Resolved: Homing - Quick question...
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@nightowl999
What does "homing" mean to you?
What is the purpose of "homing" to back, right?
I ask because many folks believe homing means moving to 0, 0 when it really doesn't.
Frederick
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@fcwilt My previous experience with a CNC (a Shapeoko 3) is that 'homing' moved the X, Y and Z to the right rear and up, respectively. The machine co-ordinates at that point are X = -3, Y = -3 and Z = -3 (all mm) as a 'stand off' from the proximity sensors. I'm assuming this 'homing' is designed for the machine to 'know' where it is. This was done (on the Shapeoko), on initialisation, i.e. when it was turned on the machine would move to the rear, right, top location. I was trying to replicate that - on the assumption it's necessary - or at least desirable.
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@nightowl999
You are correct in that homing is used to let the machine controller know where the active bit (nozzle, spindle, etc) is.
Where you want the machine to "park" is another issue.
On my printers the homing sensors are at axis min or axis max but 0, 0 is at the center of the bed, which is my preference.
The other common location for 0, 0 is at the left front.
So on your machine where is 0, 0 and where are the homing sensors located?
Frederick
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@fcwilt When I run homeall.g on my machine, it goes to the back, left, up with Y home at 787-3mm and Z home at 100-3mm (the -3 being the back-off from the proximity switches)
The X home location is currently -535-3mm but the limit switch was on the left. I've since installed a proximity switch to the right to facilitate a right, rear, up home location, hence my question.
These settings are different to the S3, because the machine location after homing was at -3, -3, -3, so I'm assuming(!) X moving left and Y moving forward would be +ve moves, and X moving down a -ve move.
So, in answer to your question, 0, 0, 0 would be front, left, down.
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@nightowl999 said in Homing - Quick question...:
The X home location is currently -535-3mm but the limit switch was on the left. I've since installed a proximity switch to the right to facilitate a right, rear, up home location, hence my question.
You current homing code is fine. If you still want to use the X axis limit switch on the left all you need to do is add a final G1 X532 F6000 to move to the desired location on X, assuming 532 is the desired location.
While your homing code doesn't do this it is fairly common to do two G1 H1 moves, first a fast one, then a slow one. Something like:
G1 H1 X-550 F6000
G1 X5 F6000
G1 H1 X-10 F1800Frederick
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Thanks, @fcwilt, but just so I'm clear, all I need do is change the X value to a positive number if I want to use the proximity sensor on the right, rather than the left?
I also see your comment about the two homing speeds. The RepRap Config Tool does include these, but the maximum speed of my stepper motors is 2500, so 6000 seemed a lot!
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@nightowl999 said in Homing - Quick question...:
Thanks, @fcwilt, but just so I'm clear, all I need do is change the X value to a positive number if I want to use the proximity sensor on the right, rather than the left?
The sign of each X move would change, the G1 H1 move would become a positive number but the G1 back-off move would become a negative number.
Of course you have to wire in the new sensor and configure it correctly as the X endstop.
I also see your comment about the two homing speeds. The RepRap Config Tool does include these, but the maximum speed of my stepper motors is 2500, so 6000 seemed a lot!
The speeds are up to you. For example you could use F2500 and F250 as your fast and slow speeds. It's not really essential. The assumption is that the second, slower move will result in greater accuracy of the homed position. Does it really do that? I don't know. I do both fast and slow just to be safe.
Frederick
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Thank you @fcwilt.
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@nightowl999 said in Homing - Quick question...:
Thank you @fcwilt.
Always glad to be of help when I can.
Frederick
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When I home my Duet-controlled KillerBee CNC machine to the rear, right, up, the machine position is shown in DWC as X=-3, Y=784 and Z=97, all of which are 3mm off the proximity sensors. This isn't logical to me (except for X).
What I would like to see is X=-3, Y=-3 and Z=-3, i.e. 3mm off their respective 0's.
Is this something I can adjust in my config.g file or their respective homing files, please?
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@nightowl999 said in Homing - Quick question...:
When I home my Duet-controlled KillerBee CNC machine to the rear, right, up, the machine position is shown in DWC as X=-3, Y=784 and Z=97, all of which are 3mm off the proximity sensors. This isn't logical to me (except for X).
