Flexible shaft - the best of both worlds?

[foehnsturm 969]

The flexible filament just arrived.

This is a test print with Formfutura's FlexiFil (a thermoplastic Co-Polyester with a shore hardness 45D).

It feeds and prints without any issues, however I had bad inter-layer bonding so far. Therefore I increased layer height to 0.15 mm and wall thickness to 1.6 mm.

 

 

[foehnsturm 969]

Definitely one of the ugliest robots I ever printed ...

but without doubt the most flexible so far.

 

Now looking for some serious applications.

 

[pm_dude 27]

I'm sure you can improve on inter layer bonding. There are a good set of setting here:

http://umforum.ultimaker.com/index.php?/topic/3904-flexible-filaments-comparison/?p=50375

I use those on both NinjaFlex and FlexPLA.

[foehnsturm 969]

Well, better, way better now

 

[BasVanDeursen 0]

Hi,

I must say that I am really impressed by your design. Very cool that you've built this!

I see that you use a hobbed extruder drive wheel and was wondering whether you've had any issues with the wheel clogging. I've done some tests with different types of grip patterns on the feeder wheel and the hobbed wheel performed best. However it also had the problem that it was prone to clogging. I was wondering whether you had any issues with clogging.

Cheers,

-Bas

 

[foehnsturm 969]

Hi Bas,

Thanks for the compliments.

My experience with the hobbed wheel is limited so far. But yes, I'd say it is slightly more prone to clogging. I had no issues until now but I already noticed one or two grooves filled with some PLA residues.

I still a little uncertain about the correct contact pressure. The grip is very good although the marks in the filament are less visible than those produced by the UM bolt.

 

[jhertzberg 19]

That's really good quality for flex! What were your print settings?

 

Well, better, way better now

 

[rick 0]

Looks like an awesome system !

I have a question though. What made you go with the 1:20 worm wheel gears ? And not for example a 1:1 conical gearset ?

 

[foehnsturm 969]

That part is not my idea. It's http://mutley3d.com/ work. Without the high gear ratio the flexible shaft would not handle the necessary torque.

 

[foehnsturm 969]

@jhertzberg

If I remember correctly settings were almost normal: 0.1 mm layer height, 1.2 wall thickness, 30 mm/s printing speed, retraction speed 30 mm/s, temp 215°C (for FlexiFil)

 

[BasVanDeursen 0]

Hi!

I've also noticed that the hobbed wheel seems to cut more into the filament while the knurled wheel seems to push and deform more. The only disadvantage that I found was that when the wheel really slips over the filament (e.g. in case of a clogged nozzle) then the grip pattern really clogs which dramatically decreases grip. However the grip was superior to the grip that I could reach with a knurled feeder wheel.

I have the suspicion that the hobbed wheel is also a bit more efficient in transferring power to the filament because the grip pattern cuts better into the filament, resulting in lower losses. A while ago I've done some measurements on the grip versus the idler wheel pressure for different grip patterns, If you'd like I could send you the results.

I've also done some measurements on the feeder loss versus the idler wheel pressure (the higher the pressure, the higher the grip, but also the higher the losses induced by deformation of the filament). I'll try to repeat this measurement this afternoon but then with a hobbed wheel. That way I can seen if the hobbed wheel is more efficient.

Cheers!

Bas

 

[BasVanDeursen 0]

I did a quick comparison between the hobbed and the knurled feeder wheel. I fed a piece of PLA through a feeder while measuring the torque on the feeder motor axis with a torque sensor (no bowden tube and no hotend present). I used a hobbed wheel and a knurled wheel of the same diameter (8mm, for the hobbed wheel the diameter at the lowest part of the curved surface).

At the same idler setting, a higher torque was needed to feed the material through with the hobbed wheel. However the hobbed wheel also had a higher grip than the knurled wheel at the same idler setting. So in the end it doesn't seem to make too much difference.

-Bas

 

[eldrick 65]

Ordered one today for use on my UM2. It has to be an improvement over trying to push spaghetti thru a tube...

 

[Nicolinux 288]

EldRick please post about it when you have assembled it.

 

[Dim3nsioneer 557]

Ordered one today for use on my UM2. It has to be an improvement over trying to push spaghetti thru a tube...

 

I see. You will remote-pull the spaghetti...

I'm also looking forward to get more news on this.

 

[IRobertI 520]

I'm really really starting to get an itch to try this. But I don't know if I can... kinda need my machine to be somewhat stock for work... Maybe I could get another head assembly so I can "quick swap", hmm.

 

[Nicolinux 288]

Nooo - don't do it! You _need_ to improve your awesome feeder

 

[IRobertI 520]

Hah I accept bribes, PM for Paypal address

But if this could be made to work "perfectly" I think it's the way to go, it would remove a lot of head aches.

 

[Nicolinux 288]

Lets wait for the announcement tomorrow. Maybe they'll just present the UM3 with flexible shaft...

About bribing... come on, what else would you need other than a (non gay) man hug?

 

[pm_dude 27]

UM3 would be wrong... unless its actually a UM mini or bigger and no one noticed it in the videos

 

[Dim3nsioneer 557]

UM3 would be wrong... unless its actually a UM mini or bigger and no one noticed it in the videos

 

Hmmm... interesting thoughts... :ph34r:

 

[Blizz 53]

Will it be that UM-mini that Daid was working on 2 Ulti-eve's ago?

 

I mean...Just saying

 

[Dim3nsioneer 557]

So you expect a SMALLER printer to be announced in AMERICA?

 

[Blizz 53]

Actually I don't, but since pm_dude was saying that nobody noticed, I just wanted to say: i did!

 

[ovidiu 0]

@Bas: I remember reading your report, but I cannot seem to find it anymore. Would you mind posting it again?

Also, what hobbed wheel have you used?

The knurled wheel on my Ultimaker 2 has a tendency to slip off the drive shaft after few hours of printing. It's getting really annoying so I'd like to try some alternative.

Thanks!