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Help with using Nylon

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SubseaUK
(@subseauk)
Member

Hi, I have been approached with regards to printing a nozzle cover, similar to the one in the attached photos, but there is a requirement for it to be made of Nylon if possible as it is subject to knocks and being dragged about. 

Does anyone know if this would be:

a: possible to print in nylon on a Prusa Mk3.

b: made to a similar finish in PETG with regards to abrasion & impact resistance.

c: what would be the best / easiest way to create the STL file required to print a prototype, ie Tinkercad, Fusion 360 etc.

Thanks for the help.

Rgds

Kev

 

Main Body dimensions are 144.26mm Dia,  98.25mm high, 8.15mm thick but gets thinner in the flutes at 4.94mm.  

The flutes are 22.15mm wide and 73.54mm long

IMG 7188
IMG 7194
IMG 7189

 

 

 

 

Quote
Topic starter Posted : 22/02/2021 2:40 pm
Luke
 Luke
(@lmf5000)
Expert Moderator

Hi Kev,

I haven't personally tried nylon myself, but the Prusa knowledge base has a write-up on Nylon that suggests that it should be possible on the stock printer as long as you keep it absolutely dry (that means using a dedicated dry box for it even while printing). Here's the knowledge base article: https://help.prusa3d.com/en/article/nylon_167188

And here's an example of a DIY dry box for materials like nylon that absorb moisture so fast that they practically get ruined if they stay out in the atmosphere for the duration of a typical print - https://www.youtube.com/watch?v=OY5n9q-wS7k

The general idea is to enclose the filament in a box of dessicant and leave just a small hole (typically a bowden coupler) for the filament to exit out of. Something like this:

image

(source: https://www.instructables.com/3D-Printer-Filament-Dry-Box/ )

Nylon is expensive and prone to warping (like ABS) so if I were you I'd perfect the print on PETG before moving on to Nylon. If you're lucky you might find PETG has adequate properties for the part in question (perhaps give the customer a prototype part in PETG to try for fit and finish and fitness-for-purpose, then deliver a nylon part if they find the PETG one doesn't live up to the task). PETG doesn't have the abrasion or heat resistance of nylon, but it sounds like in this application the rubbing and knocks are incidental rather than an integral part of the operation of the part (like gears, which constantly slide over one another and hence benefit from being made of nylon as its surface can easily handle the constant sliding wear).

As for designing it, definitely Fusion 360. A design like this would take just 5-10 minutes. Probably the easiest way would be to sketch half of the cross-section of it to capture the internal profile, revolve around an axis to get most of the rough shape done, then make a sketch on the end to draw the flutes (use circular pattern to repeat 8 times), cut with an extrude, and fillet to get the final shape.

Took me 7 minutes to make this (it's a .f3d file, open in Fusion360 then use the timeline to follow the steps I took):

No guarantee the dimensions are correct 😇 (I would advise measuring inside diameter top and bottom to check whether it's tapered). I've left the hole in the side as an exercise for you 😆. I encourage you to try to make it yourself from scratch to become more familiar with the software. My method wasn't the most-time efficient - it would've been faster to extrude one flute and fillet it, then repeat it with a circular pattern (that way I'd have saved selecting 8 areas to extrude and selecting 24 lines to fillet, which I had to do because I did my circular pattern within the 2D sketch not within the 3D space).

Hope this helps! 🙂

Regards,
Luke

ReplyQuote
Posted : 22/02/2021 9:48 pm
SubseaUK
(@subseauk)
Member

Thanks Luke, I will be looking at the drawing production today ( on 360 ) and have already started working on producing a PETG sample for the guy to have a look at. I am really hoping this comes off as it will pay for a 2nd printer!!!

Kev

ReplyQuote
Topic starter Posted : 23/02/2021 9:11 am
nighthawk
(@nighthawk)
Prominent Member

Just thought I'd chime in on the Nylon...

