Thanks for that, explains a lot then ;) Don't think I've ever used RFH...reaches for manual ;)
I think for what I am doing - small batch production - saving the offsets is a good idea??
All the raw plates are pre-cut to the same size and pre-drilled for fixing to the bed so each part will always start in the same position or work-offset.
Is that what offsets are for?
Could I then have re-homed the machine and loaded the offset then carried on with part I had stopped on??
Lots to learn....
If you don't close Mach3, the offsets should still remain after homing. (I think)
Yes, if you have a specific part that you always run in the same place, use an offset like G55,G56,G57...
Add the G -code to the beginning of your code, and save the offsets. Then when you turn on your machine, you just home, load the code and run.
Sounds good, an offset will do what i need, i have never checked if the work position remains after a home, something else to check.
Regards Homing and Stop. It actually goes further than that regards homing. If you have stopped the G-code with feedhold and in controlled manner then if you for any reason power down the drives, which a safe E-stop system should. Then you should home the machine when they power back up.?
This is because they often jump to next full Step so your then out of positon to where mach thinks it is.
Then if your trying to get back to position use RFH. I use RFH all the time it's a great tools when shit hits the Fan.!!!
Last edited by JAZZCNC; 10-04-2016 at 06:48 PM.
If I'm using say G55 for my job, it will still be there next time i load?? That sounds like a recipe for fun ;) Can it be programmed to always load into G54?
The G55 could/should be added to the start of the specific G-Code file?
Stuff to learn...
If you save the Offsets when closing or by Saving directly in work offsets then G55 will be saved but by default Mach on start up will load G54 so your safe.
If you want G55 or any other offset you'll have to call it with MDI or Thru G-code.
To use different Offset with in one G-code file you'll first need to create the offset and save it.
To see it work Try this.!!
By default your in G54 so set Zero work coordinate. Then Type G55 in MDI now jog away and set Zero again in different place.
Now in MDi Type G54 G0 x0 y0 and it will got back to zero you set for G54. Now type G55 G0 x0 y0 and it will go back to zero for G55.
So say you have one part you need to make but in two different materials. First set up the Zero Offsets for each material G54 & G55.
Then use copy and paste. The first part will most likely have G54 at the begining by default. So paste the code again for the second part and replace G54 with G55.
Now when code runs and gets to second run of part it will use the new Zero at G55.
If you want to keep thses offsets then go into Offests and save work offsets.
To be honest saving Offsets before starting job is a good habbit to get into because if Mach crashes or PC then you lose the offsets and have no way easy way to get back into position. This happens often with parallel port machines when being run hard.
Last edited by JAZZCNC; 10-04-2016 at 06:47 PM.
Excellent, that makes sense.
I have "optional offset save" turned off so it only saves what i want to save into the offset table.
I don't think sheetcam has a work offset option so it'll have to be a manual add, but can't have everything i guess ;)
Hmm, back to school, two issues tonight.
Offsets, seems i have not grasped it yet or I am in the wrong work sequence...
Yesterday I saved the work offsets for my production job - G55, I also added G55 to the start of the code. I then loaded up the material, changed the tool & set my top-of-material Z zero. Pressed cycle-start and got Soft-Limits warning on Z, looking at the numbers on the DRO's I could see something was wrong.
I deleted the the G55 from the code, switched to G54 Offset, reset my tool zero just in case, set work X&Y zero as normal, and ran the job as before.
So, not sure what i am doing wrong but clearly offsets do not work totally how I envisaged them to work. Do you have to be in the correct offset BEFORE setting the tool and Z zero?? If yes then that was likely mistake No1 as I was in default G54 when I set the tool. What I expected was for the offset to only affect X & Y not Z (i think)
Z Zero, again.
yesterday the job cut perfectly, onion skin just about held it together and a nice part came out. Tonight, same file, onion skin failed as the tool chewed the bed by about 0.1mm or a bit less - this meant the part got 90% of the way and failed on the finish pass, luckily the cutter survived but the part was toast and now resides in the scrap bin.
So, I have two issues here, top-of-material setting and work-holding.
Here is the part before it went flying to the bin in a red-mist
Now, after cooling down, I miked the metal up and it seems the thickness is not very reliable, the 7 bits i have left ranging from 5.05mm to 5.25mm depending where you measure it - I think this accounts for the failed onion-skinning and subsequent junk output.
My first resolution to this is to mark a spot with a sharpie, measure it, note it, CAM the part specifically for that thickness, set the tool zero exactly on the sharpie mark and try again - I do not think this is a machine error, more a material error.
Work-holding, these parts must be 100% flat and clean, if I tried adding some carpet tape etc under it, would I be able to get the part off the bed when cut?
Last edited by Davek0974; 13-04-2016 at 07:07 PM.
If this is a regular job I cannot see why you do not create a jig waste board to hold material in a recess with appropriate hold downs permenantly in place so 4 nuts or so to lock jig onto bed, material in recess and locking tabs clamps (cheap chinese 120kg hold downs or similar you could have a couple to swing in after finishing pass goes by if needed and cut clean threough each time) to hold material off you go, no more biting into the bed, cutting through not going to matter occasionally one out quick vacuum next one one in, seems to me a lot of wheels being reinvented.
On my website, there are some modified macros that will zero the Z axis for all of the G54-G59 offsets at once, regardless of which one you are currently in.
As for material thickness, there's another option in the 2010 Screenset called "Material Offset". When checked, you zero the Z axis to the table, and Z zero is set at the material thickness value above the table. It's works basically the same as setting Z zero to the bottom of your material. If you are doing pockets, note that this will affect the pocket depth if the material thickness varies.
Last edited by Ger21; 13-04-2016 at 08:09 PM.
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