bulges in my print - NinjaFlex

Just done my first NinjaFlex pint. (this stuff is AMAZING)
it's a very simple print, a stubby circular tube with a smaller circumference at the top.

instead of being perfectly circular there seems to be a bulge on opposite sides, all the way up the vertical...
it only petrudes about .3mm but is obvious when holding the item and flexing

any idea what is causing this??

Hi Sardi

Difficult to tell what the problem would be, when it's not clear what the orientation of the part is on the bed. I'd think it was mechanical; see: [reprappro.com]
Most likely, I'd think one of your motor pulleys (X or Y) is loose.

Ian
RepRapPro tech support

It's not the point that your slicer moves the head inwards or outwards is it? Or possibly when it retracts/extrudes on each layer? If I print tubes I normally have a slight bump down one side for those reasons - adjusting my retraction amount normally improves it.

I'm quite impressed that you got the Ninjaflex to work with the Ormerod - I was under the impression that it requires a very short feedpath and the bowden-style extruder wouldn't work.

Hi VortyZA, we've had Ninjaflex working here, though we did have to have the temperature quite high; 225C I seem to remember. The main problem with Ninjaflex and other soft filament is that it buckles in the extruder. The Ormerod extruder is very good in this respect; the filament can't escape anywhere. The Bowden tube doesn't help, and there is extra hysteresis, but you can tune the retractions to help.

Ian
RepRapPro tech support

@ droftarts
I think you might be right...
I did a small experiment where i tried the same print with ABS, the bulge issue was still present. (image attached with axis ref.)
I also did a quick video; there seems to be some slack at 0:04 (I think);
[www.youtube.com]
this looks like it could be the cause of the top bulge on teh image but there didnt seem to be any obvious reason for the bottom bulge (on the attached image)...


@VortyZA
The NinjaFlex worked much better than I expected.
I haven’t had much of an opportunity to experiment but I set bed temp to 35 (onto kapton tape) & nozzle to 235... I believe it would have extruded at a slightly lower temp though.
As said it was a very simple print, I'm not very confident that it would handle bridges too well, especially at that high temperature.

Edited 1 time(s). Last edit at 06/30/2014 06:34AM by 88Zombies.

I found I had to print at a much slower speed than usual with ninjaflex. It works best if you can print without retractions.

Dave
(#106)

That's interesting - I would also have thought you'd need more retraction than normal due to the compression in the Bowden tube.

I must get a hold of some of this stuff - sounds interesting! How compressible / stretchable is it? Similar to silicon glue? More like an eraser?

Hi 88Zombies,

My guess is, that it's a problem in the y-axis. I have been fighting mechanical issues in my Ormerod like crazy :-)

Your Y-belt is definitely too loose (great video). I used a cable-tie to pull my belt towards the platform close to the belt-fixing to tighten the belt. It worked wonders for my prints. My platform is modified, but I guess it's possible on the original platform also.

Static friction in the y-bearings will accentuate cable-slack. I had to replace one of my Y-bearings that was worn out after printing a couple of kilos of filament.

There are a lot of y-belt tighteners, that you can print yourself. It might be a good upgrade.

Best regards,

Carsten

Quote
VortyZA
That's interesting - I would also have thought you'd need more retraction than normal due to the compression in the Bowden tube.

I must get a hold of some of this stuff - sounds interesting! How compressible / stretchable is it? Similar to silicon glue? More like an eraser?

What I meant was that it has greater extruder lag, so retractions and re-starts are effectively time-delayed - you get a blob at the point it retracts and then no extrusion for a while after it starts printing again, so you are usually better off with no retraction and live with the stringing, though that depends on the shape you are printing. It is extremely flexible - I estimate about the same as silicon sealant. I printed a couple of camera lens caps, which work better than the usual lens caps - they are soft so no risk of scratching, and I tapered the part that goes around the lens barrel so that its elasticity grips it more tightly than normal caps and it won't fall off.

In case it's of interest I've attached the simple SCAD file to make a lens cap - it is parametric so you can alter the dimensions to suit any lens.

Dave
(#106)

Quote
dmould
What I meant was that it has greater extruder lag, so retractions and re-starts are effectively time-delayed - you get a blob at the point it retracts and then no extrusion for a while after it starts printing again...

