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Multi colour printing without wipe or prime towers

Posted by deckingman 
Re: Multi colour printing without wipe or prime towers
January 17, 2017 01:16AM
Yes, if my theory is right, then if the speed of filament through the extruder is constant the amount needed to purge the hot end will be constant. What I think is happening is that the melt zone effectively expands and contracts inversely proportional to speed of filament through the extruder, so the amount of filament needed to purge also changes. There is probably a time element in this as well. This is something that I had observed at the start of every print where there seemed to be "bleeding" of colours after printing the perimeters to purge each tool and then starting the print proper. i.e the first tool change or two. I thought it was an error in my script but I'm now leaning towards the theory that it is due to the long heat soak that the hot end is subject to while it is warming up which effectively increases the melt zone. This can easily be overcome buy increasing the purge amount for the first tool change or two but I need to do more testing to determine how much by.

The difficulty arises when there are significant changes to print speed, for example the fist layer is usually printed more slowly so more filament will need to be purged than for other layers. Having said that, it won't be a huge problem if some of the inner layers are slightly out, as long as the outer perimeters and visible surfaces are correct. What is obvious though is that if the "purge amount" is optimised for an object printed at 80mm/sec, then it won't work for another object printed at 40mm/sec. It is possible to get the correct purge amount for any object by trial and error but it would be nice to have an algorithm that calculates it automatically. So, I need to do a lot more testing to determine the relationship between extruder speed and purge amount required.

The thing that will really balls this up is that if the user changes the print speed after the script has been run and during a print. In which case, the purge amount needs to be dynamically variable in "real time" depending on extrusion speed and that could only be achieved through firmware and not by a static "pre-print" script. (are you listening dc42?) winking smiley

In the end, it may be that a small wipe of prime "tower" or mechanism is still required but it won't need to be anything like as large.
Re: Multi colour printing without wipe or prime towers
January 17, 2017 03:45AM
Maybe your tool change calculation based on extruded filament is the problem and you have better results with a purge-time?
You'd have to calculate how long ( in seconds, not in mm ) it takes until the new color appears.
Re: Multi colour printing without wipe or prime towers
January 17, 2017 07:56AM
Quote
o_lampe
Maybe your tool change calculation based on extruded filament is the problem and you have better results with a purge-time?
You'd have to calculate how long ( in seconds, not in mm ) it takes until the new color appears.

That's an interesting hypothesis but time information isn't readily available in a gcode file. It could be calculated from the extruder moves and feed rates but then it just becomes a function of speed.
Re: Multi colour printing without wipe or prime towers
January 22, 2017 01:42AM
Quick update if anyone is interested. The issue that I reported earlier isn't anything to do with printing speed as I had suspected. To save me typing it all again, details and explanation can be found here [somei3deas.wordpress.com].
Re: Multi colour printing without wipe or prime towers
January 26, 2017 12:10AM
Final update. I've fixed all the issues with the script and the technique is working very well.

It seems that very few people are interested in this, so I won't bother posting any more updates here but I will keep my blog updated - at least for a little while longer.


[somei3deas.wordpress.com]
Re: Multi colour printing without wipe or prime towers
January 26, 2017 04:57PM
hello Deckingman, At the momento none of mine printers is multicolor but for sure i' m really interested in your work. I think is simply amazing. You have my totally cacht in it here and in your blog. Thanks for your work. ( hope my english was better but...)
Re: Multi colour printing without wipe or prime towers
January 26, 2017 11:22PM
Quote
deckingman
It seems that very few people are interested in this

Over 1200 views - I wouldn't be discouraged.

Quote
deckingman
Final update. I've fixed all the issues with the script and the technique is working very well.

That's really excellent, you've advanced the art. If I had a multi-color hot-end I'd be digging into the code.


My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!
Re: Multi colour printing without wipe or prime towers
January 27, 2017 12:09AM
Your work inspired me to buy a second Diamond hotend and try it on my Prusa, too.
Only the clogged nozzle of my first Diamond cooled my interest a bit...
Re: Multi colour printing without wipe or prime towers
January 27, 2017 01:40AM
Quote
deckingman
Final update. I've fixed all the issues with the script and the technique is working very well.

It seems that very few people are interested in this, so I won't bother posting any more updates here but I will keep my blog updated - at least for a little while longer.

From my point i think the guy`s at the Ultimaker forums would be VERY interessted in this technics, because there have been sold alot of UM2`s to guy`s who wanted to upgrade their printer some time to Dual Extrusion, and it never came out, but the printer is prepaired for dual-extrusion.

i´m also interessed in this thechnics for my orca, is it possible to integrate that into marlin or so ( i`m no software developer) ?

Chri

Edited 1 time(s). Last edit at 01/27/2017 01:43AM by Chri.

