[smokediver576]

Well.... the time has come for me to jump into 3 axis machining for some upcoming thermoforming projects. I'll be making most of my bucks for now from Delrin or a similar plastic. Once I get more production, I could see these changing over to aluminum. So, my phase one questions are outlined below:

(1) I will be using the 3/4" Hog Shear to remove bulk product followed up by a 1/4" single flute plastics end mill. At what point/size do you change over to ball end mill? Radius will be .05" or larger.

(2) What "type" ball end mill - number of flutes and so on?

(3) Depth of cuts, feeds and speeds.... I'm assuming the feeds are much faster since the EM is taking such a light cut...?

Thanks for helping me with round one of questions. BTW, my first test - 1" square loft to 3/8" circle 1/2" high with .05" radius on all corners is in the mill right now. 3/4" Hog Shear, 1/4 single flute EM, .085" 2 flute ball EM. Man, that's a ton of code out of Fusion 360!

Later,
Awall

[smokediver576]

Here's the finished part. Okay, I know it's not much but I didn't crash anything, the part turned out pretty much what I designed and with a few tweaks I can see how I should be able to get the results I'm looking for!

[MikeC8]

One thing I would recommend is either us a 2 or 4 flute. 3 flutes only have a single flute that is center cutting, which seems to be more prone to breaking in my experience.

[C*H*U*D]

Have you thought of using a bull nose? I'm making parts now where my biggest radius was .030". I tried a 1/4" ball end mill first, but found I got better results with a .030" radius, 1/4" bull nose. It gave me a much better surface finish on flat areas too. My taper is a bit shallower than yours but similar operation. Just a thought.

[MichaelHenry]

Have you thought of using a bull nose? I'm making parts now where my biggest radius was .030". I tried a 1/4" ball end mill first, but found I got better results with a .030" radius, 1/4" bull nose. It gave me a much better surface finish on flat areas too. My taper is a bit shallower than yours but similar operation. Just a thought.

Whose bull nose end mills do you use? I checked YG-1, Mari-Tool, and Lakeshore Carbide and none of them seemed to make bull nose end mills.

[cobrakai]

+1 on bull nose

Otherwise I like 2-flute carbide ball end mills. I grabbed some Kyocera off eBay and they work well.

[Steve Seebold]

Most carbide end mills are not sharp enough to efficiently cut plastic.

High speed steel cutters would be better. If you push an end mill too hard in plastic, it starts to just melt the material.

[cobrakai]

I've heard this before Steve. Not sure I understand. A nice bright finish carbide end mill is super duper sharp. I've cut delrin at mach speeds with it and left a really good finish. I ended up going about 50% faster than I calculated and the finish was amazing for this machine. When I cut slowly is when it looked real bad, because the plastic would spring back and rub.

[CadRhino]

Check Harvey tools http://www.harveytool.com

Whose bull nose end mills do you use? I checked YG-1, Mari-Tool, and Lakeshore Carbide and none of them seemed to make bull nose end mills.

[MikeC8]

Bullnose endmills are also called corner radius endmills.

[MichaelHenry]

Check Harvey tools Find Specialty Carbide End Mills and Cutting Tools at Harvey Tool

Thanks!

[Steve Seebold]

The carbide I'm referring to is from 20 or more years ago. The carbide we get today is a LOT sharper than what we had them.

I can remember trying to cut plastic then and when I pulled the cutter out of the part, the flutes were loaded with plastic and the cutter was just blazing hot.

Carbide today isn't like that. Today, we can buy carbide with polished flutes that cut plastic beautifully, leaves an amazing finish and it doesn't get the cutter hot.

I use "only" carbide end mills in my machine. I'll use HSS drills taps and resmers, but all end mills are YG1. I have a 3/8 3 flute end mill in a holder that I've been using for over 2 years.