I use Polymaker CoPa. It's more expensive than some and only comes in black AFAIK. However it is a breeze to print with compared to a few others I've tried(MH Nylon Pro and Dremel Nylon). You want to use the smooth PEI and coat it with gluestick. I use the Kores glue that comes with the MK3S. An enclosure is necessary too. I've had no issues with the filament as long as I keep it dry.

ReplyQuote
Posted : 23/02/2021 12:26 pm
SubseaUK
(@subseauk)
Member

Hi, thanks for the input but unfortunately the customer needs the printed item in yellow so I am restricted to what I have to use. We are currently trying a PETG prototype with a view to producing a nylon print if required but we are also trying to get an idea of how much a yellow colour would change from reel to print as this could be a job stopper if it is not at least similar in the resulting print!!!  Thanks

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Topic starter Posted : 23/02/2021 12:56 pm
SubseaUK
(@subseauk)
Member

 

Hi Luke, since the print started I am getting build up on the nozzle which is resulting in the depositing of plastic on the bed & print ( see the photos attached, video can be provided but too big to upload here!!! ). Any ideas on the cause of this?

Thanks
Kev

IMG 7231
Screen Shot 2021 02 23 at 13.10.19

 

ReplyQuote
Topic starter Posted : 23/02/2021 1:50 pm
Luke
 Luke
(@lmf5000)
Expert Moderator

Hi Ken,

That's unfortunately a common characteristic of PETG. It curls up and sticks to the nozzle, then gets deposited everywhere. You could try reducing your extrusion multiplier a little so there won't be so much "extra" plastic on your print to stick to the nozzle, and you could try using a higher temperature (230°C) to prevent those strings from being able to get too large (it tends to melt them rather than allowing them to stretch). But with PETG some fuzzy stringing is normal - after the print you can burn them off with a flame or a heat gun and pick off the residue with the cutters that come with the printer or with tweezers. Make sure the PETG you're using is dry (always store in a sealed bag with desiccant) because moisture absorption makes PETG more stringy.

Regards,
Luke

ReplyQuote
Posted : 23/02/2021 7:09 pm
SubseaUK
(@subseauk)
Member

Thanks Luke, I will reduce the multiplier as it was 0.94 then I believe you said to bump it up after the hot end change out but that is the only real change in settings. I must admit this is the first really long print ( over 15mins ) since the change so that might be why it has not shown up before. The temp was also reduced from 230 to 220 but I will do one thing at a time and hopefully will find the solution quickly.

Cheers

Kev

ReplyQuote
Topic starter Posted : 23/02/2021 9:12 pm
Luke
 Luke
(@lmf5000)
Expert Moderator

Hi Kev,

If you're still at an extrusion multiplier of 100% then you'll definitely see an improvement if you lower it a bit 🙃. I did advise 100% after the hot end change as the initial setting (since that's the default setting and takes one more variable out of the mix as we didn't know at the time whether the new hardware would be overextruding or underextruding). Now that it's printing well again you might want to print some extrusion multiplier testers (the top couple of millimeters of a calibration cube) to see which values work best. My printers hover around 96-97% but of course every printer is different so you'll have to find your optimal value experimentally.

Generally speaking, it's a good idea to always to examine what the prints look like, formulate a theory as to how they could be improved (say, you notice an excess of plastic and wonder whether EM should be decreased slightly), note the old value down and then test your theory on your next print to see if the tweak makes it better. These will be small tweaks so even if it turns out to make things worse the print will still be usable, but this way you move away from printing endless tests and start using actual prints for continuous improvement (not final production pieces for customers - but prototypes and personal prints are perfect candidates). That way you'll incrementally improve your printer's quality with every print (and learn along the way what works and what doesn't) 🙂