I am hoping to implement variable extruder lead time in a future version of my firmware fork - but first I need to catch-up with RRP's 0.78 that they have in testing.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dmould

Quote
VortyZA
That's interesting - I would also have thought you'd need more retraction than normal due to the compression in the Bowden tube.

I must get a hold of some of this stuff - sounds interesting! How compressible / stretchable is it? Similar to silicon glue? More like an eraser?

What I meant was that it has greater extruder lag, so retractions and re-starts are effectively time-delayed - you get a blob at the point it retracts and then no extrusion for a while after it starts printing again, so you are usually better off with no retraction and live with the stringing, though that depends on the shape you are printing. It is extremely flexible - I estimate about the same as silicon sealant. I printed a couple of camera lens caps, which work better than the usual lens caps - they are soft so no risk of scratching, and I tapered the part that goes around the lens barrel so that its elasticity grips it more tightly than normal caps and it won't fall off.

In case it's of interest I've attached the simple SCAD file to make a lens cap - it is parametric so you can alter the dimensions to suit any lens.

Dave
(#106)

Ahh, that does make sense!

Quote
dc42
I am hoping to implement variable extruder lead time in a future version of my firmware fork - but first I need to catch-up with RRP's 0.78 that they have in testing.

Sounds like a good idea!

The material is a lot stronger than I expected! i tried ripping that print shown in the original post but failed to do so.


@colsenfoto
thanks for the tips, I'm going to print and attach the y-belt tightener tonight. Fingers crossed.

This seems to have worked!!!!

Only done one print so far but was a better quality than all 4 prints prior to adding iamburnys upgrade.

Edited 2 time(s). Last edit at 07/04/2014 05:28AM by 88Zombies.

I'm glad that seems to have fixed it. I am also using iamburny's y-belt clamps, along with some spacers (see [github.com]) to allow me to get the y-belt tension just right.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Great to see,@88Zombies

Do you also use the tightener er something similar?
[www.thingiverse.com]

If you apply too much tension, the motor begins to skip steps and you get sort of jagged motion.
If you have too little tension....well, you already know

I tightened mine until I could hear and feel vibrations from the teeth - and then backed up a little bit, until the sound and motion were smooth again.

My next experiment will be high quality IGUS sliding plastic bearings. My original roller bearings are beginning to show considerable sticktion.

Best regards,

Carsten

Quote
colsenfoto
My next experiment will be high quality IGUS sliding plastic bearings. My original roller bearings are beginning to show considerable sticktion.
Best regards,
Carsten

I've just added a section in 'maintenance' about lubrication: [reprappro.com]
It's often the rubber seals that need a little lubrication, not the roller bearings inside the linear bearing.

Ian
RepRapPro tech support

Hi Ian,

Thanks for the suggestion, but I'm afraid a bit of oil won't do the job. I forgot to mention the sound from the bearings....

Have you ever tried dragging a newly lubricated bicycle chain through a sandbox and then going for a ride

Best regards,

Carsten

Ouch! Yes, that sounds gritty. Washing the bearing in petrol usually gets rid of that, then repacking in Lithium grease. However, if it's actually a ball that is malformed, the bearing will need to be replaced. If you continue to have problems, email me on support at reprappro dot com and I'll send a replacement. Send me all your details, and reference this thread.

Funnily enough, we had a rep from Igus here the other day, who then sent us 12mm Igus rod and their linear bearing replacement bushings, so we can build an Ormerod with them... Lovely and smooth running, but I'm pretty sure it would add significantly to the kit cost!

Ian
RepRapPro tech support

Hi Ian,

Thanks for the offer. I'll probably take the noisy bearing apart and have a look at the balls. I'll let you know, if I find something interesting. A part of my daily job is building servo-systems and testing mechanics.

I think the best money would be spend on upgrading the bed to a stiffer frame and making a stiffer x-axis. The bearings are way low on priority compared to those two. Nevertheless upgrading my Ormerod to the very smooth Igus-types is very interesting - seen from a professional perspective for me.

Best regards,

Carsten

PS. By the way, your 0.78 release has been running totally stable. I'm not sure, what happened when I made my multi-extruder experiments.