On 14/07/2020 15:28, Reinhard wrote:
The machine moves (assuming it does not have absolute encoders that are battery buffered) toward the home switch until the switch signals contact. That's the axis origin - and I thought, this is what the word "home"-position means. With any professional cnc I know about it is the case. Obviously not with linuxcnc :(
Referencing is simply a way for the machine to identify it's position in space. Where the home switches are positioned is immaterial. They just say 'you are here'. It is up to the machine integrator to decide where the axis 0 is.
So if linuxcnc has different behaviour, it is far from being flexible. It's just crap! Crap from people that don't know machine behaviour.
You can set up LCNC to use the home switch exactly as you describe. You can define your axis zero to be anywhere you like.
No programmer will ever use machine-coordinates (G53) - only in case of trouble or for maintenance.
Nope. G53 is pretty common. For example on a lot of machines Z0 is the highest point the Z axis can move. G53G0Z0 will give the maximum possible Z clearance without needing to know about any offsets.
On my router for instance my parking sequence is: G53G0Z0 G53G0x1250Y1300
And that a user needs to use negative tool offsets is bullshit.
Tool offsets are added to the commanded position, just like any other control. They specify the position of the tip of the tool relative to some standardized reference position. For instance on a mill the reference may be the tool holder gauge line. On a mill or router you are very unlikely to need negative tool offsets. If you do, the problem is to do with how you have your work or fixture offsets set up.
On a lathe however there are some situations where you would need negative offsets. For instance if you are using a lathe with two tool posts on one X axis. Everything will be negative for the tool post behind the spindle centre line. Some lathe controllers have have compensation built in for this but AFAIK LCNC does not.
Its very poor, that there are so many weird workarounds in linuxcnc caused by ignorance, lack of knowledge or misunderstanding :(
It strikes me that in this case the lack of understanding is on your part, not the LCNC authors.
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