Challenges
continue with cutting out z-axis pieces for 3D Printer Build.
Autodesk's CNC Utility issues:
Current cuts – contoured portions are
not cut down to depth or the width that they need to be (about 1mm short
for each dimension), even after x-axis finishing cuts (the finishing
cut did increase dimensions somewhat but still not to design
dimensions).
14.11 after x-finish 13.54mm
before (design goal was 15mm, so still a bit small)
7.25 after x-axis finish cut, 6.19 prior to cut (still short of design of 7.5mm)
Profile cuts (all the way through) and
“Cut Out” instead of “Carve” cuts (for straight right angle
z-axis cuts) seem to be right on. I really do not know what the problem is but time is short.
Well...its back to MakerCAM for now and
I'll have to stick to square pockets instead of contoured ones (I
could do nested pockets but I expect that I'd run into others issues
if I tried that).
My main issue with Inkscape to MakerCAM
is that shape dimensions in Inkscape end up slightly smaller when
imported to MakerCAM (and I don't mean the settings for SVG import
resolution – I already encountered and found the simple solution to
that issue – change to 90px/inch). When I go the alternate route
of OpenSCAD to Autodesk's CNC utility – a cut out 9mm square is
actually 9mm. The result is that I have to run test cut dimensions
to find correct dimensions for what I design in Inkscape. Does
anyone else have this problem??? For me, at least, this seems to be
an issue with the SVG file since the cut depths that I enter into
MakerCAM do measure out as what I entered in.
On the bright side, at least I already
have the Inkscape files for the parts I'm cutting out (since I made
and used them to cut the same parts from wood). I still need to
re-do all the tool paths in MakerCAM.
It's taken me awhile to get the tool paths correct - first issue was that I had forgotten to include pockets for the X-axis guide rods, then I did not comprehensively preview an operation in OpenSCAM and missed the drill holes being set to 0.75" instead of 0.5" (extra stress on the Z-axis stepper and burned off half the collar on my endmill).
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| Test Cuts Autodesk CNC Utility |
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| Test Concave Cut Autodesk CNC Utility |
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| Test Cut Size Check With Inkscape/MakerCAM |
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| This is what I'm aiming for |
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| First Test from Autodesk CNC Utility |
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| A few of my trials from Inkscape/MakerCAM |
After all this work it seems the bed of my CNC is not level, like it
used to be - depth of cuts is not consistent across pieces. Since I need to put a new sacrificial bed on the CNC and
add some additional anchor points to hold it down better - I figured
that I'd also finally change out my Lead Screw's. I've had new Acme
Thread (single start) 1/4" lead screws for well over a month but put off
installing them.
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| Old Lead Screws with Anti-Backlash |
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| New Lead Screw- gluing Anti-Backlash |
I decided to change out my lead screws so that I can speed up my cutting procedures - currently the top speed that my CNC travels is 14"/min. This is because the threaded rods I was using for lead screws had 24 turns per inch - my new acme screws are 14 turns per inch. My GBRL settings for the threaded rods were about 200 steps per mm - potentially very high precision (current configuration not stiff enough though) but this meant that I could max out stepper speed fairly quickly. In the future - if I can come across some reasonably priced multi - start acme screws I will have to pick them up.
After I get these screws in tonight, along with a new bed - I'll get the machine re-calibrated for the X and Y axis then route the bed to make it level.
