What do you really get for a $350 desk top engraver ?

i set everything at @ 2,000 micro steps and cut another test piece. The finish seen no real difference in cut quality, but the current settings were a lot more responsive. so that part makes sense. the X axis seems to work really smooth, and the tandem Y runs better but still needs some more help.

Are there any tip or tricks for getting a tandem axis tuned? it seems like it is a lot harder to get settled into.

machinedude wrote:

Are there any tip or tricks for getting a tandem axis tuned? it seems like it is a lot harder to get settled into.
 

About the only thing I've seen that was reasonably successful was to disconnect the gantry from the motor to be tuned, and attach half the gantry weight to that motor's carriage.

This will get the inertia in the ballpark, and the values can be copied to the other motor.  From then on adjust the same on both motors.

This may be fairly easy, or it could be a royal pain - just depends on how the hardware is assembled.

i did find a dip switch setting that made a difference. SW8 is a pulse filter on is 10ms off is 1.5ms mine were off. After i turned that on the set point signal smoothed out a lot.

one other thing i found was the control loop sets based on the peak current rotary switch. and even if you want to change those the drive will default back when the power is cycled. i did have mine set at 6 but 9 is a better choice based on what the manual is saying. 9 should tighten up the position error signal.

i think the drive knows the power supply voltage and sets your current based on supply voltage. @ 36V i get 4,8A, the drive has a max of 7A but mine only go to 6A with the 36V supply.

 

i think this is good as it gets with this test program. ran this one at 50%. so 1/4 depth with .020 step over @25 IPM and i final @20 IPM
i wonder how hard i can run now i got lots of extra juice

i was not expecting this good of a cut step over or depth of cut for that matter but i probably tripled my step over on my X axis. .600 depth of cut with a .130 step over at @ 75 IMP with a 1/4 diameter 3 flute. the drive did perfect the spindle was starting to drop in rpm slightly. now i'm making some chips

 

Ok what i took away from all this was a better understanding of what i was seeing with my surface finish issues. The added torque from my micro steps was one layer of it and the other layer of it is resolution with a course lead of the drive. so now that the torque issue is out of the picture as much as i can do with it at the moment anyways i can move onto trying to come up with a reduction solution. a 3 to 1 seems like a good starting point. i have some ideas but need to design my end game while i wait for some belts and bearing, with a mechanical reduction the resolution gets 3 times better with the added torque from that i might be able to bump up the micro steps to 4,000 and get to a .0002 resolution which i think would be more than enough.

I still think the toothed idler idea has some importance with no reduction on that end and more tooth contact to distribute cutting forces better and mitigate backlash from things flexing under load. so i still think it plays into this actually since it has no reduction there the tooth count can be reduced to fit into a tighter space so that a plus i think the power supply could still factor in as well since the motors will be moving faster but that aspect is down the road still