holding mdf down to bed

[kell]

What is the best way of holding thin mdf on bed when cutting small parts out say 3cm in size.

Is there a trick ?

[Tenson]

Are you cutting the parts out of similarly small pieces of MDF to start with?

I've found one of the easiest ways is simply to put a screw in two opposing corners of the piece and hold it on to a larger sheet that makes for easy clamping.

If you are simply cutting small parts out of a larger sheet you can leave a very thin amount of material behind on the final cut so it is held in sort of like an air-fix model and you just need to cut the part out with a knife and neaten the edge up with a quick sand.

[motoxy]

Double sided carpet tape.

[Jonathan]

Double sided carpet tape.

Double sided tape is good for small parts, particularly PCBs, so long as taking it off doesn't damage the MDF.

[JAZZCNC]

Kell (Mark) wants to cut lots (hundreds) of small parts nested on say 1/4 sheet of MDF so carpet tape will workout very expensive and messy, plus it will potentially pull the paper face off.?
Suggested spray mount but same goes with messy and lots of cleanup time.!!
Vacuum wont work.!!
Tabs will leave lots of clean up and reduce qty per sheet so prefered to avoid.!!
Laser would be best but too expensive to build for material thickness's required.!!
Water jets no good for obvious reason's and even more expensive than Laser.!!

So my suggetsion because it's flat panel sheet work, was to build a sprung loaded domed pressure ring, (say from nylon or some other slippy material) that mounts to bottom Z axis or spindle clamp and surrounds the cutter. This would hold both the surrounding material and cut part just enough so it doesn't lift or move until cutter retracts.!
This ring could also be made part of a dust extraction setup.?
It would easily be removed for larger jobs or jobs that arn't flat panel work.?

So thats the problem to over come so any other suggestions.?

So

[motoxy]

Dean....genius

[Christian Knuell]

another possibility is to leave 2 or 3 thin tabs so the part stays connected to the sheet. The downside is you need to sand away the tabs on every part afterwards but with MDF this is usually done quickly...

[JAZZCNC]

not picking on you jazz lol,

Don't really give a toss if you was picking or what you think of me Chip.!! . . . . But in all honesty I hadn't seen this or any other form of device done like this.! It just seemed a logical way to over come the problem.! . . Nice to know my thoughts are not always off base.!

another possibility is to leave 2 or 3 thin tabs so the part stays connected to the sheet. The downside is you need to sand away the tabs on every part afterwards but with MDF this is usually done quickly...

Yes Christian this will work but there will be hundreds of small parts in one sheet, so this is why Tabs are a last resort and ideally to be avoided.

[Web Goblin]

Used to have a similar idea on a really old plasma system. Torch came down on its own weight on an air cylinder with the pressure off. It sat inside a stainless steel ring around 250mm diameter which had ballbearings mounted to the underside of it. Granted the idea was to set the torch height but could also have the same uses to hold down parts with a bit of modification. Good idea though.