Plasma Initial Height sensing - perceived wisdom?

[stirling]

Floating head.
G28.1 method OR G31 method?
Pro's vs Con's
Reason for asking is that G28.1 effectively prohibits using Ref All Axis to drive Z UP for homing so would seem a "strange" choice. My POST uses G28.1 and I'm thinking of changing it to G31. Or am I missing something?

Cheers

Ian

[manmeran]

i use G31 and "probe" pin
if you want use G28.1 ,then you must configure Z home.

Amir

[BR549]

THe G31 seems to be the best bet.

The plasma will also NOT run G68 with the G28.1 style. G68 can be darn handy sometimes.

[stirling]

Thanks Terry I'll give it a whirl. Must admit I've never really got why you would use G28.1 when G31 seems taylor made for the job. The only reason I was using it was because the "default" thc300 post is that way. Another look at the posts available and I found thc300-g31. Job done as long as G31 doesn't play up :-)

Cheers

Ian

[BR549]

HI Ian, I think they picked the G28.1 for its ease of use. Its motion is perfect it goes down till it hits the switch then back up to untrip the switch.

AND it works every time(;-) . Most Jet cutting is very basic 2d work with the z  just to get the head to the proper height. so really the homing is not missed.

BUT it looses some of the functions that I think are handy, such as z homing UP(;-) G68, softlimits for z ,etc

[stirling]

Hi Terry, yes after thinking a bit more I can see the advantages of G28.1 over G31 and visa virsa. However neither actually do a complete job. G28.1 has the particular advantage that the switch can be both home and limit, wheras if you use G31 the switch can't afterwards take over as a limit (well AFAIK anyway). Then as you say G28.1 screws homing north, wheras G31 doesn't. Seems to me we could do with a bespoke floating head command that allows everything to work - i.e. IHS, *normal* homing and limits. Don't suppose there's a way to toggle homing direction at run time is there?

[poppabear]

stirling,

   Look under VB Parameters and see if you can swap directions that way, I am not at the work comp, so can t look it up for you,
another option may be, Made 2 (or more), custom macros one that does the G 28 or 30 thing, a second one that flips the dirctions, or sends a VarifySingleAxis(2) command....

scott

[BR549]

well limits are not a problem as the floating head does not contain the limit switches just the home switch for the TOM routine.

HUM let me think on this one for a while.

IT really would be nice to have a specific TOM gcode for JET cutting.

BUT the G31 seems to be the best OVERALL solution. and it allows the G28.1 to function normally, that way you can still have softlimits in z,the g68 works. G30 home is where it is suppose to be for safety reasons,etc,etc

both work and both have their quirks(;-)

[BR549]

HIYA Scott, The general Idea is to stay inside of Gcode. That way the CAM does what it needs to do directly AND it works for everyone.

IF we run a macro THEN everyone must be supplied the  macro.

Must operators do NOT want to fiddle with macro code they just want to cut metal as simply as possible.

(;-)

[stirling]

Thanks both - I'll take a look asap - I'm a bit otherwise involved for the next couple of days.

Cheers

Ian