Mill material

[powerstechteacher]

Using Matercam X and a Dynapath mill, what is a good material to begin instructing students without the risk of speeds and feeds being a problem. I have used butterboard and machinable wax but they are proving too expensive, any ideas?

[Guest]

A simple piece of 1018 CRS, should be good enough to show the risks of machining with improper speeds and feeds

[powerstechteacher]

I guess I wasn't as clear as I need to be but I was looking for a cheap material to mill, possibly a foam?

[Rich Musson]

Have you tried to mill hard wood like cherry, maple, oak. I used these materials (woods) and acrylic.

I had my students machine their cad drawings of machine parts - cog gears, cams cog gears that would be installed in Automata projects. Name plate desk plates in Cherry and Oak were a big hit for parents and teachers.

[TeccBoxx]

You may try looking into decking material. You can get a piece that is 8 feet long, by 1" thick and 6" wide for $15 to $25.

[Mike S @ S4A]

another possibility if you like wood - culls from the local lumber yard...or referencing the previous post, decking material thats blemished is useless to carpenters, but cutting small pieces out (assuming student projects are typically small enough to fit in your hand) of a damaged board might work?

[Will Slota]

Pink or blue insulation foam boards amke for good practice material. It is cheap too.

[John Summers]

MDF (Medium density fiberboard). I haven't found anything cheaper. Masonite is good for 2d projects. There is now .080 masonite.

Auto body putty machines well.

[Keith Butzgy CNC Software Inc.]

I also use MDF. Home Depot and Lowes will sell 4x8 ft sheet, 0.750 thick for about $20-$25. If you need thicker, cut and glue. You may want to watch out because if you're cutting a lot of MDF, the dust can get hazardous. It's also pretty rough on your cutters.

[Exodus]

We did our milling projects with aluminum and acrylic. Probably not the cheapest material though I'd recommend attempting to teach the students what is actually happening when and end mill plunges, or faces material and the forces involved. And why sometimes lower feed with a slower spindle speed would be better.

[Colin Gilchrist]

When I took CNC Programming, we also had the same issue of trying to find cheap material. We used a re-usable casting wax. We had an electrically heated tank with a ball valve at the bottom (open top) and we would pour ingots of wax and let them cool. When a student was done cutting their project, we would throw the cut block and all of the chips back into the tank and re-melt it again. The best thing about cutting the wax was the cleanup. No dust to deal with. Just make sure you take a big enough chip with a slower RPM so you don't melt the block.

[shopdoug]

I use 20 to 40 lb. polyurethane foam... I get drop from our local manufacture (General Plastics, Tacoma, WA) who makes it for the Airospace industry (Boeing)

 

See Generals link for machinable foam blanks

 

http://www.generalplastics.com/products/pr...ail.php?pid=28&

 

and Last-A-Foam FR-7100 for modeling and CNC machining....

 

http://www.generalplastics.com/products/pr...ail.php?pid=19&

[Torr Man]

Colin

 

Can you suggest feed & speeds for cutting wax. I have been through this whole process many times and I keep coming back to waxes. I presume you are talking about wax that is used in the investment casting process, which is a lot harder than normal crystaline wax. I did have a supplier that mixed me a batch of special wax that was a combination of crystaline wax and polyurathane (Poly that is used in hot glue guns)this wax was a dream to machine, it produced a good chip, And like you said once everything is done the wax can be re-used.

[Colin Gilchrist]

Hi Torr,

 

The biggest thing with the wax is not getting it hot. You should be using sharp High Speed Steel cutters (no need for carbide), lower RPMs, with a thick chip load.

 

For example, I'd run a 2 flute .250 endmill at about 1000 RPM, with about a .005-.01 chip load per tooth. So for a 2 flute endmill, .015-.02 feed per revolution would work pretty well.

 

Try experimenting.

 

I'm not exactly sure of the grade of wax we used at the college, but I don't think it was investment casting wax. Ours was really soft and wasn't very dimensionally stable, but it didn't need to be. We were just using it to prove out NC programs, so the emphasis was on getting the code right and getting it to run. Come to think of it, I don't think we measured it at all.

 

This was back in the mid-90's, and we weren't even programming real machines, we programmed these little desktop mills.

 

The machining program at LWTC has evolved quite a bit.

 

I think they still start the students off with wax, but they also get a fair amount of aluminum and other metal remnants donated now, so the students can progress to cutting real material.

 

Having the wax melting tank so you can re-use the material is a huge help...

 

HTH,

[carman]

I get scaps of the blue insalation board from construction site. I also get scap wood fron my local cabnet shop and scap plastic from my local sign shop. Most of them are glad for you to get rid of their junk for them.