Messages

1991

VB and the development of wizards / phantom code

« on: October 12, 2007, 12:46:54 PM »

Hi

Has anyone come accross Mach not actually executing a 'code' statement but "thinking" it has?

i.e. in my code this fragment works fine most of the time but every now and then there's no movement.

code "G01 X.."
while ismoving()
wend

... rest of code

1992

General Mach Discussion / Re: edge finding/2.5D probing

« on: October 12, 2007, 09:52:50 AM »

Agreed.

Bit of an update on progress. My cheap (well actually it cost me zippo ) and cheerful probe is at least allowing me to experiment with the software side of things. So far I have a working wizard that's producing some reasonable toolpaths. At the moment the main issue is the probe ocasionally "sticking" when I retract from a touch - but hey, I'm learning lots so I'll stick with it for a while longer...

1993

General Mach Discussion / Re: edge finding/2.5D probing

« on: October 10, 2007, 09:13:46 AM »

If there is extra movement in the probe mechanism you can get that. When moving slowly you can actually bump the trip switch but when it stops it losses contact and the led goes out. When moving faster there is always a touch of overun that will keep the switch in contact.

yes - I've done a bit more experimenting and I agree. It seems to be all about tweaking the motor tuning to make sure you get a good trip! - reduce accel and up feedrate etc.

It would be nice if the G31 cycle would be movement to trip switch then back off switch untill it untrips THEN record position.

Indeed it would, but I think I've found a way to get round it.

1994

General Mach Discussion / Re: edge finding/2.5D probing

« on: October 10, 2007, 05:04:03 AM »

I've taken a bit more of a look at the digitize LED lighting/not lighting. It seems that sometimes it does and sometimes it doesn't. If you have a moment, try this code in the VB Script window. I'd be grateful for your findings on your system.

code "G21"
code "G31 Y100"
While IsMoving()
Wend
MsgBox GetOEMLed(825)

arrange for the probe to be tripped by some obstacle (i.e. not your finger) at somewhere around Y50 mm. Try it with different feedrates. On my system at feeds around 1000mm/min the LED always lights fine but when you get down to lower feeds around 100mm/min, although the probe trips - i.e. it stops! - the LED doesn't light.

1995

General Mach Discussion / Re: edge finding/2.5D probing

« on: October 09, 2007, 02:35:36 PM »

Hmmmmm. I tried that but there's a problem. If I drive into an obstacle with a jog, or a G01 or a G00 then the LED changes state. BUT if I drive into an obstacle with a G31 it doesn't, even though the trip has been actioned by Mach.
I even tried reading the parallel port with a GetPortByte and that doesn't work either with a G31 but does with a jog, G01 or G00.

I'm beginning to think that there are more issues with G31 than you/me/we thought - I'm even thinking of writing my own simulation of a G31 with a G01 and testing the LED as you've suggested.

Any thoughts?

1996

General Mach Discussion / Re: edge finding/2.5D probing

« on: October 09, 2007, 11:00:57 AM »

OK so I now have myself a working probe. However I've hit the first snag and am wondering if anyone can help me through it.

It seems that there is no way of telling with G31 whether the probe actually gets tripped or not.
i.e. at the end of G31 it stores X,Y and Z in machine params 2000, 2001 and 2002 whatever happens.

For example: if I start at X0 and have an obstacle at X100 and program G31 X120 then I get (correctly) 100 in parameter 2000.
However if I program G31 X80 I get 80 in parameter 2000 whereas I would have expected some sort of error indication.

Anyone know how to tell if the probe is actually tripped?

1997

General Mach Discussion / Re: edge finding/2.5D probing

« on: October 05, 2007, 07:11:45 AM »

My thinking is that Art & co. probably have enough on their plate at the moment so I think I'll go ahead and have a go. First I'll make a probe and try Art's wizard.

1998

General Mach Discussion / Re: Steppers have no torque.

« on: October 05, 2007, 05:16:26 AM »

Hello all;
 I have a Taig cnc mill , and have been running the demo of Mach 3 for a while. I use a Xylotec board and have Oreintal motor steppers. The motors are 200 steps per rev, and on the Taig 20tpi leadscrew. I have the board set for full step and when I do a calibrate test Mach tills me 32,000 pulses for 1" of movement. Is this right ? It seems way to fast.

200 steps per rev * 20 threads or revs per inch = 4000 pulses per inch at full step.

I have the motors tuned for 14 inch per min

14 * 4000 / 60 pulses per sec = 933.33 pulses/sec. call it around 1KHz which is around 5 revs per sec - which isn't hugely fast. The faster you want to drive them the more the overdrive ratio of the drive voltage you need. what ratio are you using (supply voltage to motor voltage)?

and mid settig for accel.

whatever that means... until you get your speeds worked out and whether your motors can cut it power wise - turn you accel down pretty low - once you have motors that can run at the speeds you want then you can figure out what accel your motors/rig can handle.

If I run them faster they stall and hum. I can grab the coupling on the stepper and stall it with very light force.

Two (of many) possibilities are a) too low drive voltage ratio b) resonance.

I have had the motors for years in a box , cuold they be bad ?

motors are neither like wine nor milk, they don't get better or worse with age :-)

I got some specs years ago and they were 180 in/oz motors. Is this to weak for mill ?

Well that depends. Of more interest to you at the moment is: Their Amps/phase, Voltage, inductance, PS voltage, whether they're resonating etc. as above.

If I bypass some start settings and get to the meat of the code it works better.

What settings are you bipassing?

1999

General Mach Discussion / Re: Constant velocity

« on: October 02, 2007, 01:45:58 PM »

No problem Brian.

Great avatar by the way - did you have it specially designed for you? 

Thanks

Ian

2000

General Mach Discussion / Re: edge finding/2.5D probing

« on: October 02, 2007, 11:36:53 AM »

Hi TP - thanks for your reply

the radius of the probe tip AND any movement error associated with the length of the probe arm AND the direction of axis TRAVEL  HAVE to be corrected to give you the exact touch point center line

Understood - but isn't this a problem that can be solved by either post-processing of, or on-the-fly-processing of the data? What I'm getting at is that there seems to be the idea that currently 2.5D probing can NOT be achieved in Mach. Is it not simply the case that no-one has yet written a plugin/wizard whatever to do it?

i.e. I'm thinking of writing one - I have all the algorithms worked out and tested but if there's something that Mach can't do (that I don't know about) then I'll shelve it for the time being.