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

[justinds89]

Wow, I upped the temp by 20 degrees and it is now printing fine.

I guess it was grinding filament because it wasn't hot enough to melt it properly.

Looks like I will be PID tuning it when I figure out how.

Thanks for the help man!

[dc42]

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

Wow, I upped the temp by 20 degrees and it is now printing fine.
I guess it was grinding filament because it wasn't hot enough to melt it properly.

Your slicer may be configured to reduce the extrusion temperature after the first layer. Also, if your print cooling fan is directing too much air at the heater block and the nozzle instead of at the print, the nozzle temperature may drop a little when the print cooling fan turns on, which is usually at the start of the second layer.

[justinds89]

@dc42

That makes sense, but when monitoring what the temperature shows in the web interface it shows that the temperature is what is set and steady.

I'm using 200 for PLA which is what I've always used in the past. Now though I had to up it to 220 to get a successful print.

I still have no clue on how to PID tune things if that is the route I need to go after reading the wiki.

I can confirm my Slicer isn't dropping the temperature after the first layer.

[justinds89]

@dc42

I will try to check again and make sure the temperature doesn't drop when the fan kicks on.

[Phaedrux]

Did you correct the PT1000 configuration for heater 1 as mentioned above? That could easily explain why you're 20 degrees off expected.

[justinds89]

@phaedrux

I didn't change anything as my configuration has this set for heater 1:

M305 P1 X200 ; Configure thermocouple for heater 1
M143 H1 S280

I thought this was correct?

[justinds89]

@phaedrux

I should note I have a PT100 connected to the daughterboard.

[Phaedrux]

Ah I see. Earlier you had said pt1000. Easy typo to make. I wish they had slightly different names.

The link I posted earlier for PID tuning has a lot of information but basically start from a cold machine and run the M303 command with the parameters for the heater you want to tune.

https://duet3d.dozuki.com/Wiki/Gcode#Section_M303_Run_heater_tuning

M303 H1 S220 ; tune hot end to 220c
M303 H0 S60 ; tune bed to 60c

After they are finished you can send M500 to save the values to config-overide so they are loaded at startup, or send m303 again with no parameters Send M307 H1 and it will report the PID values it found for heater 1 which can manually be entered into config.g. it's easier to just use m500 and then copy and paste the values over if you wish. M307 H0 will give the results for the heated bed.

[justinds89]

@phaedrux

Sorry for the confusion.

As I understand I need to just run the M303 command? I don't need to plug in specific values?

Appreciate all the help. Getting closer to having this up and running!

[Phaedrux]

M303 H1 S220 The H1 tells it to tune heater 1 which is the hotend, and to target 220c as the temperature. The tuning will give some messages about what it's doing in the console. It will heat up and cool down the hotend which can take 10 or more minutes. When it's done you can send M307 H1 and it will tell you the values it came up with for heater 1. Then send M500 to save the values.

[justinds89]

@phaedrux

Ah okay, I will try this tonight!

Thanks again.

I will post back if it helped or not.

I'm assuming I'm good to go as soon as I get this temp issue sorted.

[Phaedrux]

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.

[justinds89]

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?

[Phaedrux]

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.

[justinds89]

@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.

[justinds89]

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.

[Phaedrux]

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.

[justinds89]

@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

[Phaedrux]

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.

[justinds89]

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.