Strange Movement

[tuffduck]

The spindle is 4 HP. Cutting area is 48"x42". Machine Corian, solid wood, plywood and acrylic.

[martyscncgarage]

NEMA 23?
You might consider Clear path SDSK motors.
What are the specs or model number on the current stepper?

They'll probably work fine if you watch your feedrates.

[tuffduck]

Here are the motors the cnc came with:
34HS38-3008S on Z
34HST980537B2 on X
34HS740014I34J6 on Y

[tuffduck]

I checked the Clearpath site and found this one.
https://www.teknic.com/model-info/CPM-S ... tage=48VDC
By time I pay for shipping, duty, taxes and exchange, they are more than what I paid for the machine.

[martyscncgarage]

I checked the Clearpath site and found this one.
https://www.teknic.com/model-info/CPM-S ... tage=48VDC
By time I pay for shipping, duty, taxes and exchange, they are more than what I paid for the machine.

Then look for a closed loop hybrid stepper motor with torque specs close to yours or slightly over that you can buy locally. Check ebay...

[tuffduck]

Perhaps something along this line?

[tuffduck]

Or this one for additional torque.

[martyscncgarage]

Would have been nice if you took the time to look up the motor specs...I did it for you, they are listed below:

Here are the motors the cnc came with:
34HS38-3008S on Z 1001oz-in
34HST980537B2 on X 878 oz-in
34HS740014I34J6 on Y Can not find, recheck part number

Those are some pretty large steppers. Curiously, what is the voltage of the power supply driving the motors?

[martyscncgarage]

Perhaps something along this line?

More than enough in my opinion....others may chime in.
Marty

[Richards]

Let's step back for a minute. You're losing steps with your current motors. The solution to solve that problem is to reduce the load on the motors by making shallower cuts or by using slower speeds. Slower speeds can mess up the chip load, so making shallower cuts would solve the problem.

If you decide to use a closed loop system, and if you use motors of similar size, the motors will fault if you overload them by making too deep of a cut, i.e, the motor can make a cut a 1/4" depth but will fault if the cut is 1/2". So, you'll need larger motors.

Steppers and servos are two different animals. Steppers have their greatest torque when not moving. As soon as they start to move, they start to lose torque. At normal jog speeds or at high cutting speeds, their torque may be only 20% or less of their holding torque. If that is enough torque to do the job, then you're okay. Stepper motors get hot. Many stepper drivers reduce the holding current to 50% or less when the motor is stopped to reduce heat. Oriental Motor recommends a 50% duty cycle or less. They also recommend a 8"x10" 1/4" thick aluminum mounting plate to reduce heat. They specify a temperature rise of less than 100-degrees. I ran significant tests with various motors and various motor drives somewhere around 2005. When using the Geckodrive formula to calculate maximum voltage and when using Oriental Motors motor mounts, the Oriental Motor steppers ran hot. Room temperature was 75-degrees. The motors heated up to 150-160 degrees. That's within specs, but it made the motors too hot to touch. I recently checked the temperature of the Oriental Motor PK268-02AA motors that I have on my Taig mill. After 1/2 hour, they were at 150-degrees. Hot. (I'm still using steppers on the Taig mill as I learn how to use the Centroid software and how to cut metal. All of my previous experience was with a Shopbot router cutting wood. Before too long, I'll convert the mill to use the three SDSK2321S-RLN servos that I run on my test bench.)

Servo motors are more expensive, but I highly recommend using them. The ClearPath motors that I use have constant torque at any useful speed. They also have 4X or more startup torque that gets things moving without losing position. Teknic's Clearview MSP software tunes the motors and has a built in oscilloscope so that you can see exactly how the motor is performing. You can see any lag between a commanded move and the actual move. Yes, they cost more, but they are built for 100% duty. They run much, much cooler than steppers.

If your use of they router is for hobby use rather than for production, then using steppers, open loop or closed loop, might be adequate. If you use your router for production, then make a break-even analysis spread sheet to see how many "widgets" it would take to justify installing servo motors.

One last note: There are many different servo motors and servo drivers available. I have one DMM DYN4 driver and a 750W servo. It is an awesome driver/servo. I have seven Teknic ClearPath servos with IPC5 power supplies. They do the job. They are easily tuned. They are easily monitored and they take up less physical room in the control box (one power supply vs a power supply/driver for each DMM DYN4.) I'm certainly not trying to tell you what to do, but spending $1,000 - $1,500 once for motors and then getting full use of your machine is something that can be handled by taking on a part-time job for a week or two.