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Ward indexer - Pololu DRV8825 Stepper Motor Driver

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philf:

--- Quote from: PekkaNF on February 12, 2018, 08:22:45 AM ---Those brass gears are pretty!

I am torn between ER32 collet for the stepper (need to build the whole taper part) and small three jaw chuck. I need to consider that tightening of the ER32 collet to nominal torque might be more than that harmonic drive is designed, on the other hand, ER collet would most likely produce good enough centering for most of the time.

Pekka

--- End quote ---

Pekka,

My 4th axis has a Myford spindle nose to take 2MT collets or a chuck or a faceplate. The spindle takes a c-spanner to counteract the tightening torque but there's still a risk of damaging the harmonic drive. What I should have done (and it probably won't be too difficult to retrofit) would be to fit a split clamp to prevent the spindle rotating whilst tightening or undoing any attachments.



Phil.

PekkaNF:
Thank you Phil.

That is a problem I have to consider too.

I got a Chinese driver from the mail and proceed to test that one.

Tehnical spesification claims it's perfect:
https://www.banggood.com/TB6600-Upgraded-Version-32-Segments-4A-42V-5786-Stepper-Motor-Driver-p-981997.html?rmmds=search&cur_warehouse=CN

But when I cross referenced the spesicication and TB67S109AFTG data sheet I noticed that word "upgrade" is very missleading and they have kept overly optimistic TB6600 numbers there to attract noob buyers. I don't even go trough the mistakes, it's all lies.

Anyway I got it, hookes it up to 16VDC/7A PSU and signal generator. Motor is NEMA 17 1,7A 200 step model.

Motor sound sick, moved erratically and hardly any moment on any mode. Also the motor current was all over the wall.

The front cover DIP settings have something wrong, I don't think same settings produce differet current limit.

Also motor connection differes on PCB and cover.

Found that current sense resistors had cold solder on the other end and unsoldered from the other end. Also the capacitors were pretty much unsoldered.

Pretty sure it was completely untested.

chipenter:
Ive bought two TB6600 from Bangood no problems , but had a problem with Arduino megga board complained and they sent me a new one , just had to wait tree weeks for it .

JHovel:

--- Quote from: PekkaNF on February 18, 2018, 04:45:41 AM ---.....
Pretty sure it was completely untested.

--- End quote ---

There is no Chinese word for testing....

Actually, it is more complicated and sad than that: when Chinese workers find a fault on the production line, they are indeed required to report it so that things can be done to fix the problem. However, that means invariably 'dobbing in' a person up the line - maybe your best friend working next to you. The person who made the mistake then gets their pay cut to pay for the amount of their labour on the dud parts. So everyone keeps their mouths shut and passes the dud parts along the line as if nothing was wrong.
Until there is a change in attitudes of making people responsible for removing dud parts from the production line without either incriminating someone or the person who made the mistake being trained better instead of losing pay, there will be no reliability in quality of Chinese products... That will take another generation I'm afraid.
What would you do if you were working on the production line in China today????

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