[TheProCreator]

Can anyone shed some light why my stepper motors slip at relatively slow speeds? I have a hobby grade 4 axis CNC machine (all aluminum purchased from china through ebay) with a 30VDC power supply/ IT is controlled by a gecko g540. I have checked all my ball screws, tightened an re-tightened everything. Supposedly I should get speeds of up to 8 meters a minute (8000mm). Anything near 3000mm a minute slips. My settings for the X&Y are 2250mm per min with a 60mm per minute acceleration, my Z axis is 2000mm per min and a 25mm per minute acceleration, and my rotary table is set at 289mm per minute with acceleration starting at 25mm per min. Anything above these settings I get motor slip or it sounds like my carriages are running over rocks.

I make small jewelry sized objects, but it is taking an entire day or more to mill one piece. My question is, where do I start? Should I select a bigger capacity stepper in volts or torque? Do i need more power, Could something be wired wrong? is there a setting on mach3 I'm neglecting?

I use my 4th axis a lot and is my biggest concern. It takes 2 minutes to do one revolution, some times more. How do I double my current speeds, have plenty of toque, but most of all, leave slipping issues behind?

[ger21]

Is this leadscrew or rack and pinion? What pitch are the screws if screw drive?
What are the specs of your motors.

What is the gear ratio of the 4th axis, and motor specs?
Velocity in motor tuning is degrees/minute, ans you have it set to 289. Try increasing that.

[aarggh]

Ït sounds straight off like the 30VDC PSU simply isn't powerful enough unless your running NEMA17's, NEMA23's or above it sounds definately shy of what you'd really want.

More than likely you also maybe have some tuning parameters not optimal which would also contribute to the issues.

The standard 4th axis units from China are also generally extemely weak, and it takes very little to stop most of them under load, but another thing to check is if you have any binding on any of the axis. If you can reasonably easily move any of the axis by pushing against them, then under load they will flex and move, contributing to binding and lost steps, or the noises you've been hearing.

cheers, Ian

[TheProCreator]

The motor specs on X and Z are:

57BYGH311-01 Stepper Motor Hi-torque 15 Kg.cm
Hi-torque stepping motor specifications:
- Model: 57BYGH311-01
- Step Angle 1.8°±5%
- Insulation Resistant 500V DC 100MΩ Min
- Insulation Strength 50Hz 1Minute 500V Min
- Ambient Temperature -20℃~+50℃
- Temperature Rise 80℃ Max.
- Radial Play 0.02mm Max.
- End Play 0.1-0.3mm
- Winding: 2 Phase
- Current: 3 A
- Shaft diameter: 8mm
- Resistant: 1.2 Ohm
- Torque: 15 Kg.cm
- Weight: 1.1KG
- Overall Dimension: 57x57x111.5mm

I do not have any info on the Y axis other than it is 4 wire and you can see by the pics it is 86mm square. The 4th axis is a 5" parker RT rotary table with a Keling stepper (Nema 23). The table has a gear ratio of 1000/1. Keling is a NEMA 23 BIPOLAR STEPPER MOTOR 425 oz-in, 1/4” Diameter shaft with a flat KL23H286-20-8B (Dual Shaft) Rated Current: 2.8A, Rated Voltage: 4.17V (in Bipolar Parallel) A custom aluminum adapter was machined for the chuck. I do have a resistor on the A axis limiting it to 1.5A.

Everything is powered by an antek PS-430N 30V 400W power supply and controlled by the Gecko G540. I built a control box to the homann specks (except I use a small 12v power supply to trigger a 12v relay for spindle on/off). No other controllers or add-ons or BOB's.

Really I need the speed on the rotary axis. I'd like to get about 30 seconds on the 360 turn.

[TheProCreator]

Well, I found part of the issue. I had a 1.5k resistor on the rotary axis. This is when I was using a cheapo stepper on a worm drive. I did not upgrade the resister to 2.7k until today. Now I'm getting rotations just over one minute. Better, but still when tool paths are .3mm next to each other a 70mm part takes 3 hours to make one pass.

[BuckNaked31]

That 425oz stepper requires a whole lot more than 30 volts for decent torque at high RPM's.

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[ger21]

And that 1000:1 isn't helping. You need a smaller motor and higher voltage to get more speed. The 425oz steppers are about the slowest Nema 23's you can get, due to their high inductance.

[TheProCreator]

How large (voltage) of a power supply should I replace it with?

[BuckNaked31]

I would go with 48 volts and a stepper with low inductance, less than 2mH , that 425 is a real dog, it would take 80 volts to drive it, your G540 would top out at 50. I'm using 320oz low inductance with a G540 and it'll move a truck

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[UA_Iron]

Single Stack, Double Stack and Triple Stack are all common terminologies for stepper motors/sizes/power ratings. The stack refers to the number of magnet structures in the stepper motor. The more stacks in the stepper, the greater its torque will be at the lower RPMs and they fall off very aggressively. The lesser stack motors have a smoother torque curve over the RPM range. They do not fall off as aggressively as the higher stack orders, and even outperform them at higher RPMs. Higher stack orders have higher a inductance value due to the physical mass of the stacks.

With a 1000/1 reduction you are severely limited in your stepper options if you ever want to achieve a decent RPM on that rotary table. It would take a stepper operating at 2000RPMs to get 2 RPM at the rotary table. Stepper motor operating ranges are typically a lot lower than this. Not only that, you're further neutering your steppers by driving them at such a low RPM.

That KL23H286-20-8BT sucks at high RPM (at 30volts it sucks at all RPMs to be honest).
http://www.kelinginc.net/KL23H286-20-8BT.pdf
[for reference: 1000PPS=150 RPM, 1Nm=141.6oz-in (for this graph)]

I'm not impressed by anything keling, automation technologies, or leadshine offer as far as steppers having sufficient torque in the higher RPMs.

This should be a drop in replacement for the rotary table stepper: STP-MTRH-23079
AutomationDirect.com | The common sense way to buy industrial controls

At 2000RPM it produces good torque compared to most other popular motors.

[TheProCreator]

Ok, Im going to give that STP-MTRH-23079 a shot on the rotary table and upgrade the power supply to a 48v 600w 12.5AMP unit. I'll check back in once the items are received and installed. Thanks a million!