3D Printing with Flexible Materials

I went to a meet-up last week where the topic of flexible material filament came up. It was a local South Los Angeles event: CM3D. I went there because our good friends at FeelColor was showing some new things. This is an Italian filament company that is not yet distributing in the United States, but they provided us with some of their material, and I love printing with it. They have beautiful colors, a really amazing color palette. These guys are Italian, and they care about it. We really like them. This is in no way an ad for them, but we will be doing a review of their material in the future when their material is out and you can actually buy it in the U.S. Since you can’t buy it yet, I don’t want to tease everybody. But I think I just teased everybody anyway. Oh well.

Alessandro invited us to this event because they had some new material they were going to be showing. I’m sorry Tracy missed it; she stayed home with the girls. We didn’t have a babysitter; everybody was on spring break that week. In any case, it was a better meet-up than I expected. I saw some people I had known and met from other meet-ups and shows around Southern California who I didn’t expect to see. And that was great.

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3D Printing with Flexible Materials

One of the discussions that came up amongst us—this meet-up was very material-focused—was about flexible materials. I remembered some past experience I had had printing with flexible materials, and some discussions I had had with Russell Singer from MAKEiT who was there about printing with certain materials and how difficult it can be, especially with flexible materials. I realized there are some good tips and tricks we can share to help you if you are trying to print with flexible materials.

Flexible material might mean Ninja Flex or any of these things that are actually flexible materials, but also it could mean support materials. Many of the support materials are softer, so they are a bit flexible in and of themselves. Especially if you are working with PLA and have a dual extruding machine and want to have some dissolvable support material, then PVA is really your compatible choice. That is a very soft material. I throw it into the flexible material category even though it is not a flex material, but it is a soft material. In 3D printers, a lot of them have the same issues printing them.

WTFFF 227 | 3D Printing with Flexible Materials

Bowden Tubes

Here we go. Any machine that is a Bowden-type machine has that long white tube where the filament is feeding and the filament drive motor is on the back of the machine. You’re pushing the material from that point up and over the top to your extruder. That tube can easily be 18 inches, even 24 inches long. If you have a big bed, it has to be able to move all around that XY platform, and it has to stretch out all the way.

The problem with printing a flexible material in that type of machine is when that material is traveling over that 18 inches, and maybe if your machine can push the material that way, even though it is soft, all the way down to your extruder, when you get to retraction, which is a thing that has to take place in many 3D prints, if not the majority, what that retraction is going to do is your filament drive motor is going to pull that material back. If your material is really flexible, it’s just going to stretch your material, and it won’t pull it back. You are going to end up with a lot of problems in printing, usually with material that continues to flow when you don’t want it to or is dripping out of the nozzle, and it makes a mess. Now that it’s stretched out, it has a thin area, so it’s not as consistent in how it’s laying down. That’s true, too. Even so, your machine pulls it back and stretches it. Now when it starts to push it forward, it’s not actually pushing it forward, it’s just the material is recovering from where it stretched to.

How do you deal with that? There are a few tricks. Before I get to those tips, I could say the machines we find that print the flexible materials more consistently and better are the ones—we referenced this in a previous episode about material handling—that have the filament drive motor right at the extruder, above it, next to it, traveling around the whole printer with the extruder. Those ones are not pushing this flexible material as far. The shorter distance that you have, the less the material can and will stretch. It works better. But it can be done with Bowden-type printers. I have done it myself.

There are a few different tips that can help you do this. That white tube you are using, I would suggest to buy a second one if you don’t have it, get the same material or similar material. If you shorten the length of that tube, then that distance that material is being pushed is less, and the distance it can stretch is less. There is less play in the whole situation. That will improve your print performance right there.

When I was looking at the MAKEiT printer, which is definitely a prosumer printer, and they are a relatively new company so there is not a ton of them out there yet, but the way their printer worked, they have this tube on there that was at least 12-15 inches long, and it really didn’t need to be. Their printer is not that big. The way it works, their extruder is only moving on one axis, and they have their build platform moving in the other axis. One is moving X, one is moving Y. When you are doing that, that tube, from where it is pushing the material, has a shorter distance. You could cut that tube down to about six inches. If you do that, those flexible materials will print better. It will have a better chance. You may still have some problems, but you have a better chance.

