Strange axis not home error
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Hi,
OK I understand about all of the G28s.
Below is your homeall.g file - I have added some comments. Most of it is fine.
And since you leave X and Y at your XY undefinedreference point you don't need to do it again unless something you do later changes the XY position. If something does just remember to move back to your reference point when doing a G30.
M564 H0 ; remove this - see below M280 P0 S17 ; why is this here T0 P0 ; this is not typically something that is done when homing. G91 G1 Z5 ; use G1 H2 Z5 instead which allows moving Z when it is not yet homed. M564 H1 ; remove this -see above G90 ; remove this as you need relative for homing x/y below ; HOME X/Y G91 ; remove this since G90 above should not be there G1 H1 X-400 F3000 ; coarse home X or Y G1 H1 Y-400 F3000 G1 X4 Y4 F600 ; move away from the endstops G1 H1 X-10 F80 ; fine home X G1 H1 Y-10 F80 ; fine home Y G90 ; absolute positioning ; Z HOMING G1 X175 Y175 F5000 ; did you take into account the X and Y offsets of the probe when deciding on these X and Y values? M400 M913 Z55 G30 M400 M913 Z100Printers: a E3D MS/TC setup and a RatRig Hybrid. Using Duet 3 hardware running 3.4.6
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@fcwilt Thanks for the nfo and corrections:
The G91 before the G1 Z5 is because in some situations the nozzle is touching the bed (when I turn off the printer in some emergency for example). So when turned on, the first thing the machines does is move down the nozzle in order to let other movements happen.
G1 X175 Y175 F5000 ; did you take into account the X and Y offsets of the probe when deciding on these X and Y values? >>>>> I didnt, should I? I gues yes?
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@fcwilt Also, I guess I see your point: the datum 0 I stablish with G30 right?
Should I move to X175 Y175 (my center), then switch to relative and move so the sensor is at the centter, then do the G30, then switch back to Absolute positioning? -
@tinchus said in Strange axis not home error:
@fcwilt Thanks for the nfo and corrections:
The G91 before the G1 Z5 is because in some situations the nozzle is touching the bed (when I turn off the printer in some emergency for example). So when turned on, the first thing the machines does is move down the nozzle in order to let other movements happen.
The first G91 is needed - it's the following G90 which is immediately followed by G91 - no need to switch to absolute then back to relative.
G1 X175 Y175 F5000 ; did you take into account the X and Y offsets of the probe when deciding on these X and Y values? >>>>> I didnt, should I? I gues yes?
Yes you should.
Let's say 175,175 is the center of the bed.
G1 X175 Y175 will move the nozzle there. But the probe is usually somewhere to the left/right and/or forward/back of the nozzle.
So let's say your probe offsets are X-10 and Y5.
To compute the needed X value for the G1 just subtract the X offset from the X value for the center of the bed.
175 - -10 = 185 So the parameter would be X185.
Do the same for the Y value.
175 - 5 = 165 So the parameter would be Y170.
G1 X185 Y170 should move the probe to the center of the bed.
So just to the same math using your probe's actual X and Y offset values.
Frederick
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@fcwilt this thing about the probe is confusing me: I understand your statement but what I dont understnd is: if I move the head in a way the probe is at the center, the nozzle will not be at the center, but the machine all it cares is the nozzle. So when positioning the nozzle outseide the center and doing the G28, wont the machine think it is probing outside the center?
So what do I do when doing the mesh calibration? O should also position the probe and not the nozzle at the center? Following your thinking I must asume the firmware already knows Im taking into account the probe offsets?
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@tinchus said in Strange axis not home error:
@fcwilt this thing about the probe is confusing me: I understand your statement but what I dont understnd is: if I move the head in a way the probe is at the center, the nozzle will not be at the center, but the machine all it cares is the nozzle. So when positioning the nozzle outseide the center and doing the G28, wont the machine think it is probing outside the center?
You are mostly correct in thinking the nozzle is what we are interested in.
