Oh one thing I forgot to mention...I measured the current into one driver (using both an ammeter and a shunt resistor) and when idle it's about 0.3 amps. It goes up a bit when the motors running, but either way that seems a bit low to me? I've got the driver set to 4.09A peak, I take it this is correct for these motors in bipolar parallel? The motor is only a little warm, nowhere near 80°C.
I'm currently using a 225VA toroid for just the one motor. There's no perceivable temperature rise on it so maybe I can run more than one motor from this transformer?
you need 66% of the total motor peak current... so 3 steppers at 4A/phase = 3 * 4 *.66 = 7.9A. @ 60v thats 420VA
remember that measuring phase current with an analogue device will show the RMS phase current. With a digital meter you are unlikely to get a useful reading because its highly spikey.
Anyway, I got lucky and won a 500VA toroidal transformer for £20 on eBay so I'll be using that.
I changed the pulleys round (had to bore them out to the right diameter and stuff) to get 1:1. Now I'm getting 42mm/s on the X axis :)
Bad news is the Y-axis for some reason refuses to even go at 25mm/s without stalling the motor. Not really sure why, maybe something to do with the belt tension and how tight the nut is...
Not tested the Z yet.
Its usual to quote feed speeds in mm/min for milling - so 2520mm/min is good, 1500mm/min isnt bad tho
Strange... if you haven't already, try swapping driver channels to validate its not a driver issue, then motors (assuming they are the same) to validate its not a motor issue
I've only wired up one driver so far, so that can't be the issue. I'll try swapping the motors though. All the motors are the 3N-M ones.
The handle for the Y axis (before I removed it) did seem a little harder to turn than the X-axis so I may try loosening the nut. I tightened it to reduce the backlash. Annoyingly to get to the nut you have to take the bed off the machine and all sorts...takes ages :(
Surely its the gibs that determine how tight the slide is? although I'll accept endfloat is another contender
Yes that's true, I'll check the gib strip. There's no end-float on the screw since there's thrust bearings, unless you're referring to something else?
The nut is slotted with a bolt to tighten the two parts enabling you to adjust the backlash. Quite recently I tightened it to reduce the backlash, but maybe I tightened it too much and increased the friction excessively.
AH, I was confused by the statement
The handle for the Y axis (before I removed it) did seem a little harder to turn than the X-axis so I may try loosening the nut. I tightened it to reduce the backlash
I've had some luck with the Y axis now. I loosened the gib strip which helped a bit however it strikes me as being too loose now. I adjusted the backlash adjustment and now I've got 2300mm/min on the Y axis, but about 0.2mm of backlash instead of 0.065mm.
Good news with the Z, 4600mm/min with 1:1 pulley!!!! It will do more if I change the motor to half stepping because the computer is limiting the pulse rate I can use at 1/4 microstep, however 4600 is plenty fast enough for an axis that's only got 92mm travel. I'll keep it at this ratio to preserve torque for drilling etc
So to summarise:
Overall I'm very happy with this - can't wait to start machining things again! Thanks for all the help that's enabled me to do this...
Also, could someone point me to a simple program to import a 2D .dxf and generate g code for '2.5D' milling from it?
By hoppo in forum Motor Drivers & ControllersReplies: 4Last Post: 21-11-2012, 12:19 PM
By sebring115 in forum Motor Drivers & ControllersReplies: 14Last Post: 30-11-2011, 10:32 PM
By Mad Professor in forum Stepper & Servo MotorsReplies: 12Last Post: 01-09-2011, 09:09 AM
By Jonathan in forum Stepper & Servo MotorsReplies: 2Last Post: 24-03-2011, 01:24 PM
By Davidh in forum Motor Drivers & ControllersReplies: 3Last Post: 12-06-2009, 04:59 PM