Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: alex850 on March 14, 2009, 10:16:22 PM

Title: home position problem
Post by: alex850 on March 14, 2009, 10:16:22 PM
i am haveing a problem with my home position . when i bring a drawing from autcad into lazycam the tool is always in the lower left corner of my parts so i make my fixture and drill a hole so i can always line my tool up on zero. i have been doing this for two years no problem. i went into autocad to bring in some of the drawings that i have used before in lazy cam and have made a fixture for the parts . the tool in lazy cam was not in the same place it was directly on the front of the part.i tried other drawings same thing none of my fixtures will now line up with the tool. need help please.

thanks alex
Title: Re: home position problem
Post by: jimpinder on March 15, 2009, 05:51:59 AM
Alex - I will explain how it works, although it might not actually help you directly.

When you say "home" the machine, this is a term that refers to the machine going to a certain place on its own - usually to switches set in that position. The machine is then "home". The machine co-ordinates - displayed when the "machine co-ordinates" button is pressed and the led is lit is turned to zero (usualy automatically) see Config/Homing. If you do not have switches fitted, you can make a home position - one to which your machines goes accurately, and then zero the machine co-ordinates by pressing re"RefAllHome"

This position is not the "program position" As you have found, programs have different 0.0.0. positions for which you can make jigs to hold the workpiece.

What you do to bring the machine to that position is apply an offset to the machine co-ordinates 0.0.0. position by using one of the offsets G55 to G59(then 250 others on G59.***). These offsets are entered into your fixtures table (see Config/Fixtures). If the offset is then entered at the beginning of the GCode program, the machine will home to it's home position, then will move to the new 0.0.0 position determined by the offset.(or any other point referenced to the new 0.0.0 position).

So - select a set position to home your machine to, then for each program jog the tool to the 0.0.0 position of the particular program you are doing. Type in an offset e.g. g56 on the MDI line, and then zero the Program Co-ordinates. If you check the fixtures table, G56 will now show the offset for this program. Enter the line "G56" at the beginning of the program, and that is it.

Your program will now run from your "home" position, and then move to the correct start position. If you then have a new program, with a different start position (or 0.0.0 position) you use a different offset. Then for each program you run, the machine automatically moves to the correct start position for that program.

It is useful to keep a note of the offsets (I usually put a message line is the GCode program) so that, if I loose any settings, I can always set them up again.

As I say, this might not be a direct answer to you question, but it explains how it works, and I am sure you will be able to work it out from that.

Title: Re: home position problem
Post by: alex850 on March 15, 2009, 10:32:02 AM
this is my question. when i open lazy cam  my tool is alwys in the same location when i bring the same file in,up until yesyerday. is there anything that i could have done that made the tool shift over? and also the part envelope is larger on the screen than usal. if i pull the same program out of the g code files directory in mach the tool is in the right place . i have never had this problem.

Title: Re: home position problem
Post by: jimpinder on March 17, 2009, 05:12:23 AM
I'm sorry. I know very little about Lazy Cam. I had a look at it , and what seemed to be the tool (the circle with four quarters in) responded to the shift draw (blue box) instruction, and with that you could move it round the screen.

Had you been running the program somehow - it might be at the position that it was left when the program ended.

I don't think this will affect the 0.0.0 position of the whole system, though. Your point of origin will still be in the same place.
Title: Re: home position problem
Post by: alex850 on March 17, 2009, 08:53:21 PM
i will look at it tomorrow when i go back in the shop. yhanks fro the help>