Regards,
Luke

ReplyQuote
Posted : 23/02/2021 9:25 pm
SubseaUK
(@subseauk)
Member

Hi Luke, jumping back to your drawing, I tried looking at the timeline but could not manipulate it to be of much use to me as I only seemed to show completed steps but not how they were achieved. Am I missing something here?  Also how do I edit the dimensions you have used in your drawing?  Sorry but as a total newb to 360 I am following a user book but if the process I want to do strays from the demo in the book I get lost pretty quick. What seems simple to you is far from that to me 😀 

Cheers Kev

ReplyQuote
Topic starter Posted : 24/02/2021 3:33 pm
Luke
 Luke
(@lmf5000)
Expert Moderator

Hi Kev,

To go through the timeline you move the slider left and right with your mouse, that's this thing -

image

You won't be able to see how I made the sketches because the timeline treats the whole sketch as one "step" but it's the same as AutoCAD or other 2D software.

To edit dimensions, double click the sketch:

image

Sketch 1 is the side profile for revolving (inner and outer diameters and height), sketch 2 is the top profile for extruding (the dimensions of the flutes).

Once in sketch editing mode, double-click any dimension to edit it:

image

 

image

In that example, I had entered the dimension as a formula - I knew I wanted a diameter of 144.26mm, but I was inputting the radius (since when revolved that will be half of the shape) - so I inputted "144.26/2" in the box and fusion automatically calculated the answer (72.13). It's one of those time-saving little features in Fusion 🙂

To exit a sketch click "finish sketch" at the top right:

image

To display/hide sketches, bodies etc click the eyes next to the entries:

image

For example here's the shape with everything shown (all sketches):

image

As for learning the ropes, I learnt almost everything I know from Lars Christensen's youtube videos, I suggest you watch the 3-part introductory series starting from this video: https://www.youtube.com/watch?v=A5bc9c3S12g

If you go through that, along with part 2 and part 3, you should be able to recreate this shape (and much more) very easily yourself 🙂

 

Regards,
Luke

ReplyQuote
Posted : 24/02/2021 6:20 pm
SubseaUK
(@subseauk)
Member

That's great Luke, thank you very much. By a strange coincidence I had just found Lars' videos on YouTube earlier today and will certainly have a good look at them. I am going through an Australian guys 16 part tutorial at the moment which I started just before finding Lars' videos!! 😀 

Thanks again

Kev

ReplyQuote
Topic starter Posted : 24/02/2021 8:53 pm
SubseaUK
(@subseauk)
Member

Well here we are again Luke, cleared one stumbling block and run straight into another!!!   I managed to change the dimensions as far a possible based on your drawing but now have another problem 🤔 .  I have noticed that there are two steps internally on the surface of the cylinder but no matter what method I use I cannot seem to get them to start and stop in the right places or I end up out of the drawing / sketch mode and lost in the 3d mode!!. Could you have a look at the dimensional drawings attached and see if you could suggest the best way forward?  It probably does not help if I started from the outside working in as it were.

Thanks

Kev

Screen Shot 2021 02 25 at 15.08.20
Screen Shot 2021 02 25 at 15.08.57
ReplyQuote
Topic starter Posted : 25/02/2021 3:56 pm
Luke
 Luke
(@lmf5000)
Expert Moderator

Hi Kev,

Sure, looks simple enough, but first I need to understand the drawing a bit. Is the bottom one a cross-section with the shape upright? Do those 3 steps go all the way around the interior? If you could take a photo of the physical sample it would help for context 🙂

Regards,
Luke

ReplyQuote
Posted : 25/02/2021 4:11 pm
SubseaUK
(@subseauk)
Member

Hi Luke,  Simple for a cad/cam genius such as yourself 😀 ,   me I find it a little harder LoL!!!

Yes, the steps go all the way around inside the cylinder and I have attached a photo of what I am actually trying to achieve below if that would help. I think you can just make out the internal steps in the 2nd photo.

Don't forget to keep answers in idiot format 🤣 

Thanks

Kev

IMG 7189
IMG 7188
ReplyQuote
Topic starter Posted : 25/02/2021 4:29 pm
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