sprocket with 4 inch ID hole, 1 inch thick uhmw plastic)? With small profile parts, I normally show customers how to leave a onion skin on their material or leave tabs on the parts. With the onion skin, you would cut the majority of material out of your part and leave behind .03-.04, cut your entire sheet leave this amount of material behind, since you have not cut your item out you are still maintaining your full vacuum. Then come back on a final pass to remove the onion skin, this final pass does not have the same amount of force being generated as would be the amount if you cut the parts out in one pass.

Now this procedure won't be prefect, but the chances of your parts being flung off the table will be considerably less. Hope this help you.

[ger21]

When cutting thru your material, what stops you from routing into your table?

You use an MDF spoilboard, and pull the vacuum through it to hold parts down. These machines are typically used for cutting sheet goods. We cut about .003 into the spoilboard, and resurface it every 30-50 sheets.
Small parts can be very difficult to hold, and are typically onion skinned or tabbed, as the previous poster mentioned. No way can you cut a part that small with vacuum through a spoilboard. We cut 3/4" thick sheets at about 800ipm, and anything smaller than 250sq. inches gets onion skinned, to prevent it from moving. This is a 5x12 table with two 25HP pumps.

Some machines have ports to allow you to block the vacuum to the spoilboard and mount dedicated vacuum fixtures. This would probably be a better option for what you're doing, but I still think you'd have problems holding that part with vacuum alone.

[Shane1234]

thanks for the replies guys. i think onion skinning is the way i will have to go. tabbing things might get a little troublesome for different parts. and since its plastic, it will deburr easily......