Geeetech

Hello everyone,

A friend of mine asked me to help her to make her 3D printer work. It's an i3 Pro B and never worked after the build.

The first problem is that the Z-axis motors seems to weak to be able to handle the small friction in the threaded rod (i'm even able to stop the motors by hand!).
The PSU is set on 220V, so this is ok. I don't see what else I can try.

I don't know that printer so maybe I skip something obvious :)
One detail that can be important: the building was made by her father (who could'nt read the manual in english) and her sister (who translated for her father). So i'm not completely sure they did the thing right.

Do you see something I could try to solve thoses problems? Thank you! :D

[quote]The first problem is that the Z-axis motors seems to weak to be able to handle the small friction in the threaded rod (i'm even able to stop the motors by hand!).[/quote] Yes, you can generally stop a stepper motor by hand, it doesn't work the same way as a DC motor.

Make sure you level the X-axis properly. The height from the Z motor plate to the leadscrew nut should be exactly the same at the right and left hand sides of the printer. If not, the nuts will bind on the screws and the motors will stall. The threaded rods should be as straight as possible as, again, a bent rod can cause the nuts to bind and the motors to stall. (you'll hear a clicking noise if it stalls)

You can also increase the current through the motor windings by adjusting the z-axis driver, there are instructions within the forums but I'm not sure where at the moment. Check for binding before pursuing this option as turning the current up can cause overheating and component failure if there's too much friction to overcome.

Play Bonny!

Soadyheid.

Apparently, there is only 4 of 5 driver motors A4988.

Do you think it could it be the origin of the problem?

[quote=Potamogale post_id=83769 time=1523668066 user_id=65162]
Apparently, there is only 4 of 5 driver motors A4988.

Do you think it could it be the origin of the problem?
[/quote]

It is a problem that the printer, like many other 3D printers, just connect the two Z motors in parallel. This is fundamentally wrong design seen from the electrical engineering perspective. You should NEVER connect stepper motors in parallel, you MUST use one driver for EACH stepper. This can be solved fairly easy in four different ways.

1. Configure Marlin so that it uses the second extruder motor as Z slave. You must be familiar with Marlin and Arduino programming to be able to do that, but if you are familiar then this is very simple, modify, compile and upload the firmware and just move one of the Z motor cables to the second extruder connector.

2. Use a sort of a "piggyback" solution, solder a second driver in parallel to (on top of, or via wires) the one plugged into the board. Just be careful not to connect the motor contacts together. This needs some soldering and electrical knowledge, but only takes a few minutes to do.

3. Use a CNC shield and wire the X, Y and Z to this shield through an adapter. This has the advantages that now you can power the X, Y and Z motors with 36V instead of maximum 24V, so you will get a speed increase. You will also get a nicer installation than the piggy back solution. The disadvantage is that you need to buy a shield. I bought this one, which I am using in my next DIY design:

[attachment=0]expansion top.jpg[/attachment]

It is a fairly simple job, but once again, you must have some electronics knowledge and soldering practice.

4. A purely mechanical solution. It is the most complicated solution, since it requires rebuilding the printer. One Z motor is better than two motors in parallel connection. I modified my printer this way, and I promise you, it is now a very speedy and accurate printer.

https://youtu.be/aq4qBsM0jPs

Just have a look and decide what you do.

Of course, you can also increase the driver current, as been suggested, but it is not going to be much better, even if it may work. Also, the driver will get considerably hotter, so make sure you have a good fan cooling the drivers. Another thing is that you should not have friction at all, the screws must turn easily and the X beam must be aligned (left and right screws).