06/23/2015 at 20:32 •
I received the parts to be machined and everything went better than I thought possible. I only ruined one part and that was because I pressed the button while the drill was still in the hole, preventing the stepper from turning. I was lifting the spindle, so the stepper turned only a portion of the 60 degrees. I discovered the mistake when the last hole ended up too close to the first one.
I made a quick drawing of the tooling in the vice:
And the firmware for the Arduino is in this Github Gist. It's really only the sample code from Rugged Circuits changed slightly for serial debugging and with values appropriate for this stepper and the 24V supply.
06/04/2015 at 19:11 •
I really like the design of the Samsung cheap laser printer we bought for front office's desk. It lasted longer than expected and when it eventually died, I took it apart to keep all the guts. The back of this PSU has a legend printed on the PCB of the connections with voltage and current. CON1 is the 115vac input. CON3 had 24V at 1.6 A and 5V at some other amps. CON3 is the small gray connector with lots of pins at the end away from the 115 input connector. CON2 is the white connector and supplies 115VAC to the high voltage power board.
I really appreciate how this PSU came with switch and IEC socket. I cut (well, machined) slots in the lower half of the case to hold these. The IEC's socket was designed for thin sheet metal, so I had to cut back the locking tabs and bend them out some to secure the socket in the case.
Red wire is soldered to the large pad underneath feeding 5V to the gray CON3. Green is soldered to the 24V pad. The black wires are soldered to the ground plane surrounding the DC section. This ground does not have continuity to the metal heatsinks nor either pin of the input 115V.
I placed clear acrylic plate above the PSU to keep my wires and the various 115V lines and connections away from the PSU's internals.
This highlights what I consider one of the bigger obstacles to small projects: connections between modules. I really like the 4 way screw terminal connection block. It has no exposed metal that can touch other bits and accommodates all wire sizes I use in projects. The output is trailer wiring, which is cable tied to the bottom of the case's battery holder. The psu uses a "trailer connector" and my project has the plug normally at the back of a car. While backwards-ish, I had only 1 "trailer" end and 2 "tow vehicle" ends, so thought this would allow the PSU to be used again.
Plus, the tow-side connector is available at many local stores, so it's easy to buy more. Second advantage to using the trailer wiring is how durable they are made; I can step on these wires without fear of damaging them.
06/04/2015 at 07:42 •
Using the drawings from the NEMA 34's data sheet, I threaded M6 holes in the base plate to attach the motor. At the other end of the plate is a "design" that applies pressure against the end of the stepper motor's shaft. The clamp's purpose is to allow the easy removal and replacement of the part to receive machining.
The big round thing is just a cylinder to hold the central shaft and the clamp. The central shaft has a bearing at the CNC end. This allows pressure along the shaft and also rotation about the shaft. The other end of the big round thing is a simple plate that holds the Harbor Freight toggle clamp.
The toggle clamp acts on a M6 x 50 socket head cap screw that's threaded into the right end of the central shaft. The springs on the right end of the bolt retract the device when the toggle is opened to allow easier change of the part to be machined.
Affixed to the stepper's shaft is an arbor I made. The items to be machined have a hex recess broached into them, so the arbor firmly holds the part to the stepper. There is a picture of me machining the arbor while it is in a hexagonal collet block. The other end of the shaft was bored to 14 mm to make a snug fit on the NEMA's shaft and a set screw clamps the arbor to a flat on the shaft.
06/04/2015 at 06:49 •
SainSmart CNC controller:
I went and bought a SainSmart CNC controller. It's all professional and serious, so I thought it would be a great start. I watched various youtube videos of the module to better understand this device and gained some confidence so tried it out. I worked through the various switch settings and arrived at what I believed to be the setting with the best holding power and I was still able to turn the stepper's shaft with my fingers. It was quite strong, but not enough.
To make sure it wasn't the power supply's fault, I bought a lab power supply off Amazon and hooked it up. It read 24V and max current draw was just under 1 amp. With this "bench" power supply, I could still turn the shaft with my fingers.
Rugged Motor Driver:
Next up is the "Rugged Motor Driver" from rugged circuits. I was able to get this shield to work with the stepper motor. I was eventually able to coax the sample sketch to manipulate the stepper into doing things I want. And then I was able to gain confidence in what was happening and I was happy. Happy-ish, anyway, but the stepper would "sing" loudly. Everything seemed ok otherwise, as the stepper remained cool to the touch and the driver chips on the shield were only slightly warm to the touch.
Big Easy Driver:
I purchased one of these for a previous project. The small easy driver was super easy to use for the big one should be, too. What could possibly go wrong? Oh, the smoke. It fell out of the big easy driver. I hooked it up the same as the other two boards prior (and the small driver with 12V prior) and then zzzzzzzzzip pop smoke.
OK so Rugger Motor Driver it is...
05/28/2015 at 04:10 •
12V with lots of amps (4 or 5 from power supply's label) isn't enough to hold the spindle in place while machining. Going to try a 24V 1.8A supply next.
05/27/2015 at 04:37 •
I used the "spare" parts left over from the TPS test bench's Arduino stage as the quick start to this project. That's a proto shield with a SparkFun Easy Motor Driver soldered to it. I found an Arduino Uno and a SparkLite project case and spacer.
I also reused the code from the TPS bench and worked up code to alter the magic numbers from the stepper code there to work with the huge NEMA34. ( hmmm, how do we share code here? )
I did fab up some aluminum to make "the tooling" and I'll share that once it's proven working. Which next brings up the question of how do we share CAD work here? :D