What I would like to see is X=-3, Y=-3 and Z=-3, i.e. 3mm off their respective 0's.
Is this something I can adjust in my config.g file or their respective homing files, please?
ThanksIs it normal for CNC machines to have the XY origin (0, 0) at the right rear as opposed to FDM printers where it is usually left front?
So on a CNC machine is the left front position XY two negative values?
Thanks.
Frederick
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As I understand it, @fcwilt, machine 'home' can be either rear, right, up or front. left, up - as they're essentially the same (as it was explained to me).
The reason CNC machines use right, rear, up is to ensure the working area is clear of sharp, jaggy things when fixing stock, etc. I don't know anything about 3D printers, though.
My old Shapeoko had it's machine home at right, rear, up and that made sense to me. Project 'home' is slightly different, in that it's the starting point for cutting the stock (wood, metal, plastic, etc) which is mounted on a spoil board. Normally (but not exclusively) the front left hand corner coordinates of the stock is X=0, Y=0 and Z being measured from the top of the stock, so all Z cuts are down. some people prefer to set Z0 on the waste board, though.
Does that help?
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@nightowl999 said in Homing - Quick question...:
As I understand it, @fcwilt, machine 'home' can be either rear, right, up or front. left, up - as they're essentially the same (as it was explained to me).
The reason CNC machines use right, rear, up is to ensure the working area is clear of sharp, jaggy things when fixing stock, etc. I don't know anything about 3D printers, though.
My old Shapeoko had it's machine home at right, rear, up and that made sense to me. Project 'home' is slightly different, in that it's the starting point for cutting the stock (wood, metal, plastic, etc) which is mounted on a spoil board. Normally (but not exclusively) the front left hand corner coordinates of the stock is X=0, Y=0 and Z being measured from the top of the stock, so all Z cuts are down. some people prefer to set Z0 on the waste board, though.
Does that help?
Thanks.
I think the confusion is from the terms "home" and "homing".
To me in the FDM printer world "homing" is the process of "synchronizing" the logical position of each axis (where the controller "thinks" things are) to the physical position of each axis (where things actually are).
Homing can be done to either the min or max end of an axis. And there is no requirement that all axes home to the same end, min or max.
The "origin" (0, 0) has no fixed relationship to the position used for homing. The origin is often the left, front but I use the center of the bed.
I generally mount the endstop sensors to the rear of the printer. This means that Y would home to the max end. X would home to either the min or max end depending on where it was easiest to mount the endstop sensor.
When a print is finished I position the extruder out of the way. Typically to X=0, Y=max which on my printers is the rear center of the bed. I call this the "parked" position to distinguish it from the "origin" or the "home" position.
So where do wish 0,0 to be? The left front or the right rear?
Frederick
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@fcwilt OK, but to me, homing is the process by which the machine understands where everything is. This is particularly relevant where the settings aren't stored in an EEPROM and retained, but configured during startup.
And there does seem a significant difference between CNC and 3D printing in that respect, too!
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@nightowl999 said in Homing - Quick question...:
@fcwilt OK, but to me, homing is the process by which the machine understands where everything is. This is particularly relevant where the settings aren't stored in an EEPROM and retained, but configured during startup.
Isn't that what I said?
To me in the FDM printer world "homing" is the process of "synchronizing" the logical position of each axis (where the controller "thinks" things are) to the physical position of each axis (where things actually are).
Frederick
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You did, sorry @fcwilt. I'm switching between two threads and trying to cook my dinner!!
I would like the 0,0 to be right rear, in answer to your question (which I also missed
)Printers do have a Z height too, don't they? My knowledge of 3D printing is non-existent, in case you were wondering!
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Right rear 0,0 position is fine. It's the typical right hand coordinate system just rotated 180 degrees. The problem occurs when you only rotate it 90 degrees in which case you'll get a mirrored axis.
The physical endstop position is defined in the M574 command. If you want the homed position to be 0,0 set it to 1 for the low end of travel.
The homing moves in your macros will need to be negative to move towards the endstop.
Now it's up to you to define the motor rotation direction such that a negative move goes in the rear/right direction.
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Thank you, @phaedrux
