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

justinds89

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.

Phaedrux

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.

dc42

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

justinds89

Appreciate the help guys. I will checkout that link.

justinds89

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.

dc42

@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.

justinds89

@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.

dc42

@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.

justinds89

@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.

dc42

@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?

justinds89

@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.

dc42

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.

justinds89

@dc42

Well I'm not exactly sure how close the nozzle is to be honest. It prints great now and the first layer looks really good too. I think it is just a hair too close though and would be better if it was backed off just a bit. Really just trying to get everything as good as possible and accurate as possible.

I will try out the G92 command. I was just trying to avoid shoving a hot nozzle into my BuildTak by going the wrong direction with the offset.

I think I can test this out without having the nozzle heated up.

Phaedrux

I was able to open Cura and find where they tucked z offset. It can be found under Build plate adhesion, but it may be hidden by default. You could add your offset there, or you could use the baby stepping buttons at the start of the print.

justinds89

@phaedrux

Appreciate that! I looked around and even used the search box in the settings, but didn't see anything. I guess I just overlooked it.

I will just use that as it will probably be easier.

Thanks!

BTW - The new fan duct and the silicon sock solved my temperature drop issue and my prints are better than ever with this printer.