Hi All,
Thought I’d give you an update on where EasyMaker is at this moment. I’ve redesigned 2 parts recently, but haven’t manufactured them yet. I’ve been working on electronic issues — I’ve swapped control of the Y and Z axis in RAMPS, so that I can use dual motors on Y. This took more debugging time than expected, as I don’t have enough codebase familiarity to know all the variables that had to be changed to get the new pin assignments to actually work. I mostly figured it out last night, and have counter-rotating Y motors working intermittently. I believe there’s a loose wiring connector to the pin header, and I have to figure out which pin is not making good contact — or there’s a code problem.
The reason I swapped Y and Z is that Z has a dual pin-header conenctor ( in RepRaps, Z is electrically coupled to 2 motors ), and I wanted to use this existing coupler. I then cross-wired the stepper to be 180 degrees out of phase, so that the two steppers will step in opposite directions ( a left and a right, one for each side of the Y axis ).Once I get this working, I have some alignment to do. Driving 2 motors is taking the Alegro driver to its maximum. The motors love it — they’re running nice and cool now, whereas previously, the Y motor would run hot( Y is the most loaded axis, and as such, has been hard to load manage in terms of control this close to the edge. It currently takes a lot of calibration time to change between modes, as Y current must be re-calibrated. This change increases the power on Y to better handle the load. It also should reduce calibration time — just max the Y stepper driver.)
I’m also re-examining driving via RJ-45 connectors. My previous experiments with it were a bust. I spent some time analyzing the failures, and have re-wired the changed Y axis to use RJ-45/Cat-6 ether cables. If this works, then I’ve made it a lot easier to wire this in production. I’m still designing an IEEE 1394 breakout board to test using IEEE 1394 wiring. IEEE 1394 is rated to deliver 45 watts — I currently draw 24 watts on any axis. Cat6 is power rated to 15 watts, with PoE rated to 25.5. Y splits the 24 watts to 2 motors — each using 12 — so Y should work with Cat6 no problem. I’m already using a Cat6 configuration to drive the hot end, and using Cat6 really helped fix reliability problems on the hot end. Basically, whenever I remove pin header and switch to a locking connector system, reliability and ease of use go way up. So, even though it’s adding to BOM costs — I’m becoming more convinced that an electronic design with either RJ-45 or IEEE-1394 between endpoints and screw terminal breakouts is the right thing to do. It makes the product much easier to work with — and that’s worth the added cost in my mind.
It’ll likely take me the rest of the week and into next week to make all these changes and manufacture the redesigned parts. Then I can go on to test the design change. I have decided that one more part needs to be designed, that I hadn’t accounted for — an electronics enclosure. I have a fan to keep the electronics cool. This fan is pretty high thrust — it wants to fly away( literally ), and controlling it on an open table is getting silly. I need to design a way to keep it down and blowing on the electronics. The only way is an enclosure. But I still need access to the calibration pots. So, an open-top box or maybe a box with a lid is what’s needed.
Anyway, thanks for reading!
–Imran
Peerbhai Robotics 