201 lines
8.1 KiB
Markdown
201 lines
8.1 KiB
Markdown
This document describes tools for calibrating a Z endstop and for
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performing adjustments to bed leveling screws.
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# Calibrating a Z endstop
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An accurate Z endstop position is critical to obtaining high quality
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prints.
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Note, though, the accuracy of the Z endstop switch itself can be a
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limiting factor. If one is using Trinamic stepper motor drivers then
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consider enabling [endstop phase](Endstop_Phase.md) detection to
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improve the accuracy of the switch.
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To perform a Z endstop calibration, home the printer, command the head
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to move to a Z position that is at least five millimeters above the
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bed (if it is not already), command the head to move to an XY position
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near the center of the bed, then navigate to the OctoPrint terminal
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tab and run:
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```
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Z_ENDSTOP_CALIBRATE
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```
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Then follow the steps described at
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["the paper test"](Bed_Level.md#the-paper-test) to determine the
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actual distance between the nozzle and bed at the given location. Once
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those steps are complete one can `ACCEPT` the position and save the
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results to the config file with:
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```
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SAVE_CONFIG
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```
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It's preferable to use a Z endstop switch on the opposite end of the Z
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axis from the bed. (Homing away from the bed is more robust as then it
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is generally always safe to home the Z.) However, if one must home
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towards the bed it is recommended to adjust the endstop so that it
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triggers a small distance (eg, .5mm) above the bed. Almost all endstop
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switches can safely be depressed a small distance beyond their trigger
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point. When this is done, one should find that the
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`Z_ENDSTOP_CALIBRATE` command reports a small positive value (eg,
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.5mm) for the Z position_endstop. Triggering the endstop while it is
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still some distance from the bed reduces the risk of inadvertent bed
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crashes.
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Some printers have the ability to manually adjust the location of the
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physical endstop switch. However, it's recommended to perform Z
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endstop positioning in software with Klipper - once the physical
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location of the endstop is in a convenient location, one can make any
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further adjustments by running Z_ENDSTOP_CALIBRATE or by manually
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updating the Z position_endstop in the configuration file.
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# Adjusting bed leveling screws
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The secret to getting good bed leveling with bed leveling screws is to
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utilize the printer's high precision motion system during the bed
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leveling process itself. This is done by commanding the nozzle to a
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position near each bed screw and then adjusting that screw until the
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bed is a set distance from the nozzle. Klipper has a tool to assist
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with this. In order to use the tool it is necessary to specify each
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screw XY location.
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This is done by creating a `[bed_screws]` config section. For example,
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it might look something similar to:
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```
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[bed_screws]
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screw1: 100,50
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screw2: 100,150
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screw3: 150,100
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```
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If a bed screw is under the bed, then specify the XY position directly
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above the screw. If the screw is outside the bed then specify an XY
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position closest to the screw that is still within the range of the
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bed.
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Once the config file is ready, run `RESTART` to load that config, and
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then one can start the tool by running:
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```
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BED_SCREWS_ADJUST
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```
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This tool will move the printer's nozzle to each screw XY location and
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then move the nozzle to a Z=0 height. At this point one can use the
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"paper test" to adjust the bed screw directly under the nozzle. See
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the information described in
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["the paper test"](Bed_Level.md#the-paper-test), but adjust the bed
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screw instead of commanding the nozzle to different heights. Adjust
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the bed screw until there is a small amount of friction when pushing
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the paper back and forth.
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Once the screw is adjusted so that a small amount of friction is felt,
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run either the `ACCEPT` or `ADJUSTED` command. Use the `ADJUSTED`
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command if the bed screw needed an adjustment (typically anything more
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than about 1/8th of a turn of the screw). Use the `ACCEPT` command if
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no significant adjustment is necessary. Both commands will cause the
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tool to proceed to the next screw. (When an `ADJUSTED` command is
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used, the tool will schedule an additional cycle of bed screw
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adjustments; the tool completes successfully when all bed screws are
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verified to not require any significant adjustments.) One can use the
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`ABORT` command to exit the tool early.
