G76, Troubleshooting needed!

Hi,

Got a suggestion for an encoder:

HEDSS - IHU4808
would this be a good choice?
What resolution should i choose 1024ppr? 2048ppr? (Mesa card is 7i76E)




Br Victor

That design looks difficult to use with a lathe spindle?

I would suggest one either with a shaft for use with a belt-drive, or with a large through-hole.
Maybe one of these?
www.aliexpress.com/item/Good-quality-GHH...-CE/32852630034.html

Hi Andy.

Today the encoder is mounted below the spindle shaft with a timing belt 1:1 to the spindle shaft.
no mater what encoder i get i think i have to make a bearing housing for the timing pulley shaft and attach the encoder to that shaft.

i'm more worried if the encoder it'self is a good choice and what ppr i should get.

Edit: found a couple images of the stock encoder online, added them to attached files

Br Victor

No eBay APP ID and/or Cert ID defined in Kunena configurationIf you get an encoder with a shaft and its own bearings then there is no need for anything more. For any sensible amount of encoder belt tension the load on the encoder bearings will be tiny.
This:
Appears to be one of these:
docs-emea.rs-online.com/webdocs/1398/0900766b813988fd.pdf
So it is an ABZ encoder (quadrature + index) with differential output (Which I think it optimal for the 7i76)

Agreed that would be the easiest way but i think the pulley is like 100-120mm in steel or alu and the belt is 12-15mm wide, and if i look at the encoders in the price range i'm looking in (max 100$) i'm a bit scared to let them handle that pulley.

I have looked at those Omron nock-offs do you know if they are any good?

Br Victor

Victor wrote: Agreed that would be the easiest way but i think the pulley is like 100-120mm in steel or alu and the belt is 12-15mm wide, and if i look at the encoders in the price range i'm looking in (max 100$) i'm a bit scared to let them handle that pulley.[/code]
Look at the specs of 6mm bore ball bearings:
simplybearings.co.uk/shop/p2624/Major-Br...mm/product_info.html
They are rated for 500N (50kg) and 52,000 rpm. There really isn't any cause for concern.

I have looked at those Omron nock-offs do you know if they are any good?

I have some, but didn't use them as I accidentally got no-index versions. So I can't really comment.

The encoder you have looks like it should be OK, though. Is it possible to move the sensor relative to the wheel? A radial movement would alter the slot-pitch as seen by the sensor and might reduce quadrature error.
Are those reflective or transmissive sensors?

It might also be interesting to change the Z axis acceleration limits.

Hi, Well i don't really know if i can adjust it or not, i have not opened the encoder myself.

I figured since the encoder is almost 30 years old and i only have A & Index pulse i might as well change it, rigid tapping would be useful.

Are there any numbers in the specifications on the one i suggested (HEDSS - IHU4808) that i should be concerned about?

And what would be a good ppr count?

Br Victor

The optimum encoder count depends on the spindle speed and the Mesa card counting rate.

Are you sure that the encoder only has A + Z? The photo shows enough pins for 0V, 5V A B Z. And the sensors look like they could be dual-channel ones.

There is an adjustment pot on the encoder board, does that improve the mark/space ratio?

Ok,

I have 6000rpm as max rpm.
Mesa 7i76E

Well i might have a different one than the photo, the one on the photo might be later model.
i have four wires, V+, GND, 1ppr and 150ppr signal.

Br Victor

Reckoning that a 7i76 can handle 2MHz counting (it can go higher with the filter turned off).
6000 rpm = 100 RPS.
So you should be OK up to about 20,000 counts per rev.
Anything in the 1000 to 5000 counts per rev range should be fine.

Did you note that the 7i76 works best with line-driver type encoders? (Like the one I linked to)