The stepper motors and the components for the drivers have arrived. I was worried that they wouldn't have enough torque to drive the stages but after test energising one phase my fears were allayed. I had to put a lot of effort into trying to turn the shaft with my fingers, whereas the threaded rod on the stages turns easily - no contest, at least in the static case. I've got a driver half wired up on breadboard, I need to finish that soon.
One motor is now mounted on the X axis. Another trip to the hardware store and I came out with short lengths of vinyl tubing, about 5mm ID, that are extremely tight on the threaded rod. Unfortunately it wasn't so tight on the motor shaft - negative air pressure did make it difficult to remove, and it seemed to turn fine, but I fully expect it would have slipped under load. A piece of heatshrink placed on the shaft first fixed all of that and made for a nice tight join; although I expect I'll add some glue to it before I start using it. The Y axis is going to be tricky; I need to somehow make a trench in the X stage for it's motor to sit in... :S
The Z axis is almost finished; all that's left is to mount the motors and threaded rod. Getting it together was tricky; my supply of aluminium U channel is almost completely used up (I don't want to buy another $10 length if I don't need to) and I mis-cut the three plates used for the Z bearings - by which I mean I cut them all to the same length. That meant the pivot bearing plate was too long, and the other plates were too short. D'oh! "Fun" was had extending the holes towards the end of the plates to gain barely enough clearance for the assembly to work.
During my work on the mill I've been evaluating what I would be using for the milling drill. Originally it was going to be the dremel, but it is way too loud for my liking. I feel uncomfortable even using it for a couple of minutes in the evening because it must be disturbing the neighbours - a prolonged period milling a piece would be far worse.
Instead I'm investigating a dodgy rotary tool I picked up from Bunnings for $10; it's insides are at the top of the above photo. It's supposed to be cordless, but the batteries are bad and don't last long, and the torque generated is pitiful. It is definitely quiet however, and the driveshaft has ridiculously low runout and end-play! Unfortunately I'm stuck with a bad collet, because the tool isn't *quite* dremel compatible. :(
The motor normally runs on either 3.7v from batteries or 6v from the plugpack; and those are definitely underdriving the motor because I can stall it without appreciably overheating it. I hope that with a PIC closed-loop PWM speed controller and a 12V or greater supply with a good current rating it could be a respectable spindle motor.
2 comments:
Hey! Don't stop. I'm starting on my mill and you've given me a lot of tips to do and to avoid.
Let me know how it turns out.
Funny you should say that - my mill has been waiting about a year for me to bother getting the electronics together, and I'm *this* close to starting it back up again :D
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