Having spent some time trying different versions of Marlin code, I must be missing some steps in setting up the Z parameters.
Basically, If I select “Home Z Axis” under the “V1 Custom Menu”, the Z axis continues to drive until it reaches the top or bottom of the bed and try’s to wreck itself as this unit has no limit switches. I obviously haven’t set something up correctly or missed a step .
So because I cannot set a Z home position the Z axis is always random, so you cant cut-out or engrave anything. I’ve tried resetting the coordinates (via the menu)… works OK, but selecting Z home drives the unit and doesn’t stop at all, either direction.
The X & Y home settings seem to work, they do however move an increment every time, so if you did this enough times it would reach one corner of the bed and crash.
Any advice please anyone?
Just to add… the board is a Rambo Mini, using 3 of the motor ports, X,Y & Z
The only thing you need to set is where z=0. In most cases this is the top surface of your material. Cuts and engraves then reference this as the start point.
If you’re not using a touch probe this is achieved by moving the tip of the tool down to the work surface and sending the gcode command
G92 Z0
You can do this various ways, through a terminal or have it in the starting code of your files.
Homing requires a limit for it to home to. So if you don’t have a limit switch on an axis you can’t use Home for that axis.
THAT WORKS A TREAT !!!
Thanks very much for the quick reply.
More info at:
Thank you very much… it’s the document I seem to have missed!
No worries. It isn’t RTFM. Just a hint for the future.
I am confused about coordinates after homing. I have setup everything OK. Axis movements. directions and homing is working fine but it doesn’t set Z to zero when homing is done and z axis backs off 2mm (as per setting) from limit/homing switch. X, Y axis are set to zero but Z still stays 200 which I have set as maximum possible z travel distance. I am expecting it to be -2 after homing because of 2mm back off. Ideally I would like it to be 0, 0, 0 (X, Y, Z) after backing off but I am even OK with 2, 2, -2. At the moment it is setting it (2, 2, 198). I am sure I am missing something but I couldn’t figure out what.
Any help will be appreciated.
That wouldn’t really be any more helpful than making the endstops Z=200.
I am assuming you are using Marlin. Marlin needs to use a positive number when homing to +Z.
But it doesn’t matter because we usually use the top of the stock as Z=0. So you need to set that after homing. Either manually or with a Z probe.
I would suggest making a new topic. This one has a lot of info not related to you and uour setup.
Well it kills the purpose of homing. Doesn’t it? It is only good for gantry levelling.
Yes I am using Marlin. It may the case for Marlin to have positive number for +Z homing but it doesn’t make sense. Does it?
Correct but as I said, it kills the purpose of homing. Even the homing documentation you referred above also says the same thing that homing means zero.
You mean in LowRider 1/2 category?I was going to open a new topic but made a search and found this topic a relative so posted a commebnt here.
No, it doesn’t.
One of the functions of homing is to set the location of the axis, but another important function is to “auto-square” the gantry in the Y and Z axis.
In the case of X homing, you are primarily setting the location of the X origin.
In the case of the Y axis, you are both setting the location of the Y origin, and squaring the gantry so that both ends are at a known location (the endstops would have been previously adjusted to ensure a 90 degree angle relative to X).
In the case of Z homing, you are primarily squaring the Z axis in relation to the spoil board. You aren’t really concerned about the Z axis location, other than to raise it to a point near the top of the travel. That position is arbitrary, and bears no relation to the position of the stock. You could just as easily set it to be 100, 300 413, or some other random number. That is because you will inevitably follow the Z homing with a Z probe (G38.2 Z0) and setting the location to Z=0 (G92 Z0 - or Z=thickness of probe) in order to set the location (origin) in relation to the top of the stock.
Note that the Z0 portion of G38.2 Z0 means that the probe will continue until it completes the probe circuit, or until it reaches 0 (200 mm total) . If you set the homing to some value less than 80, then you might have to use a negative number in the G38.2 command .
That refers to the X and Y homing. As mentioned above, Z is a bit of a special case.
Thanks for your detailed answer to my questions. I want to point out that my machine is working fine. I know homing position in terms of numbers for Z axis is not very critical because z zero will be set for every single job with probing. I have been using GRBL and the idea of Z homing position as zero got me confused if I have configured the Marlin properly.
So homing on Z axis with dual motors is just for leveling the gantry. Right?
And if Z maximum travel limit is set for example 200mm in my case and while homing it travels more than 200mm upwards lets say 230 then moving Z to zero in machine coordinates will always cause the gantry to stop 30mm away from its original position whatever was before homing and jogging from LCD will prevent it from coming down beyond zero. Because LCD jogging doesn’t allow -ve values and for Z Axis. Is my understanding correct?
That is correct in theory. In reality, maximum Z travel is typically 75-80mm (LR3 with bit installed) on a standard build, and maybe up to 125mm on a heavily modified LR3
With a Lowrider 2 your Z axis limjt is whatever you built it to, so it might well be more than 200mm. Mine was actually pretty close to 200mm. My LR3 was 128mm and the LR4 is a bit over 100, so there’s that.
For the LR2, the home Z position really didn’t matter, since I always set the Z=0 point based on what stock I had on the table. I suppose that I could have just edited the firmware for a typical distance to the spoilboard, but since that changes when I change the router bit, that didn’t seem useful either. I always probed for the Z origin, and it was fine that way.