What kind of failure my printer has?

Hello reprap community,

I have some iisues with my printer. but im not sure, what is it about.

maybe it is:


1. The Z- threaded rods

or.

2. Vref on stepper driver of my motors.

For the Vref its hard to find the right setting. I tried another stpper driver, just switched to A4988 (had DRV8825) but nothing changes.




One is printed in 0,15mm the other in 0,2mm.

Any idea?

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An unmöglichen Dingen soll man selten verzweifeln, an schweren nie. - Johann Wolfgang von Goethe

That looks like massive z wobble. Is your z rod bent?

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Nope, it is not bent.



Edited 2 time(s). Last edit at 01/25/2019 06:54PM by The_Maschinist.

With your machine, to achieve a correct print is impossible !
But don't despair, just build a serious one !

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Quote
With your machine, to achieve a correct print is impossible ! But don't despair, just build a serious one !

Thank you for your worthy responde.

So I have a DRV8825 stepper driver for two Stepper motors in use.

Thesea are the specifications for one of them:



Step angle: 1.8°

Number of phase：2

Insulation resistance：100MΩmin. (500V DC)

Insulation class：Class B

Rotor inertia：38g cm2

Mass：0.2kg

Wiring length: 700mm

Connector: XH (2.54mm-4pin)

Net weight: 232g

Shipping weight: 310g



Electrical specification

Rated voltage：5V

Rated voltage: 1.0A

Resistance per phase: 5.0Ω±10%

Inductance per phase: 6.2mH±20%

Holding torque: 300mN.m

Detent torque: 12mN.m

How much volts or amperage I should set on the stepper driver? (A4988)

Regards

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An unmöglichen Dingen soll man selten verzweifeln, an schweren nie. - Johann Wolfgang von Goethe

Depends on the MOTOR. Unless you hear it buzzing its probably too high. If its too high touch the motor after 5minutes of use, is it warm? or super hot? if super hot its too high.
I use 240-260mv for 0.4A motors.

Lookup Tom Sanladerers youtube video on setting voltages, he has a ton of details.

I also dont see a problem, that looks pretty dam good in the pic.

What is the pitch of the banding on the prints, and what is the pitch of the leadscrew?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

The size of the bend could just be a few 1/10mm and would easily produce that wobble. As dc42 said. Check the pitch of the rod against the wobble. If they match it is z-wobble.
Basically no z rod is absolutely straight. Usually you try to minimize the bend and compensate for the rest that is left by using an anti z-wobble solution (check thingiverse). Even if you were to get a perfectly straight rod, any small mishandling of the printer can bend it.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

You could remove the top plastic piece/bearing and see if the print improves. If it does, the leadscrew is bent, it doesn't take much of a bend to cause problems.

First check the direction of Z-axis motor, see if it was wrongly connected. If it’s correct connected, then swap the Z- axis motor with the Y-axis.

I agree with Stephen6309. Your Z axis is constrained at both ends, see if removing the top piece improves the print quality.