Retraction Tuning Guide

[Phaedrux]

@burtoogle Any chance of firmware retraction making it into the main Cura release without needing a plugin?

[burtoogle]

@phaedrux said in Retraction Tuning Guide:

@burtoogle Any chance of firmware retraction making it into the main Cura release without needing a plugin?

Hi, I don't think it needs the plugin to actually function. Once the setting has been set to true it should work (I don't actually use it myself so I can't verify this). The default value for that setting is this:

                    "default_value": false,
                    "value": "machine_gcode_flavor == 'RepRap (Volumetric)' or machine_gcode_flavor == 'UltiGCode' or machine_gcode_flavor == 'BFB'",

What that means is that if you are using one of those gcode flavours then firmware_retract will be true, otherwise false.

Now as far as I know you can set that value by either using the plugin as discussed above or you can create a printer definition that overrides the default definition. There's lots of printer definitions in the resources/definitions directory in the Cura installation (https://github.com/Ultimaker/Cura/tree/master/resources/definitions) that show you how you can define a new printer type and override default values. Hope this helps.

[Phaedrux]

@burtoogle Interesting. I haven't gone that deep into the innards of Cura yet, but good to know. Thanks. I guess I was just hoping for a check box like the plugin gives you for the average user to just know if it's on or not, much like relative extrusion.

[burtoogle]

Well, you can't get much simpler than installing the printer settings plugin and checking that check box.

[Phaedrux]

Has that plugin made it into the plugin browser yet?

[burtoogle]

[burtoogle]

You may have to be running the 3.4 beta to get the toolbox?

[Phaedrux]

@burtoogle seems so. I don't tend to use the betas. Experimental features is as far as I'm willing to go. But glad it will become widely available. Though I still think firmware retraction belongs in the main settings.

Thanks for the heads up.

[Ricky_Grade10]

Thanks for the good info boys, I got the plugin installed and was able to get on the fly firmware retraction working, right on! Through denial and error I was able to get some decent settings to use and I guess its working ok but I want to know more about the R and T parameters in M207. I think I can tweak this better, maybe with those parameters, but the only info I could find in the gcode wipi doesnt really tell me much

[Phaedrux]

T lets you specify an unretract speed different from the retract. This is handy because molten filament behaves a bit like a non Newtonian fluid. Kinda like cornstarch and water mixture if you have ever seen that. If you press softly on it it flows like water. If you tap it hard it feels solid. Retracting fast helps pull the whole bit up the nozzle in one piece and then unretracting more slowly lets it flow more easily out.

R let's you modify the amount of filament that gets pushed back out after a retract. If your idler tension is very high it can deform the filament as it goes through causing it to have a slightly different effective diameter which slightly changes the extrusion rate. So in times wirh lots of short retracts close together the filament can get compressed and less will come back out leading to a bit of local under extrusion.

Alternatively if you have a very oozy material like PETG that bulges out when heated it can be handy to reduce the amount that comes out after a retract to try and reduce the z scar on the outter layer.

[Danal]

@ricky_grade10 said in Retraction Tuning Guide:

Through denial and error I was able to get some decent settings...

Ok, I know it was autocorrect.

Still made me chuckle.

[Phaedrux]

@danal I dunno about you but I read that and didn't even notice it as an error. I tend to make my way through life by denial and error.

[Ricky_Grade10]

I never went to university to get a fancy PFD or whatever, I only got my grade ten.

Any suggestions on where to start with the T and R parameters? Are these usually small values?

Thanks for the help boys

[Phaedrux]

I usually use 20-40mm/s for unretracting. 90-133mm/s for retraction.

The R value is usually a very small positive or negative decimal value.

Beauty of firmware retraction is that you can adjust the values during a print. So you can start a retraction test print and make changes on the fly to see how they effect it.

[wilriker]

Something I wanted to share here because the Printer Settings plugin for Cura came up: currently there is a bug in CuraEngine (the part the does the slicing in the background) that will create broken GCODE if you enable FW Retract, Relative Extrusion (as recommended for RRF) and Coasting at the same time. This is fixed in source code but will not be part of Cura 3.4 but only the version after (probably Cura 3.5 - not sure about minor fix versions).

Just so you know, do not use this combination right now.

[Dino]

As a slight aside I spent most of my Saturday setting up pressure advance on my delta, part of that included using firmware retraction.

I use S3D as my primary slicer on the delta and for $150 software it doesn't have a nice checkbox to enable firmware retraction I used post processing scripts I found here:

http://thrinter.com/using-firmware-retraction-with-simplify3d/

I had to turn off relative extrusion distances to get the script to work properly but now that it's setup it seems to be pretty nice.

Only thing I noticed was if I sent all the parameters for retraction distance, speed, unretract extra distance, and zhop together in the same command the zhop wouldn't apply. I added a second command and moved the zhop command to it which seems to have fixed it.

I have all my default retraction gcode in my config.g and have alterations of it in the start gcode commands for different filament if different retraction is needed. Plus the ability to make on the fly changes to retraction is fantastic, I can disable retraction mid print or add more shop if I need, or even print multiple retraction tests at once with different settings easily.

[Ricky_Grade10]

So if the R value is neglative does that mean it will retract the filament even more?

I guess Im having problems trying to figure out the order of the retraction process.

In my brain compartments, I have been thinking it would retract first, then z hop and finally un-retract. Is that the way she goes?

[wilriker]

@ricky_grade10 said in Retraction Tuning Guide:

So if the R value is neglative does that mean it will retract the filament even more?

No, that would mean it would unretract less than it has retracted, e.g. if you set
M207 S5 R-0.5
that would mean it retracts 5mm but only unretracts 4.5mm (whyever you would wanna do something like this).

I guess Im having problems trying to figure out the order of the retraction process.

In my brain compartments, I have been thinking it would retract first, then z hop and finally un-retract. Is that the way she goes?

That's exactly what it does.

1. Retract amount specified by Snnn at speed of Fnnn
2. lift Z by the amount of Znnn
3. do whatever slicer has put in between
4. lower Z by the amount of Znnn
5. unretract Snnn + Rnnn at the speed of Fnnn (or Tnnn if that is given)

[burtoogle]

@phaedrux said in Retraction Tuning Guide:

@burtoogle seems so. I don't tend to use the betas. Experimental features is as far as I'm willing to go. But glad it will become widely available. Though I still think firmware retraction belongs in the main settings.

Thanks for the heads up.

FYI Cura 3.4 has been released today.

[wilriker]

@burtoogle Any idea when this release will make it to GitHub? As that is the base for the package manager in Arch Linux.