X Home to -ve value

CNCModeller

Hi All,
I think I know what's going on here but don't know for sure I'm doing the right thing to compensate for it.

If I home X at y0 it homes to 0.0, if I home X at y220 it homes to -1.6.

I'm using axis compensation to allow for my inability to correctly align the laser path in my K40 laser.

So I believe I'm seeing this due to compensation working as intended.

So to get the laser to home to Y max where my home sensors are I'm just adding a g0 x0 to the end of the home macros.

Is this sensible or am I missing something?

Many thanks
Barry M

dc42

@CNCModeller said in X Home to -ve value:

So to get the laser to home to Y max where my home sensors are I'm just adding a g0 x0 to the end of the home macros.

Won't that mean that the homing position is wrong if you home X other than at Ymax?

Can you change your homeall.g file to home Y before homing X? Or to home X and Y together to start with, then fine-home Y, then fine-home X?

CNCModeller

@dc42 said in X Home to -ve value:

@CNCModeller said in X Home to -ve value:

So to get the laser to home to Y max where my home sensors are I'm just adding a g0 x0 to the end of the home macros.

Won't that mean that the homing position is wrong if you home X other than at Ymax?

Can you change your homeall.g file to home Y before homing X? Or to home X and Y together to start with, then fine-home Y, then fine-home X?

So I'm homing to the switches at xmin ymax, which leaves the X axis at a -ve value due to skew compensation. Then I moved the head to the indicated X0.

Then when it moves to X0 Y0 I assume the compensation pushes the axes to X+1.6, but because of the laser skew it hits the bed at 0,0.

I'll check that everything is still in calibration, but that's what I assume is happening...

o_lampe

@CNCModeller When you cut a square do you see true angles? If not, you can adjust the frame in the housing. IIRC the mounting holes in the housing are bigger than the frame holes, so you can push the front and back of the frame in different directions until it's true.

CNCModeller

@o_lampe said in X Home to -ve value:

@CNCModeller When you cut a square do you see true angles? If not, you can adjust the frame in the housing. IIRC the mounting holes in the housing are bigger than the frame holes, so you can push the front and back of the frame in different directions until it's true.

The frame is square, it's my lack of ability to align the laser mirrors properly that is causing the drift.

But with skew compensation enabled I'm getting geometry and dimensions which are accurate enough for my purposes.

o_lampe

@CNCModeller said in X Home to -ve value:

it's my lack of ability to align the laser mirrors properly that is causing the drift.

I hear you! That's the most annoying task, but I found a good german discord channel where i found help.
The mistake most people do is trying to align the near and far points when they use the tape-method.
But in fact you have to "overcompensate". Can't describe it, due to lack of vocabulary. Maybe you find an engish video describing the CDA-method
Here's the german video that helped me

CNCModeller

@o_lampe said in X Home to -ve value:

@CNCModeller said in X Home to -ve value:

Here's the german video that helped me

Thanks @o_lampe, my partner is a fluent German speaker so hopefully she can translate

CNCModeller

After doing some googling I've found this which I'll try after the current sweet of upgrades...
https://youtu.be/rYX0zfWFnIM