plastic sheet material suitable for milling

[beatnik]

I'm looking to get a jig made out of sheet material with a cnc milling machine and I'm looking for cheaper materials than metals.

I am thinking about some kind of plastic like acrylic but my machinist has advised it must be something that can stand some temperature and not melt with the milling process.

He suggested Delrin which seems to me like some kind of nylon but that's bloody expensive, I am looking to pay around 200 euro for a 80cm x 40cm x 12cm piece which is about the size I need.

Do you know a cheaper material which is rigid and can be easily machined and possibly cheap ?

I thought of MDF initially but they don't want to work with woods as it messes up their cooling system.

 

[totoxraymond]

I milled a few front panels out of acrylic for my DAW controller and didn't have issue regarding melting. and my CNC is a pretty low-cost one, so pretty slow with no cooling system.

I would be more concerned about it chipping off or breaking. It is not the most solid material.

Thomas

 

[gyraf]

I use an acrylic jig for guiding hand-held router for cutting panel-meter-holes..

5mm standard acrylic, cnc cut, held in place by already-exisiting mounting holes in front plate

/Jakob E.

 

[Rusan]

Professional machinist here, with lots of experiencing machining an unbelievable variety of plastics. I'll second what totoxraymond said about acrylic; the caveat is that it's brittle and subject to chipping. Use very sharp cutters, a low chip load, and keep the feed rate on the slow end of things. But, don't run too high RPM or too low feed rate, as it can scorch. If at all possible, do some test machining on a scrap piece to get a feel for it.

Vegetable oil applied with a small brush is an excellent machining lubricant for acrylic. I've also tapped many holes in acrylic with a shot of nonstick cooking spray on the tap. Works great.

A good alternative plastic might be ABS, if you can find appropriately sized sheets where you live. It's easy to machine, and its main quirk is that too high RPM with too low feed speed can melt it. PVC and HDPE (High Density PolyEthylene) are other good alternatives, although HDPE makes stringy chips and is difficult to deburr unless you have proper deburring tools for the purpose. I agree with your machinist that Delrin (acetal) is the best-machining plastic, and it's also hard, rigid and very stable, but unfortunately also very expensive as you noted.

 

[beatnik]

I use an acrylic jig for guiding hand-held router for cutting panel-meter-holes..

5mm standard acrylic, cnc cut, held in place by already-exisiting mounting holes in front plate

/Jakob E.

I might end up making something like this actually.

I think it will be cheaper to make the jig in two pieces, one top plate with all the cutouts which is then glued or screwed together with a bottom part.

The end result looks something like the attached image. (The jig is to align front panels in a digital uv printer)

I liked the idea of machining it from a thicker sheet material better, but it's just too expensive. Delrin sheet I could find are almost as expensive as aluminium.

I was hoping that plastics would be a lot cheaper material to begin with, and also less costly to machine, but it doesn't seem to be the case.

I have been suggested to get the parts laser cut from acrylic and it looks like a much cheaper option.

 

[totoxraymond]

You're mentionning a UV printer, i would also try to look at the material resistance to UV.

Some plastics really don't like UV, but to know which is far beyond my knowledge, sorry.

Edit: a quick search on google tells me that acrylic should be ok while ABS is not recomended. Since your jig won't require much effort during its life,i would go with acrylic.

Al, i would not worry.

Bests,

Thomas

 

[Disco Volante]

You could maybe 3D-print it? I've even had some success using 3D-printed templates as guides for a hand router..

Cheers, V!

 

[sr1200]

You could maybe 3D-print it? I've even had some success using 3D-printed templates as guides for a hand router..

Cheers, V!

I've done this printing ABS. But i was routing wood. Was able to print the jig no prob. the abs needs to get REALLY hot before it starts to deform. Not sure I'd trust it though on a CNC machine trying to cut metal.

 

[gyraf]

Maybe we're misunderstanding each other here - you want a jig for exactly what purpose or process?

I assumed it was for manual-routing of faceplates, as that's what I'm using it for myself - but that does not explain the "stand some temperature and not melt" parameter of OQ?

/Jakob E.

 

[craig]

I use these nylon kitchen cutting boards for all sorts of routing and drilling templates. Most recently made some PCB card guides. Machines well and just blackens rather than melts over a flame. Can be found cheap at your local $2 shop.

 

[totoxraymond]

Nice idea!

Do you rectify them flr flatness first or are they ok?

 

[Newmarket]

Valve or Solid State rectifier

 

[craig]

Nice idea!

Do you rectify them flr flatness first or are they ok?

Yes the edges on one side are raised with a bullnose edge on the those i got. I usually take that off on the table saw leaving a flat surface. It's an inexpensive source of the material. I recently used those sawn off edges to make some PCB card guides in conjunction with a router table to make the slot to fit the PCB thickness. Turned out really well. Good for all sorts of jigs as Gyraf mentioned for routing meter cutouts in aluminium panels. Circle jigs for speaker cutouts ETC. Takes a thread OK too. You could easily perfect the surface if you have a mill and face cutter

 

[abbey road d enfer]

The end result looks something like the attached image. (The jig is to align front panels in a digital uv printer)

Since it seems the jig won't be submitted to large efforts, it opens the range of usable materials.
I've used expanded PVC with great success, as well as ... wood (OSB and MDF) for similar tasks.
1500mm/s cutting speed, 0.05mm feed rate, water-based coolant applied with brush.