[Resolved with a workaround] Over extrusion at the beginning of the printing

[Kamil Chodzynski @kamil1 I have both RoboxDual and other Robox versions]

Hi,

I have over -extrusion at the beginning at the printing stage, please look at the picture. After few centimetres it is working normally. Any clue what it can be and how I can back to normal?

Thanks

Kamil

• This topic was modified 4 months, 2 weeks ago by  Pete. Reason: resolved

Attachments:

You must be logged in to view attached files.

[BHudson @bhudson I have both RoboxDual and other Robox versions Arizona, USA]

@kamil1 This is normal per my understanding. It should be on an inside perimeter so it should not affect the quality.

I operate two Betas and four Production Robox.
I am the US/Canada Technical Support engineer for the Robox.
See my 3D Hub site at https://www.3dhubs.com/phoenix/hubs/ben

[Kamil Chodzynski @kamil1 I have both RoboxDual and other Robox versions]

Thanks for replaying. However, it does affect the quality of the printing models. It is for example much higher that the layer I chose as a result I have that place higher than other places. Only way to avoid it is to do the brim. However, as far as I know it happens after new update of software, before I did not have it at all…Correct me if I am mistaken.

[BHudson @bhudson I have both RoboxDual and other Robox versions Arizona, USA]

@kamil1 Check your filament too - it may be getting wet which will cause it to degrade in the nozzle faster and result in runny filament.

I operate two Betas and four Production Robox.
I am the US/Canada Technical Support engineer for the Robox.
See my 3D Hub site at https://www.3dhubs.com/phoenix/hubs/ben

[nebbian @nebbian I have a RoboxDual Margaret River, WA, Australia]

@kamil1, mine always does this as well. I believe it’s to do with the priming code that happens at the start of the print, the extruder really pushes the filament out of the nozzle hard, then the needle valve closes with a lot of stored pressure in the bowden tube.

When the print starts, you still have a lot of pressure in the bowden, so the filament sort of squirts out for a little bit.

I haven’t found a way to stop this happening, apart from using a brim (which I always use anyway).

Compulsive tinkerer

[Pete @pete I have both RoboxDual and other Robox versions CEL HQ Bristol UK]

Take a look at the start gcode for each print, look for the comment “;Centre head and prime”

There is an extrusion move in my SM print which looks like this

G1 E0.5 F1000

You might notice that it happens without a B command which opens or closes the nozzle. This will build pressure behind the nozzle which would be released on the next open command.

You could reduce the E number and should see a different result. E0 would work, you could build from there.

These files have the code

C:\Program Files\CEL\Common\Macros\before_print.gcode
C:\Program Files\CEL\Common\Macros\before_print#RBX01-DM#N0.gcode
C:\Program Files\CEL\Common\Macros\before_print#RBX01-DM#N1.gcode
C:\Program Files\CEL\Common\Macros\before_print#RBX01-DM#NB.gcode

If you edit one you really should make a backup.

Please note that we do not recommend altering gcode manually, we cannot support you if hardware is damaged by custom code. If a good result is repeatable we can alter this code or expose options to alter it in the software

If you are looking files: The G36 command is unique to Robox, it is “extrude until slip” which is the same used in loading filament, it will stop the extruder from feeding when the filament slip value is exceeded, basically just ensuring the filament is at the nozzle E/D and F commands are the distance for Extruder E/D and the speed.

 

For official support please visit www.cel-robox.com/support/ and create a ticket

[Jack @jack-strong My Robox is a Green Kickstarter Limited Edition]

I have a solution to overcome this. Print a sacrificial ring, one layer height and then play around with placement so that the robox prints it first. Gets rid of all issues.

Also has the added benefit of capturing loose piece from purge if your nozzle is dirty.

[Kamil Chodzynski @kamil1 I have both RoboxDual and other Robox versions]

Thanks all for replaying. It is amazing how community of the Robox is great!

@bhudson - I have just opened a new one from Robox and I have exactly the same results. However, I will dry them to check it as well.

@nebbian - I do brim as well however it can be problematic if your model becoming more complicated. It is difficult to remove brim from some parts or it takes addition time.

@pete - I do not want to interfere the code at all. It is not mine intention. However, you cough my attention regarding slip filament. As far as I remember I changed I think command M909 Set filament slip detection threshold (mm) as for some filament shows me error of slipping. Do you think it could be a reason? I will try to put back the original value and see what it can be.

@jack-strong - I was thinking about this as well but what if you need the hole surface to print? 🙂

 

[Jack @jack-strong My Robox is a Green Kickstarter Limited Edition]

@kamil1 - I do a 20mm ring, wall thickness 1-2x perimiter diameter.

[nebbian @nebbian I have a RoboxDual Margaret River, WA, Australia]

Thanks for that @pete,

Exactly what I was looking for. Well, I didn’t know that it was available to tinker with, but now I do! I can understand the defaults erring on the side of overextrusion after a prime, but I think it can be dropped a bit.

I’ll do some tests and let you know some numbers that work well for me.

 

Compulsive tinkerer

[click @click My Robox is a Green Kickstarter Limited Edition]

I think that is dependent of material @kamil1 and @nebbian what are you using when you get those blobs?

I do vaguely remember getting them occasionally but cannot say under which circumstances. In ‘normal’ operation I didn’t see them (or didn’t see them for a while now).

Is it possible that such blobs are more prevalent when material is less viscous (more runny)?

[nebbian @nebbian I have a RoboxDual Margaret River, WA, Australia]

That’s very possible @click, I’m using ABS exclusively. I can imagine that stiff PLA may require more pressure.

I’m using Robox brand ABS (designer grey) at 245degrees, with the bed at 125 degrees for the first layer.

What are your settings?

Compulsive tinkerer

[Author]

Posts