Slave Stepper Question

[mlk1950]

I'm building a 3' x 5' machine for doing mainly wood signs. It's all wood construction with black pipe for the rails and skate bearings for rollers. The lead screws are Acme single start 10 TPI. Two 1/2" screws on the X-axis and single 3/8" screws on the Y and Z. I went with the single starts to begin with because of the cost multi start screws were just to much at this time. I figured I can upgrade in the future. I bought the 4-axis pro board package from Hobby CNC, with 305oz steppers. It's going to be a 3-axis machine with 2-steppers on the X-axis. Is it a good choice to go with the slave stepper on the X-axis? I've read that the slave stepper setup can be a pain to get dialed in. Hope I made the right choice.

[ger21]

Slaving is the only way to go, imo.

If you're using Mach3, there is no "dialing in". You set up both axis' the same, and check a box to turn on slaving. That's it.

[CarveOne]

Originally Posted by mlk1950 I'm building a 3' x 5' machine for doing mainly wood signs. It's all wood construction with black pipe for the rails and skate bearings for rollers. The lead screws are Acme single start 10 TPI. Two 1/2" screws on the X-axis and single 3/8" screws on the Y and Z. I went with the single starts to begin with because of the cost multi start screws were just to much at this time. I figured I can upgrade in the future. I bought the 4-axis pro board package from Hobby CNC, with 305oz steppers. It's going to be a 3-axis machine with 2-steppers on the X-axis. Is it a good choice to go with the slave stepper on the X-axis? I've read that the slave stepper setup can be a pain to get dialed in. Hope I made the right choice.

One motor will be set up as the X axis and the other is set up as the A axis. There are slaving options in Mach3. Choose "Slave A to X".

In my case, it was a pain for months, but it ended up being resolved as Output settings in Mach3 that were incorrect. Make sure that the Dir voltage levels getting to your motor drivers are correct for TTL logic levels. 0vdc in one direction and 5vdc in the other direction.

The only other thing to add to ger21's post is that one motor direction needs to be reversed. You can wire the motors the same, and reverse them in Mach3 in a check box.

It is not a dialing in situation, just get the correct settings in Mach3 for your motor drivers and not have binding issues in your mechanical parts. When these are correct your machine will run correctly with a slaved motor axis. I have no remaining issues with slaving now, and recommend it.

CarveOne

[ger21]

In my case, it was a pain for months, but it ended up being resolved as Output settings in Mach3 that were incorrect.

Just to clarify, CarveOne had somehow turned on Outputs that were conflicting with his motors. (I think).

It's really not difficult at all.

But as he mentioned, your mechanicals need to be very carefully aligned, as any binding will cause problems.

[dave22]

Be careful here, normally you would reverse one motor if you were driving your gantry with rack and pinion or belt drive. However, you stated above that you will be using ACME lead screws, in which case both screws need to turn in the same direction to avoid ripping the gantry apart. Assuming both motors are mounted at the front of your machine or both are mounted at the rear.

Good Luck with your build

[mlk1950]

Thank you, that put my mind at ease. I am using Mach3, and from what I read that if I'm using A to slave X, I need to enable and set the pin settings for A. Then I need to select A to slave X in the slave axis window.
Both motors on X are at the rear

Thanks Mike

[CarveOne]

Originally Posted by ger21 Just to clarify, CarveOne had somehow turned on Outputs that were conflicting with his motors. (I think). It's really not difficult at all. But as he mentioned, your mechanicals need to be very carefully aligned, as any binding will cause problems.

Correct.

I don't know how they were turned on or whether it was done by me or not, but outputs 7 and 8 were enabled (check mark) when they should have been disabled. These are (in my case) assigned to the X and A axis motors. The Dir signals going to my X and A axis G203V drives were getting 0.67vdc in the direction that should have been getting ~5vdc. They were somehow running in the correct directions but they were not tracking each other due to accumulation of missed steps while cutting something fairly long cut time. It was bad enough to force my X axis R&P drive to jump over a tooth. Bummer for sure.

mlk1950,

If you want to use EMC2 instead of Mach3, I can help you with that also. It isn't real obvious, and there is very sketchy info on the web about it. I have done it successfully though.

CarveOne

[CarveOne]

Originally Posted by dave22 Be careful here, normally you would reverse one motor if you were driving your gantry with rack and pinion or belt drive. However, you stated above that you will be using ACME lead screws, in which case both screws need to turn in the same direction to avoid ripping the gantry apart. Assuming both motors are mounted at the front of your machine or both are mounted at the rear. Good Luck with your build

Be careful, yes!

Make sure you know what is going to happen before running it the first time. They also make left hand and right hand thread lead screws, so that could also need to be considered in very rare circumstances where they might become mixed on one machine. Check your screws.

CarveOne

[mlk1950]

The screws are all right hand thread. Got it all hooked up and bench tested it and "It Works" so far. The real test will be on the machine itself.

[mlabruyere]

This is how my large CNC is setup. To ensure I didn't commit an IBM I ran some tests with the lead nuts not mounted to the gantry....this way I could see that the screws were turning in the right direction before I got my gantry out of square....

I've been running mine like this for about a year without issue.

[mlk1950]

What is the standard procedure for when you get the motors all mounted to test if the machine is running in the right direction according to the G-code loaded on Mach3. Also would be a good idea to wire limit switches on the machine.
The E-stop switch. Does it just wire to a single terminal on the board?

Thanks Mike

[ger21]

Disconnect the motors from the screws and slowly jog the motors to check them.

Also would be a good idea to wire limit switches on the machine.

That's up to you. I don't have any, but if my machine runs into a stop, it'll stop without causing any damage.

The E-stop switch. Does it just wire to a single terminal on the board?

Depends how safe you want to be. I'm getting one this week, and mine will cut the incoming AC to the spindle and drives.

There are numerous discussions on different ways to wire an E-Stop. On a commercial machine, they cut the power so there is absolutely no chance of anything moving while in E-Stop.