Hybrid steppers or servos?

Before you rush out and spend money,
1. what is the maximum voltage your stepper drivers will handle?
2. What is the power supply voltage you are using? how many amps?
3. What is the sum of the motor amps (eg 3 x 2.8 amps or whatever)

In my experience, increasing voltage can solve torque related issues. (eg. Doubling voltage can quadruple torque)
Don't spend up big on motors to still find other areas that are the cause..

The drives you have selected are still only 50 volts...

Hi Rodw, nice to see you .
What I have right now are adjustable 0-80V 6A power supplies, as you advised me in another thread, you among them. I have four, one per driver, X and Z at about 60V and the two with Y at about 72V since they are the ones that must move more weight and work more, I understand. There are four motors at 3A each, 12 total masters.

I just wonder if swapping out for similar motors with similar torque will achieve what you want. If the dimensional accuracy problem is caused by missed steps, then do the new motors have enough grunt to overcome step loss when called on?
Or will they just tell you when you have a problem?

Great question rodw. Let them tell me when they lose steps, I hope so at least. If they would be able to overcome ... You mean that they are not at all suitable for the machine in terms of torque, characteristics, etc?

How can I know that, is there any kind of formula or calculation that is applied when choosing engines a grandes rasgos? I would love to know it is something I did not do in its day and it is where I should start, it will come in handy in the future.

I have found a thread from the fellow thefabricator03 in the plasma section explaining and developing the math for the choice of motors that I understand is applicable.

RoberCNC wrote:

Great question rodw. Let them tell me when they lose steps, I hope so at least. If they would be able to overcome ... You mean that they are not at all suitable for the machine in terms of torque, characteristics, etc?

How can I know that, is there any kind of formula or calculation that is applied when choosing engines a grandes rasgos? I would love to know it is something I did not do in its day and it is where I should start, it will come in handy in the future.

I have found a thread from the fellow thefabricator03 in the plasma section explaining and developing the math for the choice of motors that I understand is applicable.

I don't know if they are suitable or not. Just that you had issues which could be a result of lost steps.

The calculations are complex and most publicly available models contain errors. thefabricator's maths is not bad. We have done some modelling but for plasma machines with rack and pinion drives which I guess won't help you.

The bridge will not be more than 50kgs and the motors are 2.8 Nm, according to the mathematics of the example with 140 kgs it would come out 0.9 Nm. I also tested his day by putting extra weight on him and he was moving well. Another thing is the cutting forces that do not involve them and vary according to machining and accelerations, which if you could review and lower.
So ... Now I have no idea what to do.
I think I have to do a lot of math.

An acceleration in the INI file of 18mm / sec² makes any sense????

if you are getting lost steps there is a good chance this is something you can hear happen when it happens. the lost steps happen during rapid moves when the torque of the motor is at it lowest.

if you have a dial indicator you could set a zero on one side of the axis and make a test program to rapid from one end to the zero side. i would probably add a dwell in the program when it returns to the zero set on an indicator so you can confirm it coming back to the set zero point. you could toss the program into a loop so you don't have to keep running the program if you wanted to get a little more involved with the test program.

i would probably start with doing something along those lines.

I will do machinedude. I found the torque curve of my current steppers. Assuming a total weight of 100kgs (I doubt it will exceed 50) and a safety torque of 1.5Nm, looking at the graph, I get an acceleration of 15mm / sec²:

F=M*a => a=F/M => a=1.5Nm/100kgs => a= 0,015m/seg²*1000= 15mm/seg²

Which I don't know if it's correct or just absurd.

Regarding the speeds, putting an average of 1000 mm / min working divided by 5mm of pitch would give 200 rpms of the motor, which going to the graph I think falls within the torque range. The cutting conditions would have to be taken into account, I know, which creates the following doubt ... Will more problems come from the spindle than from the motors?

What is your maximum velocity mm/min when cutting?
If you are using these drives you linked to earlier, they might be OK. I had a look at our model using our Z axis lead screw model for a plasma machine, (eg no cutting forces but the force of gravity to overcome),

At 500 mm/min, it requires 3.0 amps RMS (3.9 amp peak). Temperature rise would be 13 deg C over ambient (whats your hottest day in your shed?).
So on those values, it passes our model. eg.
RMS amps do not exceed the max, the motor won't melt.



If all else fails, you could make say a reduction drive that is bolt on compatible with Nema 23 as I did in this thread.
forum.linuxcnc.org/30-cnc-machines/31509...-loaded-pinion-drive

Or add a planetary gear box.

Well the speed depends a bit but I usually work in a range between 800-1000, for fear above all.
As for the drivers, the ones you mention were candidates for replacement discarded for not knowing the torque curve, the ones I currently have in use are DMQ860MA with the steppers that I have attached to the curve, yes. As for the temperature, they get quite hotter than 13 degrees above the hottest day hahaha.

What do you think of the 15mm / sec² of acceleration that I get as a result?
Does it make any sense ???: blush: