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Siemens 840D axis compensation program


Mar 2, 2023
Hello Everyone,

We have some 5axis milling machines with Siemens 840D controls.
The problem with the machines is that they are not that accurate. The build quality is not that good. Not that bad also.
It's a 5axis swivel head milling machine with a large (3000mmx1500mm) vacuum bed.
Small crashes happen while making parts because parts come off the vacuum bed. A small crash is enough for the machine to make bad 5 axis parts. The machine use a toolsetter to check A and C axis with a plug. So you can correct the rotary axis with the toolsetter after a crash.
But the machine is not build that rigid and there is more moving in the machine while a "crash" then only the rotary axis. So a small crash create an geometric error in the machine. Its a lot of work to get the geometric error out. Takes me like 3 days to get it under 0.025mm if i'm lucky. Now we don't make that high end parts on that machine but we need to hold it under 0.1mm tolerance max. Normally after a crash i will do a full geometric check/rebuild and kinematic check. But that takes a lot of time. As a side solution i created a macro that i can call with an M code that will do X Y Z corrections based on the A and C position. it reads the A and C position and correct the machine offset in xyz. Works perfectly. So normally after the cycle800 it reads the mcode(M996) and correct the machine axis. The repeat the cycle800 to take effect of the corrections. But now the problem is that when we do full 5 axis toolpaths this won't work. The correction macro is not a live program. Is it possible to run a live program on the background off a Siemens 840D software? I'm normally a fanuc guy and i know this is not that easy. Only possible by using executor macros. But maybe on a siemens 840d controller this easier?

Dont you have axis home position compensation?
How do you mean? The axis positions are not the problem in my case.
It's the machines rails, rack and pinion, and frame that are build poorly in my opinion. That are the things that move even after a small crash. I know we could buy better machines.
What machine is it? If the rail and rack are moving after a crash certainly the bolts are broken
the rails can move cause the holes in the rail are bigger than the bolts. Only like 0.05mm. The rack and pinion are loose sections connected to each other. After a crash we should do a full laser check to correct the axis compensation. Only we don't have a laser and the machinebuilder ask 20k for it.

It's a belotti nova 3016.

That is because those faggots in italy are only good at controls (Fagor) and not machinery. They should have shoulders and wedges on the rails. Not just rely on single bolt shear force on a grunt of a machine.