Thread: Motorcalc spreadsheet errors
I can't find where I downloaded it from now, so I'll put this in General.
Here's what I found. Perhaps someone can check this over.
I deconstructed the spreadsheet and simplified it, getting the same results.
Then I looked at the equations.
I think I have found these errors:
1. rotor inertia conversion error. Should be 1e-7 conversion not 1e-8.
2. torque to accelerate the gantry should include the ballscrew efficiency.
3. <deleted> my error
Net result is I get different values for 2 of the 4 torque components.
Last edited by jimbo_cnc; 10-03-2015 at 03:17 PM. Reason: removed 1 non-error!
Last edited by JAZZCNC; 10-03-2015 at 02:21 PM.
Not completely different I would hope.
The acceleration torques are not much influenced by alignment.
Besides I would build accurately :)
I can't reply to that, because it makes no sense. 'Not completely different' does not equal 'exactly the same'.
This is the thread:
You have correctly identified the errors.
I made my own version, as a script posted here. I added calculations for efficiencies, friction in different parts and the pulley inertia's. The latter makes a big difference... after including those things I've found it to be a good match with reality.
Thanks Jonathan. The second link is same as the first, but if it's the octave script then I've seen that. I preferred to use the spreadsheet, but now I will pick up some of the equations from your script.
Any thoughts on nice values for acceleration for large wood panel cutting, or small plastic parts cutting?
Sorry yes, I got the wrong link:
By all means copy the equations or whatever you want...
Acceleration will limit the minimum arc radius the machine can move round whilst maintaining the specified feeedrate, so you can work it out from that.
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