The reason we set the Z=0 Datum (with a G30) is so that moving to Z=0 at that XY location will have the tip of the nozzle just touching the bed.
But since the probe is offset from the nozzle we have to do a G1 move that takes in account the probe X and Y offsets so we can probe where the nozzle will be when X=175 and Y=175.
So what do I do when doing the mesh calibration? O should also position the probe and not the nozzle at the center? Following your thinking I must asume the firmware already knows Im taking into account the probe offsets?
You always set the Z=0 Datum at the same XY reference point, in your case that seems to be a X=175, Y=175 which is the center of your bed.
So before creating the height map or loading the height map you always must have set the Z=0 Datum at some time prior to the creating/loading.
The firmware has no idea how you chose the XY point where you set the Z=0 Datum. The user (you) decide what XY position is to be your XY reference point for setting the Z=0 Datum. The firmware doesn't care.
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@fcwilt sorry, still is not clear. Following your explanation, then moving to X175 Y175, ignoring the probe offset looks lige irrelevant, because Im always doing the probing at 175,175. I understand your explanation, I dont understand your point really.
Yo say I decide where I set the Z datum. Ok I say it has to be at 175,175 and I move the head to taht position, in the dcumentation is not stated how do I tell the firmware that later when I move the probe to that position, the pobe position is really 175,175... because at the moment I move the nozzle following the offset of the probe, the machine all it knows is that the nozzle is at another position, not 175,175 anymore. -
I'm not doing a good enough job explaining things then.
Hmm..
How about this.
Imagine a empty square room with a smooth floor. You have a tennis ball and you drop it on the floor. It rolls to the south-west corner. You play around with dropping the ball at different locations and you find that if you drop the ball at the north-east corner it rolls all the way in a straight line to the south-west corner.
You conclude that the lowest point in the room is the south-west corner and the highest point is the north-east corner.
You happen to have a device that will tell you the absolute height of any point in the room.
If you wish to determine the height of the highest point in the room you take it to the north-east corner and measure there. Correct?
In somewhat the same way if you wish to determine the height of the center of the bed you must move the probe to the center of the bed and measure there.
Does that help at all?
Frederick
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@fcwilt I understan this and your explanation is correct, but the thing it is not clear to me is:
if you want to probe the center of the bed, you are telling me to move the nozzle to X175+-offset and Y175+-offset so the probe is positioned at 175,175. But the machine doesnt know that, all the machine knows is she is at position X175+-offset and Y175+-offset , not at the center. That is my trouble into understanding this
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@tinchus said in Strange axis not home error:
@fcwilt I understan this and your explanation is correct, but the thing it is not clear to me is:
if you want to probe the center of the bed, you are telling me to move the nozzle to X175+-offset and Y175+-offset so the probe is positioned at 175,175. But the machine doesnt know that, all the machine knows is she is at position X175+-offset and Y175+-offset , not at the center. That is my trouble into understanding this
That is true but the data obtained when probing is from the point the probe touches - which is 175,175.
That data is only information about Z, there is no information about X or Y.
Let's say the Z Trigger Height setting in G31 is Z2.34.
When the probe, positioned at 175,175, triggers it tells the firmware the Z position at that instant was 2.34.
If the setting in G31 is correct the logical Z position (where the firmware "thinks" Z is) will match the physical Z position - which is the whole purpose of setting the Z=0 Datum, getting the logical and physical positions in sync.
Having established the logical Z position all subsequent Z moves should be accurate so, for example, a move G1 X175 Y175 Z0 should result in the nozzle just touching the bed at 175,175.
If it does that you know that the G31 setting is correct, which is essential to creating accurate height maps.
Frederick
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@fcwilt said in Strange axis not home error:
That is true but the data obtained when probing is from the point the probe touches - which is 175,175.
OK! Then this is the answer I was looking for. Following you explanation, the the formware is actually taking into account the probe offset when I tell it to probe the bed.
