DMM, ClearPath and DM542 running together

[Richards]

I have a bunch of Oriental Motor PK268-02A steppers that I've removed from retired machinery, but I only had a few Gecko stepper drivers. At the cost of over $125 per Gecko stepper driver, it didn't seem practical to buy a bunch of drivers that might just sit in a drawer with the motors. After seeing what Gary Campbell and others have done with Leadshine stepper drivers, I decided to try two DM542S stepper drivers. At $30 each, they're probably clones, but they work very well. To keep wiring simple, I put a 2.2K resistor in series with the Step signal and a 2.2K resistor in series with the Direction signal so that I could use the 24V H2 and H3 headers on the Acorn. I set the current to 1.91A and the steps to 800. They run nicely. What's even better is that I have a Teknic ClearPath SDSK-2321S-RLN servo on the X axis, a DMM/DYN4 86N-DHT-A6MD1 on the Z axis and a DM542S/PK268-02A (sired unipolar) on the Y axis. They play together very well. The only change that I had to make was to select 200,000 pulses instead of 400,000 pulses in the Wizard because of the specifications on the DM542S. (Yes, I did try running the DM542S at 400,000 pulses and got nothing.)

What continues to impress me is that no matter what I throw at the Acorn, it handles everything. I did add a PLC to give me an easy way to handle the difference between the servo fault signals from DMM and Teknic, but that has nothing to do with Centroid. (I doubt that others would mix and match servos from different companies, so the PLC is NOT required even though it really makes things easy to configure for me.)

I also had a few Oriental Motor CSD2120-T stepper drivers in the drawer that are at least 20 years old. Even though those drivers are reliable, they are no match for the DM542S drivers. The motors run loud and much rougher sounding, so the Oriental Motor drivers will be reserved to be used only when I give demonstrations to the Boy Scouts.

[Commotion]

Yeah I have been playing with leadshine ac & dc servo drives and found them to work quite well.

I’m actually in the middle of machining up a new ball screw mounting bracket to replace the acme thread in the pc160 lathe I’m retrofitting using my dtm320 and acorn. The dimensions have been spot on and it’s so quick and easy to get a part up and running.

I have 2 mills and 3 lathes at work all mazak but I find it extremely satisfying making parts for one acorn retrofit project using another acorn retrofit project. The plan is once I have the lathe up and running I will use them to assist me in making components for my next cnc project which is a ground up mini cnc horizontal mill.

[Richards]

Commotion,
Those servos are fun, aren't they?

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I'm still fascinated with the DM542 stepper driver. I connected three motors, 2 PK268-02AA and 1 PK299-02AA to those drives. The Nema 23 motors were limited to 1.91A and the Nema 34 motor was limited to 2.84A, well within the capabilities of the DM542 drivers. I used two 24VDC switching power supplies wired in series to give just under 48VDC. The PLC was configured to not turn on the power to the DYN4 and the ClearPaths. It was also configured to generate a DriveOK signal to the Acorn. The only rewiring that I had to do was to move the STEP/DIRECTION wires from one set of terminal blocks to another, a two minute job. Preliminary tests show that the DM542 drivers perform as well or better than the Gecko G203V drivers that I used in the past. After an hour of testing, the drives and the motors are still at room temperature (no load on the motors). It may be the proper time to put some of these steppers on my little wood lathe and my little Harbor Freight metal lathe. Test benching is a lot of fun, but there should be an actual CNC machine somewhere in the process.

Please excuse the messy wiring in the photo, after all this is a test bench.

[Gary Campbell]

Mike...
As you know I have been sold on Leadshine products for a while now as a great mid-priced solution for most CNC applications. All I was ever able to get out of Gecko products was heat and motor noise. I use the DM542E on the "basic" system (48v) with upgrade to DM556 if the user wishes to allow for larger motors in the future. Also have an option for 60v and DM-870 which will throw some real amps when needed.

Thanks for doing what you do Mike. Aint it fun???

[Richards]

Gary,
Thanks for the comment and for your years of pushing for better machines.

What I'm testing right now is the point where steppers can handle the job and the point where servos are the better choice. I suffered for years with an underpowered Shopbot that supposedly had the best stepper motors and drivers available. These little DM542 drivers seem to be equal to or better than anything I've used before, particularly when paired with the motors that I have on hand. They should do a satisfactory job on that little Harbor Freight mill and on the desktop Jet wood lathe. One point that I want to study is a comparison of torque between rack and pinion with belt-drive systems and ball-screw systems. Rough calculations show that a 16X5 ball screw produces about 2-1/2 times the torque of the same motor used on a 3:1 rack/pinion system with a 1.125" pinion gear. To compare apples to oranges, the PK296 motors that I like produced 900-1,000 oz-in holding torque when geared 3:1 (disregarding the drive reducing power to reduce heating). These little PK268-02AA motors, when connected to the 16X5 ball-screws, actually put out a little more torque (at least on paper). The drawback is speed, but should I lose sleep if it takes three seconds to jog the z-axis ten inches? Anyway mental gymnastics keep old men like me looking forward to each day.