Taking the CNC Plunge

[jbolt]

I believe your X & Y motors are Wantai 85BYGH450C-012. The website says the operation range is -20c to 50c (-4f to 122f) with a max temperature rise of 80c ambient. If I read that correctly the max temp is 130c (266f) which I understand is the max temp rating for the wire insulation.

Have you measured the heat of the motors? My X & Y motors run between 100f and 115f.

What is switch SW4 on the driver set to, on or off?

Jay

 

[TomS]

Take a look at the idle current setting on the drives. It sounds like they are not switching down to idle current. That is way to hot, something is not right. The high voltage may be the cause, but the drives should limit the current.

Measure the end mill you are using. If it is oversize 0.0025, your hole would be oversize by 0.005. Most end mills are not exactly on size. You are correct in that you may need to fine tune the calibration.

Jim - I've attached the driver manual and included my motor and driver specs for reference. When you say the "idle current" setting is that the same as the "standstill current" setting referenced in the manual? Currently my switch 4 is set to half of the selected dynamic current.

Stepper Motor

Technical Specifications

Part No: WT85STH151-3004B dual shaft 85BYGH450C-012B

Frame Size: NEMA34

Step Angle: 1.8 degree

Voltage: 5.7V

Current: 3.5A/phase

Resistance: 1.9 Ohm/phase

Inductance: 22 mH/phase

Holding torque: 11.3N.m/1600oz-in

Rotor inertia: 3600g-cm2

Number of wire leads: 4

Weight: 5 kgs

Length: 151mm


Note: Nema 34 stepper motor with 1600 oz-in holding torque on single shaft, front shaft length is 37mm with 25mm flats length, the diameter for motor shaft is 14mm.


RED = A+

GREEN = A-

YELLOW = B+

BLUE = B-


Stepper Motor Driver

DQ860MA

Introduction

The DQ860MA is an economical microstepping drive based on patented technology of Wantai Motor. It is suitable for driving 2-phase & 4-phase hybrid stepping motors. By using the advanced bipolar constant-current shopping technique, it can output more speed and torque from the same motor compared with traditional drivers, such as L/R drivers. It’s 3-state current control technology allows coil currents to be well controlled and with relatively small current ripple, therefore less motor heating is achieved.

Features

◆Low cost and good high-speed torque

◆14 selectable resolutions

◆Supply voltage up to +80VD

◆Suitable for-2-phase and 4-phase motors

◆Output current up to 7.8A, 5.86A rated current, 256 Microstep.

◆Dip switch current setting 8 different values

◆Optically isolated input signals

◆Pulse frequency up to 200 KHz

◆Automatic idle-current reduction

◆Small size (107*97*48), Weight: 0.6KG

I'll measure my cutter but you raised a good point. It could also be my asian set screw holder has some runout. I'll also try my collet and see what happens.

Tom S

 

[JimDawson]

Jim - I've attached the driver manual and included my motor and driver specs for reference. When you say the "idle current" setting is that the same as the "standstill current" setting referenced in the manual? Currently my switch 4 is set to half of the selected dynamic current.

Yes, Idle current = standstill current. In the manual is also a reference to: 4) Semi-flow function: Semi-flow function is that there is not step pulse after 200 ms, the driver output current automatically reduced to 40% of rated output current, which is used to prevent motor heat. I'm not exactly sure how this is implemented, or if it it overridden by SW4 The manual is a bit vague on this subject.

I have two of almost the same setup on the bench right now, same drives, but 1200 oz/inch, 5.6 amp motors. They're getting ready to drive Alloy's Shizouka tool changer and variable speed control. I'll pull one of the drives out of the panel tomorrow and see how it reacts. We are a couple weeks away from firing it up, and I need to test the new tool changer gearbox on the bench anyway.

 

[TomS]

Yes, Idle current = standstill current. In the manual is also a reference to: 4) Semi-flow function: Semi-flow function is that there is not step pulse after 200 ms, the driver output current automatically reduced to 40% of rated output current, which is used to prevent motor heat. I'm not exactly sure how this is implemented, or if it it overridden by SW4 The manual is a bit vague on this subject.

I have two of almost the same setup on the bench right now, same drives, but 1200 oz/inch, 5.6 amp motors. They're getting ready to drive Alloy's Shizouka tool changer and variable speed control. I'll pull one of the drives out of the panel tomorrow and see how it reacts. We are a couple weeks away from firing it up, and I need to test the new tool changer gearbox on the bench anyway.

Thanks Jim. I'm going to change switch 4 to "ON" (full current) and see what happens.

Tom S

 

[JimDawson]

OK, I ran some tests on the bench.

Equipment:
Wantai WT86STH118-6004B 1200 oz/in stepper motor 5.6 amp
Wantai DQ860MA Drive
60 Volt Power Supply
Stepper Speed Controller
3M Infrared thermometer

Conditions:
Motor clamped to a wood bench with a C-clamp, 3 sides exposed to still air
800 Step / Rev, SW 5 OFF, SW 6,7,8 ON
5.6 Amp, SW1,2,3 OFF
SW4 OFF
Power Supply voltage = 60.0

I took a temperature reading every 5 minutes during the test
Ambient temperature at START of test = 77 F
Starting temperature of motor case = 88 F
The first 10 minutes was Power ON, Motor OFF to test standstill temperature rise.
At 10 minutes I turned the Motor ON, about 1 REV/Sec (equivalent to 12 IPM on a 0.200 pitch leadscrew)
Maximum temperature was at 55 minutes (45 minutes running time) = 161 F
The last 15 minutes (55-70) was power ON, Motor OFF to test standstill temperature again.
Ambient temperature at END of test = 80 F

As you can see, the temperature rise was pretty constant as long as the motor was running. I don't know what the max safe operating temperature of the motor is. The high temperature is due to running current, not standstill current.

The only suggestion that I have is to turn down the current to the minimum that will run the machine.

.
.

 

[TomS]

Thanks Jim. I'm going to change switch 4 to "ON" (full current) and see what happens.

Tom S

Well, that didn't work. The motors got hot without much movement. Did some web surfing on stepper motors running hot. Found lots of comments but no real answer on how to address it. Comments included adding cooling fans to installing heat sinks. I'm more interested in fixing the root cause. What I found interesting is some commentors say 100 to 110C is considered normal. That's 212F to about 235F! Harbor Freight has a non-contact infrared thermometer for $12. Might give that a try to determine how hot my motors are actually running.

Tom S

 

[JimDawson]

Might give that a try to determine how hot my motors are actually running.

See my post above ^^^^

 

[TomS]

Just posted then I saw your post. Were you able to hold your hand on the motor longer than a few seconds? I've read that 140F is the maximum pain threshold. If this is true then my motors may be running about the same temperature as yours.


Tom S

 

[JimDawson]

Towards the end of the test I really didn't want to touch it, pretty hot.

 

[TomS]

Towards the end of the test I really didn't want to touch it, pretty hot.

Maybe I don't have a problem. I'm off to Harbor Freight in the morning to buy the thermometer. Thanks for your help.

Tom S