CNC – First 2.5D cutting

I have designed a bracket that I used as my first attempt to manufacture something with my CNC mill. Because I’m still using python code I wrote myself and have not yet calibrated my stepper coordinates into real-world measurements, I had to design the bracket in Inkscape, print it out, and manually move my router bit to each point to determine the stepper coordinates along the path I wanted to cut out. This really sucked, and I plan on switching over to the parallel port controller board and EMC2 very soon so that I do not have to keep writing code. (I had to add code to cut out the bracket that interpolates between two endpoints so that I could route semi-accurate 60 degree lines.)

The piece of wood was secured to my sacrificial base with two wood screws, which worked out quite well. I am using a Black & Decker RTX rotary tool (low setting is 12,000 rpm) which is a relatively high powered tool, not the type of thing you buy at harbor freight for $10. Even so, my X/Y table moved too fast for it (causing my Dremel Drill press mount to be pulled out of alignment , as well as some damage to my bracket in a non-critical area).

So much for thinking that my rate was too slow! So I slowed the motion of my X/Y table by a factor of 2 and tried again. By only lowering the bit 1/32nd of an inch at a time I was able to cut out the wood without too much smoke and with a good deal of accuracy.

Needless to say, this was a LONG procedure. Each lap around the bracket took over six minutes, and it took about 25 of them to cut out the piece of wood. Once I got greedy and tried to do more than 1/32nd of an inch and knocked the dremel out of the holder with the extra pressure, so after re-calibrating to the starting point I sat down for the long haul. The entire procedure took around two hours. This makes me want two things: 1) A working Z-axis, so the computer can lower the dremel 1/32nd of an inch each time around without me, and 2) A much stronger spindle motor (trim router?) so I can cut out wood parts faster!

Wife Acceptance Factor (WAF):
The noise (especially when I was mistakenly using the 30,000 rpm setting instead of the 12,000 setting) was very loud, and the wife and cat ran upstairs to escape from it. After I was done, she noticed one good thing about the wood smoke I had produced. “[the smell] Makes me think I’m in a log cabin, [with a] burning fireplace.” If I want to transplant this device to my office, I am definitely going to need a sound dampening enclosure. (Also needed if I want to keep it at home.)

Below are a few pictures of the part and mechanism, as well as a movie of the cutting procedure in action:

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  1. Pingback: Jay’s Technical Talk › Bracket Assembly & Skate Bearings

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