loosing z axis zero setting

[contractdesign]

I have recently upgraded a BP series 1 to Mach 3 using the existing stepper motors. The retro is 100% complete with limit and x & y home switches. I do not have a homeing switch on the Z. Twice now, I have lost the z position in the middle of a run. The display on the DRO changes from what it should be and the result is a crash or a severe cut in the wrong place on the workpiece. Is this because of the need of a home switch on z? or is it something else. I was under the impression, after watching the tutorials on Mach that it is not uncommon to not have a home switch on Z, and it would be ok to use the top limit on z for a home switch. I have run about 50 parts and have had two crashes because of this.

[markhas]

Do you have a rigid ram? I do, and mine came from the factory with 3 switches on the Z. One is used for homing. Also, which BOB are you using? The Ashburn/HillBilly board has port 1 pin 12 set-up for Z home.

Mark

[contractdesign]

I have a rigid ram and yes it does have the three switches as you pointed out. My breakout board is a PMDX 122. So do you think homeing is the solution?

[snakebit95]

I doubt not having a home switch is the problem. I run a CNC'd mill-drill with Mach2 / Geckos with no home switches and never have problems with crashing on any of the axes. I would recommend double checking your programs for moves that would create the crash. What kind of computer are you running Mach3 on? Perhaps your computer is not fast enough, and is losing steps?? I did have this problem with my machine, and it took a faster computer to solve my lost Z-axis issue. If you are sure the computer is plenty fast, I would start looking for slippage in the mechanical system or noise problems (probably in that order). Hope this helps!!

[contractdesign]

My computer is at the minimum requirement but was told by Artsoft that it would be ok. 1GHz processor with Windows XP. Did you say that you actually had this same problem and that it went away with a faster computer?

[contractdesign]

Right after the previous post I went out to the machine to jog the z axis up and down. It seemed to work fine. I then pulled the ram down with my hand and hit the jog up button and the ram actually reversed direction. Now when you press the down button the ram sometimes goes down or sometimes up. The same of you press the up button. Also the motor makes some wierd noises sometimes and does not move at all. I readjusted the accel and speed curves in Mach, but it didn't solve the problem. My X and Y axis motors are Sigma. The Z motor is a Superior. I am sure the motors are wired correctly. I have only had the machine up and running for about three weeks and it ran fine until late yesterday. Would a mechanical problem actually cause the motor to reverse? To me it seems laik a motor current problem, but how is this adjustable with the Gecko drives? Confused.

[snakebit95]

Yes, I had problems with losing the Z-position due to the computer I was initially using. I had a 1 GHz AMD machine which could not seem to keep-up with Mach2 demands. I chased the problem for quite a while and tried a lot of different things with the electronics with an attempt to solve the problem. I finally switched computers, and the problem disappeared. I am now using a 1.4 GHz Intel Pentium 4 machine and it runs it flawlessly. It was strange that I only lost location on the Z-Axis though; and never on the X or Y. If you own a faster computer, I would try swapping them and see if the problem disappears as it did in my case.