Replacing with stonger steppers

[PaulS]

You are "Da Man" @csorrows. some things go without saying LOL

[Ron]

I second that.
Kudos to @csorrows for sure!

[Lockheed]

@csorrows ? - never heard of him

ha

[Lockheed]

I'm just messing with you. Welcome to the member side of things!

thanks thanks thanks - would have said that just once - but got yelled at - 20 characters ya know

[csorrows]

would have said that just once - but got yelled at - 20 characters ya know

Yup, one of the many measures the software has to discourage spam. We actually have not had one instance of a spammer on this forum that I am aware actually got to the point of posting anything.

[Keli]

I would like to replace my Z axis stepper on my FT-5 R2 with a larger Nema 17 like the one you mentioned in the text. Moving to a Nema 23 might be the better choice but it sounds like I would have to drill different mounting holes, so I prefer a larger Nema 17. My other question is what about the drivers for the stepper. Will I have to change the driver if I put in the larger Nema 17 stepper, or will just turning up the voltage be sufficient. K

[Walter]

Stepper
The large Nema17 steppers deliver quite some force (50-60 Ncm). Nema 23 are really larger steppers with also largers shafts (the ones you are using now won't fit anymore). I would stay with the nema17 ones unless you need really a lot of force to move the mechanics around. (High masses/friction)

Driver
The current a stepperdriver can deliver is limited. I use now TMC2660 drivers that can handle 2.5 amps without forced cooling (reed heatsinks and fans) and up to 4 amps with forced cooling. Proper PCB design is a must since they need to be cooled from the underside of the chip)
The standard Polulu's handle max around 1,5 amps. And even then you should be carefully the drivers.
Before that I used the TMC2100 drivers from Watterot

[Ron]

You could also just replace the lead screw pulleys with something larger, such as 36 teeth.
That way the motor's 20 tooth pulley would form a 1.8:1 reduction which would multiply the motor torque accordingly.
Because the Z motion is generally not all that fast the reduction in speed (or increase in stepping rate as you choose to view it) should not matter.
Just a thought.

[Dave]

You could also just replace the lead screw pulleys with something larger, such as 36 teeth.
That way the motor's 20 tooth pulley would form a 1.8:1 reduction which would multiply the motor torque accordingly.
Because the Z motion is generally not all that fast the reduction in speed (or increase in stepping rate as you choose to view it) should not matter.
Just a thought.

I was just going to post the same thing.

Replacing the pulleys on the lead screws was the first mod I did to my FT-5, during the initial assembly. I used 40T pulleys for a 2:1 ratio. The original 188mm belts were then not large enough, so I swapped them for 200mm belts which are the perfect length.

I don't print any tall vases, so the reduced speed of the Z-travel has never been an issue. When I convert to a single Z-stepper, I'm fully planning on keeping the larger pulleys on the leadscrews, as I believe it will be especially beneficial in that situation.

Don't forget to alter your steps-per-mm values in the Marlin config file after the change, and then do a calibration to fine-tune it. Rather than printing a calibration cube, I held up a precision ruler and moved the Z-axis "200mm", and used the difference between the actual travel and intended travel to figure out the correction factor for the Marlin config. That should be a lot more accurate than a printed calibration cube, as the calibration cube makes some assumptions on your first layer height that may or may not be correct, and using 200mm rather than 20mm reduces the impact of the precision of your measuring. It's one time where the ability to step the bed height up/down by 0.1mm comes in handy.

[Ron]

I have been running a single 1350mm belt from day one (both motors linked together) so all I would need to do to bypass one motor would be to add another idler.
I had considered 40 tooth lead screw pulleys as well but 36 seemed like a good compromise between speed, torque multiplication and pulley diameter (to me anyway).
It is "in the plans" for me to convert to a single motor setup with some reduction ratio in the near future.
It's not that I have any issues with the current linked setup (I don't) but I just like to experiment with things such as this.

Even for tall objects the Z motion rate is only a significant factor when homing from a great height IMHO.
It is so slow in stock form that even if you double that rate it is unlikely to cause any major issues.
And if you drive the motors from 24 volts, there is plenty of available step rate overhead to support a reduction of 2x such as yours.

BTW, something that has not been mentioned is that if changing to NEMA23 or NEMA34 motors the rotor inertia becomes much higher as well.
This may limit the ability of the larger motors to make rapid reversals or accelerations despite having potentially massive amounts of raw torque.
So unless you are planning on converting the machine to CNC machining later on, NEMA17 motors are still the way to go.

[csorrows]

Please don't bump a 7 month old thread. Because of the multiple replies though, I'll let it go.