Learning the hard way

When I was a CNC girl, I thought things like “Once you make one, you can do thousands, easily!”, “Acetal is the perfect plastic for precision parts and cuts like butter!”. OMG I was so naive. Making these parts were really a pain in the ass. That’s why.



Acetal has internal stresses. This mean that if you remove a significant mass from a block of acetal, the final shape will warp a bit. I knew that. But what I didn’t know was that sometimes this natural “stress relief” can take hours. So one day I was turning a lot of these parts, everyone having a perfect bearing fit. But then, on the next day, the bearing fit was really tight; the parts have had shrank a little bit. May be acetal I got wasn’t annealed? Or may be I should anneal these parts? (yes, plastic annealing is a topic).

BTW, in this specific case, a bearing housing should, ideally, not divert more than 5-7um from the nominal size: 10um less and the bearing will not fit; 10um more and the bearing fit will be too loose.

Now the other issue: long aluminum crosslide = noticeable thermal expansion. So the table temperature will change after stepper warm-up. And, it will change again after some machined parts. From what I remember a machined radius can easily divert 0.03um because of thermal expansion. And rehomming after temperature changes can be a bit misleading.

The good thing is that, once you understand these issues, making something to avoid or reduce them is not too hard. The bad is that now I have a full bag of black plastic decoracion parts (not the ones in the pictures, of course).

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There’s a nasty thing in my nose

Have you ever checked your nose?. I did. Three ones. Here’s how it looks just after some retouch (saddly I didn’t take a before pic):

IMG_2653 And here’s a nose from a new spindle (9/16″ through hole version). It’s not just aesthetics… trust me.

IMG_2655Now, if you are happy with your nose, please don’t worry.

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Since a time ago I’ve got really lazy about writing things. So hereafter I will, mainly, publish just pictures of some of my work here: https://instagram.com/i3micro/. After all, pics are all what matter!

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So here is how my CNC lathe looks right now.


I did the same abominable things to my manual lathe. No tailstock (by now). My soul is damned, but my ways will stay clean.

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i3lib – native gcode CAM subroutines

One of the things I’ve been working is a set of gcode subroutines meant to make easy to write gcode. Well, in the end you write very little gcode if you use it. Here are some examples:


So, for example, here the code for the hexagon pocket milling:

    #<s> = 30
    #<h> = [SQRT[3] * #<s>]
    o<i3_c_new_group> call [80] [0]
    o<i3_v_add_vertex> call [#<s> / 2] [0]
    o<i3_v_add_vertex> call [#<s>] [#<h> / 2]
    o<i3_v_add_vertex> call [#<s> / 2] [#<h>]
    o<i3_c_mirror> call [0] [1] [0] [1]
    o<i3_do_cut_mill_by_layer> call [19] [10] [0] [-1] [0] [0]

Most of hard work has been done, there’s some cleanup and documentation left. At some point I would like to release this code as open source. It makes really easy to create paths for simple parts (please note all the generated paths account for tool compensation, not G4X).

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