Choosing on a stepper Motor for new printer

Hi,

I'm about to build my 3rd printer, even though I'm getting quite some experience already I'd like to hear some other advices regarding stepper motor.

I currently have a customized Prusa i3 printer and a customized Wilson II printer.

I currently run both printers with 0.9° step NEMA 17 motors (4200g.cm holding torque) for X and Y axis, I did run the i8 with 1.8° step NEMA 17 motors before, beside noise improvement I didn't see significant quality improvement.

I have make numerous experiments, and I have made the following observations

Microstepping seems to have very little influence on print quality at 1/4, 1/8, 1/16 or 1/32 microsteps @ 0.9° or 1/8, 1/16, 1/32 @ 1.8° below that noise and vibration will affect the print.

the belts have a high impact on print quality, Neoprene/glass fiber belts (standard black belts) give much more vibrations than Polyurethane/steel core belts (White belts), however the later might have other troubles due to their rigidity and tension force necessary, these are the one I use on the Wilson II but I had to strongly reinforce the structure.

I have made movement tests up to 400mm/s with the Wilson II and I didn't notice losing steps (1/8 microstepping with 0.9° motors)

Now my new printer will be a different design, it'll be a 40x40x40cm 100% metal structure cube, printing platform will be moving on the Z axis and X carriage will be moving along Y axis (I considered a corexy but rejected it). Since I expect much higher rigidity than my current printers and I might want to have a heavier carriage (converting to CNC maybe), I'm thinking about using NEMA23 motors.

I have options to go with 1.8 or 0.9° motors, I can get 23HS7628 1.8°/step motors with 18.9Kg.cm holding torque , 23HS5628 1.8°/step motors with 12.6Kg.cm holding torque or 23HM1430 0.9°/step motors with 18Kg.cm holding torque. I would use TB6600 drivers at max 1/16 microstepping.

Since motor prices are quite different, I'm curious to have a second opinion. I think the 0.9° will probably not bring any quality improvement since the limitation will still be mecanical, and anyway since the motors are much stronger than nema17 I can go further in useful microstepping. I can get a sweet deal on the 12.6Kg.cm motors, and I'm hesitating with the 18.9Kg.cm ones (1.8°) which are 50% more expensive.

Or... should I just stay with cheap Nema17 motors?

Any thought?

Control sequences of Stepping Motor

There are four types of waveforms, or sequences, through which stepper motors are driven. These are:

1. Wave drive;

2. Full step drive;

3. Half step drive;

4. Micro stepping – we will present this method and when it is employed in another article.

Wave drive
By using this method, a single phase of a nema 23 stepper motor is energized at a time. If we refer to figure 1 below we can see how a stepper motor is driven. We can observe that there are 3 phases (f=3), AA’, BB’ and CC’ and 2 teeth (z=2) North and South. The rotor will perform full steps, with the angle: Theta=360/(f*z)=60 degrees.

Full step drive

When the rotor of the motor depicted in figure 1 reaches position 3 we can see that the motor can also be driven by having two phases energized at the same time. The rotor will perform full steps, according to the formula above, aligning itself exactly in the middle of the angle between the stator poles, North and South. This drive method provides full torque of the motor.

The sequence will be:

AA’BB CC’

1 1 0

0 1 1

1 0 1

1 1 0

Half step drive

This method implies alternately powering either one phase or two phases at a time. The rotor will align itself either with stator poles, as in wave drive, or between them, as in full step drive. In this case the rotor will have 30 degree step angles.

The sequence is:

AA’BB  CC’

1 0 0

1 1 0

0 1 0

0 1 1

0 0 1

1 0 1

1 0 0

The direction of rotation in either case is determined on how the sequence is started. Sequences presented above assume clockwise rotation when applied starting from the first row and counter-clockwise rotation when started from back to front.

So, if we look at figure 1, depicting a 2-phase bipolar nema 42 stepper motor like the one we want to control, we can determine the control sequences for each method mentioned above. It can be observed that such a motor has 4 leads, corresponding to 4 pins of an output controller or interface. So the sequences will be:

• Wave drive: 1000 0100 0010 0001;

• Full step drive: 1100 0110 0011 1001;

• Half step drive: 1000 1100 0100 0110 0010 0011 0001 1001.

See more:
http://www.techsite.io/p/930613
https://yanguilai.katari.be/DcwbY8sy