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Question on Z-Offset and Start Script, Also Nozzle Adjustment.

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Tuning and tweaking
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  • undefined
    Phaedrux Moderator
    last edited by 2 Aug 2018, 21:09

    PID tuning will help the temperatures be more stable, but won't account for being off by 20 degrees.

    Definitely keep an eye on the temperature graph as it transitions from the first layer to the next. Does the set temperature get lowered? That would indicate that the slicer has a too low temp set for later layers.

    Z-Bot CoreXY Build | Thingiverse Profile

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    • undefined
      justinds89
      last edited by 2 Aug 2018, 21:31

      It looks like my cooling fan is dropping the temperature of the nozzle down for a little bit before it picks back up and stabilizes.

      I take it at this point I need to figure out a way to direct the cooling more downward away from the nozzle and heat block?

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      • undefined
        Phaedrux Moderator
        last edited by 2 Aug 2018, 21:49

        You have 3 options, choose any or all.

        1. Find a better cooling shroud that can direct the airflow better.
        2. Insulate the hotend block in some way. This can be as simple as kapton tape and a high temp insulation pad. Or you can maybe find a silicone sock that can slide over the hotend. If you have the means you can also make your own.
        3. PID tune the hotend while the fan is running at a speed similar to what it would see during an actual print, That way the system can adjust for the heat loss and maintain a more stable temperature.

        Z-Bot CoreXY Build | Thingiverse Profile

        undefined 1 Reply Last reply 3 Aug 2018, 13:27 Reply Quote 0
        • undefined
          justinds89 @Phaedrux
          last edited by 3 Aug 2018, 13:27

          @phaedrux

          I printed a new shroud that I believe will direct the airflow downwards more away from the cooling block.
          I added a silicone cover to the block.
          I have not tuned the hotend yet.

          I plan on testing this fix out and see if the temp holds steady. I am fairly certain it will now.

          I can't test this until Sunday evening though unfortunately.

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          • undefined
            justinds89
            last edited by 5 Aug 2018, 22:49

            How can I set the Z-Offset? It is too close to the bed and I want to lower it some. I am using G31 Z2.0 in the Config.g, but it has absolutely no affect on the height regardless what I set this too.

            I do not have a probe, but figured I could just use my Z Axis endstop.

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            • undefined
              Phaedrux Moderator
              last edited by 5 Aug 2018, 23:46

              To use just a simple endstop you'll have to comment out or remove this from your config.g

              ; Z-Probe
              M558 P0 H-5 F120 T4800 ; Disable Z probe but set dive height, probe speed and travel speed
              M557 X25:140 Y25:130 S20 ; Define mesh grid
              G31 Z0.26

              Then you'll have to make some changes to your homeall and homez. If you post those we can let you know what needs to be changed.

              But basically if you're using a g30 command to find z0 right now you'll have to remove that and use a G1 S1 Z move similar to how the X and Y end stops are found.

              Z-Bot CoreXY Build | Thingiverse Profile

              undefined 1 Reply Last reply 6 Aug 2018, 00:11 Reply Quote 1
              • undefined
                justinds89 @Phaedrux
                last edited by 6 Aug 2018, 00:11

                @phaedrux

                Ah makes sense! I think I understand now and was going about this completely wrong. Here is my homeall and home z.

                ; homeall.g
                ; called to home all axes
                ;
                ; generated by RepRapFirmware Configuration Tool on Mon Jul 30 2018 18:48:50 GMT-0500 (Central Daylight Time)
                G91 ; relative mode
                G1 S1 Z-250 F300 ; move Z towards the switch until it triggers
                G1 Z5 F100 S2 ; move Z back 5mm
                G1 S1 Z-10 F100 ; move Z slowly towards the switch until it triggers
                G1 S1 X235 Y155 F1800 ; move quickly to X and Y axis endstops and stop there (first pass)
                G1 X-5 Y-5 F4800 ; go back a few mm
                G1 S1 X235 Y155 F360 ; move slowly to X and Y axis endstops once more (second pass)
                G90 ; absolute positioning

                ; homez.g
                ; called to home the Z axis
                ;
                ; generated by RepRapFirmware Configuration Tool on Mon Jul 30 2018 18:48:50 GMT-0500 (Central Daylight Time)
                G91 ; relative positioning
                G1 S1 Z-250 F300 ; move Z towards the switch until it triggers
                G1 Z5 F100 S2 ; move Z back 5mm
                G1 S1 Z-10 F100 ; move Z slowly towards the switch until it triggers
                G90 ; absolute positioning

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                • undefined
                  Phaedrux Moderator
                  last edited by 6 Aug 2018, 02:45

                  That looks fine for homing Z with an endstop I think. When the end stop triggers how far from the bed is the nozzle? Your homing files would assume that it is at 0. You can either adjust your endstop trigger physically or use an offset in the slicer or you could add a G92 Zn command to the homing files where n is the distance from the bed.

                  Z-Bot CoreXY Build | Thingiverse Profile

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                  • undefined
                    justinds89
                    last edited by 6 Aug 2018, 02:52

                    I couldn't find a way to set z offset in Cura.

                    The nozzle barely touched, but it is now a hair under .1mm gap.

                    I would prefer to be able to add in a bit of extra distance in the home config when needed for fine adjustment.

                    Thanks for the help.

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                    • undefined
                      Phaedrux Moderator
                      last edited by 6 Aug 2018, 02:59

                      It's available in Cura but I think it may be hidden by default. You'd have to do a search in the settings widget.

                      You can also use baby stepping on the DWC or panel due for fine adjustments.

                      Z-Bot CoreXY Build | Thingiverse Profile

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                      • undefined
                        dc42 administrators
                        last edited by 6 Aug 2018, 10:21

                        I suggest you read https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwareCartesianPrinter#Section_Homing_Z_using_a_Z_min_endstop_switch.

