Motor vibration and faulty microstepping - Help needed!

Hi guys,

Here's a long message describing my issues with my first 3D-printer built. Sincerly hope you can provide me with some help!

I have a problem with my newly built and first Reprap Prusa i3. Its assembled and everything is moving. However, at the accerlation and feedrates needed for printing (3000mm/sec^2 and 500 mm/sec, respective), the motors vibrate very much at 0.4V from the Pololu. I can largely overcome this problem by turning the potentiator on the Pololu stepper drivers to minimum and it moves okay - however, this is hardly normal behaviour and suggests that something is going wrong.

Also, it seems that the motors do not properly microstep, although the jumpers are in place, as the steps the motors need to take pr mm is as low as about 5 rather than the usual 73 or so (funny coindicidence: 73/16 = 4.56). Does it make sense that the motor requires less voltage when run without microstepping? If it does, then faulty microstepping might be the cause of the motor vibration. I should say that this problem is only evident for the X and Y axis. The Z-axis is moving smoothly and the default settings using 0.4V from the Pololu.

With 1 axis is moving fine, I have ruled out the power supply giving too many or too few amps as this should affect all axis. I have ruled out the Arduino electronics. So what im ending up with is the soldering of the pins for X- and Y-axis microstepping jumpers. I dont think that this is likely as I havnt got any other bad solderings, so should be extremely unlucky to have 12 bad ones in close succession. Is there any good way to test if these pins are working? Can the problem be with pin assignment in the Arduino firmware? I don't think the Pololu Stepper Drivers themselves are the problem as I order new ones when I first encountered the problem. Wiring to the motor shouldn't affect microstepping so I dont think that is the issue either.

Have anyone encounter such problems before and have any other ideas how to troubleshoot?

Did you also rule out cooling, firmware settings and the software you are using? I have also heard there can be a problem with the data being fed from USB bandwidth. I had the same problem once and it was two things: 1 was the power setting of the motor, it was too low, the potmeter on the stepper driver had to be turned up a bit. But, here comes problem #2, since I am using 2.5amp stepper motors, and my stepper drivers are designed for MAX 2 Amps with good cooling, my stepper drivers would overheat too fast so I had to add a cooling fan that would blow on the aluminum cooling elements. Now it's working flawless.

I'm very new to the whole RepRap so troubleshooting the software is somewhat difficult, but I wouldn't expect that stock Marlin firmware is set to enable microstepping on Z-axis but not XY and to my knowledge I havnt change anything to do with microstepping. I don't think cooling is the problem, but I havnt ruled it out per se.

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at the accerlation and feedrates needed for printing (3000mm/sec^2 and 500 mm/sec, respective)

There is no "need" for 500 mm/s. In fact, I'm not aware of an extruder which can achieve such speeds just closely. The best ones I've heard of manage extrusion for about 280 mm/s head speed.

That said, printing at 20 mm/s or even slower will work just fine. I think you should approach the matter from the slow, reliable end of the spectrum and experiment with supersonic speeds like 500 mm/s later.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

I have made a temp. fix by changing the X axis to E1 and swapping Y and Z axis. The lack of microstepping seems less severe on the Z axis as this axis is threaded on an M5 rod and still require 160 steps / mm on full stepping. But the cause of the lack of microstepping is still escaping me

Well, what does a voltage meter say? You can actually measure those pins as soon as 5V is applied. Comparing to the other ones is a good idea.

And ... there's always a chance you Pololu is simply at fault. If all the others work on this axis but not the suspect one, replacing it might be advised. The electronic circuitry for each of the axes is identical, so you can swap stuff as much as you want.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Thanks for helping me out here Traumflug. What pins are you thinking about when you say I can measure across them as soon as the 5V is applied. The jumper pins for enabling microstepping?

Also do you know if the following settings in the Marlin firmware:

// For Inverting Stepper Enable Pins (Active Low) use 0, Non Inverting (Active High) use 1
#define X_ENABLE_ON 0
#define Y_ENABLE_ON 0
#define Z_ENABLE_ON 0
#define E_ENABLE_ON 0 // For all extruders

is concerning microstepper and if I can reverse the logic of the jumpers using these firmware settings?

Edited 1 time(s). Last edit at 05/05/2013 05:02PM by JesperG.

Those settings determine whether a motor is energized while idle. Its common to shut down Z motor while not moving Z to save power, since a screw driven Z cannot be reverse driven by the weight of the axis. Your firmware is set to energize all motors at all times, which uses a little more power but is better for print quality.

Microstepping is not under firmware control, the jumpers simply supply voltage to the microstep pins, or not. For 1/16th microstepping, all three MS pins on the pololu should read 5V. Meter all three pins, if any of them are low then you know where to start looking for a bad solder joint.