Making Gaps in Filament for Epoxy

[ShuttleSpace 0]

I did a thin walled print with .32 layer height for speed, the part was very weak, it was almost like a woven basket, but I thought I would like to try a print with similar looseness in a print for primer or epoxy to penetrate into.

Is there a way to do this that would hold together better? Thanks from the newb.

[gr5 2,173]

It sounds like you are trying to print faster and don't care about beautiful walls then you probably want to use a larger nozzle.  A 2mm can make much thicker layers (and stronger) than a 0.4mm nozzle.  Even just a 0.8mm nozzle prints 4X faster (in volume) than a 0.4 (twice as thick and twice as wide of a bead). (disclaimer - I sell nozzles).

 

It would really help if you showed some photos of the part either completely printed or the cad view.  Or both.  There are other tricks to save printing time.

 

Also, what kind of printer is this?  It doesn't have to be an Ultimaker to get answers here.

[gr5 2,173]

Oh - and I'm guessing you had gaps because of something we call "underextrusion".  It's not great to rely on that as lots of things can go wrong when you have it this severe - like grinding the filament enough such that the print fails because it can't extrude anymore.  One solution is to raise the temperature.  I've done many prints at 240C which works okay for PLA (quality goes down but it works).  The higher temperature means lower viscosity so it flows more like water than honey.

[ShuttleSpace 0]

On 11/26/2018 at 9:00 AM, gr5 said:

It sounds like you are trying to print faster and don't care about beautiful walls then you probably want to use a larger nozzle.  A 2mm can make much thicker layers (and stronger) than a 0.4mm nozzle.  Even just a 0.8mm nozzle prints 4X faster (in volume) than a 0.4 (twice as thick and twice as wide of a bead). (disclaimer - I sell nozzles).

 

It would really help if you showed some photos of the part either completely printed or the cad view.  Or both.  There are other tricks to save printing time.

 

Also, what kind of printer is this?  It doesn't have to be an Ultimaker to get answers here.

I usually print at our libraries and there is a 2 hr limitation, they have Ultimakers..  I was hoping for a fast print setting because I'm mostly making my own prototypes for test fitting and improving,  also the epoxy impregnated prints could be viable for the marine products I'm doing. PLA alone won't do. Some kind of 'basketweave' pattern for the prints would be ideal. The 'pockets' will hold the epoxy, resin, etc. so there is no concern of it detaching when sanding, coating, etc.

I tossed the failed print, but it was basically a 1.2mm thick wall of a 10mm cylinder, .4 nozzel https://3dorchard.com/app/single/5865c94e5fa09b0c8fd1f18a/5bf714d28d30b10c992d7687

Thanks, Rob

[ShuttleSpace 0]

On 11/26/2018 at 9:01 AM, gr5 said:

Oh - and I'm guessing you had gaps because of something we call "underextrusion".  It's not great to rely on that as lots of things can go wrong when you have it this severe - like grinding the filament enough such that the print fails because it can't extrude anymore.  One solution is to raise the temperature.  I've done many prints at 240C which works okay for PLA (quality goes down but it works).  The higher temperature means lower viscosity so it flows more like water than honey.

 

[ShuttleSpace 0]

There just wasnt enough material to hold together. I replied to the other comment, pplease look there, thanks

[P3D 46]

Holes in walls are usually what one tries to avoid at all costs in 3D printing, so I'm afraid there hasn't been much work in the opposite direction.

 

To achieve holes in the walls, you can try to lower the material flow, so you get underextrusion - just don't expect the model to hold together very well.

 

One thought, though: Wouldn't it make more sense to 3D-print molds for your marine parts? You could pour the epoxy into the molds (you'd most probably have to use a release agent), wait till it is cured, and then either "sacrifice" the mold for more complex parts, or try to extract the part without damaging the mold and re-using it. Still another option would be to print a positive of the part, make a silicone mold around it, extract the printed positive and then pour the epoxy into the silicone mold.

Edited November 27, 2018 by P3D

[ShuttleSpace 0]

I just want to see if this is possible after seeing the new 'woven' fill option in Cura, and I want to make my prototypes fast so this is possibly something that could be useful, and again, the library's 2 hour limitation is an obstacle for the parts I am doing.

