dennisjm
Posts: 342
Joined: Wed May 07, 2014 9:51 pm

Re: Purge Wall for dual prints

Wed Aug 06, 2014 8:46 pm

Actually I just have one process since I"m printing supports with the alternate material, not printing two models. But yeah, if I added fake wall objects then I'd need two processes. Again, it might work, but would be easier to have a feature to do it.

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TenKOhms
Posts: 172
Joined: Wed May 14, 2014 3:04 pm

Re: Purge Wall for dual prints

Wed Aug 06, 2014 9:06 pm

dennisjm wrote:Actually I just have one process since I"m printing supports with the alternate material, not printing two models. But yeah, if I added fake wall objects then I'd need two processes. Again, it might work, but would be easier to have a feature to do it.
Ahhhh I see, a non-dual extrusion STL with a primary extruder doing the printing and the second extruder doing the support material.

I just tried a quick test, nothing in-depth, to see if something I thought up could work and it did. Set the first process to your_machine(both extruders) and set all the print settings and your primary extruder, do NOT generate supports. Add a second process your_Machine(both extruders), enable support generation with the support extruder, and then set top layers, bottom layers, shells/perimeters to zero as well as no skirt and 0% infill. slice with all processes && continuous. Didn't test out to see if tool head change scripts were implemented, but it did do the support gneration and print slicing properly (i believe). I don't have a dual extruder printer with me to actually test it. Again, a bit more work, but after it's set up it can be used for all future prints.

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BaronWilliams
Posts: 159
Joined: Tue Jul 15, 2014 8:30 pm

Re: Purge Wall for dual prints

Tue Aug 19, 2014 11:59 pm

+1 WE NEED PURGE WALLS!

I've tried all the tricks I could think of, and without a "purge wall", dual extrusion doesn't work well for large objects.

In a large object, whenever it switches between the extruders, there's problems that can't be addressed without a "purge wall". When a nozzle is idling too long, depending on the filament type used, it will either drip onto your print or get in a state where it doesn't print well when it needs to (causing gaps whenever the print head starts extruding after sitting idle).

With a properly implemented "purge wall" feature you can prevent dripping because the "purge wall" feature will greatly retract the nozzle you're not using, and then purge it out on the "purge wall" when it's time to use it. This solves the dripping issue. It also solves the stuck filament issue where a nozzle fails to flow well when it first starts printing after sitting idle for a while.

lkeppner
Posts: 27
Joined: Sun Aug 10, 2014 10:58 pm

Re: Purge Wall for dual prints

Wed Aug 20, 2014 12:09 pm

While I've been printing for some time now, I'm relatively new to the dual extrusion printing and only started with small pieces. I hadn't run in to some of these problems with the small parts. However, as you point out, as soon as you start working with larger parts that require one head to idle long enough, the material has flow start issues because you are creating a small void with the larger "tool change" retraction. I have stripped material while trying to push it through the head before it has had a chance to start flowing if I try to push too fast; while pushing slower creates a drippy mess before actually starting the print again and, in the best case, leaves debris on the outside of my part.

I would have to add my voice into the request for the purge wall feature. That, along with a separate tool change retraction spec, would go a long way to making dual extrusion usable in many more situations.

krouviere
Posts: 18
Joined: Wed Aug 27, 2014 6:21 pm

Re: Purge Wall for dual prints

Wed Aug 27, 2014 6:48 pm

purge-rect-nut-ffc.zip
(566.11 KiB) Downloaded 125 times
A lot of neat ideas here. I also would really like to see a purge wall implemented. I'm interested to see wipers and brushes people have implemented too. A brush seems like a good way to go, but getting the gcode optimized seems tricky. I liked the technique of getting the support material only into its own process as described above. After some tinkering I got it to work fairly well. In the attached image you can see a cutaway view of the setup. The only thing that's cut away here is the front section of the skirts, so you can see support material under the part. In the left rear position there is a box with a brim that uses the left extruder. In the right rear there is the same thing for the right extruder. The object (a nut) is elevated from the table on purpose just to force support material under the part for a test. There are 4 processes. First is the left extruder object, followed by the nut support material (both using left extruder) followed by right extruder object and finally the nut object build material. I used 2mm retract. This is a case where I just want support material and build material, not necessarily "2 colors". I found the brims on the rectangle objects necessary because on the printer I was testing with (Flash Forge Creator) did not seem to prime well before printing began. Also support in S3D for priming both nozzles leave something to be desired. Anyway, the tall skirts worked well to brush off most of the bad stuff before the nozzles reached the object.

