Building a printer for nylon

Hello Everyone,

A friend of mine is very interested in printing large nylon parts. I have also started thinking that nylon is the next fun thing to get into with 3D printing, so I'm looking for ideas.

I have not fully fleshed out the idea yet but the basic notion I have at the moment is to use an all metal hot end of some type, somehow make the structure of the machine stiffer and more accurate than typical RepRaps, and possibly have some basic option for enclosing it too increase air temp around the workpiece.

So far all I have is a roll of 618 and 645, I need to build something that can print nice parts with that nylon!

Any suggestions?

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Yvan

Singularity Machine

I have done some printing with Taulman 618 and am totally in love with it. You need temperatures only slightly higher than with ABS - so all metal hot end is not strictly needed. As the filament is quite a bit more flexible than ABS or PLA, there is a risk of the nylon kinking and excaping from the extruder - redesign the plastic arround whatever extruder to maximise the containment of the filament around the hobbed bolt.

I have found that nylon benefits from drying of the filament (70 degrees in a fruit dessicator for 4 hours seems about right) and a nice touch would be a semi sealed container for the filament to be drawn from which is fed with a slight positive pressure of dried air.

Delightful as it is to work with, so far I have not found a lot that justifies the extra expense of nylon - possibly just a failure of immmagination - but i have done lots of flexible vases tie dyed by the Richrap method.

Mike

Thanks, very good tips. My friend is planning on making parts that need the heat resistance of nylon. ABS is marginal. I will try with some of the extruders I have available, but eventually I would like to have a good margin of error heat wise. Some parts need to be rather big, so who wants things to be at the limit right?

I also want to move past the ridgidity issues of the machines I have, trying to find a good evolutionary step up from the threaded rod approach.

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Yvan

Singularity Machine

Having come from home made CNC machines to 3D printing, I know what you mean about rigidity - I tend to automatically make everything as rigid as possible; this usually means extra mass. My first machine is a sort of Prusa with X and Y carriages built like the incredible hulk, but even the vibration ripples on the prints from this printer were cured by little corner braces to stabilise the rectangular parts.

I will admit that I am building much lighter carriages for these at the moment - but my mantra remains rigidity, rigidity, rigidity.

Mike

Have you ever posted a photo of your 3D printer? I can't recall if I have seen one or not.

My problem with rigidity is I can't spell the damn word! I'm going to build a CNC router at some point, it would speed up some of the work I do. It might end up having a massive welded steel frame. But first I want to build more 3D printers.

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Yvan

Singularity Machine

I have played with Nylon printing on The TAZ we got at work. The hotend can handle it fine, but shrinkage with the Nylon is fairly large so large parts could be a real problem. I also modified the TAZ for a little more accuracy and more rigidity (a few stiffer parts and linear ball bearings)....but that was after playing with the Nylon.

finding a good base to get it to stick to took a while. Ended up using a Nylon base, which works well, but large parts will try to pull away from the base more.

I do like the printer design though, and plan on printing one for home.

Edited 1 time(s). Last edit at 07/12/2013 09:54PM by 1013.

1013, looked up the TAZ. I'm going to give that one a closer look.

I have corrected the "infrared cooking" problem with my home made hot end, so I might just try some nylon with it. I should be able to repair it easily if I burned the PTFE tube inside. Also, if I really wanted to, I could alter the design and withdraw the PTFE tube up and above the main aluminium heat sink. Heck maybe I could even print with polycarbonate then!

The shrinkage issue might be moderated by enclosing the printer in some way. Even a simple cardboard box may be enough to test things...?

The tip about printing on a nylon base makes sense. What did you use?

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Yvan

Singularity Machine

Hi Yvan,
You asked if I have put any photos of my Prusa printer on the web - I haven't, but may do when it looks a little more "concours d' adequate" *

I have attached some pictures of my latest hot end with the PTFE tube moved up away from the heater. As the lowest part of the PTFE never geta above 70 - 80 degrees C, it is a sort of semi-all-metal hot end. You can also see on the pictures that cold air is directed as close as possible to the just printed area from a ring around the nozzle. Although it hasn't yet been proven, my theory is that the right cooling is "immediately after extrusion, and just enough - but no more"




* My Rostock printer is more "concours d' quite neat" - you can see it on: [www.youtube.com]
This also shows earlier directed cooling and an earlier hot end

Great-looking extruder obviously you've experimented with this what I do is I have a fish tank air pump pumps all the way through the filament tube exits inside atop the drive wheel and then active water cooling on the side mine is very heavy I use a Mig wire serrated drive wheel works extremely well was a little on a large diameter side so I have to use 100 to 1 planetary gearbox

leadinglight, amazing stuff! So what are you using for insulation around your heater block?

