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Author Topic: Am I loosing Steps, and what should I do  (Read 13990 times)

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Re: Am I loosing Steps, and what should I do
« Reply #10 on: July 08, 2016, 12:37:42 PM »
I had the same problem but mine was the acceleration and deceleration of the steppers in the Motor tuning. I had not allowed time for the stepper to slow down. This was more pronounced in the Z axis due to the weight of the vertical column overriding the steppers. Mach counts the steps then moves on, if there is overrun being as there is no travel feed back it continues with the next command.  Just though I would throw in my thoughts.

Offline russh

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Re: Am I loosing Steps, and what should I do
« Reply #11 on: July 08, 2016, 12:38:44 PM »
I think the wires to the stepper drivers are on the right of the USB card???

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Re: Am I loosing Steps, and what should I do
« Reply #12 on: July 08, 2016, 12:39:54 PM »
I think the wires to the stepper drivers are on the right of the USB card???

Hi, what did you end up slowing your acceleration and deceleration down to?
Re: Am I loosing Steps, and what should I do
« Reply #13 on: July 08, 2016, 12:44:17 PM »
Trial and error, before you do anything put some slow feeds in and see if you loose steps if you don't it has time to slow down so keep adjusting till its gives you the correct position (manual measured)

Offline russh

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Re: Am I loosing Steps, and what should I do
« Reply #14 on: July 08, 2016, 12:46:24 PM »
Ive actually had this issue for some time now, and posted quite a few months ago, the recommendation then was to play with the motor tuning, and while it did start to stabilise at low acceleration and deceleration (although still loosing steps slightly), unfortunately it was unrealistically slow
Re: Am I loosing Steps, and what should I do
« Reply #15 on: July 08, 2016, 01:23:18 PM »
Not sure how the velocity V acceleration/deceleration works but I think you can maintain the velocity its just the amount of steps you use to decelerate. One other suggestion is to check you jib strips especially on the Z axis if they are to loose the head drops so fast it overruns your intended stop, I used a digital vernier clamped to the table and kept mechanically measuring the overrun until it stopped at zero. adjusting the jib strip helped with the fine tuning. Early hobbyist machines had a damper/assist shock absorber fitted to solve the Z axis over/under run.  If your main problem is with the Z axis that could be your problem
Hope this helps
Jim
Re: Am I loosing Steps, and what should I do
« Reply #16 on: July 08, 2016, 01:36:13 PM »
just checked and the acceleration/deceleration can vary from 0 to 0.25 seconds at the start and end of the axis travel whilst maintaining the velocity.
Re: Am I loosing Steps, and what should I do
« Reply #17 on: July 08, 2016, 01:51:06 PM »
Ok just looked at your video, if its just your Z that's loosing position that's the problem. I noticed you have a dampers fitted, is it still working correctly and then tighten up your jibs. If you overtighten them the Z will loose steps in the Z+ too loose it will be the Z - 

Offline russh

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Re: Am I loosing Steps, and what should I do
« Reply #18 on: July 08, 2016, 01:56:16 PM »
what are jibs?
Re: Am I loosing Steps, and what should I do
« Reply #19 on: July 08, 2016, 02:17:24 PM »
They are usually strip of metal inserted between the column and the spindle head Vee slides. They take up the slack in the wear of the slides. My Machin has 3 grub screws you adjust to push the jib out to adjust the possible play in the slides. Don't overtighten as you might put a strain on your motors. Jim