Messages

2071

Works in progress / Re: 1st 'Beta' release of the MachSteelBlue Screenset

« on: June 12, 2007, 09:59:29 AM »

Hi - hope I'm not treading on anyone's toes and that this is the correct place to post this. Apologies if not. Also can't find this posted previously so here goes.

I'm using the SteelBlue set and like it. However here's a problem I noted (to my cost! ).

On the program run screen, set off-line. Switch to MDI and enter new coords. Ooooops, I just snapped the tool. The LED is indicating "de-ref all axis" and is definitely NOT offline.

FWIW the reason I swapped from the default Mach3 set was to see if the line number DRO on the program screen would display the whole number rather than miss off the last digit - however the SteelBlue does the same. Why is this?

best regards

Stirling

2072

General Mach Discussion / magnetic home switches

« on: June 12, 2007, 04:28:52 AM »

anyone use these? I'm having intermittent problems. Sometimes homing works fine but sometimes the first axis homes and then everything stops with the error message "home switch active". It seems that even after the "backoff" the switch hasn't opened again. Is there a way to increase the backoff distance or should I switch to mechanical switches?

2073

General Mach Discussion / Re: home and limits question

« on: May 27, 2007, 07:34:41 AM »

Nope. Just a thought but it didn't happen on my last post and I'd just cleaned out the cache etc. so I'm wondering if I had a double clicker or something in there. Anyway, if it's not happening for you it must be a local problem - I'll sort it.

Thanks

2074

General Mach Discussion / Re: home and limits question

« on: May 27, 2007, 05:02:22 AM »

IE 6 on XP pro

2075

General Mach Discussion / grex comp

« on: May 25, 2007, 06:43:20 PM »

so how do I edit my first guess now that I know the real answer ??

2076

General Mach Discussion / Re: home and limits question

« on: May 25, 2007, 06:51:27 AM »

All's good - I have reasonably broad shoulders This whole question came to me after using a machine for a couple of years without any switches at all. I decided to add them really cos I wanted a home function and thought I'd do limits while I was at it. I'd had very few crashing problems before but thought it might be a good idea as I've (more or less) gained the confidence to leave the machine doing it's thing unattended.

That said I'm still thinking about it cos far from crashing into fixtures etc. the problem I've had more often than anything else is with "shifting islands", and no limits (soft or hard) can help with that one.

Maybe I'll look at spindle and stepper current overload monitoring!!!! - that should sort it

On a completely different tack - has anyone noticed that if you preview a post, when you try to actually post it the board thinks you've already sent it and hacks you off for maybe double clicking the post button? Never happens if I don't preview first.

2077

General Mach Discussion / Re: home and limits question

« on: May 24, 2007, 01:40:43 PM »

Thanks Hood

Maybe I havn't been explaining myself very well, but you've obviously understood what I was trying (obviously badly) to say. Also you've given a good reason why the soft limit approach in conjunction with the hard limit switches are the better approach. I now understand why Mach3 opts for this method, which was all I was trying to discuss.

Thanks all for your input. Much appreciated.

2078

General Mach Discussion / Re: home and limits question

« on: May 24, 2007, 03:04:17 AM »

Hi again lemo - this could run

It doesn't matter that the machine doesn't know where a limit switch is. It's how it can respond, if and when it hits one that I'm discussing. The software writer (Art in Mach3's case) has basically two options.

if limit switch hit then
stop dead
end if

or

if limit switch hit then
stop in a controlled manner
end if

it's like when you're driving your car, you don't know when a child is going to run out in front of you but you have the same options if one does

if child runs out then
break so hard you're head comes off
end if

or

if child runs out then
break as hard as you can without causing your neck to snap.
end if

Another approach is to play the caution card i.e. when there's a likelyhood of children being around, drive slowly enough that if you have to do a dead stop, you can do so without your eyes flying out of your head and splatting on the windscreen. This is the Mach3 approach. It's a perfectly good approach but not the only one possible is all I'm saying.

2079

General Mach Discussion / Re: home and limits question

« on: May 23, 2007, 06:02:57 PM »

Hi lemo - understood.

My question was based around the fact that suddenly stopping an axis is generally best avoided except when you're about to lose a body part.
I'd thought that there would be a way in Mach3 to avoid this happening and indeed as Chaoticone stated, there is.
I'd expected the algorythm to be "if you hit a limit then brake hard as you can to a stop" and the op would position the limit switches appropriately. Wheras it's actually "on entering the soft limit zone, slow down to a velocity slow enough that IF you hit a limit, a sudden stop will not be too hard".

Which is the better approach? I don't know - I can see advantages/disadvantages to both approaches.

2080

General Mach Discussion / Re: home and limits question

« on: May 23, 2007, 09:07:42 AM »

hi Chaoticone

got it - thanks very much