G53-Z SHIFT AMOUNT NEGATIVE

[coondog]

I have a Daewoo Lathe model puma 12L with a Fanuc 11T control 1988 date mfg.
When I first powered the machine up and homed the machine I noticed that my machine coordinate Z had a very large positive number, I am wondering why the Machine Z at home position is not zero. Also I have my tool offsets set with tool #1 at Z0 and the face of my part is Z0 in G54, my program runs fine with Z0 being the face of the part. If I load a Z shift in offset 00(G53) of +1.0000 the program moves Z-1.000 closer to the chuck instead of making the part longer. If anyone has had this problem or can help in any way it would be very appreciated. This machine was bought new by this company but the original operator/programmer has since retired.

Thanks for all the help that this Forum teaches and provides for everyone, I have been machining for 25 years and have concluded that we all are always just learning thus we should all be thankfull for all of our teachers.

[g-codeguy]

I am not familiar with that particular model, but have to assume that it isn't that much different than newer models when it comes to G53. So I have a question. Why are you using G53 to move your work shift? G53 is suppose to be machine home position as far as I know. I don't use it except for my subspindle (B-axis). The command G53B0 sends the subspindle to machine home regardless of the work offset being used (G54 thru G59).

I have to think that by increasing the G53 by one inch you are telling the machine that the turret is one inch further from wherever Z0 is located on the spindle. Thus it moves in an extra inch. This is similar to how the work shift works on our Hitachi. There is no G53, G54 etc. Making the work shift larger makes the part an equal amount shorter. Add a minus number to make the part longer.

Edit: I'm quite certain that the large reading for G53 when it is used to send the turret home is because that is how far the turret is from the machine's Z0 on the spindle. I think you are confusing the turret's home position with the machine's Z home position.

[HuFlungDung]

G53 is the machine coordinate system. When a workshift (G54) is called, the actual amount of the shift for the G54 origin is relative to the G53 origin (X0Z0). This is why commands prefaced with a G53 cause direct movements that are not subject to any workshift that might happen to be in effect. So a G53 X0Z0 always will position the machine to the same position relative to the machine, not relative to the work.

Now it is possible to shift the G53 origin with G50 (lathe) or G92 (mill) command. These commands rename the axis coordinates of the G53 coordinate system. Thus, invoking this kind of a shift also moves all the workshifts because they rely on the G53. I think that G50 is no longer recommended to be used because it has inherent dangers that can cause serious machine crashes.

Now for lathe that does use a workshift, you really only need to use G54, and only a Z value should be necessary to shift the part zero towards or away from the chuck face. If you had a project where you wanted to cut several parts from one chucking operation, you might use additional workshifts, because the part zero would keep moving as you parted off each part.

These comments are only of a general nature, the specifics of your machine operation may differ in some aspects.

[g-codeguy]

G53 is the machine coordinate system. When a workshift (G54) is called, the actual amount of the shift for the G54 origin is relative to the G53 origin (X0Z0). This is why commands prefaced with a G53 cause direct movements that are not subject to any workshift that might happen to be in effect. So a G53 X0Z0 always will position the machine to the same position relative to the machine, not relative to the work.

Now it is possible to shift the G53 origin with G50 (lathe) or G92 (mill) command. These commands rename the axis coordinates of the G53 coordinate system. Thus, invoking this kind of a shift also moves all the workshifts because they rely on the G53. I think that G50 is no longer recommended to be used because it has inherent dangers that can cause serious machine crashes.

Now for lathe that does use a workshift, you really only need to use G54, and only a Z value should be necessary to shift the part zero towards or away from the chuck face. If you had a project where you wanted to cut several parts from one chucking operation, you might use additional workshifts, because the part zero would keep moving as you parted off each part.

These comments are only of a general nature, the specifics of your machine operation may differ in some aspects.

I definitely can't explain it as well as you have. Probably because I don't have as good a grasp on it. Lathes are all I work on. Otherwise I might have a better understanding myself.