servo gears for chinese laser

[Keith Winter]

Hi Guys,
With my other problem of the stepper malfunctioning and running into the side on the x axis + that laser also having a poor engraving problem I'm starting to wonder if I have a defective servo motor controlling the X axis.

I was going to swap to my spare motor to try it to see if it fixed both issues at once, but the good folks I bought my laser from and the spare servo didn't think to include a spare gear or a gear puller. I've been to harbor freight bought two different pullers but nether would fit and I've looked around online but haven't found any pullers I can get quickly.

The Gear is 18mm wide by 20mm tall. Photo of the gear attached, I need to pull it off the one on the right and get it on the one on the left. Servo is a 573HBM20 by leadshine.

Any idea on where I can get a spare gear? Or other ideas on how I can get it off without damaging anything?

20160609_142312.jpg

[Dave Sheldrake]

Lightobject DOT com, ask for Marco they will have all manner of leadshine bits pretty cheap

[Rich Harman]

You can pry the pulley off using two large flat blade screwdrivers. Make sure to to use two so that you apply pressure to both sides equally. Small open end wrenches also work well. I've done it many times, haven't damaged one yet.

[Keith Winter]

How do you put the back on rich? Rubber mallet? I saw on you tube some people using a flame to heat up the gear on small motors and pinons on rc cars. Made it pop off easy and back on easy. Do you think this would work or risk damaging the stepper servo?

[Rich Harman]

If you can't press it on I would tap it on with a hammer, not a rubber mallet - use something between the hammer and pulley if necessary to protect it. Rest the stepper on something solid while doing so. Heating is okay as long as you don't get carried away, and don't heat the motor.

FYI, servos and steppers are different things. While the technical definition of "servo" could include a stepper, in CNC applications servos are either brushed or brushless motors that require an encoder to be moved with precision, either mounted to the motor shaft or to the apparatus that is being driven. They are essentially just a regular motor with some feedback attached, closed loop. A driver moves the motor and the encoder keeps track of how it is moved, the driver can then apply power to get the motor to where it is supposed to be.

Stepper motors are very different, they are controlled by energizing their coils in sequence - steps. The driver energizes the coils to move the motor but there is no feedback reporting on whether or not the motor has moved - open loop.

[Matt McCoy]

What do you mean by poor engraving problem?

[Keith Winter]

I think the 573HBM20 is a micro stepper but they call it a hybrid servo. If you type it into google maybe you can clarify because I am curious if it's worth the extra $$ I paid? Regardless of what we call it, it performs a similar function to what most chinese machines call a stepper anyway

Matt, so I bought a Thunder laser, I liked it, then I bought a couple more. The new ones the engraving isn't crisp, it's kind of blurry like it's slightly out of focus. We've realigned them multiple times all the way around from tube through all the mirrors, 3 people have tried in fact, and we've swapped the optics with the "good" original laser to no effect. They also had us copy the settings from the old laser and update the firmware on the controller, no effect or improvement. I also tightened the belts with no improvement. Thunders only solution so far as been to run it at unilateral and 300mm/s speed when the original runs at bi-directional and 700mm/s with crisp engraving on the exact same files. Which is like having a v8 and them telling you to only run it on 2 cylinders, essentially running at 1/4th speed and calling it fixed. Total BS. So that's been going on since we got the new lasers. We had tried everything Thunder can think of and nothing fixes it, so today we had the weird problem in my other thread when I did the step length setup test so I thought I'd try swapping out the servo/stepper motor and then the servo controller if needed to see if that fixed things. However I ran into this snag because they didn't give me another gear when I bought the spare servo/stepper from them. So that's the full story. :/

[Rich Harman]

I think the 573HBM20 is a micro stepper but they call it a hybrid servo. If you type it into google maybe you can clarify because I am curious if it's worth the extra $$ I paid? Regardless of what we call it, it performs a similar function to what most chinese machines call a stepper anyway.

That is a stepper with an encoder attached, making it a closed loop stepper. Any stepper can be made closed loop by adding an encoder, but you'll need a driver that accepts the encoder inputs. Any stepper can be a micro-stepper. That is accomplished by partially energizing the coils, it's done in the driver, not the motor.

[Keith Winter]

Heat did the trick, heated up the gear for just a few seconds while the motor spindle was left cool, and it popped right off with two flat head screwdrivers and equal force on each side.