I've been using a set of Shinano Kenshi STP-42D3018 stepper motors for the X, Y, and E motors in my RepStrap that are 8.8V 0.64A 11.6Ω bipolar and 5.2V 0.9A 5.8Ω unipolar. I've been using them as unipolar motors because the bipolar resistance of 11.6 Ohms is apparently too high. They've actually worked quite well, especially the XY, with 47 oz.in. of holding torque. But it seemed like a waste to use these bipolar motors as unipolar. With so many different voltage ratings for stepper motors it also seemed like a waste to use 5.2V if there are motors using 3V and under. Plus the extruder motor was getting pretty warm; so if nothing else I wanted a stronger bipolar motor for that.
So I found a new set of motors that seem more ideally suited, especially for the E motor. These KL17H247-168-4B motors are bipolar with 62 oz in. torque. They use 2.8V at 1.68A 1.65Ω, which is a bit less current than 5.2V 0.9A 5.8Ω (or is it?). I installed one as my E motor and it works great, barely gets warm after hours of printing.
So I just installed one of these as the Y motor and tuned the stepper driver to the point where the motor has a reasonable amount of torque. But a couple of things are apparent right away. First, it seems to need me to dial up more current from the stepper driver than the 5.2V unipolar motor did. So that's interesting. And the motor is significantly louder than the previous motor, to the point where I'm thinking of going back to the old motor even though it's got a slightly higher power rating and gets a little warmer.
So I have a couple of questions...
So I found a new set of motors that seem more ideally suited, especially for the E motor. These KL17H247-168-4B motors are bipolar with 62 oz in. torque. They use 2.8V at 1.68A 1.65Ω, which is a bit less current than 5.2V 0.9A 5.8Ω (or is it?). I installed one as my E motor and it works great, barely gets warm after hours of printing.
So I just installed one of these as the Y motor and tuned the stepper driver to the point where the motor has a reasonable amount of torque. But a couple of things are apparent right away. First, it seems to need me to dial up more current from the stepper driver than the 5.2V unipolar motor did. So that's interesting. And the motor is significantly louder than the previous motor, to the point where I'm thinking of going back to the old motor even though it's got a slightly higher power rating and gets a little warmer.
So I have a couple of questions...
- Is loudness the result of a combination of factors that are hard to gauge? Bipolar motors are supposed to have more torque at lower speeds. Does this extra power come with additional vibration as a consequence? Are bipolar motors just generally louder?
Unipolar motors are supposed to be better for high speed. Am I better off having unipolar motors in my XY anyway, where torque is less important than speed?
When it comes to stepper motor current, sure I can run three 5.2V / 5.8A stepper motors and the printer will be a little more quiet, but am I wasting energy?
What values matter when considering compatibility with RepRap electronics? In stepper motor spec sheets they give helpful values like Driver Vref (2.4V), Inductance/Phase (2.4mH), voltage of course, and Current/Phase (0.9A). How do these values relate to the voltage and signals that stepper drivers are sending out?
As a buyer of stepper motors, how can I know ahead of time whether motors might be loud? Are certain voltage ranges louder than others? Are bipolar motors going to have more vibration than unipolar motors?
How can we reduce the loudness of stepper motors? Hanging the printer from the ceiling helps! But short of total isolation, and within the typical RepRap power range, how is motor noise best kept down?
