Tronxy Z Axis wont move (Melzi V2)

A friend of mine decided to dive into 3d printing and bought a Tronxy P802 m from GearBest. He got the thing together but we could not get the Z axis to move as it should.

The motors vibrate and the motor shaft visibly sort of "hammers" back and forth. When I assembled my Folger tech I had a similar issue due to driver adjustment needed. We tries adjusting the Melzi but had no luck. Here is what we did.

mechanically, we plugged each of the two z axis motors into the Y axis driver and verified they work properly as the y axis worked at the start.
With the Y axis motor plugged into the Z axis driver the Y axis would behave as the Z axis. So that tells me that there is problem with the Z axis driver or its configure.
Searching we found lots of posts about adjusting the v-ref on the driver as I had to on my printer initially.

The label on the motor indicates a Tronxy sl 42sth40-1684a-23 as the motors model number. As I read the data sheet, that motor is a 1.68 amp motor. The resistors are R100.
So If I understand the maths right it should be as follows:
1.68 X 8 X.1 = 1.344v
90% of 1.344 = 1.209v

That looked too high and I didn't trust it. I had read that the Melzi v2 should be between .4v and.8v on the driver.
We began with the Voltage at .4v
Stepped up the voltage by roughly +.1v and tried it until we reached 1.201v.

The behavior didn't change. The axis is running two motors, but from what I could find I didn't see any mathematical adjustment for that.

At this point were stumped. Any ideas?

This sounds like the usual max z feedrate being set too high in the configuration.h in marlin default firmware
ie
#define DEFAULT_MAX_FEEDRATE { 300, 300, 5, 25 }

try reduceing the 5 to a 2 and recompiling firmware

Quote
obewan
This sounds like the usual max z feedrate being set too high in the configuration.h in marlin default firmware
ie
#define DEFAULT_MAX_FEEDRATE { 300, 300, 5, 25 }

try reduceing the 5 to a 2 and recompiling firmware

Ill give that a shot this weekend when I see him.

Other than that, I am still concerned that I calculated the v-ref wrong. Can anyone verify it?

Its been a long while since my last post on this. I don't live near my friend so can work on getting this printer running too fast. We still havent got this printer running. I also have not made adjustments to the firmware too.

Attached is a video showing what the printers z axis does and some close ups of the board.

I haven't made any firmware changes because i have not had any luck finding instructions that i understand on how to properly upload the new firmware. Im sure there's some good guides out there but i haven't had any luck. I find that the steps don't line up or the tutorial videos are in a different language that i don't understand.

My initial thought was the z axis wouldn't move. I was a little wrong there. The printer will move the z axis down slowly while "thumping" and will not raise. Based on that and the video; would you think that reducing the max feedrate as suggested by

Quote
obewan
This sounds like the usual max z feedrate being set too high in the configuration.h in marlin default firmware
ie
#define DEFAULT_MAX_FEEDRATE { 300, 300, 5, 25 }

try reduceing the 5 to a 2 and recompiling firmware

Also, could someone post the arduino software settings i should be using for this board (board and processor)? I think its sanguino but im clueless on the processor

Edited 1 time(s). Last edit at 08/03/2018 06:57PM by eatumup.

Couldn't watch the video but sounds like what happens if not all the steppermotor wires are connected. Found that out when one of mine came loose.
Since it didn't move when you swapped motors check the controller board for dry joints, damaged tracks, missing pin (???).

Keep an eye on those green connectors for the heaters. They tend to melt. You can improve this by wiring the power direct to the heaters and just leaving the switched earth connection. That way you only use one terminal of the pair so it only has half the current and half the heat to deal with.

Melzi's are a PITA

You have to add the sanguino. support to the arduino IDE, as it doesn't come with it...

But before you go that that extreme Just adjust the max fead rate of Z in eeprom

ie send this to the printer

M203 Z2
M500

The first line sets the Z max feed rate to 2
the second saves this to eeprom. (as long as it replied ok)

If you still want to compile the firmware see this [dustsreprap.blogspot.com]
Its still the same for all newer arduino IDE's

as for what cpu is either a 644p or a 1284p

Look at the number of the large black chip
if its a 644p it crap, not enough flash memory to run current marlin,
even the 1284p is getting tight (can't enable all features)

Edited 1 time(s). Last edit at 08/07/2018 09:02AM by Dust.

Quote
Dust
Melzi's are a PITA

You have to add the sanguino. support to the arduino IDE, as it doesn't come with it...

But before you go that that extreme Just adjust the max fead rate of Z in eeprom

ie send this to the printer

M203 Z2
M500

The first line sets the Z max feed rate to 2
the second saves this to eeprom. (as long as it replied ok)

If you still want to compile the firmware see this [dustsreprap.blogspot.com]
Its still the same for all newer arduino IDE's

as for what cpu is either a 644p or a 1284p

Look at the number of the large black chip
if its a 644p it crap, not enough flash memory to run current marlin,
even the 1284p is getting tight (can't enable all features)

Thank you for the tip! I did not realize you could modify those settings without recompiling the firmware. I thought the M code lines just did temporary adjustments.

MCcarman, its a new printer.and we have pulled it apart i dunno how many times.If your right, then im inclined to believe that he got a bad board. I hope its not that.