1000x500mm high permission granite router build - closed loop STEPPERS CALCULATIONS

[NUDEcnc]

-- in red color are questions for the forum --
After many years working on China's CNC machine SYIL X5 with Mach3 with Smoothstepper
I decided to build my own CNC https://www.forum.cncdrive.com/image...on_e_smile.gif

This is the early version of the machine which I want to build.
https://www.forum.cncdrive.com/downl...hp?id=1478&t=1

https://www.forum.cncdrive.com/downl...hp?id=1479&t=1


BUILD INFO:
The main chassis will be made from granite.
Controller: UCCNC

LINEAR RAILS AND SLIDERS FROM HIWIN
Y axis- 2x 1340mm HGR25R;
X axis 1x 800mm HGR20R;
Z axis 1X 420mm HGR20R
slider blocks
4X HGW25HA
8X HGH20CA
ballscrews TBI
Y axis 2x L1280mm
X axis 1x L930mm
Z axis 1x L400m

Spindle
JGL-100/2.5R24-25 - ATC spindle 24000rpm 2.5kW from :

Minimal performance:
speed: 300ipm (7600mm/min) cut, 400ipm (10.000mm/min) travel
Resolution: 0.0001in (0.0025mm)

I try to calculate motors for setup: please check if correct.
(I will limit myself to Y axis)
All these pieces of information are based on this what I was able to find over last week. Please verify and correct if needed.

1. Closed loop CONTROLLERS - options
HSS86 - AC24~70 or DC30~100 - parameters are not adjustable
2HSS86H
All HBS driver can be programed by ProTuner SW
manual to software: http://www.cncshop.cz/PDF/HBS/HBSprotunermanual.pdf
HBS86 30-80V, 8.2A Peak
HBS86H 24-70VAC or 30-100VDC, 8.2A Peak
HBS860H 20~80VAC or 30-110V

What are differences between this controllers?

2. Torque vs power supply
https://www.cnczone.com/forums/attac...d=407006&stc=1
If HBS860H connected to the power supply
Is it better to connect VAC or VDC ?


3. BALLSCREWS Pitch and diameter
pitch - as I want 0.0025mm resolution I can choose 5mm and 2000 microsteps or 10mm and 4000 microsteps.
If I want to run 10k mm/min screw would need to run 2000rpm for 5mm or 1000of 10mm. 2000 is out of range for steppers motors.

diameter - for the length 1280mm I have option 20mm or 25 mm diameter screw.

4. INERTIA of Y axis
https://www.cnczone.com/forums/attac...d=407000&stc=1

"nertia mismatch greatly affects how stepper motors operate. The motors cannot accelerate and decelerate rapidly with an extreme inertia mismatch. If they have sufficient torque, but an inertia mismatch is present, the load may not start or stop at the proper time or place."
Link: https://www.motioncontroltips.com/fa...rtia-mismatch/


https://www.cnczone.com/forums/attac...d=407002&stc=1
total weight of Y axis is 120kg

I found the great calculator to calculate inertia.
https://www.servotak.eu/tools/engineering_calculator

Linear speed-

10000 millimeter/minute = 0.1666666666667 meter/second

https://www.cnczone.com/forums/attac...d=406998&stc=1


The inertia of the Y-axis with ball screw 20mm dia and the 10mm pitch is:
Load and Ball Screw Inertia - 3.0982 kg*cm2
in the calculation, there is also Load and Ball Screw Inertia as Seen by the Motor - 3.0957 kg*cm2

But if I'd like to choose Y-axis with ball screw 25mm dia and the 5mm pitch is:

Load and Ball Screw Inertia is not that much different from above: 4.2333 kg*cm2
Load and Ball Screw Inertia as Seen by the Motor 16.9197 kg*cm2 !!!

5. Stepper Motor Inductance / Torque

Major Rule 2: The relationship between motor power output, power supply voltage (V) and motor inductance (L) is:
Power = Volts / Square Root of L

Taken: http://www.piclist.com/techref/io/st...inductance.htm


6. Microsteping vs torque

Microsteps per full-step	Incremental holding torque per microstep
1	100 %
2	70.71 %
4	38.27 %
8	19.51 %
16	9.80 %
32	4.91 %
64	2.45 %
128	1.23 %
256	0.61 %

link: https://hackaday.com/2016/08/29/how-...epping-really/

That this means if I chose 10Nm 200 full-step motor and I will have 2000 microsteps per revolution this will be 10 steps per full-step.
Does it means max torque I will have available will be (8 steps is 19.51% and 16 steps is 9.80%) aprox 17% of initial 10Nm torque ??
And if I chose 4000 microsteps (20 per full-step) it will be only "very approx" 8% of torque ??

Well, it looks like its wrong. At least for closed-loop stepper motors.
This is the torque graph of 8Nm motor @ AC-60V.
https://www.cnczone.com/forums/attac...d=407004&stc=1
The graph shows 8 divisions per step - 1600 microsteps and max torque is ~ +6.5Nm

7. MOTOR torque
This is few motors which I found on different auctions.

motor model	MOTOR LENGTH	PHASE RESISTANCE	PHASE INDUCTANCE	HOLDING TORQUE	ROTOR INERTIA	Current (A/phase)
34SSM1460	142	0,4	4,2	9,0	2300	6,0
86HSE118/ DW86HSE8N-BC38	118	0,44	3,7	8,0	missing	6,0
LC86H298	98	0.5	4,3	6,5	2800	6,0
LC86H2128	130	0,4	4,6	10	4200	7,5
86HS80-EC-1000		0,44	3,73	8,0	2580	6,0
86HBS85	118	0,6	5,5	8,5	2500	5,6
86J1895EC-1000		0,37	3,3	7,0	1850	5,0

CAN ANYBODY FROM THIS GREAT FORUM HELP ME PICK MOTOR FOR THE PROJECT? AFTER ALL THIS KNOWLEDGE I'M MORE CONFUSED THAN EVER.

Regards Arek


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[ger21]

Resolution: 0.0001in (0.0025mm)

I think this is incredibly optimistic, and likely unattainable.
What are the specs of the screws? Can you fabricate the machine to these tolerances? Will it be in a temperature controlled room?

I would forget about steppers, and look at AC servos in the .75-1Kw range. Much higher resolution, and a lot more power.

[skrubol]

.0001" resolution isn't too hard, it's just math (screw pitch/encoder resolution.) .0001" repeatability is hard. .0001" accuracy is very hard.

I'm not sure that the microstep torque stuff applies to closed loop steppers. I think inertia missmatch is less of an issue as well.
I think I agree with Gerry though, that's a tough task for steppers. You'd need at least 10mm pitch screws to get your speeds with steppers. As long as the encoders are at least 1000 line (4000 count,) and you don't need to do any pulse multiplying, you should meet your resolution requirement as well.
Not sure if you'll have enough torque though, might have to deal with pretty slow acceleration and limit your cut aggressiveness.