Messages

1

General Mach Discussion / Re: Homing and Limits

« on: February 15, 2017, 05:45:18 AM »

Hi Kolias, my limit switches are inductive proximity, two wire and ground the pin when tripped so they are effectively NO. I know this is not the safest option but the rebuild on this machine has been 'extensive' and expensive and as the sensor limit plates are welded in place (and the sensor adjusts) I decided to run with them. I can jog away from a soft limit as the 'reset' is not flashing but if you hit a hard limit (any of my 3 sensors) then machine stops and you CANNOT move ANY axis while Mach3 is in 'reset' or E-stop. Having the 'auto limit override' solves it to an extent but it would still have been nice to have the software detect which way the limit switch had been hit and know that it will now only allow jogging 'away' from that direction.

Not the end of the world..!

2

General Mach Discussion / Re: Homing and Limits

« on: February 14, 2017, 11:26:14 AM »

Hi Guys,

Thanks for the replies but Dave...I can jog into and away from a soft limit like you can... but if I hit a full limit (as opposed to a soft limit) movement stops (correctly) but I can't reset to allow me to manually 'back-off' as the reset says 'no reset while a limit switch is active'.

I set all the pins manually with no issues but there does exist this anomaly in Mach3 that once on a full limit you can do nothing to get off it manually without going back into the program, altering a parameter, coming out the program, moving the axis OFF the limit, going back into the program, returning the parameters to normal and then carrying on! Mach3 is so comprehensive that I had imagined there would be a couple of lines of code that allowed you to jog AWAY from a hit limit switch with a jog button. I'm sure the coder had a reason to not include it...probably safety or something.

I'll live with it

3

General Mach Discussion / Re: Homing and Limits

« on: February 14, 2017, 03:45:54 AM »

  ...mmm..OK. Well I've changed a few things, set the soft limits before the physical switch limits, set the auto limits override and ditched having both + and - limits on the same input pin and although it's not perfect it doesn't get into the irreversible lock-up situation that it did before! Does Mach4 address the problem??

4

General Mach Discussion / Re: Homing and Limits

« on: February 13, 2017, 06:03:09 AM »

Hi Ger,

Thing is there is a switch per axis and if Mach3 moves, say ++ and hits a limit switch then surely it is kids play in software for it to disallow further ++ movement and only allow -- movement??

Tim

5

General Mach Discussion / Re: Homing and Limits

« on: February 12, 2017, 11:21:21 AM »

Hi Kolias..Not yet as I am trying to find a way where Mach allows you to move 'away' from the triggered limit but only stops you from barging any further 'into' the switch.
Tim

6

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

7

General Mach Discussion / Re: Homing switch concerns

« on: January 17, 2017, 03:12:28 PM »

Thanks guys, all good suggestions. I guess the proof of the pudding etcetera will be when the refurb is finished and I am actually moving things and can see if what I am worrying about is actually an issue.

Regs
Tim

8

General Mach Discussion / Re: Homing switch concerns

« on: January 12, 2017, 05:24:54 AM »

Hi Dave,

The inductive sensors have a coil fed from an oscillator circuit. When the coil is brought near a metallic surface there is a change in the absorbed emf from the coil which can be detected. Basically at 0.1mm repeatability it means that each time the machine head is homed the tool could end up up to 0.2mm from the previous position in all three axes. Not a tolerance that is any good for precise machining operations

I think I need to design/make a precise tool origin widget

Regards

Tim

9

General Mach Discussion / Re: Homing switch concerns

« on: January 09, 2017, 02:50:04 PM »

Hi Davek,

Yes they are the original sensors but as they connect directly to Pacers own driver/interface board which is heading to the scrap bin I have to interface them to my breakout board which doesn't accept non-polarity conscious, 2 wire inductive sensors, so I have to add a dry-contact relay switching board which will of course add an extra element of error as there is a finite time for the relay contacts to respond and tell Mach3 it has arrived. Ironically it has £200's worth of exceptional sensors which with a relay in the circuit may just as well be a £2 microswitch!

I suppose my biggest question is that with the amount of machines out there under Mach3, with microswitches, there is an awful lot of inaccuracy going on and I'm puzzled why this forum (or any of the others) isn't/aren't awash with questions about how it can be overcome??

10

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