Thursday, 16 March 2017

Stage 5 - 101superhero

I don’t expect a 3D printer selling at USD49 in kickstarter (Now at USD99 in their eshop) can provide decent print. However the 28BYJ-48 just can’t do the job. You can find more information about the 28BYJ-48 from https://grahamwideman.wikispaces.com/Motors-+28BYJ-48+Stepper+motor+notes.

101hero team knew the problem, instead of using the standard 1/64 reducing ratio motor, they use a special built 1/32 ratio motor to reduce the steps per mm from 975 to 539. As the torque of the motor will drop dramatically at high speed, the max speed of 101hero stock motor is 14mm/s. Since it is impossible to get the 1/32 motor in the market, some users replace their broken motor with 1/64 one but need to reduce the print speed to 6mm/s to get the acceptable quality.

Luckily, 101hero is using the controller with bipolar stepper motor driver A2988We able to replace the 28BYJ-48 with NEMA stepper motor without changing the electronics. 

To replace the 28BYJ-48, you need an adaptor to mount the NEMA motor to the pylon. There are two type of NEMA motor widely used in 3D printer. They are NEMA 14 and NEMA 17. NEMA 14 is smaller in size and in general NEMA 17 is lower at cost.

Download NEMA 14 Adaptor from here
Download NEMA 17 Adaptor from here

I used to use the adapter design by Dan Delaney to mount the NEMA 17 motor, it is sample and work. The only drawback is printer only stand on the three motors that is not very stable. I has to add a base to the pylon to stabilized the printer. 

Eventually I combined the design from Don Delaney and Matt Dolan into an adapter in one piece.

To replace the motor, first release T2 belt, then you can easily remove the 28BYJ-48.
After release the T2 belt, release the two screw of the 28BYJ-48 and take it out.
Remember to put the two screw back after took out the 28BYJ-48
Take out the timing belt pulley from the 28BYJ-48 and install it to the NEMA motor and mount the NEMA 17 to the adapter with 4 x M3 screw
This is how the adaper mounted to the pylon
There is two holes at the bottom of the pylon, use two short screw to join the adapter to the pylon

You can use the 6 pin to 4 pin cable that came with the motor to connect to the 5 pin connector in 101hero. Please refer to the below picture for wiring method. Follow the pin location not the color as the color arrangement is not always the same. The 1-3-4-6 pin on the motor side is mapped to 4-3-2-1 pin on the controller side.



Remember to insert the M92 command before printing or moving the arm, otherwise, the controller will use the default setting for the 28BYJ-48 that is 5 times faster than the standard NEMA 1.8 degree motor. I am using M92 X101.4 Y101.4 Z101.4 E95.2. You may need to calibrate the setting and I am using the XYZ 20mm Calibration Cube as the reference.

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