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This system works best when the printer has a flat printing surface
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(such as glass) and has straight rails. Upon successful completion of
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the bed leveling tool the bed should be ready for printing.
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## Fine grained bed screw adjustments
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If the printer uses three bed screws and all three screws are under
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the bed, then it may be possible to perform a second "high precision"
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bed leveling step. This is done by commanding the nozzle to locations
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where the bed moves a larger distance with each bed screw adjustment.
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For example, consider a bed with screws at locations A, B, and C:
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For each adjustment made to the bed screw at location C, the bed will
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swing along a pendulum defined by the remaining two bed screws (shown
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here as a green line). In this situation, each adjustment to the bed
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screw at C will move the bed at position D a further amount than
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directly at C. It is thus possible to make an improved C screw
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adjustment when the nozzle is at position D.
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To enable this feature, one would determine the additional nozzle
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coordinates and add them to the config file. For example, it might
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look like:
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```
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[bed_screws]
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screw1: 100,50
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screw1_fine_adjust: 0,0
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screw2: 100,150
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screw2_fine_adjust: 300,300
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screw3: 150,100
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screw3_fine_adjust: 0,100
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```
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When this feature is enabled, the `BED_SCREWS_ADJUST` tool will first
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prompt for coarse adjustments directly above each screw position, and
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once those are accepted, it will prompt for fine adjustments at the
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additional locations. Continue to use `ACCEPT` and `ADJUSTED` at each
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position.
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# Adjusting bed leveling screws using the bed probe
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This is another way to calibrate the bed level using the bed probe. To
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use it you must have a Z probe (BL Touch, Inductive sensor, etc).
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To enable this feature, one would determine the nozzle coordinates
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such that the Z probe is above the screws, and then add them to the
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config file. For example, it might look like:
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```
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[screws_tilt_adjust]
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screw1: -5,30
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screw1_name: front left screw
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screw2: 155,30
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screw2_name: front right screw
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screw3: 155,190
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screw3_name: rear right screw
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screw4: -5,190
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screw4_name: rear left screw
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horizontal_move_z: 10.
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speed: 50.
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screw_thread: CW-M3
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```
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The screw1 is always the reference point for the others, so the system
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assumes that screw1 is in the correct height. Always run `G28` first
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and then run `SCREWS_TILT_CALCULATE` - it should produce output
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similar to:
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```
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Send: G28
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Recv: ok
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Send: SCREWS_TILT_CALCULATE
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Recv: // front left screw (Base): X -5.0, Y 30.0, Z 2.48750
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Recv: // front right screw : X 155.0, Y 30.0, Z 2.36000 : Adjust -> CW 01:15
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Recv: // rear right screw : X 155.0, Y 190.0, Z 2.71500 : Adjust -> CCW 00:50
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Recv: // read left screw : X -5.0, Y 190.0, Z 2.47250 : Adjust -> CW 00:02
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Recv: ok
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```
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This means that:
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- front left screw is the reference point you must not change it.
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- front right screw must be turned clockwise 1 full turn and a quarter turn
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- rear right screw must be turned counter-clockwise 50 minutes
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- read left screw must be turned clockwise 2 minutes (not need it's ok)
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Repeat the process several times until you get a good level bed -
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normally when all adjustments are below 6 minutes.
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If using a probe that is mounted on the side of the hotend (that is,
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it has an X or Y offset) then note that adjusting the bed tilt will
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invalidate any previous probe calibration that was performed with a
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tilted bed. Be sure to run [probe calibration](Probe_Calibrate.md)
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after the bed screws have been adjusted.
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The `MAX_DEVIATION` parameter is useful when a saved bed mesh is used,
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to ensure that the bed level has not drifted too far from where it was when
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the mesh was created. For example, `SCREWS_TILT_CALCULATE MAX_DEVIATION=0.01`
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can be added to the custom start gcode of the slicer before the mesh is loaded.
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It will abort the print if the configured limit is exceeded (0.01mm in this
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example), giving the user a chance to adjust the screws and restart the print.
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