The part would be reasonably strong if the bonds where there is contact were good. Thanks

[P3D 46]

13 hours ago, ShuttleSpace said:

I just want to see if this is possible after seeing the new 'woven' fill option in Cura, and I want to make my prototypes fast so this is possibly something that could be useful, and again, the library's 2 hour limitation is an obstacle for the parts I am doing.

The part would be reasonably strong if the bonds where there is contact were good. Thanks

 

Where do you see a "woven" infill option? I don't, on Cura 3.6.0. Do you mean the "gyroid" infill? You could try printing your parts without walls or top/bottom layers ("infill only"), but I don't know if that will get you the results you expect. You could also try to model your part the way you want it in your modeling application... but once again, if your goal is epoxy parts, you could print molds for them, and as you can print these with just a few walls, they should print quite fast.

[geert_2 557]

If you want a sort of sponge look, then after the print starts, manually reduce material flow to 30, 40 or 50%. Try this on a small test cube first.

 

Of course, this "sponge" won't be very strong, but it will have the general shape of the model, except for fine details like text which are totally lost of course.

 

But I don't think it will get very strong after impregnating with epoxy. The bonding between the epoxy and the PLA (or whatever else filament you use) will be critical. Normally in particle-filled epoxies, the particles need to be specially treated to make the epoxy bond well to them. So you would first need to treat and chemically activate the PLA-surface. It might work with a special "plastic activator" spray? But then the procedure would become complex: print, post process, activate, let dry, impregnate a little bit with epoxy (not too much, otherwise it leaks away), apply next epoxy layer, post process,...

 

Then I think printing a mould and fill that with epoxy might be better. Definitely use multiple layers of a good release spray or release liquid. But even then releasing might be a problem.

 

Or print a master model and make a silicone mould of it, and fill that mould with epoxy. You could also print a "shell" around the silicone mould for more stability. If well designed, you can put the model into the shell, and then pour silicone into it. So the shell acts as a container for the silicone too. Let cure, open shell, cut silicone, remove master, and your mould is ready.

 

Use plenty of silicone oil as release spray to saturate the silicone, and prolong mould life. Such a mould can be re-used several times (depending on shape, up to 50x), which saves a lot of time in the end. It's messy, but if you use epoxy anyway...

 

Flexible silicone mould release much easier than hard plastic or plaster moulds. That is why I would go with a hard shell as container, but pour silicone into it for the actual mould.  The shell is only for stability, and for containing the silicone. Make sure you can easily open the shell.

 

Probably you are familiar with mould making. If not, search on Youtube for mould making and casting. There are lots of excellent tutorials, both with thin liquid silicone and thick silicone paste (brush-on types).

 

[geert_2 557]

Forgot to say: the original poster is obviously familiar with epoxies, but for other readers who are not: epoxy-curing is a very exothermic reaction: it generates a lot of heat. I have had epoxies going far above 100°C when curing, melting the plastic cups in which they were mixed, and once even melting a thin lead container. In extreme cases the part could cause fire or explode due to internal stresses (fortunately I haven't had that).

 

So, temp while curing is likely to go above the 50°C limit of PLA, and the mould may deform or even completely melt. This could also happen when impregnating larger volumes of the "sponge PLA" I mentioned above. Silicone usually is quite heat-resistant for a short while (~200°C or more), so that is less of a problem.

 

Use a slow-curing low-exothermic epoxy, or apply in very small quantities, in contact with PLA.

 

Also, slower curing versions tend to shrink less, which might also be an issue in some cases: shrinking could cause gaps in the material, or deformations, just like shrinking in injection moulding.

 

[ShuttleSpace 0]

On 11/28/2018 at 2:51 AM, P3D said:

 

Where do you see a "woven" infill option? I don't, on Cura 3.6.0. Do you mean the "gyroid" infill? You could try printing your parts without walls or top/bottom layers ("infill only"), but I don't know if that will get you the results you expect. You could also try to model your part the way you want it in your modeling application... but once again, if your goal is epoxy parts, you could print molds for them, and as you can print these with just a few walls, they should print quite fast.

I'd rather have a consistent finish so I can tune it for the epoxy to 'key' into the pockets generated. 

