BigBrain3D Purge Mechanism  

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allen.m2
(@allen-m2)
Estimable Member

Just finished my first successful test print and I think I’m going to like it.  I had to make modifications to my right z motor mount and their mechanism to make it work with my Bondtech Extruder and Mosquito Hotend.  They give you .step files for their mechanism once you purchase and have been very responsive to email.

Link: https://www.bigbrain3d.com/product/retractable-purge-mechanism/

 

 

Posted : 28/11/2019 4:05 pm
vintagepc
(@vintagepc)
Noble Member

I got in on the kickstarter. They are looking at a revision for my Skelestruder setup, once that's done I intend to update the purge bucket post-processing script I was working on previously for use with this mechanism.

 

Posted : 28/11/2019 4:46 pm
allen.m2
(@allen-m2)
Estimable Member

@vintagepc

Here is a link to the right Z motor mount I had to design to give enough clearance.

 

https://www.thingiverse.com/thing:4013705

 

Posted : 01/12/2019 3:16 pm
vintagepc
(@vintagepc)
Noble Member

Unfortunately that's not the only issue, there's some interference with the fan shroud, pinda, and trigger mechanism. I'll wait to see what solution they come up with.

 

Posted : 01/12/2019 8:54 pm
CybrSage
(@cybrsage)
Honorable Member

How does the software know not to make the purge block and use the wiper instead?

Posted : 03/12/2019 5:37 pm
vintagepc
(@vintagepc)
Noble Member

Custom slicer they offer or  a post-processing script.

Posted : 03/12/2019 5:50 pm
CybrSage liked
allen.m2
(@allen-m2)
Estimable Member

@cybrsage

You can turn off the purge block and put custom tool change g-code in Prusaslicer.  They have example g-code available on their forum.  I have it working very good.  Only problem I’m having is being caused by Octoprint.  I only use Prusaslicer, not any of their software.

Posted : 03/12/2019 11:27 pm
vintagepc
(@vintagepc)
Noble Member
Posted by: @allen-m2

@cybrsage

You can turn off the purge block and put custom tool change g-code in Prusaslicer.  They have example g-code available on their forum.  I have it working very good.  Only problem I’m having is being caused by Octoprint.  I only use Prusaslicer, not any of their software.

Interesting. Does the custom code take into account custom purge volumes, etc?

 

Posted : 04/12/2019 1:34 am
allen.m2
(@allen-m2)
Estimable Member

@vintagepc

You put in g-code for the number of purges you want to do.  I’m running 4 purges right now (first 2 no material extrudes) and have a clean color change from black to white pla.  The two blobs that purge are about .2-.25 grams of filament combined weight.

This post was modified 8 months ago by allen.m2
Posted : 04/12/2019 1:41 am
CybrSage liked
kenny.b2
(@kenny-b2)
Trusted Member

If you turn off the purge block and use their custom tool change g-code, do you lose the ability to use the settings from PrusaSlicer for #of cooling moves and the other ramming parameters?  Or is that not affected?

Also, I bought the kit to try on my mk2.5s MMU2s but looks like it doesn't quite fit.  Traveling to the furthest +X axis distance doesn't push on the mechanism enough to get it to extend out under the nozzle far enough.  I think maybe I can just change the dimensions on the push rod..  I'll print it up and see.  

This post was modified 7 months ago by kenny.b2
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Posted : 05/01/2020 9:00 pm
allen.m2
(@allen-m2)
Estimable Member

@kenny-b2

You cannot use the cooling and ramming moves.  I am using example g-code generated by prusaslicr and the dribbling version to work on mine.  The bigger issue I just solved was the mechanism flexing and not consistently putting the bucket in the right position.  I made a bracket that connects the bottom of their bracket to my x-axis rail to stop this.  Now back to working on tip shapes.

Posted : 06/01/2020 4:49 pm
kenny.b2
(@kenny-b2)
Trusted Member

@allen-m2

I wish PrusaSlicer had some more functionality of what it recognizes in the "Tool Change G-code" section.   Seems like currently the best bet it to make a post processing script.  You'd have to slice it without all the purge mechanism bits and with the wipe tower enabled.  Then maybe the post processing script strips out the wipe tower but pulls the parameters for the tip shaping and adds in the purge mechanism movements.  The gcode that PrusaSlicer generates looks pretty well identified in the tool changes and wiper tower.  I've never used python but maybe I'll give it a try to see if I can fix that.  

On mine, I ended up modifying the firmware instead of printing longer parts to deal with the MK2.5s not being able to travel past 250mm on the x-axis.  I just changed the software endstop to like 254mm (right before it hits the Y carriage).  That seemed to work for me for now.  I haven't had an issue with stiffness but I did take 2 of the springs off because they overwhelmed my stepper.  

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Posted : 13/01/2020 12:04 am
vintagepc
(@vintagepc)
Noble Member

I'm actually working on a modified version of my bucket toolchange post processing script that works with the RPM, while respecting ramming, cooling moves, etc.

I think I've got the changes done, just haven't had time to verify the output gcode or actually run tests. 

At some point I want to make it a built-in feature in a PS fork, but that is probably a ways away.

Posted : 13/01/2020 1:28 am
kenny.b2 liked
kenny.b2
(@kenny-b2)
Trusted Member
Posted by: @vintagepc

I'm actually working on a modified version of my bucket toolchange post processing script that works with the RPM, while respecting ramming, cooling moves, etc.

I think I've got the changes done, just haven't had time to verify the output gcode or actually run tests. 

At some point I want to make it a built-in feature in a PS fork, but that is probably a ways away.

That's awesome!  If you need someone to test your code, let me know.  Do you have it on GitHub?

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Posted : 13/01/2020 1:35 am
vintagepc
(@vintagepc)
Noble Member

The original bucket code is available via a post here on my and Gnat's WIP bucket mod. Progress kinda stagnated on that  with the release of the BB3D mechanism and other real life priorities. 

I can't make any guarantees but perhaps I'll manage to work on it throughout the week and have something in the near future. I will likely share it in multiple places then, I'll be sure to post here once I do.

 

 

Posted : 13/01/2020 1:53 am
allen.m2
(@allen-m2)
Estimable Member

@vintagepc

Thank you!

Posted : 13/01/2020 2:20 am
vintagepc
(@vintagepc)
Noble Member

Update - I've dumped an alpha version of the script in a new github repo I created, it is available here. 

You're welcome to take it for a spin, but do read the README first. 

https://github.com/vintagepc/RPM-Post/blob/master/README.md

You're welcome to report issues and request features in github, I can't guarantee I'll get to them but will certainly try.

Posted : 20/01/2020 2:10 pm
kenny.b2 liked
allen.m2
(@allen-m2)
Estimable Member

@vintagepc

I have several days of printing lined up right now, but will give this a try as soon as I can.  Thank You!!

Posted : 20/01/2020 6:16 pm
kenny.b2
(@kenny-b2)
Trusted Member

@vintagepc

Thanks for doing this!  I'll give it a try too in the next few days.  

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Posted : 21/01/2020 11:29 pm
vintagepc
(@vintagepc)
Noble Member

Thanks guys - interested to hear your feedback! I did file a feature request with PrusaSlicer to leave the purge volumes button enabled even if the wipe tower is disabled so that those settings can be more easily accessed when a custom toolchange script is in use, and for available wipe-to-infill and part wipe volumes to be exposed as variables. Feels like this is the start of something cool!

Posted : 22/01/2020 12:24 am
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