Improving Aluminum Finish

21

So heres my experience because i got a lot of conflicting info from people.

Arcs and circles thst are not splines will ignore any of the tolerance or smoothing settings in the tooltmpath config. There simply arent points used between xy movements. You can verify this 2 ways. 1. Look at the tool path data and show points. 2. Export a circular toolpath and compare the gcode with tolerance set to .1 no smoothing and .0001 with. The gcode is the same because the machine determines the resolution for arcs in the controller.

In the post processor there are settings for minimum and maximum (im mm) arcs and circle diameters. One of these is ā€œbuilt in toleranceā€ this does NOT affect arcs and circles unless its outside of those mins and maxes. Its defaulted to .002 now i did set mine to .001 but it doesnt really matter

You can use MDI to look at the default value for the shapeoko its $12 id imsgine theyre the same but on the 5 its defaults to .002. I noticed it only displays 3 decimal places in the log console but it did accept .0004 as a value and i did hear an audible change in movement after this but no visual chsnge in my surface finish for arcs though so i set it to .001 for now.

I THINK a lot of this has to do with the vibrations from using this style of a stepper driver. Its not the snoothest and you can feel the vibrations induced if you just touch the spindle as its making an arc.

Doc for finishing, spring passes, travel cut speeds none of those really made a difference in any of my testing ive done.

I did turna cceleration way down partly for finish and partly becsuse the 80mm spindle is pretty heavy and it was actually violent when it changed directions. Im cirrently at 50% and its pretty happy. I may even go lower when doing aluminum work tbh. Im not in it to save 5min im in it to make a processional looking part.

Misting made no difference other than making the ridges in the finish more shiny.

Maybe this helps some of you out.

Set arc resolution lower in the grbl settings
Slow the finishing/spring passes way down
Set acceleration to 200 or 250
Remove vacuum attachments for finishing passes (any extra weight on the spindle)
Odd number flute finishing mills with a shallow helix

inbound4945215154276865977
inbound49452151542768659771800Ɨ4000 265 KB

5 Likes
22

I use Cool lube 2210AL in their jr mql and even after 200+ parts I havenā€™t had to refill the small res yet. It does leave a film on the part but comes right off with 70% iso and the finish is great but it was not cheap.

1 Like
23

Denatured alcohol would probably have the same effect. You would also need to better manage the fumes with denatured. There are ingredients in it that are much more toxic than isopropyl (which isnā€™t good for you either) when inhaled.

1 Like
24

@BlueMeanieTsi this is great information and sounds like you spent quite some time trying to chase down the root cause. Are you using Carbide Motion? How did you adjust these settings?

25

You can change acceleration and toleance through MDI in CM.

$120-122 is acceleration xyz
$12 is the tolerance for arcs.

Im still not getting what i want out if it surface finish wise on arcs but its the best i think im going to get. I still suspect the jerky stepper drivers are to blame here though. Higher end machines have much smoother stepper drivers

26

Thank you! I will try these settings and see if it helps. The arcs I can understand. Hopefully the acceleration lowering will help with some of the heeling marks on direction changes.

27

This topic was automatically closed after 30 days. New replies are no longer allowed.