Unit 4 – Program Zero Discussion Mach 153B John Branlund

Learning Objectives: At the end of this unit you will be able to write a CNC program that will center the workpiece on the worktable using: The machine 'Home' position as program zero. One of the 'Translation' codes. 'Work Offset' techniques. Programmable work offsets.

Translation ?? Make the same thing but in a different place. The translation is a 'Vector' or signed X and Y quantity. The vector is 'Added' to the original program coordinates.

Sample of translation: I want to make this series -12. away in X and -7. away in Y. I ADD X-12. to each X coordinate, and Y-7. to each Y coordinate. Original X0. Y0. Y6. X6. Y0. X0. Translated X-12. Y-7. Y-1. X-6. Y-7. X-12.

Home Position (Zero Return, Machine Zero) Discussion Some 'early' machines did not even have this ('Zero' was where the spindle was when you pressed the 'Cycle Start' button or where the spindle was when the machine was powered on). In the 'early' days this was also part zero, as there were no work offsets. New machines find their Machine Zero with a ‘Zero Return’ function right after power-up.

'Machine Zero' can be in different Locations depending on the machinery maker

Where is it? Observe where the ‘Zero Return’ function positions the spindle. Or MDI the following lines, depending on machine, in and execute. E0 X0. Y0. Z0. (Fadal) G53 X0. Y0. Z0 (Haas)

How do you figure out the table size? Jog machine to extremes like using a DRO on a manual mill, recording the X & Y coordinates. Manufacturers' data sheets.

First two … translation Two assignments to center part on the table w/o work offsets (change part program coordinates into machine coordinates). Ma-401 use Ma-201 program as basis. Ma-402 use Ma-301 program as basis.

Ma-401 on Haas Top picture is Ma-201 part made at machine zero (will alarm). Bottom shows Ma-401 part centered by changing program coordinates.

Ma-401 on Fadal Top picture is Ma-201 part made at machine zero. Bottom shows Ma-401 part centered by changing program coordinates.

Ma-403 Assignment Part 1 Write a program to put a 6" Square in the middle of the table. Clear all offsets from control. Calculate the required coordinates from machine home position to program zero. Begin each program as shown on the following slides….

Haas Begins with: % O403 (MA-403 Haas) G90 G10 L2 P1 X0. Y0. Z0. (Set G54 XYZ to Zeros) G10 L10 P1 R0 (Set T1 Height Offset to Zero) G54 (Use G54 Offset) - Complete the rest of the program to make a 6" square using the G92 command to 'Translate' your zero. - Save your program as Ma-403h

Fadal Begins with: % O403 (Ma-403 Fadal) G90 E0 (Use Machine Coordinates) (Do not use any other E number or G54) - Complete the rest of the program to make a 6" square using the G52 command to 'Translate' your zero. - Save your program as Ma-403f

Ma-403 Part 2 Use your Part 1 programs at the machines. Print two copies of pages 18 & 19 in the text, to fill out at the machine. Begin program execution at Machine Zero the first time, and 1 inch away in X and Y the second time. You may have to power down the machine in order to get things 'Reset' after another student. If you are on the Fadal, make sure you are within 0.05" of the X, Y, & Z marks when 'Cold' starting.

Ma-404 & Ma-405: Using the techniques you learned in Ma-403, create the following centered on the table: Ma-404 use Ma-201 program as basis. Ma-405 use Ma-301 program as basis.

Work Offsets Discussion: Overcomes G92's problems, but not available on really old machines unless implemented with a macro. Offset values may be interpreted by parameter setting, or hardwired in control. (i.e. should they be unsigned or signed). The offsets are really a ‘translation’ routine implemented within the control. Can be set using G10's or manually set by the operator.

Multiple Parts Discussion: The same part program may be used as a subroutine to create multiple parts. The main program sets the work offset before calling the sub. A work offset is created for each copy of the part desired.

Ma-406 & Ma-407: Program using work offset techniques without G10's (i.e. set the offsets in the control). Ma-406 use Ma-201 program as basis. Ma-407 use Ma-301 program as basis.

Ma-408 & Ma-409 Program using work offset techniques with G10's (i.e. set the offsets with commands in your program). Ma-408 use Ma-406 program as basis. Ma-409 use Ma-407 program as basis.

Be sure…. That you completely understand the setting and use of work offsets. Avoid the use of G92 / G52 on modern machinery, and know why. Realize others may be using the wrong techniques, and the steps you would take to correct them. Know which offsets you are setting with G10 commands, and the differences between manufacturers on the G10 usage.