                        Duet WiFi hardware designer and firmware engineer
                        Please do not ask me for Duet support via PM or email, use the forum
                        http://www.escher3d.com, https://miscsolutions.wordpress.com

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                        • undefined
                          justinds89
                          last edited by 6 Aug 2018, 12:59

                          Appreciate the help guys. I will checkout that link.

                          undefined 1 Reply Last reply 6 Aug 2018, 18:55 Reply Quote 0
                          • undefined
                            justinds89 @justinds89
                            last edited by justinds89 8 Jun 2018, 18:57 6 Aug 2018, 18:55

                            So just to confirm.

                            If I use the G92 Zn command with my current configuration I need to use a negative number (G92 Z-0.2) to move the bed down 0.2mm correct?

                            Homing Z is 0 and when I lower the bed the numbers are positive. so basically Z lowered is 140mm.

                            undefined 1 Reply Last reply 7 Aug 2018, 07:26 Reply Quote 0
                            • undefined
                              dc42 administrators @justinds89
                              last edited by 7 Aug 2018, 07:26

                              @justinds89 said in Question on Z-Offset and Start Script, Also Nozzle Adjustment.:

                              If I use the G92 Zn command with my current configuration I need to use a negative number (G92 Z-0.2) to move the bed down 0.2mm correct?

                              No, a positive number. G92 tells the firmware where the machine is. So if the nozzle is 0.2mm above the bed when the endstop switch triggers, G92 Z0.2 will tell the firmware that.

                              Duet WiFi hardware designer and firmware engineer
                              Please do not ask me for Duet support via PM or email, use the forum
                              http://www.escher3d.com, https://miscsolutions.wordpress.com

                              undefined 1 Reply Last reply 7 Aug 2018, 13:03 Reply Quote 0
                              • undefined
                                justinds89 @dc42
                                last edited by 7 Aug 2018, 13:03

                                @dc42

                                Hmm interesting. I guess I was looking at this wrong.

                                I thought a negative number was what I was looking for.

                                Basically if the nozzle is too close when printing and I need to lower the bed just 0.1 mm I would still use a positive number?

                                Sorry for so many questions, just trying to understand everything.

                                undefined 1 Reply Last reply 7 Aug 2018, 14:11 Reply Quote 0
                                • undefined
                                  dc42 administrators @justinds89
                                  last edited by 7 Aug 2018, 14:11

                                  @justinds89 said in Question on Z-Offset and Start Script, Also Nozzle Adjustment.:

                                  Basically if the nozzle is too close when printing and I need to lower the bed just 0.1 mm I would still use a positive number?

                                  If the nozzle is too close to the bed then the number in your G92 command needs to be made smaller. It should never be negative, because that would mean that the nozzle touches the bed before the Z min endstop switch triggers.

                                  Duet WiFi hardware designer and firmware engineer
                                  Please do not ask me for Duet support via PM or email, use the forum
                                  http://www.escher3d.com, https://miscsolutions.wordpress.com

                                  undefined 1 Reply Last reply 7 Aug 2018, 14:26 Reply Quote 0
                                  • undefined
                                    justinds89 @dc42
                                    last edited by 7 Aug 2018, 14:26

                                    @dc42

                                    Ah okay, to be honest I'm still a bit confused haha.

                                    I may have to just try adjusting the number and see what happens. I just don't wan't the bed to end up going the wrong direction and going to far up and hitting the nozzle.

                                    Right now without the G92 command the nozzle is a hair too close. I know I could manually adjust the thumb screws on the bed, but it would be much easier and more accurate to just bring the bed down a bit for the print.

                                    undefined 1 Reply Last reply 8 Aug 2018, 06:34 Reply Quote 0
                                    • undefined
                                      dc42 administrators @justinds89
                                      last edited by 8 Aug 2018, 06:34

                                      @justinds89 said in Question on Z-Offset and Start Script, Also Nozzle Adjustment.:

                                      Right now without the G92 command the nozzle is a hair too close.

                                      That implies that the nozzle touches the bed before the endstop triggers - is that really the case?

                                      Duet WiFi hardware designer and firmware engineer
                                      Please do not ask me for Duet support via PM or email, use the forum
                                      http://www.escher3d.com, https://miscsolutions.wordpress.com

                                      undefined 1 Reply Last reply 8 Aug 2018, 12:37 Reply Quote 0
                                      • undefined
                                        justinds89 @dc42
                                        last edited by 8 Aug 2018, 12:37

                                        @dc42

                                        No, when the endstop triggers the nozzle is a hair under 0.1 mm away from the bed.

                                        Basically I am looking to add something like a 0.02mm gap to the existing gap to increase distance between the nozzle to get an optimal first layer.

                                        Right now it works, but the plastic is a bit too squished. If I could just get the bed to go down a bit further with an offset it would solve the issue.

                                        I'm hoping all that makes sense.

                                        undefined 1 Reply Last reply 8 Aug 2018, 13:03 Reply Quote 0
                                        • undefined
                                          dc42 administrators @justinds89
                                          last edited by 8 Aug 2018, 13:03

                                          If your Z=0 position leaves the nozzle nearly 0.1mm above the bed, but that is still too close to get a good first layer, then something else is wrong. Perhaps you have configured a negative tool Z offset using G10; or perhaps in your slicer settings you are telling it to over-extrude the first layer.

                                          Duet WiFi hardware designer and firmware engineer
                                          Please do not ask me for Duet support via PM or email, use the forum
                                          http://www.escher3d.com, https://miscsolutions.wordpress.com

                                          undefined 1 Reply Last reply 8 Aug 2018, 13:18 Reply Quote 0
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