Well, three months later I’m finally getting to expanding my machine to meet my original goals 😀
I spent the last three months struggling with my needle cutter before finally breaking down and buying a servo tester and a tachometer. Turns out I had forgotten that RC ESC’s are totally non-linear so my guesstimate at throttle values to get the RPM I was after were WAY off. I had it at about 80% throttle but it turns out I only need about 20%. No wonder my machine sounded so angry! $13 tach was well worth the money. Purring along at just over 6krpm the needle cutter is MUCH happier and I I’m getting much nicer results.
I also redrew djk4linux’s needle cutter in openSCAD and shared it on Thingiverse as a customizer: http://www.thingiverse.com/thing:1723915 The defaults will give a working cutter with hicwic’s QC mount. I’m still working on adding the new default mount but haven’t printed the parts to upgrade my own machine yet so it’s been a slow process. I put the scad file up on github so it would be easy for others to collaborate if anyone is more motivated than me about adding the new default mounts: https://github.com/jhitesma/parametric_needle_cutter
Additionally I found that a new lipo charger I was given to review has a “motor driver” mode that’s designed for driving brushed motors – but can power a brushless ESC just fine which gave me a good way to dial in my cutter without having to worry about varying voltage from batteries.
I’ve also been thinking about the cutter RPM more and think I’m going to experiment with the closed loop governor options in BLheli (the firmware I’m running on my ESC) to see if I can get it to give me a precisely set RPM and hold it reliably.
I also finally got a DW660 which blows away my old dremel…and really has me wanting to print those new Z parts 😀
So with everything working so well I decided it’s finally time to expand it so I can cut full sheets of foam board. Spent most of yesterday prepping then an hour and a half or so to rebuild:
I also have footage from the next 2 hours I spent squaring it up…forgot how much I hate that step 😛
One thing that did help somewhat was the corner check tool I designed based on a post someone made to the vicious1 FB group:
On the smaller setup it worked great, on the big one…well…I ended up calling my wife in to help hold the tape. It still made it easier to get consistent measurements but the magnet I used to hold my tape to the corner tool wasn’t strong enough so it kept falling off and frustrating me.
But the machine is back together on the big rails again – at least mechanically. I still have to lengthen two sets of stepper wires (and shorten the other two) then re-wire and install my new belts before it will be moving again. Can’t wait to start cutting full sheets of foam!