
02-09-2005, 02:59 PM
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 | | | Join Date: Nov 2003 Location: United States
Posts: 634
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Originally Posted by twombo
Here are the questions:
1. Seems to me once I have repeatable homing (I'm using proximity sensors and the accuracy remains to be seen). How may I best tell the system where the fixture and stock are? Is that the job for the G code editor. |
It depends. In the simplest method, your home is always fixture zero and you don't have to worry about it. You simply draw the tabletop in your CAD program and always insert your part and fixture drawings on the tabletop (in CAD). For example, if the part is located 3" up in the Y and 3" over in the X, then the CAM program will output G Code that has and extra 3" added to all the dimensions. You just need a way to mechanically insure that the real part is located on the tabletop where you want it.
Originally Posted by twombo 2. If assumption 1. is correct, is the general process to?:
a. Define the path to a point of reference in relation fixture and stock? G code editor? |
Another way to do this is with the offset tables in your controller. Let's say you are using Mach 2. There are G code commands, G54, G55, G56, etc. that allow you to set up program zeros wherever you want on the table and call them up in the program. Once the offset tables are set up. (a one time deal if you never move your fixtures). You simply insert the appropriate G code at the beginning of your program. (Or better yet, set up your post processor to do it for you.)
Originally Posted by twombo b. Does it make sense to design the part and fixture simultaneously and with a x,y,z references embeded into the model. |
Originally Posted by twombo
It will work either way, this question is a matter of preference and what type of work you are doing. I personally like to keep the part independant of the fixture.
c. Is there any value to establishing a set of pre-established datums for all fixtures and using that geometry as a G-code subroutine that can be appended to part files for the purpose of semi automating machine setup for production. My guess is that fine zeroing and tool setting reference positions can be built into these subroutines!. |
Yes, that is what the G54, etc commands are for. On a well made machine, you shouldn't need much fine zeroing, tool setting is done with G code commands and another table for tool length and tool dia. No subroutines are needed. |