Printrbot LC issues

Troubleshooting talk for software

Printrbot LC issues

Postby kdiggity » 2015-Feb-Sun-02-Feb

I am having issues with getting my Printrbot LC to work, and I am out of ideas.

I had the printer up and running fine and then I ordered some upgrades. I bought the aluminum direct extruder and installed it with no issues, however the printer kept jamming. So after some research I found out that upgrade is only for the 1.75mm extruders and not the 3mm extruder currently installed on the Printrbot LC. So I replaced it with the original extruder gearing setup and then the extruder stepper motor did not work correctly. The stepper motor was sort of "sputtering", it would run very slowly when I pressed the extrude button on the Pronterface GUI.

At first, I thought the stepper motor was bad because it kept jamming. I ordered a replacement and installed it, but with the same problem. I then decided to swap the motor connection with another working axis (like the y-axis) and the extruder motor worked perfectly fine. I removed all the gearing for the extruder just to verify it wasn't locked, and the motor did the same thing without any gearing. So I thought it was an issue with the driver chip, so I ordered a new board. I installed the board (Printrbot Rev. D) and reflashed the firmware. It then did the exact same thing as before.

Next, I installed the new version of Pronterface and now I have an issue with x-axis motor (before it was only the extruder motor). Now, the x-axis motor will only move in one direction before reaching its end point. So I did the same check as before, swapped the motor connection to verify the motor, it works fine. I pulled out the DMM to check the end stop switches and the 3 switches installed are working fine (NC as default then NO when pressed).

I am out of ideas, any help would be great.

-Adam
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Re: Printrbot LC issues

Postby RetireeJay » 2015-Feb-Sun-06-Feb

Could it be that your steps per mm are drastically wrong? On the geared extruder, you should be in the ballpark of 550 - 600.

Also, try adjusting the drive current (on Rev D boards, there are potentiometers for this).
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
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Re: Printrbot LC issues

Postby kdiggity » 2015-Feb-Sat-01-Feb

I checked the steps per mm and it was in the range you mentioned, 550-600. I then tried adjusting the drive current but without any improvements.

Printrbot support responded and said there might be something wrong with the board. There recommendation was to just upgrade to the Rev F board.
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Re: Printrbot LC issues

Postby RetireeJay » 2015-Feb-Sat-08-Feb

You've already replaced both the motor and the board. I don't think Rev F is going to do anything for you that Rev D didn't do (except give you software control of the motor current). So I wonder about the wiring that goes between the board and the motors.

A stepper motor has two electromagnetic coils inside. In order for it to move correctly, there has to be a "dance" of sort where the current shifts back and forth between the different coils and shifts back and forth in direction. For example, for simplicity's sake we'll ignore microstepping and say that for clockwise rotation we start with all the current flowing in the plus direction through coil A, and later all the current is flowing in the plus direction through coil B, then current flows in the minus direction through A, and finally all the current is flowing in the minus direction through B.

If there's a poor connection for any reason which constrains the current through one of the coils to zero (or less than the programmed amount) then the motor will "stutter." It may move - but it may move in a random direction, and even reverse directions during a move. This poor connection could be due to a plug that's not fully seated, or a wire that's been pinched or pulled excessively.
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
"My next printer is..." Prusa i3 MK3, upgraded to MK3S
User avatar
RetireeJay
My next printer is...
 
Posts: 5003
Joined: 2013-Jan-Wed-13-Jan
Location: Greenville, SC
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Re: Printrbot LC issues

Postby kdiggity » 2015-Mar-Sun-00-Mar

I tried a few things the other night.

I checked around the wiring and noticed that one of the crimps for the Power Supply connector was pulled out (the 4 pin). I noticed that both power connectors would get hot. I pushed the crimp back in and then connected the 4 pin connector to the main connection (not the Y split).

I went back to my original PCB Rev. D and the issue with the x-axis went away. I suspect that the replacement Rev. D board that I bought had an issue with the x-axis drive circuitry. So onto the main issue.

The extruder motor was still doing the "stuttering" thing, so I adjusted the potentiometer on the PCB. The only impact this had was to amplify or attenuate the motor "stuttering" noise and did not correct the issue. I then decided to open the Repetier software instead of the Pronterface software. This asked me to download the latest version. After doing so, I checked all four motors and all worked perfectly. The issue with the extruder motor went away. I think something in the calibration for the Pronterface software got messed up.

So it seems to be working fine now.

Thanks for the help.
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