[chrisu02.wordpress.com] Quadmax Intel Delid Tools
Re: Multi colour printing without wipe or prime towers
January 27, 2017 01:53AM
Thanks for the encouragement guys. As you can appreciate, writing up all this stuff takes a fair bit of time and I get nothing out of it apart from the knowledge that it might help others.

@ Paul Wanamaker. Yes, 1200 views of this thread but only 70 visitors to the blog I set up to explain what I'm doing in detail, and only a handful of comments and followers. Hence my somewhat downbeat moodsmiling smiley. Also, the code comes with a health warning - if you are a professional writer of code, digging in to it will likely raise your blood pressure or cause severe fits of depressionsmiling smiley

@ o lampe. Yes I had blockage problems when I first started using the Diamond. Not in the nozzle itself but at the heat break and inside the heat sinks. Since then, I've learned never to turn the fan off until the hot end is below around 45degC, which of course means never turning the machine itself off until the hot end has cooled down. The other thing I do is never retract filament when I'm changing it. I just cut it off where it enters the extruder and feed it through the hot end until it purges out all the old. It costs me about 450mm of filament but since doing it that way, I've never had a problem with blockages. HTH

@ everyone. The next thing I need to test is what effect, if any, that using the Diamond as a true mixing hot end has in relation to the amount of filament needed to purge the mixing chamber. To date, all my testing has involved switching between single filaments. Now I need to evaluate what happens when I mix filaments. i.e. have the mixing ratio set to (say) 0.50:0.50:0.00 for one tool and 0:00:0.00:1.00 for another so that one tool is using 50% each of colours A and B and tool 2 is using 100% of colour C. In fact there are 6 of these combinations and I have already defined a 6 tool config. I'll post the findings on my blog

Ian
Re: Multi colour printing without wipe or prime towers
January 27, 2017 02:13AM
Quote
Chri


From my point i think the guy`s at the Ultimaker forums would be VERY interessted in this technics, because there have been sold alot of UM2`s to guy`s who wanted to upgrade their printer some time to Dual Extrusion, and it never came out, but the printer is prepaired for dual-extrusion.

i´m also interessed in this thechnics for my orca, is it possible to integrate that into marlin or so ( i`m no software developer) ?

Chri

Hi Chri,

It's a post processing script that takes the sliced gcode file and moves the tool (colour) change commands forward to an earlier point in the file. So in that respect, it is completely independent of printer make\model, or firmware version.

The technique should work for any set up that takes multiply filaments and feeds them into a single nozzle. I'm not on the Ultimaker forums (or any other printer manufacturers forums) so just point them to my blog (link in signature).

Ian
Gad
Re: Multi colour printing without wipe or prime towers
January 27, 2017 03:05AM
Hi Ian,
I'm one of the silent followers of your work and I bet there are more out there. You did a great job at documenting it and I thank you for that !

Reason of my silence is that I find the Diamond setup quite heavy and bulky so if your solution works for them, I'd rather go for either the work of Davide Dalfiume (in italian only I'm afraid : [immaginaecrea.wordpress.com] or a less detailed one in English : [www.thingiverse.com]) or the future equivalent implementation on Prusa MK2 (I think the first customers have just been delivered the upgrade : [www.prusaprinters.org]).

So first of all, do you see any difference between the Diamond setup and the setups I mention with respect to your technic?

Also, although color switching is nice, I'm rather interested in switching (temperature compatible) filaments with support filament (such as PLA/PVA or ABS/HIPS). Did you test this ?

Thanks
Gad
Re: Multi colour printing without wipe or prime towers
January 27, 2017 05:29AM
Hi Gad,

I agree, the Diamond is big and heavy and with the 3 heat sinks set at an angle, it takes up quite a lot of space.

I took a quick look at the link on thingiverse. It looks very like the Prometheus set up and there is mention of getting Cura to do the nozzle wipe off of the build platform. So I'd guess it still uses some sort of wipe/prime system between one filament and the next. That being the case, then you could of course use my technique with that device and do away with the wiping. I've seen a video of the Prometheus system and for sure, that uses what looks like a very large priming tower, so again I would have thought that my technique would work well and negate (or at least severely reduce) the need for the tower. Prusa uses what he describes as "smart" towers but I don't see any reason why my technique couldn't be implemented on that printer as well.

Obviously, I'm unable to test the idea on every multi filament design. I'm just an old guy who happens to have a Diamond hot end that I can use as a mechanism for testing the idea. But the fundamental problem is the same for all these multi-filament, single output designs. i.e. When switching from one filament to another, the old filament has to be purged before the new one comes through. The usual approach is to do that by moving the print head away from the print, extruding some filament until the new one comes through, then moving back and resuming the print. My technique simply replaces that wipe/prime method.

Switching temperature compatible filaments would work just as well. You could also use it for filaments with different temperature requirements but you would have to wait for the hot end to heat up and/or cool down between filament changes which might lead to some oozing and therefore a mechanical wiping system might still be needed as well.

