Index Homing odd offset

Glad you got it working.
What drives and encoders are you using if I may ask?

Yes, for this machine we have installed HNC servo system model HSD2 very convenient and cheap they are made by HNC electric China, also the inverter is HNC model HV590 using a Mesa 7i76E & 7i85.
The encoders I'm using the encoder output that came with the servo drivers.
Best regards.

Hey Guys

Not to dredge up an old topic. Just a questions to the geniuses out there. The new (2. manual does NOT mention the need for Stepgen in velocity mode or closed loop to have Index homing. Is velocity mode etc still required?

Secondly, If I want Absolute Encoder Homing, do I need closed loop (I would venture to guess so).

Thanks a ton for the help.
Clint

CNCCustoms wrote: The new (2. manual does NOT mention the need for Stepgen in velocity mode or closed loop to have Index homing. Is velocity mode etc still required?

Velocity mode is generally only used with stepper systems if you are using Mesa hardware. And I don't think that any of the Mesa spcs go in to that much detail of HAL setup.

Secondly, If I want Absolute Encoder Homing, do I need closed loop (I would venture to guess so).

I am not really able to imagine a system that has absolute encoders that isn't closed-loop anyway?

Thanks Andy

I am using Mesa hardware. What I was referring to is that according to other posts elsehwere, to be able to use Index homing, stepgen needs to be in velocity mode and closed loop. Is this still the case? Or can I use the index Homing while in open loop (with the encoder connected in hal of course)

I want to use the absolute encoders for homing. Is there a way to add a permanent offset to the absolute encoder values read by Linux which can thus negate homing? Perhaps the position file can be updated with the current encoder value and offset before homing. This is specifically due to the fact that my Z may move as the brake is applied. My home switches are not as accurate as I would have hoped for.

Strange questions I know.
I'm sorry.

Thanks so much for all the input you give. Ive solved COUNTLESS issues just by looking through the posts and your replies usually nail it for me. I just have not been able to get reliable homing so was hoping to make use of the encoder without having to go through the trouble of tuning for closed loop.

There has been a recent tweak to the Mesa stepgen, and it's driver, that allows homing a stepgen to index.

linuxcnc.org/docs/master/html/man/man9/hostmot2.9.html#stepgen

Shows that the Mesa stepgens have an index-enable (and probe latching).

Only in Master at the moment.

Thanks Andy

I'm reluctant to move to 2.9 just yet on my machine. I guess its time to put my big girl pants on and tune for closedloop control.

Hey Guys

I completed setting the machine up in closed loop over the weekend. I have it setup using step gen in Position control. I even got index homing working. This morning when I homed the machine, Z was off by 3.4mm which is very strange! My ball screws are 10mm screws so its not a multiple. When I subsequently home the machine... it again repeats to 0.002mm as it did over the weekend (but at its current 3.4mm offset from what it was over the weekend)

Am I getting this result because I have it set up in Position control mode? My following error is less than 0.01mm at rapid. Test cuts were great and on Dimension.

I am at a complete loss and would love some help please?

What am I missing?
Any help would be greatly appreciated!

CNCCustoms wrote: This morning when I homed the machine, Z was off by 3.4mm which is very strange!

Could this be a tool or coordinate system offset?

How have you determined that it is 3.4mm off?

It seems every time I restart the PC and home then things change.