This is by no means optimized, but does seem to work. I'm going to try it on my Replicator 2X later. The nice thing is that using this as a template and dropping in new models then assigning the models to the processes may make things easier for me to use S3D for dual extrusion. I too was going back to Makerware which really bugs me due to the lack of good profile editing support and less features than S3D.

I'll attach the factory file too in case anyone's interested.
Attachments
purge-setup.png

krouviere
Posts: 18
Joined: Wed Aug 27, 2014 6:21 pm

Re: Purge Wall for dual prints

Thu Aug 28, 2014 11:56 am

Is there a way anyone knows of to get just the infill into its own process? Like what was done with the support material in examples in this thread? It seems that support can be generated when everything else is turned off, but infill seems to need top/bottom/outline on to generate proper infill.

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BaronWilliams
Posts: 159
Joined: Tue Jul 15, 2014 8:30 pm

Re: Purge Wall for dual prints

Thu Aug 28, 2014 10:11 pm

Krouviere, in another thread here I posted about using two processes much like you are doing. I learned that you can make the skirts have an auto-height calculated by simply setting the skirt height super high (like 99999). Simplify3D clips the skirt to be as high as your highest point in your model, so you don't need to know how high your model is to get the skirts to simulate a purge wall. Just set them to 99999 layers and Simply3D takes care of their height for you automatically. Nice little trick.

Using the 2 skirts like that actually works pretty well. It's not completely a purge wall, but it works good enough.

If a model is very large, you need to purge more often, and that's not possible (as far as I know).

For example, if your print takes up almost the entire layer, then you have each head idle for very long during a dual head print. It can take many minutes before a head change takes place. By that time the idling head has been either drooling, dripping, or is now pretty stuck (depending on the filament) and needs a long purge. It would be better if you could somehow force a head change and tiny purge once every minute through the print to keep the heads flowing better. Having heads idle for many minutes during a large print is never going to work well no matter how good your purge wall is. Some filament will darken while it's idling, form hard lumps, drip, burn slightly, etc. It's just not a good idea having heads idling for more than a minute, ESPECIALLY IF ONE OF YOUR FILAMENTS ARE TPE (like NinjaFlex and others)!

I would like to see Simplify3D one up the Makerware purge wall and address this idling problem too. A purge wall can help kick start an idling head, but it's better not to get the head in a bad shape to begin with. More frequent tiny purges would be good. Wipe structures, head cleaning structure, and some other printing tricks could also help a lot.

Simplify3D is so much better than Makerware in almost every way except for dual head printing and infill. If they could concentrate on improving those two weak points, that would be fantastic.

krouviere
Posts: 18
Joined: Wed Aug 27, 2014 6:21 pm

Re: Purge Wall for dual prints

Thu Aug 28, 2014 10:27 pm

Thanks BaronWilliams, and everyone else here who have provided a lot of great tips. The 99999 trick is pretty useful. Purging every so often (via programmable timer) would be great. I really like S3D. It's a lot moe CAM like than other SW I've used. It seems tackling this purge issue would be well worth the effort. It sure would make me happy to spend less time doing complicated setups and more time printing. It would seem a timer based purge action shouldn't be that hard in theory. Maybe even a firmware level operation (Sailfish etc).

blaknite7
Posts: 29
Joined: Fri Aug 22, 2014 6:57 pm

Re: Purge Wall for dual prints

Thu Sep 04, 2014 11:55 pm

I too seem to be having the same issues though i experienced something strange and i was curious if anyone else has seen this:

Setup:
I have 3 STL files on the bed and 2 processes. 2 of the STL files are what i am printing, a clear rectangle and the other is a colored cylinder in the middle of the rectangle. The 3rd part is a dummy block to help purge the colored filament. the 1st process (for the clear rect) has 100% fill and only the rectangle STL selected. the second process has both colored cylinder and dummy block selected with 100% fill as well.

Now for some reason the first lay of the print was clear (as it should be) but the second layer of the rectangle (which should have also been clear) was put down by the opposite extruder...? it seems to be alternating the fill layers between the right and left extruders when it should only be using the one... it seems to me to be a bug since non of my processes has the left extruder (color) putting infill for the rectangle.

Has anyone ever seen weird nozzle swapping like that?

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BaronWilliams
Posts: 159
Joined: Tue Jul 15, 2014 8:30 pm

Re: Purge Wall for dual prints

Fri Sep 05, 2014 4:37 pm

I never saw that kind of nozzle swap happen.

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