Analog DC servo very big response delay

Hi,
I am going similar path with WF 31 CH. Can you share your setup, please?
Did you get it all sorted?

thanks
Josef

Hi Josef,
This is mostly a mechanical problem with a friction in hard linear slides. You have to overcome sticking which translates into this following error. I firstly though that this can be some issue with analog input filter inside the BOSCH regulator card, so i reduced the time constant of this RC filter, but it didn't help. Adding another feed forward term again doesn't help much, but makes machine more jerkier. With those machines the only viable way to reduce this error is to reduce acceleration. Other possible way is to integrate some low friction polymers into the slide, this was done on our machine on Y axis due to mechanical wear. This did reduce the following error by really small value.
Also you should check the ball screw, those machines are old and very likely you may need to replace the balls and re tighten the ball screw

Hi,
thank you for the info much appreciated. I am actually thinking if it was possible to replace those monster analog servo drives with something smaller. I am having bit of a space issue that is why I would like to use some different smaller servo drivers.
How do you drive the main spindle motor have you kept the original drive?
How do you all drive it do you drive it direct from PC or I am actually thinking of using Mesa card.
And last question I am having hard time finding manual for it I have electrical manual which is getting bit useless with all the changes. Could you share the manual with me if you have one?

thank you
Josef

Hi Josef,
This was a complete retrofit with Mesa 6i25/7i77+7i84. Spindle drive was replaced with Delta VFD, as well as the spindle itself for some aluminium work. We got the original spindle motor running with this VFD but high frequency noise from it is unbearable no matter which PWM frequency was selected. Possibly this motor is not well suited for modern VFD. Anyway it's unused now.
If the original BOSCH servo drive is working, there is virtually no reason to change it on such machine. Some manuals for it: www.dropbox.com/sh/8owpaoax31ehf2x/AACji...older_nav_tracking=1
As for the HEIDENHAIN linear scales, a custom made interpolator based on iC-TW28 chip is used, unfortunately I don't have schematics for it You may find a luck some EXE box, or try to figure out iC-TW28 yourselves.
If you have paper electrical schematics for WF31CH, that's all we needed for the retrofit.

Hi,
Thank you, You are wealth of information. I am going to test the spindle motor but the biggest problem is in my case that it draws way too much power I don't have fuses heavy enough to run it all with this monster motor. I should have VFD here this week and will give it a go. if it does not work I will replace it with different (smaller) motor anyway.
The only valid reason for me to change the servo drives is space, I am very limited. I will look into those drives this week too and if I can get the originals going and find room for them I will try to keep them.
Thanks for the ic-tw28 info I wish I knew that few days earlier I already got EXE boxes. But if they fail me I will definitely look into those chips.
I do have electrical schematics I already stripped it down and I am ready for retrofit just need to decide on those drives and decide what mesa boards to get.
I don't have any user/ mechanical manuals I got manuals for wrong machine when I got it. If you have those I would really appreciate them too. I don't even know where you put some oil in and what type.

Thank you very much for your help
Josef

Be aware that original Siemens motor draws almost 14 Amps in no load condition.
Still don't understand the problem with space in that case) As for retrofit you are likely to remove original TNC 155 and put Mesa cards and PC inside it's chassis, as all the control wires are going to TNC 155. Do you want to strip off the electrical cabin completely?
We are not using original lubrication oil for slides, but some replacement designed specifically for them with viscosity of ISO 150. Machine should have Willy vogel lubrication pump.