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yellowshark

My first tests with nGenflex

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Having a Bowden tube printer I have never tried flexible filament; just reading people’s painful experience with it on the Forum!

So Colorfabb launched nGenflex stating it worked with Bowden tubes and my first reel arrived last week 

Firstly, having never seen flexible filament before, I was surprised by how flexible it was on the reel; hold the reel up and let some unreel and gravity gives you a straight vertical (almost) line of filament. I was concerned if it would feed through the Bowden and into and through the drive wheel but it did. Feeding all the way to the nozzle without a problem.

The initial bed adhesion is better than PLA (for me). With PLA I often find the first few mm do not adhere meaning I need to be ready with a long screwdriver to move the “tail” out of the way. This flex filament just sticks starting with the first pixel.

So up to now it has been a very easy filament to work with.

The finish on a large flat top surfaces and on layer 0 is just awesome, significantly better than I have ever achieved with PLA. Not so good on small complex top surfaces but I will come to tha n a moment.

For my testing I setup initially with…

• Fully enclosed printer

• Glass bed with hairspray

• Ambient temp 29c (yes that was a mistake!)

• Bed temp. 80

• Extruder temp. 245 (that was a mistake as I meant to use 250)

• Flow 99% (taken from my nGen settings)

• .300 layer height

• 0.4mm line width

• All printing speeds 30mm/s (apart from layer 0 at 20mm/s)

• Fan 50%

• Retraction speed 40 (nGen setting)

• Retraction length 5.5 (nGen setting)

The first piece attaches to the wrist and I thought some flexibility would provide a tighter fit, important as it has a gps positional sensor attached and zero relative movement on the arm is vital. A great finish in the bottom but a mess on the top!

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For the 2nd print I change the fan from 50% to 0%, on the basis that people have reported good results with nGen with no fan. The top face was improved but still poor.

 

During the print I noticed that in the narrow areas of infill there seemed to be too much material being laid down, i.e. at the point of the retraction/z move as the line finished 0 it was almost if it could not cope with the very short printing distance. So for the next print I pushed the retraction speed to 50 and the distance to 6.5. But that made no difference. I think will try it with coasting next.

At this point I moved onto a different model and I am going to have to spend some considerable time I think trying to get an acceptable top surface for this type of model, it is unusable for me and I suspect the dimensional accuracy is very poor, which I need to check.

BTW it seems to me that you need to remove the brim immediately. If you leave it on for any time the brim and model just “glue” themselves together and you have to remove with scissors/blade. I ripped several of the bottom layers off one of the prints after leaving the brim on the model for a minute, maybe two.

The next pic is of my 2nd attempt to print this model. For this model I reset the fans back to 50%. The first attempt was going fine and I left to make myself a coffee. When I returned there were 2 or 3 layers with what looked like under-extrusuin and as I arrivde the piece was in serious under extrusion; on the z move I would often hear a sort of whoosh sound. I quickly changed the flow up from 99% to 103% and it did recover. On reflection I concluded that the under extrusion was due to poor filament. I had the teeth set very lightly on the filament and felt that the diameter of the filament must have reduced so that the drive wheel was not engaging, giving the whooshing sound I was hearing, unusual for ColorFabb for sure. It has not happened again.

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There is one broken line around the middle. I am now wondering if that, and the 2 or 3 lines on the previous print, is poor layer adhesion rather than under extrusion. The rest is good apart form the holes at the top which are poor. The next two pics are the flex filament followed by a PLA example - you can see the difference in quality.

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To test bed adhesion I then tried a larger model using a box with the size 150mm * 130mm on the X/Y axes. Again with a simple flat surface a beautiful top layer finish.

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The print was about two hours and when I returned it had detached from the bed. To be fair to the filament the bed had not been cleaned for months, so I need to do that and retest.

For my last test I printed a simple 150mm oblong with a height of 1.2mm. As you can see it is flexible!

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Stop press: I have just printed the hydraulic cylinder at 255 (up from 245) and layer adhesion looks much better; will try and post an update this weekend

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ngf7.jpg.5869156986a21b720da3140c72a959ce.jpg

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Interesting, i had quite some problems getting it to stick, but i was using glass with PVA glue...

 

I wonder if you are measuring the temperature of the bed or the glass? On my printer the temp sensor measures the bed not the glass plate. So to have the plate at 80 I set the bed to 88, checking with an IR thermometer.

It might be worth trying some changes to nozzle to bed distance, although I just went ahead with my PLA setting and it worked fine.

You could mail Colorfabb and ask if they were using a glass bed and if so what adhesive they used.

Maybe I was lucky but I never have any problems with PLA adhesion and nGen worked fine first time too.

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Interesting, i had quite some problems getting it to stick, but i was using glass with PVA glue...

 

I wonder if you are measuring the temperature of the bed or the glass? On my printer the temp sensor measures the bed not the glass plate. So to have the plate at 80 I set the bed to 88, checking with an IR thermometer.

It might be worth trying some changes to nozzle to bed distance, although I just went ahead with my PLA setting and it worked fine.

You could mail Colorfabb and ask if they were using a glass bed and if so what adhesive they used.

Maybe I was lucky but I never have any problems with PLA adhesion and nGen worked fine first time too.

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Ok I printed another two copies of the hydraulic cylinder shown above. This time I pushed the temp from 245 to 255. I also raised the speed from 30mm/s to 40mm/s. This time the layer adhesion was so much better. The first I ran with 50% fans and pushing in the cylinder hard I eventually got a single layer separation at a point I would call a "point of weakness" where the circumference narrows.

The second print I ran at 20% and when I gave this print the same physical abuse it remained perfect. Cannot recall if the discussion on nGen had a view on best fan rate

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Hi, I've been experimenting a little with nGenFlex.

So far, the only way I can get reliable bed adhesion is with BuildTak (which is what ColorFabb recommend). Using the S3D settings recommended by ColorFabb.

Head temp: 255

Plate temp: 85

Fan: 0%

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Just an update - I'm giving up with this stuff for the time being :(

After some good results with small parts, I thought I'd go for a bigger print (around 15 hours running at 30mm/s at 260 degrees)

It's failed at the same point 3 times now - it seems to be around the 2 hour mark where the material jams in the extruder.

What seems to be happening is that as the material is fed through the extruder it twists, and after around 2 hours it's twisted so much that it eventually coils and jams in the extruder.

This is in an UM2+

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I discovered that the tension on my extruder was more towards the top than towards the middle of it's range. So I'm going to give it one more attempt with the extruder tension turned up some more and see if that helps.

I'd really love this stuff to work, the tests I've tried with it have been very encouraging.

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Success!

I think it was a combination of two factors causing me problems, firstly the tension on the extruder needs to be firm and secondly, with a full roll of the material it was coming unravelled slightly and wrapping around the spool holder.

Printed a pistol grip with 40% infill over 15 hours (checking regularly for the filament getting caught up) and it's come out very well I'd say.

Running at 260 degrees at 30mm/s I had a little bit of stringing between the open section at the top - Unfortunately I cleaned it up with a scalpel before I took the photo's so you can't really see.  Running at a lower temp would help a little there but I'm not unhappy with the way it turned out.

40% infill and 1.2mm walls makes the grip fairly solid but still with a little give in it and it feels very nice to hold.

The slightly shiny finish on the black NGEN Flex and a combination of running at 260 has worked quite well to hide the layer lines (this was printed at 0.16mm layer height with a 0.4mm nozzle).

Anyhoo... I'm happy with it and I'll be experimenting some more.

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Edited by Guest

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