Machining plastic

[bpimm]

Hi all,I'm making some adjustable micro switch mounts for limit switches, I was thinking of machining them out of Aluminum but then plastic came to mind as a possible less expensive alternative. I have machined ABS on the lathe and it worked fine but this will be cutting slots on the mill and I'm wondering how the ABS would cut and what kind of speed and feeds I would shoot for using a 1/16" 4 flute Carbide end mill cutting a .100" slot in 1/8" thick ABS? would melting be a problem? would flood cooling help.

2 of the slots would be cut with a 1/8" endmill in the full 1/4" thickness and 2 would be .125 depth those are both .200" wide but it's the 1/16" I worry about breakage on, they're just so tiny.

The stepped slot is to keep the nut captive when the micro switch is mounted (on the back side in the picture) so it can be adjusted up and down. the nut measures .190" on the flats.

The machine in question is cnc converted Grizzly G0705 round column Drill/Mill

Thanks
Brian

 

[Ulma Doctor]

abs may work, but it may be prone to cracking in thin sections.
nylon or delrin are materials that would be less apt to crack in thin sections

 

[bpimm]

I think I'll try one out of HDPE, I have a 1/4" thick discarded cutting board laying here... see what happens.

 

[Dave Paine]

I have drilled UHMW. It drills easily. A lot ribbon shaving which I did not like. I think HDPE would be similar. It should machine, but the hole/slots may not sloppy. This should not be a problem for this use.

 

[EmilioG]

Harvey Tool makes special cutters for plastics. Take a look at their website.

 

[David S]

I recently did some milling with UHMW and it machined nicely but there were some burrs on the edges of slots. I was using two flute HSS end mills. I would think that two flute my clear the chips better, but don't know for sure.

I also machine acrylic with small details and it works fine as well.

David

 

[RJSakowski]

My choice for plastic would be Delrin (acetal). It machines well and is not subject to melting like some of the other plastics are. It also has fairly good mechanical properties and I have never experienced stress cracking. If you decide on one of the more easily melting plastics, using coolant will give a better finish and prevent melting issues.

If you price it out, you may find that there is not that much of a cost advantage compared to aluminum. Aluminum is definitely stronger and dimensionally more stable.

 

[bpimm]

My choice for plastic would be Delrin (acetal). It machines well and is not subject to melting like some of the other plastics are. It also has fairly good mechanical properties and I have never experienced stress cracking. If you decide on one of the more easily melting plastics, using coolant will give a better finish and prevent melting issues.

If you price it out, you may find that there is not that much of a cost advantage compared to aluminum. Aluminum is definitely stronger and dimensionally more stable.

I've worked with acetal a couple times, it is nice stuff I haven't machined it yet I didn't know it wasn't subject to melting like other plastics. The reason I'm thinking about plastic is the cost factor and you're right acetal is right there with the Aluminum maybe even more when you consider buying Aluminum drops by the pound.

I'm going to try one out of the HDPE and see what happens seeing that I have it laying here.

 

[fretsman]

I love hdpe for certain things, and it would probably be strong and last, but it's a pain to deburr. I would also recommend delrin (acetal).

Dave

 

[RJSakowski]

I've worked with acetal a couple times, it is nice stuff I haven't machined it yet I didn't know it wasn't subject to melting like other plastics. The reason I'm thinking about plastic is the cost factor and you're right acetal is right there with the Aluminum maybe even more when you consider buying Aluminum drops by the pound.

I'm going to try one out of the HDPE and see what happens seeing that I have it laying here.

Delrin will melt. I have welded it in the past. But I don't recall ever having an issue with melting while machining. I suspect it is because it has some lubricating qualities. I certainly have had issues with PVC, acrylic, and polystyrene.