Thread: Backlash , Any suggestions ?
The easiest way to measure the backlash is with a dial indicator and manual jogging. There are a lot of vids on youtube about it.
To find out if you had lost steps, just program and run in the air a straight line for each axes and the same speed you did the circles (with a higher Z) and try to stop the movement by grabbing the Z axis with your hands and determine how much force is needed for the motors to start skipping. You can even measure it with a hook scale.
The Following User Says Thank You to paulus.v For This Useful Post:
There is one thing you can try that does happen and will cause a missed step on each directional change.
This happens when the Step Pulse is sent out on the wrong pulse edge to what the drive is set to expect. Resulting in the drive sees the Step pulse at the wrong time and one step or micro step is dropped on every direction change due to the fact step pulse comes before the direction pulse so it gets dropped.
This is easy tested by knocking some G-code to move each axis back n forth 1000's times then returning back to start. Make a mark before running and see if it returns to same mark after run the test.
If it doesn't then you have the Pulse edge set wrong. Easy fixed by changing the Active Lo setting in Motor tuning. ( Or some drives have a setting for this) This will then make your motors turn the wrong way so you'll have to go into Homing and limits and use the Reverse axis option.
People Often make the mistake of thinking swapping the Dir active low is for changing axis direction when it's not. It does but it's not correct way.
Last edited by JAZZCNC; 11-10-2015 at 01:36 PM.
The first thing i did was go around and check every relevant nut bolt and coupler ! They all seemed to be fine. But no harm to have another look.
Rack and Pinion are 20' pitch, pinion moves 94.2mm per revolution. Geared down by 5:1. Ball screw on Y is a 2010 its ran from a belt 1:1 (2 no 34-5M-15mm (TL) Timing Pulley) and on Z its a direct drive 2505,
I was having some resonance issues at slow speeds when i first started cutting so i upped the microstep setting on the driver and it helped a lot. I upped it to 4000. When i talked to company they suggested putting it back down to 800. I will try this on Monday.
Im pretty sure its not a binding issue. I can jog around no hassle as 10/12 m/min. Although maybe that could change under load. I need to eliminate it 1 thing at a time.
Acceleration is set to 100 ( this is low i think ) Max speed is set to 5m/min.
If i cut below 2.5m/min i have no issue its when i go above this the problem starts....
Last edited by philgiggins; 11-10-2015 at 01:42 PM.
Problem solved... I think. I have a breakout board which can be set ro different states with jumpers. I set it to special mode which was apparently for leadshine drivers. I changed it today to normal mode. I also changed the microsteps to 800 and retuned all my motors.
I then test cut a piece for a job im doing. I was able to up the feed rate to over 5m/min and i can now rapid at 12m/min.
So happy days! Thanks to everyone who replied.
any chance of showing us your breakout board?www.emvioeng.com
Machine tools and 3D printing supplies. Expanding constantly.
Thanks, here is a link to it http://www.sorotec.de/shop/CNC-Contr...anced-PRO.html . Its an Advanced PRO from Benezan electrics. I bought adaptors for the drivers also. This made wiring a lot easier.
Heres the options i had
• Stepper motors, no VFD speed control: 4-5, 7-8
Relay 1 controlled by LPT pin 1, no PWM, current reduction by pin 17, watchdog signal at pin 16
• Stepper motors with VFD and analogue output: 3-4, 5-6, 7-8
Relay 1 on if PWM>10%, PWM at pin 1, current reduction pin 17, watchdog pin 16
• Servo drives and VFD: 4-5. 6-7
Relay 1 at pin 1, PWM at pin 17, no current reduction, watchdog pin 16
• Special mode for Leadshine stepper drives: 4-5, 6-7, 10-11
Relay 1 at pin 1, PWM at pin 17, enable signal instead of current reduction, watchdog pin 16
I used the last one , now i am using the 2nd one.
The Following User Says Thank You to philgiggins For This Useful Post:
Erm would be interesting to know what that "special Mode " does or why.? . . . I've checked the Manual and no mention of it other than settings.!
Never had any problems with Leadshine drives to be honest but I'm very fussy when it comes to BOB's so only use PMDX which are high quality or better still Cslabs controllers which don't have one.!
I dont know exactly what it does but i think i can explain why i was having the problem i was having. I was using cnc all day today and yesterday and the motors never got more than warm. Before this if i ran any sort of a long programme the motors where getting hot. This might explain why when i tried to go faster the motors overheated and then stalled causing the big steps in the cut i was getting ? So whatever the special mode does the drivers and motors dont like it, or they should be set as certain way. I might email Sorotec and see can they offer any information.
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