Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: dman65 on July 02, 2017, 03:47:29 PM

Title: Z movement is random
Post by: dman65 on July 02, 2017, 03:47:29 PM: Hello,

I am using Mach 3 with a UC100 connected to a Chinese 6040T CNC router.

Everything has been running fine until this afternoon. The machine was in the middle of a lengthy beveling operation and I went to eat some lunch. When I returned the X and Y were moving along fine but the Z was a couple of inches above the work piece even though Mach 3 was showing that it should be 4mm below the work surface zero.

I stopped the cut to see if I could rezero the Z and backup to the last tool change and start over. Unfortunately, pressing the keys to control the Z resulted in random action. The Z always moves, but whether it is moving up or down is random.

I reset the computer as well as the control box and I double checked the Z configuration in Mach 3, but the issue persists.

Does anyone have any idea how I might determine what the issue is?
Title: Re: Z movement is random
Post by: ger21 on July 02, 2017, 04:53:44 PM: Loose wires would be the first thing I'd look for.
Title: Re: Z movement is random
Post by: reuelt on July 02, 2017, 05:26:03 PM: Quote from: dman65 on July 02, 2017, 03:47:29 PM
Hello,

I am using Mach 3 with a UC100 connected to a Chinese 6040T CNC router.

Everything has been running fine until this afternoon. The machine was in the middle of a lengthy beveling operation and I went to eat some lunch. When I returned the X and Y were moving along fine but the Z was a couple of inches above the work piece even though Mach 3 was showing that it should be 4mm below the work surface zero.

I stopped the cut to see if I could rezero the Z and backup to the last tool change and start over. Unfortunately, pressing the keys to control the Z resulted in random action. The Z always moves, but whether it is moving up or down is random.

I reset the computer as well as the control box and I double checked the Z configuration in Mach 3, but the issue persists.

Does anyone have any idea how I might determine what the issue is?

Perhaps the coupling between the (stepper?) motor and the ball/lead screw has become loose or is broken.
Title: Re: Z movement is random
Post by: dman65 on July 02, 2017, 06:17:24 PM: Thanks Gerry,

I unplugged both ends of the motor cable for the Z and plugged them back in and am receiving the same behavior. I will have to see if I can find the connectors they are using so I can make up my own cable and see if it fixes the problem.

Thanks Reuelt,
It is definitely not a mechanical issue. The Z is moving the correct distance, but the direction is random.
Title: Re: Z movement is random
Post by: ger21 on July 02, 2017, 06:38:10 PM: It won't be the motor cable. Look at the step/direction wires, or parallel cable.
Title: Re: Z movement is random
Post by: reuelt on July 02, 2017, 08:40:15 PM: "direction is random"

In the motor tuning what is the pulse and direction length set? I set mine to 15us and 5us respectively because the MY BOB-driver board of the 6040T has slower buffer chips and opto-coupler chips compared to other break out boards (BOB).
Title: Re: Z movement is random
Post by: dman65 on August 03, 2017, 08:23:10 AM: Sorry I didn't come back with the resolution sooner. It turned out to be the Z axis cable. I made a new one and everything worked fine after that.