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

Phaedrux · 2 Aug 2018, 18:55

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 · 2 Aug 2018, 19:52

@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 · 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.

justinds89 · 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?

Phaedrux · 2 Aug 2018, 21:49

You have 3 options, choose any or all.

Find a better cooling shroud that can direct the airflow better.
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.
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 · 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.

justinds89 · 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.

Phaedrux · 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.

justinds89 · 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

Phaedrux · 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.

justinds89 · 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.

Phaedrux · 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.

dc42 · 6 Aug 2018, 10:21

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

justinds89 · 6 Aug 2018, 12:59

Appreciate the help guys. I will checkout that link.

justinds89 · 8 Jun 2018, 18:57

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 · 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.

justinds89 · 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.

dc42 · 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.

justinds89 · 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.

dc42 · 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?

	; 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