Topics

1

General Mach Discussion / Homing and Limits

« on: February 12, 2017, 11:00:07 AM »

There's a million hits when I search for this but not a simple answer! I have single inductive proximities on each axis. Told Mach3 to use each signal (each on separate pin) as a combination home, limit+ and limit- trigger. When I 'ref all' machine homes and backs-off in all axes as it should but if I inadvertently jog in the wrong direction the 'limit' switch is re-triggered and all stops...as it should...but then Mach won't let me reset as it 'sees' a limit switch STILL triggered??? I would have thought that it would allow you to manually 'back-off' the limit switch in the opposite direction but until 'reset' is hit (which it won't accept) you can't. I'm sure I have something not set right as each time this happens I have to go into Ports and Pins and disable the X++ and X-- detection just to allow me to move off the limit switch! What am I doing wrong!! This can't be the normal operation of any controller as it ends up in a logical lock-up situation...'Limit switch hit therefore NOTHING moves, reset needed...Oh...you can't reset while a limit switch is STILL hit' therefore solid lock-up??

Tim

2

General Mach Discussion / Homing switch concerns

« on: January 09, 2017, 11:37:41 AM »

Hi Guys, sort of newbie here. Have run a Pacer Cadet for some years with antiquated control and driver software (Pacers own) on a W95 (yes W95) dedicated PC. I'm an engineer (mechanical and electronic) by trade so decided to make use of the excellent mechanical construction of the unit and put all new drivers, controls and software in. All is going OK and I've answered lots of my questions by trawling through this excellent forum but I am concerned about the accuracy/repeatability of the homing sensors. Mine are two-wire inductive but any sensor, microswitch, opto, capacitive etc. can't be considered as 'absolute' position switches as lots of outside factors (temperature, vibration, dust, electrical noise etc.) can affect the trip point. These switches are fine as ultimate 'limit' switches to stop carriages mashing into things but not for accurate origin setting AFAIK... I've worked on a lot of precision industrial machines and we would normally use a Renishaw (or similar) absolute position sensor to determine a repeatable and accurate origin for toolset.

As Mach3 (which I am running) goes I understand that it takes the home position (all three axes) as the point from which to calculate the 0,0,0 location?? Is that so? If so how can I guarantee that 0,0,0 will be in the same place after each 'homing'??

Crazy thing is I've used this machine for 5 years and never questioned it, just run the machine, and it's only now that I am into the rebuild that the question has arisen.

I'm sure you guys will have an answer!

Regards

Tim