First, TinyG software works, this is not a bug report.
I find that it is possible to misconfigure parameters, specifically on homing: My application uses G28.4 (homing without resetting values) to probe Z heights. I normally have Zmin on top, and that is where I get a reference 0. On probing, I configure the switches to home down towards Zmax, which triggers the switch.
Now, with some combination of homing speed, acceleration and latch parameters, it can happen that speed is so high and acceleration is slow, that the machine can't stop within the given travel. The stop travel is so long that the backup travel does not clear the switch. The machine does what the user asked, but not what the user wanted, and the unexpected error is confusing.
The questions:
- Is there a way to find out which combination of values are safe and which are not? (I would think there is no easy way, but I'm asking anyway...)
- Even if not, can I somehow find out from the log that the error was due to misconfiguration and not a real mishap on the machine?
I don’t remember where I found it, maybe Alden told me:-). But for the discussion, it doesn’t matter if we are talking about g28.2 or g28.4; the difference is only that the latter doesn’t zero the coordinates after the homing cycle. The point is, that it is possible for the user to set parameters so that it isn’t possible for the homing to work; I would like to detect the condition. (Also perhaps to point out for the other readers that a failed homing might be about their settings, not a TinyG problem.)
Understand your goal, have some thoughts but not a working machine to test them on at the moment.
I am not sure there is a numerical solution for what you describe, if I understand correctly. My understanding is that traverse to Zmin has too much momentum when the switch is first contacted to stop and backoff properly.
Unknowns to tinyG and likely a typical user:
Mass of the moving element (in this case, a spindle?)
Strength of the Z axis motor (NEMA 17, 23, ec.)
Current setting on tinyG driver.
I think you'll understand my list - do I understand the issue correctly?
This topic is from the original forum (August 2019). Your reply starts a new discussion linked to it.