The other biggest problem that I see: I had a Leapfrog Creatr HS from this company Leapfrog in the Netherlands. I didn’t have a lot of support here in the United States working with it. You did have some support, but you had to call them at 2 am. I am not good at night, so that was not a good thing. I was determined to solve my problem, though.

I was trying to print with PVA, this support material that is more flexible. It was jamming up in the machine. The filament drive motor was on the back, and it was going through a long 18-24-inch tube. I would find that I would start printing, and then it would stop. It wouldn’t come back. I would look in the machine, and it was all jammed up. I have filament everywhere.

Filament everywhere due to jam.

What happened was the material was so flexible it wouldn’t go where the motor was pushing it. There was a gap. There was all this space in there from the gear that is pushing it and the wheel that the gear is pushing it against, it had space to move. I needed there to be no space.

CAD rendering to fix filament jam issue.

Here is what I did. There were some aluminum fittings in this machine that are creating a funnel for when the material comes out, to guide it to where it is supposed to go and then eventually into that white tube. That funnel had too much space; it wasn’t working. So I took that piece out, measured it, created a model in my CAD program of a new part, and 3D printed myself a new fitting to put in there. I made it so there was no space for that filament to move. Once it came out from that drive and that gear was pushing it toward the tube, it had no space to move.

The idea was that you were taking out of all the space and creating a fitting within a fitting. If it went really well, then we would go and have it 3D printed in metal so you would have a metal fitting so it didn’t have any melt issues or sticky issues of itself as it got warm. But we never kept the machine, so it didn’t happen. I sold the machine for other reasons. But something like this may work for your machine as well. Certainly the concept of what I did was good.

My intention was that we would either 3D print it in metal eventually, or it would have a local machinist make it out of aluminum. It might have cost $50 to have someone make it for me at most. I didn’t need to. The 3D printed part actually worked. I used it for months that way before I sold the machine.

It had no room to move. So what I found is the filament drive motor could grip the soft material, and it could push and move the soft material. The problem was when it pushed it, it needs to push it in only one place. If that is the case, it worked a lot better.

3D printed part to fix flex filament jam

Part at work in printer

There are a lot of different 3D printers out there, a lot of these Bowden-style machines. You want to take a close look. If you are going to use some softer, more flexible material, look at that filament feed system. It’s common sense to determine if you can see the filament on the plus side of that filament drive gear after it’s been pushing it where it’s going. Can you see the filament? If you can see it, there is probably too much space to be using a flexible material. Can you make a fitting, or can you adjust it in any way so that it can’t send it anywhere it doesn’t want to go?

One other tip that I thought of is that we had seen at CES that there are some companies out there making flexible materials with a hard candy shell, like an M&M. It’s a hard shell on it, so it allows you to push it in, but it has soft characteristics once it’s melted. So it’s like a simple coating on the material. We haven’t tried it yet. We heard about some of this, and we have tried to get some to test it, and it’s not available yet. Apparently it will be available. When it does, we will use it. But I felt some pieces that were made from it, and it does have flexibility. Maybe not as much as a Ninja Flex or something like that, but it did have flexibility. That might be possible also, so keep an eye out for that. It certainly would open up printing with flexible material to any 3D printer.

Big filament issue with old fitting

The last technical tip would be using flexible material in your actual Bowden 3D printer is that retraction is still going to be an issue, even if you modify your tube so you have less distance to go or if you are able to modify your filament drive system so the filament has nowhere to go so it actually works where it is pushing it forward. Retraction is still going to be a problem. You need to make sure in your settings you give yourself a larger amount of retraction than normal and a lot of extra restart distance when you are starting to push it forward again. The length of time it’s going to take for the filament to react to the command is going to be longer. You’re going to need to increase those times in your retraction settings. It will be different and unique for everybody. There is no magic bullet. Just keep it in mind, and do the best you can. I have successfully printed with this stuff, and those kind of printers—I remember a dealer of the Leapfrog printers asked, “You’ve printed PVA in a Creator HS?”

I was like, “Yeah, I have.”

He said, “Wow, how did you do it?”

I hacked it. You have to hack your machine a bit. This was a hardware hack, not a software hack. But sometimes you have to think that way. It may be a combination of both.

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3D Printing with Flexible Materials

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