Awesome, thank you so much for that. I will give it a shot. Hopefully I’m back home early tomorrow afternoon - fingers crossed that my meeting in the morning is short!
This site has quite a cache of information about the milling we do with the MPCNC.
Specifically, here’s a tutorial that covers cutting lexan/acrylic.
http://www.precisebits.com/materials/plastics/PMMA.htm
I have found the entire site valuable.
Great! Thanks Tom, I will definitely spend some on that website.
Alright, so I used Barry’s trochoidal settings. I think it is still possible to improve from here, but it is a huge improvement already. The chips are looking pretty good, not stringy and not dust, but somewhere in between.
Here is a picture of the results: https://www.amazon.com/photos/share/EHLOxQSol5cnrZEX032pMF9RR8uuDK8Bb5bEWIUfOQE
Here is a video: https://www.amazon.com/photos/share/GTR6oTgFQ7wjNDe09bx7OYBsBlbg0GwoQrMjz5l9LhR
And here is a screencap of Estlcam settings - you’ll have to click on the picture after clicking the link, the columns are all visible in the picture (I used a Makita RT0701C on speed setting #1): https://www.amazon.com/photos/share/4WB8iRK57wmpxQrel3rP8iBj4vlqTaCgOtMDJoDEvpT
Question about this fancy method of milling “trochoidal”… Would it be beneficial and make better cuts in wood too? Could the depth of cut per pass be deeper with this method?
Yep. You’ll need to do a final finish pass most likely.
I experimented with spindle speeds and adjusting the trochoidal parameters, but being at the absolute slowest spindle RPM I can accomplish limits my options. I also tried running a straight finishing pass, but it didn’t do much for me. I’m assuming that I would have to take more material off for the finishing pass to help.
With my setup, I think I’ve reached the point of diminishing returns and I found that a quick once over with fine grit wet/dry paper gave me a really nice edge. For this small 1-inch square, it took about 10 quick back and forth strokes per side, which is probably faster and less effort than any improvement I could eek out of my MPCNC setup until I get my Super PID.
Here’s a picture of what it looks like after sanding: https://www.amazon.com/photos/share/0QTTUvodq4UPhRtwIs7sLwYDcNkZXu26sVwcOXzNfQm
Not too shabby, if you ask me!
That’s much better!?
Thanks Barry!
I’m going to start testing HDPE next. Should I start with the same settings?
Yea, it’s pretty safe to start there.
Need some help/guidance here… I got some scrap plexi at Ace Hardware today in order to test cutting before trying out the 1/4" acrylic I got for some parts…
see the pictures for my results… seems the combination I have does not work and the material gets too hot and gums to the bit.
I am using these bits - https://www.amazon.com/gp/product/B010NI39WO
I am using this spindle - https://www.amazon.com/gp/product/B01LNBOCDA - at full speed so that is 12k rpms.
Looking at the other screen print I set up the trochoidal settings that someone mentioned here in this thread.
Barry - I slowed it down with the same bit… same results…
Then I switched to a single flute at the full 12k rpms and I think it did good. I didn’t have the depth as deep as it should have been but all in all first cut… pretty good I think…
I’ll try your settings on another cut too.
I’d also like to learn how you engrave/etch on acrylic… what bits / depths / speed etc…
It might be those 2 flute cutters. They look more like rotozip bits than endmills. Single flute cutters work better with plastics anyway, especially at these speeds. Plastic likes slow rotational speeds, so a single flute is “slower” than a 2 flute. I also can’t tell if you have a dust collector in place. They’ll help keep the plastic cooler with the airflow.
No mounted collection… I was running my shop vac along the side when cutting. I am going to try some more parts tomorrow but this evening I was trying to figure out how to engrave onto the plexi.
Now I am trying to engrave with a 45 degree V bit but if I go any deeper than .50mm the tip gets clogged.
Also, when trying to engrave onto acrylic I am not sure how fast you should have the feedrate.
Read through here. You might need to slow down your spindle.
Thanks Barry I will check it out…
One final question for today ---- What is the correct orientation for the Logo that Ryan has on his low rider parts?
One of the bearing spaces needs to point up.
Well just when I thought I had things down for trying to engrave into the acrylic I ended up wasting a huge amount of it last night. I am not sure if I am using the wrong type of bit or my feed rates are all wrong.
Basically the end of the bit develops a small ball of the acrylic and then overtime it just get larger and ruins the rest of the engraving.
I was using this bit - http://www.ebay.com/itm/380982067909
My toolpath depth was set at .65mm
The step down was set at .10mm, Plunge angle 90degrees, Feedrate 200mm/s, Plunge Feedrate 8mm/s and the spindle was at full speed which I think is 12k.
I also ran compressed air on the bit at the same time.
Some parts turned out fine and others due to the bit getting the acrylic melted ruined the rest of the engraving.
I would go slower and deeper per pass. The machine is firmware limited to 190mm/s and does not perform well at those kinds of speeds you should be between 5-40 for the Xand y.
You are going to have to just mill squares or something into some scrap to get the settings correct. Plastic is fairly difficult, just under metal, so the settings are much more important than wood.