Machinable material

[eTraxx]

I made a small jig for a project using Poplar from the dowel section at my local Lowes. It worked .. just. Working on this I found myself wondering if there is a plastic that would machine well for such small projects? Thinking something like a block of PVC would work better then wood.

Just for size .. that's a 1/4" Dremel router bit doing the work ..

[nalmeida]

I there Ed, I've been using styrene for that but it's a thin line between spindle speed, feed rate and the number of consecutive cuts! Then again it's great for prototype work but a nightmare if you are thinking production wise. Oh and everything above 2mm it's even harder to get right (without melting the stuff up).

[Bexley]

Delrin would likely work. Or even a urethane resin- I've seen fixtures made by pouring resin around an oddly shaped part, then cutting it in half and machining away spots for tool access, effectively giving you a workholding device that snugly fits around complex shapes.

[eTraxx]

Found a discussion on this subject online. Derlin was mentioned along with Noryl. Found a website that sells the stuff in reasonable sized blocks ... aka .. .75" x 12" x12" - NORUL and - Acteal/Derlin. Dang .. the prices. The HDPE is affordable .. and is said to be easy to machine. I may order a sheet to experiment with.

[Bexley]

Do you have any local plastics dealers? Many of them cut to size for their customers, and this can leave off-cuts they may sell for cheap. There used to be a Cadllac Plastics here in the Twin Towns of Terror, and they sold their scraps by the pound. You might even try local machine shops- they may have small scraps they'd be willing to part with for little or nothing, and Delrin is a pretty common material these days.

[marc_reusser]

I second Bexley's recommendation of visiting a local plastics/acrylics dealer. I usually buy a small box of misc sizes and shapes whenever I'm in their neighborhood. (FWIW styrene dulls your cutters much faster than acrylic.). Take note, when buying scraps for miliing, make sure you get "cast" acrylic, and not "extruded", cast mills far better, and is much more stable in regards to shrinkage and expansion.

I am having a brain fart at the momment...and maybe somone else here can help, but there is a wonderful reddish material (about the color of Bondo) that mills and machines like butter, and holds small fine detail and edges beautifully....and is completely stable. My mind wants to call it "millcor" or "corex", but I don't think that that is ccorrect.

[marc_reusser]

Still haven't thought of the mterial....but n option to it would be something like "Renshape 460"

On the less expensive end of the scale, "Jelutong" wood is a nice dense wood that mills esily and cleanly, and I have seen it sold in various sizes, including blocks up to 18 sq. 

[marc_reusser]

Here iss a place in ohio, that specializes, carries and ships in millable/machineable materials....including the two in the last post.  http://www.freemansupply.com/MachinableMedia.htm

Marc

[Bexley]

I am having a brain fart at the momment...and maybe somone else here can help, but there is a wonderful reddish material (about the color of Bondo) that mills and machines like butter, and holds small fine detail and edges beautifully....and is completely stable. My mind wants to call it "millcor" or "corex", but I don't think that that is ccorrect.

Marc: sounds like some sort of epoxy or urethane tooling board. There's a ton of different brands of both. It's basically MDF with ground plastic replacing the wood pulp. The variety I can get around here is epoxy, and pink in color. It's also super easy to shape and smooth by sanding, and gets used a lot to make casting patterns. Unfortunately, it's also really expensive. (Last I looked, a 12" x 24" x 1" piece was about $300.) I have a few small scraps I've been holding onto for years, and I'm always reluctant to use them for anything. It's a fantastic material, though, and I always wish I had more lying around. It glues really well with superglue, has no grain, and unlike MDF, sandded edges don't take paints differently than unmachined surfaces. I'd even considered buying blocks, cutting them into smaller pieces on my table saw, and trying to sell them to other modelers. But it's so spendy already, I can't really mark up the price much, so at best I'd break even (minus labor).

[marc_reusser]

Bexley,

Yeah...its pretty much like that, but came in block form as well.  Yes itms not cheap...but like you, I like scroungimg scraps whenever I can .

The cost of this type of material is why I suggested the Jelutong wood...has some similar characteristics....at a more realistic price.

[Bexley]

Yeah, it comes in all kinds of shapes- that was just the one I recall the price for. I've seen 18" cubes of the stuff, though usually you just laminate sheets together to get thicknesses like that. You can get rods and cylinders for lathe prototyping, too.

[SandiaPaul]

The Renshape material is I think an excellent choice for many projects like this. It machines well and holds very fine detail. It is pretty nice to cutters but is somewhat abrasive. I have machined a TON of it and yes it is expensive.  As mentioned a generic name is Urethane tooling board, having used a bunch of it the Ren is the best I think.

Marc, re: styrene vs acrylic, the acrylic is much harder on tools, the thing to watch on the styrene is the melting, slow your cutters way down and go slow. As soon as you get some chips built up, get them off or it will soon melt into a blob stuck on the end of the cutter.

Back to the Ren, if you have any pro model shops, especially ones that do industrial design type modeling see if you can buy their scraps. I used to save every little piece but after too many moves it went away except for the few pieces that I too, keep holding on to for the right project.

Paul

[eTraxx]

Ran up on this .. this morning

BUTTER-BOARD®

The blurb for it states .. "Nonabrasive for machining, glass smooth, modeling board for signs, in schools, machine trade shows and CNC proofing, thermoforming tool, that you can carve, mill, sand, rout, paint. Density is 48 to 101 lbs. pcf.  1.65" to 6" thick."

[marc_reusser]

Paul,

You clearly have hd more experience than I with this, so not trying to argue.....just being curious.
I have only had the melting issue with etruded acrylic....not with the cast....same thing with chipping (extuded chips much easier).. On the styrene dulling the bit faster than acrylic...this is something I was once told...so I may well be confused...apparently IIRC it is because the the addative to make the styrene white is something like a titanium oxide or such.

[eTraxx]

Well ... RATS! I asked the BUTTER-BOARD guys for a quote .. *sigh* .. reminds me of like when I watch a Lamborghini whiz by .. can admire ...