Lathe with stepper motors - limit switch crash

[ScotY]

Just finished the initial setup of my mini lathe. It’s running steppers and Chinese drivers, using the Leadshine wiring diagram. I noticed it seems to home a little differently compared to my mini mill with ClearPath servos. The lathe will hit the limit switch, back off, then move towards the switch again, almost like it’s bouncing off the switch. I’m not sure if it’s opening the switch on the second move...I’ll have to investigate further.

Anyway, while moving the machine around at the higher jog speeds, I managed to crash it into and damage the limit switch. When doing the same with the mill (servo motors), this hasn’t happened...the axis will coast to a stop and rest on the switch.

Do I have something setup incorrectly or is this just because of the stepper motors?

Or, I suppose the third option would be operator error.

Video - weird homing behavior
http://www.youtube.com/watch?v=RuBDG7RHFkI

[ScotY]

Hmmm...I'm having some issues with CNC12 Lathe. The VCP (and also the Xbox) can be unresponsive, then suddenly respond, often moving an axis close to over travelling. I'm still in the initial setup stage and don't have soft limits set. It's quite unusual, and nothing like the Acorn on my mill. I just did an update to Windows 10 because it wanted to install one and restart, etc. so not sure if that has anything to do with it.

[ScotY]

Can someone watch the video link in my first post and tell me if it seems normal?

[ScotY]

I still think the homing is weird...I don't quite get what it's doing.

However, I learned something...if you don't set travel limits, you WILL crash into your limit switches on rapid jog moves. For some reason, it does not "remember" where the limit switch is and will jog until the switch opens. If you're moving fast, it may not stop in time. Once I set a travel limit, it then remembers where the limit switch is and will coast to a stop before smashing into it. I would guess this info may be in the manual, but I'm a bit behind in my reading.

[martyscncgarage]

I still think the homing is weird...I don't quite get what it's doing.

However, I learned something...if you don't set travel limits, you WILL crash into your limit switches on rapid jog moves. For some reason, it does not "remember" where the limit switch is and will jog until the switch opens. If you're moving fast, it may not stop in time. Once I set a travel limit, it then remembers where the limit switch is and will coast to a stop before smashing into it. I would guess this info may be in the manual, but I'm a bit behind in my reading.

It looks ok to me....
I assume DRO's zero after homing?
Yes, set your soft limits once motor direction and homing is setup....

[martyscncgarage]

You also should be posting your REPORT file when asking questions about your setup, pictures or screenshots of your wizard pages....otherwise were just guessing...

[martyscncgarage]

I still think the homing is weird...I don't quite get what it's doing.

However, I learned something...if you don't set travel limits, you WILL crash into your limit switches on rapid jog moves. For some reason, it does not "remember" where the limit switch is and will jog until the switch opens. If you're moving fast, it may not stop in time. Once I set a travel limit, it then remembers where the limit switch is and will coast to a stop before smashing into it. I would guess this info may be in the manual, but I'm a bit behind in my reading.

Scot, I think you are your own worst enemy, short cuts, not reading up on the process and diving in. So you experience the consequences of doing so.
Not trying to be mean, but you can't take short cuts, maybe on a stepper driven machine where a motor just stalls if you hit a hard stop, but more powerful motors are not forgiving.

I tried my best to make it easy with my videos covering the basics, which included limit switch setup, soft limit setup, fine tuning of DRO.
Take a step back, regroup, rethink....
Marty

[ScotY]

I still think the homing is weird...I don't quite get what it's doing.

However, I learned something...if you don't set travel limits, you WILL crash into your limit switches on rapid jog moves. For some reason, it does not "remember" where the limit switch is and will jog until the switch opens. If you're moving fast, it may not stop in time. Once I set a travel limit, it then remembers where the limit switch is and will coast to a stop before smashing into it. I would guess this info may be in the manual, but I'm a bit behind in my reading.

It looks ok to me....
I assume DRO's zero after homing?
Yes, set your soft limits once motor direction and homing is setup....

It opens the switch, backs off, then seems to move back towards the switch again with an extra pulse. I don’t know, it happens pretty quick but it seems odd. The mill seems much smoother.

[ScotY]

I still think the homing is weird...I don't quite get what it's doing.

However, I learned something...if you don't set travel limits, you WILL crash into your limit switches on rapid jog moves. For some reason, it does not "remember" where the limit switch is and will jog until the switch opens. If you're moving fast, it may not stop in time. Once I set a travel limit, it then remembers where the limit switch is and will coast to a stop before smashing into it. I would guess this info may be in the manual, but I'm a bit behind in my reading.

Scot, I think you are your own worst enemy, short cuts, not reading up on the process and diving in. So you experience the consequences of doing so.
Not trying to be mean, but you can't take short cuts, maybe on a stepper driven machine where a motor just stalls if you hit a hard stop, but more powerful motors are not forgiving.

I tried my best to make it easy with my videos covering the basics, which included limit switch setup, soft limit setup, fine tuning of DRO.
Take a step back, regroup, rethink....
Marty

I am, no question about that! I have little free time and am constantly being interrupted by wife, kid, dog, etc. While my methods are far from desirable, I am sure I am not alone. Your videos are incredibly helpful but videos are hard to reference, especially when you’re short on time. Once I get this stuff all figured out, I plan to put together a quick cheat sheet, of sorts, to aid in initial setup for busy and lazy people like myself. It’s mostly so I can remember what I did if/when I need to redo something.

[martyscncgarage]

I still think the homing is weird...I don't quite get what it's doing.

However, I learned something...if you don't set travel limits, you WILL crash into your limit switches on rapid jog moves. For some reason, it does not "remember" where the limit switch is and will jog until the switch opens. If you're moving fast, it may not stop in time. Once I set a travel limit, it then remembers where the limit switch is and will coast to a stop before smashing into it. I would guess this info may be in the manual, but I'm a bit behind in my reading.

It looks ok to me....
I assume DRO's zero after homing?
Yes, set your soft limits once motor direction and homing is setup....

It opens the switch, backs off, then seems to move back towards the switch again with an extra pulse. I don’t know, it happens pretty quick but it seems odd. The mill seems much smoother.

Your Z axis seems to sound ok, but your X seems noisy.....
Get your machine setup, fine tune the DRO's and then do repeatability tests with an indicator.