In essence, all I'm doing is moving the tool change commands to a point earlier in the gcode file. It's a simple idea but the implementation is a little complicated.

The results aren't perfect because there is some small amount of transitional mixing after switching from one filament and the next. But then using wipe and prime towers which essentially require one to pause the print, go away and do something, then resume printing isn't perfect as it is practically impossible to do without leaving some sort of blemish on the print, (and of course it wastes time and filament). HTH

Ian
Gad
Re: Multi colour printing without wipe or prime towers
January 27, 2017 05:54AM
Thanks Ian,

the Prometheus setup looks promising but rather expensive for my wallet. If I'm not mistaken, the only piece of HW that is really needed for experimenting this technique with a "standard" E3D hotend is what they call the "ProFeeder" (and a dual bowden extruder if like me you have everything in direct drive).

I have almost all the stuff needed for an extra printer so I will give a try to filament switching with your technique in the coming months. No doubt I'll update here once i'm there.

(N.B. we are plenty of "old" guys around here smiling smiley)

Gad
Re: Multi colour printing without wipe or prime towers
January 27, 2017 09:50AM
Quote
Gad

(N.B. we are plenty of "old" guys around here smiling smiley)

Gad

I think I have the record though - DOB 16/08/1953 smiling smiley Can you top that?
Re: Multi colour printing without wipe or prime towers
February 14, 2017 06:35PM
Thanks for the work you have done on this. I'm currently saving for the cyclops hotend. I can't wait to start experimenting with multi colored prints. Your post processing script looks really interesting. I saw on your blog that the script was taken down. Do you have plans to replace it?

Conscripted
Re: Multi colour printing without wipe or prime towers
February 15, 2017 01:22AM
Quote
conscripted
Thanks for the work you have done on this. I'm currently saving for the cyclops hotend. I can't wait to start experimenting with multi colored prints. Your post processing script looks really interesting. I saw on your blog that the script was taken down. Do you have plans to replace it?

Conscripted

Maybe. I haven't exactly ironed out all the bugs. It mostly works but there are still instances where the segmented moves can occur at slightly the wrong time. Life would be so much easier if the gcode file was just a series of G1 XYE moves. Unfortunately there are retract and unretract commands, fan switching commands, non print moves etc. and if the new tool change position happens to fall where one of theses commands exists, the new position has to be modified either further back or further forward depending on what the non print command is.

TBH, I've been busy doing other things and haven't had much chance to look at it. I've left the annotated script on the blog so that others can see the thought processes involved which be copied and pasted but beware, there are bugs.

Ian
Re: Multi colour printing without wipe or prime towers
February 18, 2017 12:02PM
You might try adding your blog link to the top post so it is easier to find.


www.rustynoob.com
Re: Multi colour printing without wipe or prime towers
February 19, 2017 03:55AM
Quote
rustynoob
You might try adding your blog link to the top post so it is easier to find.

Can't see how to edit that post. Anyone know?

I've added my sig to this post which has a link.

Edit. How come I can edit this post but none of the earlier ones. Is there a time limit or something?

Edited 1 time(s). Last edit at 02/19/2017 09:04AM by deckingman.

[somei3deas.wordpress.com]
Re: Multi colour printing without wipe or prime towers
March 31, 2017 12:05PM
Hi all reprapers, I am also an old guy, DOB. 26.02.45 very interested in colour mixing I have built a prusa i3 from scratch using ardurino ramps 1.4 with a 3rd extruder driver running off AUX 2, I made a copy of the diamond hot end from a drawing I downloaded and copied the aluminium fins, my problem is that my standard heater cartridge will not lift the temperature above 150 deg so I have ordered a 40 watt cartridge from Ebay and awaiting its arrival I hope this will fix the issue. I am useing Pronterface as an interface but I cannot get my head around how to mix colours, I have found how to switch extruder steppers no 1 - 2 & 3 but not how to run more than one at a time to achieve mixed colours. I noticed in marlins configuration.h that there is an option for mixing extruders is this the first step?.
Re: Multi colour printing without wipe or prime towers
March 31, 2017 11:02PM
You can get a cloned Diamond hotend for less than 30€ and you've built one on your own?
Anyway, make sure the heatsink bodies don't touch the hotend. The original hotend comes with a 25W heater, so it should work with yours, too.

Yes, you have to define mixing extruder in Marlin and then define mixing ratios for the different tools.
The details are described in this thread
Re: Multi colour printing without wipe or prime towers
March 31, 2017 11:53PM
Thanks o_lampe, I appreciate what you say about cost, that is not the point making it provides a challenge and therefor more satisfaction when one gets thing working, after all I could have bought a clone i3 but unboxing does not do it for me. However thanks for the info and the link, mixing now seams a little clearer.
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