Plexi cutout problems

[MarkB611]

I'm making a clock cut from 1/4" plexi. I have some problems I haven't resolved yet.

I am using the slowest router speed which is 10,000 rpm.
I am at 40% cut speed.
2 cuts .125 each
Still quite a bit of melting of shavings on the edges

[milo30]

For plexi you want your router speed low and your feed rate high to help prevent melting. You might also blow some compressed air across it as the bit cuts to help cool it. If it is just the edges, you can sand or even use a torch to fix some of the problems. As far as what speeds you need to be running, it is a little trial and error to get it right.

[Eagle55]

Just wondering, where are you setting the RPM to 10,000 at? Is it on the router or in the software? Most know that setting it in the software does nothing since there is no control of the "spindle" speed as the software is designed to handle because we use a router with its own speed control (not software control) Just wondering, because I use a router with 28,000 rpm router speed and I can't change it (yet)

Roger

[Keith Hodges]

If its regular plexiglass you'll likely not get a good cut. Acrylic will cut much better.

[tonydude]

You have to have a variable speed router in order to change the speed manualIy have a porter cable 892 which I like a lot. I set my router speed to about 18,500 rpms when carving wood and 10,000 rpms when doing cast acrylic carvings.

Tony

[MarkB611]

Hi everyone,
Thanks for your responses.
I found a Tooling company about 1hr from where I live and I now have a distributer agent..
They don't sell to individuals but you can find a distributer online.
GREAT info, response, technical help. This is what I found out and will test later today. I will post results.

Company: Harvey Tool..Great catalog online

http://www.harveytool.com

Recommended tool.
Square Upcut - Single Flute. # 14018-10 (Also recommended 2 Flute but they only had it with 1/8" shank)
Speed to use 25,000rpm if my router goes that high
Feed Rate 75-100 ipm
----------------------------
One way to cut out shape in 1/4" plexi
Cut out first slightly larger ..2 passes
Cut out exact (final) 1 pass

I will try 2 passes exact and if needed 2 passes over first.

Wish me luck.

[Consultingwoodworker]

Look into cutters made for plastics. Onsrud specializes in them.

Single flute is best. Fewer flutes means less friction, so less heat.

"O" flute bits are excellent, they tend to curl the chips rather than breaking them into pieces.

Low RPM with higher feeds are better. You want big chips that fly away from the cut path taking heat with them. Chips that stay in the tool path get recut adding to the friction and heat.

You mentioned running at 40% of the feed speed but did not specify the actual programmed feed speed.

Ralph

[MarkB611]

Thanks Ralph for your info.
Well, did my first cut with my new bit.
Single Spiral Upcut Flute #14108-10 This bit is for cutting plastic.
Harveytool.com

Feed rate of 80 ipm
Speed 23,000

Absolutely no melting at all. I do have some chatter in the cut. Most goes away when I flame the edge with Mapp gas torch.
I used 2 cuts.
Next I will increase the speed to 100 ipm

If that doesn't give me a smooth cut I will go with the technique of cutting slightly oversize first then 1 final cut.

[tonydude]

Mark,

When Ralph asked you what your actual programmed feed speed, he means what is it programmed at in the tool data base. So when you say you run at Feed rate of 80 ipm that means your running at 80% of your programmed feed rate in the data base. Example attachment. So if your data base says 100 ipm and your saying the feed rate is 80ipm that is 80% of 100 = 80ipm. The feed rate on the control panel is the % of feed rate in data base of the tool your using.

Tony

[MarkB611]

Thank you Tony,
I added my own tool for my new bit.
I set the feed rate for the tool at 80 ipm.
I didn't change the Feed Rate in the control panel which is still set at 100%

My next test I increased the rate in the tool database to 100 ipm. I'll post what happens.

Mark