To correct my flawed heater block positioning, I added insulation under it to prevent it from radiating heat onto the still warm printed parts. This was causing them to sag and get toasty brown in some spots. I ended up using fibreglass cloth held in place by kapton tape(aka "concours de cobble"). Warmup time for the hot end has now been reduced substantially. No need for fancy ceramic insulation at this temp range. I suspect one current limition for small parts (in any plastic) on many printers is that some hot end designs radiate stray infrared down onto the extrudate.

Your idea of shielding and cooling with air flow right after extrusion is very close to optimal I suspect.

cnc, how did your extruder end up being heavy? Got photos?

Edited 1 time(s). Last edit at 07/14/2013 12:20AM by Yvan.

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Yvan

Singularity Machine

I used cuttlefish bone as it can take the temperature and is much better than plastic foams -which mostly are no good above about 100 degrees. In previous iterations I used a PEEK shelll.

On the Prusa, my X and Y carriages broke and/or didn't have good linear bearings -so I machined parts from aluminium, added fans extruders etc and had 1kg of heavy metal.Very accurate but very slow.

leadinglights Wrote:
-------------------------------------------------------
> I used cuttlefish bone as it can take the
> temperature and is much better than plastic foams
> -which mostly are no good above about 100
> degrees. In previous iterations I used a PEEK
> shelll.
>
> On the Prusa, my X and Y carriages broke and/or
> didn't have good linear bearings -so I machined
> parts from aluminium, added fans extruders etc
> and had 1kg of heavy metal.Very accurate but very
> slow. How slow are you talking about mechanically obviously has to be very strong but usually you can make something that takes the acceleration and deceleration

Cuttlebone is not something I would have thought of! An alternative I have been looking into is plaster of paris. Like cuttlebone it is also used for metal casting. What kind of experiance and tools to you have to be building slick machines like this?!?

1kg on 8mm rods would require rather slow speeds I suppose. I'm looking into 10 and 12mm rods for the next projects, if I start building my own designs or modifing established ones.

Right now I'm printing up the Eckertech extruder to go with their hot end, and I will install that on my Prusa i1. Trying to stick to basic configurations while I plan out machine #4. It might have several upgrades all in one.

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Yvan

Singularity Machine

I tried some experiments a while ago. Quoting from an earlier post:

Quote

I have just tried out cuttlefish bone for it's thermal properties and was mightily impressed: I set up a block of cuttlefish bone 25mm thick with a 25mm deep hole 12.5 mm from the bottom surface and a type K thermocouple in the hole. A similar block of expanded polystyrene was made. Both blocks were put on a heated bulld stage whcih was then brought up to 100 degrees over a period on 30 minutes. The temperature in the polystyrene rose by 50 degrees over this time, but only by 38 degrees in the cuttlefish bone.

It is however almost absurdly fragile - hence building a brass box around it.

Although I have a small CNC milling machine and a 10" lathe, most of my machines are built with hand tools - one of the advantages of having been around many years is that you learn how little is actually needed to build anything.

Mike

leadinglights Wrote:
-------------------------------------------------------

> Although I have a small CNC milling machine and a
> 10" lathe, most of my machines are built with hand
> tools - one of the advantages of having been
> around many years is that you learn how little is
> actually needed to build anything.
>
> Mike

Yes I know what you mean. I also find that it is extremely easy to overspend on any project. Cost/design/tools are all related, but finding the balance is not obvious.

So far the machine that is shaping up in my mind would have two half inch MDF triangular panels to replace the six threaded rods used on the two side of most reprap designs. Some of the M8 threaded rods might get replaced by 1/2 inch threaded rods which I have available. I may slip some of them into steel pipe to put them in tension.

If the 12 x 12 inch heated bed works out, I would also step up to 12mm or 1/2 drill rod and matching linear bearings.

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Yvan

Singularity Machine