Several newbie questions.

[bill-the-cat]

I'm just getting started with my Taig mill, Gecko controller and Keling steppers. After researching this forum for weeks to educate myself, I've still got several questions.

1) After my system has been powered up for a while, my stepper motors are relatively warm/hot to the touch. This is true even if I haven't been moving the axes. I would expect this a little due to the current that is holding the stepper in position, but I am concerned that they might be warmer than they should be. Is this normal? How warm should they be?

2) I've read countless posts about losing steps. They often mention that you can "hear" that you are losing steps. What exactly should I be listening for?

3) There is a "Verify" button on the Mach "MDI" page, but I'm not sure I understand exactly how I use this to determine if I've lost steps. Can someone explain the process?

Thanks for any help with these questions!

[awerby]

I'm just getting started with my Taig mill, Gecko controller and Keling steppers. After researching this forum for weeks to educate myself, I've still got several questions.

1) After my system has been powered up for a while, my stepper motors are relatively warm/hot to the touch. This is true even if I haven't been moving the axes. I would expect this a little due to the current that is holding the stepper in position, but I am concerned that they might be warmer than they should be. Is this normal? How warm should they be?

[They can be pretty warm without causing any problems. You are correct that the stepper is using power just holding its position. As long as it doesn't burn your finger when you touch it, I wouldn't worry about it.]

2) I've read countless posts about losing steps. They often mention that you can "hear" that you are losing steps. What exactly should I be listening for?

[The motor will stutter, or growl. When it's happy, the sound is somewhere between "Whirr" and "Zing". When it's not, it will let you know...]

3) There is a "Verify" button on the Mach "MDI" page, but I'm not sure I understand exactly how I use this to determine if I've lost steps. Can someone explain the process?

[I don't think that's what it does; as far as I know, it just checks if the code is possible for it to run (no illegal characters, or out-of-limits moves). I don't think Mach has any mechanism to determine if steps have been lost, although some controllers may close a feedback loop at the drive, and will shut down if the commanded steps versus achieved steps are out of a certain ratio.]

Thanks for any help with these questions!

[No problem, Bill - it sounds like things are basically working for you, so happy milling!]

Andrew Werby
www.computersculpture.com

[bill-the-cat]

Thanks Andrew!

After you mentioned it, I think I remember something in one of the tutorial videos about using Verify to check your code. I'll have to go back and watch that one again. I'm not sure where I got the idea that it checked for lost steps, but I think I read something about it on this or another forum

Since I posted my original questions, I came up with one more. I recently experienced a phantom limit switch event. I use shielded cable for my limit switches, but, I guess I'm still getting some electrical noise from somewhere. In my reading, I've found that setting a "Debounce" value can correct this problem. One thing about setting this value was asked in one of the posts that I read, but was never answered. Is there a downside to setting this value TOO high?

[Mini Beast]

I don't have an answer, but I know that my steppers are actually too hot to touch. It really gets my attention when I bump one with my arm when taking the part off the table. Sometimes, they make a bit of a hissing sound too.

I had a phantom limit switch too one time. It took me awhile, but I finally realized what the problem was (and got a good laugh out of it). I forgot to move my keyboard out of the way, and the cable for the x-axis stepper ended up pushing the 'esc' key on my keyboard.

[bill-the-cat]

I reviewed the tutorial video and I was correct. It states that pressing the Verify button on the MDI screen will send the machine to the Home position and then back to your current position. It will them report if you have lost any steps. I haven't tried it yet. If anyone has any experience with this feature, I'd like to hear about it before I try it.

Also still wanting to hear opinions on debounce settings. I'm using shielded cable for my limit switches (grounded at the control box), but I still got two phantom limit switch events so far. Since these events are so rare, I'm not sure I can determine the exact cause and I'm thinking that setting a minimal debouce value will prevent them from happening. I know that ideally the debounce should be zero, but is a small value to deal with the "occassional" noise problem OK as a general rule? At what level is the debounce value to be considered excessive? Are there other drawbacks to having the debounce value TOO high?

Thanks!

[awerby]

[QUOTE=bill-the-cat;646098]I reviewed the tutorial video and I was correct. It states that pressing the Verify button on the MDI screen will send the machine to the Home position and then back to your current position. It will them report if you have lost any steps. I haven't tried it yet. If anyone has any experience with this feature, I'd like to hear about it before I try it.

[If you've got a Taig mill, I don't think this is going to be much help, unless you retrofit it with home switches. Lacking those, sending it to the Home position will just crash it, since the homing routine sends it to the limit of each axis until a switch is triggered.

I'd suggest you address your debounce questions to the Mach3 forum on machsupport.com, since that's where the real Mach experts hang out...]

Andrew Werby
www.computersculpture.com

[bill-the-cat]

[quote=awerby;646137]

I reviewed the tutorial video and I was correct. It states that pressing the Verify button on the MDI screen will send the machine to the Home position and then back to your current position. It will them report if you have lost any steps. I haven't tried it yet. If anyone has any experience with this feature, I'd like to hear about it before I try it.

[If you've got a Taig mill, I don't think this is going to be much help, unless you retrofit it with home switches. Lacking those, sending it to the Home position will just crash it, since the homing routine sends it to the limit of each axis until a switch is triggered.

I'd suggest you address your debounce questions to the Mach3 forum on machsupport.com, since that's where the real Mach experts hang out...]

Andrew Werby
www.computersculpture.com

I do have limit/home switches installed on my Taig. I'll just have to play around with the verify and see what is does.

As for the debounce, I have posted the question on the MACH forum as well. You're right there are some very knowledgable people on that forum and I've gotten some great help from them at times. However, on the debounce question I keep getting text book answers about what debounce is. Along with that, I'm told that, if I have noise problems, they should be addressed and not covered up with debounce. I understand the concept and, if I had phantom limit switch events happening constantly, I'd start with trying to figure out where the noise was comming from. I've had two phantom limit switch events in the two weeks since I've started using the machine. It would be hard to diagnose this problem due to the lack of repeatability. I know that setting a debounce would be "covering up" this situation, but, due to it's infrequency, I view it as an acceptable option. What I need to know are any adverse effects of setting a debounce value too high and just what is considered too high.

[Jeff-Birt]

Mechanical switches do not switch cleanly, there is always a little contact 'bounce' that gives you a small succession of make/break events as the switch closes. Every mechanical switch will require some debounce (from keyboards to limit switches.) There is no default value that works but something on the order of 10~100ms should be plenty. If you have an o-scope you can get a better idea of the settling time of the contacts.

The other thing to keep in mind is what type of switch your using. Using a switch rated for high current on a 5V circuit will cause lots of problems. High current switches have contacts that are designed to be self cleaning via the high current that they are switching. Using a switch that is rated for 5V/100ma will be much more reliable.

[noisillator]

Isn't there a proven way to do this electrically, rather than through software? Maybe a RC network at the switches?

[Jeff-Birt]

Isn't there a proven way to do this electrically,

Why? Switch debounce is generally done in software. Everything from pocket calculators to your PC's keyboard use it as it is the simplest most reliable way to fix the problem.

[noisillator]

Why? Switch debounce is generally done in software. Everything from pocket calculators to your PC's keyboard use it as it is the simplest most reliable way to fix the problem.

Does that mean you're offering to uprev his software?

[bill-the-cat]

Well, I did find one problem with my system. One of the wire connections on one of my limit switches was loose. I tightened the connection and have not had any more phantom limit switch events.

I tend to agree with Jeff. So, as a precaution, I've decided to set a minimal debounce value of 100.