Making molds for test fitting would take too much time, I have a bit of an time and attention limit for non paying things. Yes, gyroid was the setting,couldnt see it in time.

thanks

Edited November 29, 2018 by ShuttleSpace

[ShuttleSpace 0]

On 11/28/2018 at 8:45 AM, geert_2 said:

Forgot to say: the original poster is obviously familiar with epoxies, but for other readers who are not: epoxy-curing is a very exothermic reaction: it generates a lot of heat. I have had epoxies going far above 100°C when curing, melting the plastic cups in which they were mixed, and once even melting a thin lead container. In extreme cases the part could cause fire or explode due to internal stresses (fortunately I haven't had that).

 

So, temp while curing is likely to go above the 50°C limit of PLA, and the mould may deform or even completely melt. This could also happen when impregnating larger volumes of the "sponge PLA" I mentioned above. Silicone usually is quite heat-resistant for a short while (~200°C or more), so that is less of a problem.

 

Use a slow-curing low-exothermic epoxy, or apply in very small quantities, in contact with PLA.

 

Also, slower curing versions tend to shrink less, which might also be an issue in some cases: shrinking could cause gaps in the material, or deformations, just like shrinking in injection moulding.

 

Those are good suggestions but I just want fast. I have a lot of limitations atm. 

I don't see any reason there cant be a pocketed/keyed shell option on a print - for bonding any type of coating.

I cant see the epoxy doing too much distorting of the print if there some fill, it only cooks like that when it doesn't get used in time. Thanks 

[gr5 2,173]

I'd have to know more about your part.  I followed your link but I just don't quite get why it needs holes to do the epoxy coating.  Why not just coat it even if it doesn't have holes?  The strength of the part is mostly in the outer shell anyway.  Anyway here are some ideas:

 

Disable the wall completely (set wall thickness to 0 and probably top and bottom to 0).  This way you only see the infill.  You can do gyroad or a 3d pattern like cubes.

 

To save time I usually tell people the opposite.  Don't print any infill.  It usually doesn't add much strength to the material - especially for these cylinders you showed.

 

To save time I also strongly recommend a bigger nozzle.  The 0.8mm nozzle prints 4X faster than the 0.4mm nozzle.  I know this is a public printer but it only takes seconds to change nozzles.  But to achieve these speeds you print twice as wide (0.8mm lines instead of 0.4) and twice as thick (around .0.3 to 0.5 thick layers instead of 0.1 to 0.2).  DON'T try to get faster speeds by setting the "print speed" faster.

 

Like someone else said you can set the infill to 50% in the TUNE menu while it's printing live.  And you can play with that to get the effect you want (strength and holes).

 

2 hours is not a reasonable time limit by the way.

[P3D 46]

10 hours ago, ShuttleSpace said:

I don't see any reason there cant be a pocketed/keyed shell option on a print - for bonding any type of coating.

 

Well, the reason is that there aren't too many people who are keen on holes in their prints 😉 (and also that usually the as-printed or a slightly sanded surface works well for most coatings, provided the material is compatible with the coating in the first place).

[geert_2 557]

16 hours ago, ShuttleSpace said:

I don't see any reason there cant be a pocketed/keyed shell option on a print - for bonding any type of coating.

Technically, it is not easy to print little holes. When layed down, the molten sausages need something to grip too, otherwise they sag and go all places, out of control. Retracting and extruding again every 0.5mm also isn't going to work. Zigzagging the surface also doesn't work well, since corners are way too rounded.

 

Apart from post processing like sanding or sandblasting, or so, the only method I know is setting the material flow to 30...70%, which will give a sponge look. But you have no control over the pattern: it will differ very much from material to material. See my flow tests on PLA here, which show the patterns (I made photos this week):

https://community.ultimaker.com/topic/25522-photos-of-under-and-overextrusion-patterns/

 

Or see these photos, where another user has undesired underextrusion (probably ca. 40% flowrate), but his photos excellently demonstrate the sponge-effect:

https://community.ultimaker.com/topic/25460-help-needed-on-layers-printed-with-random-patterns/

 

 

I don't know if it is possible to set only the flow rate of the outer surface layers to a lower value, but keep 100% for the inner surface layers and infill, for strength? (I don't have the latest versions of Cura yet.)

 

[ShuttleSpace 0]

Some idears are flowing now that I know the right word.

 

[ShuttleSpace 0]

Possibly even something like the https://www.voronator.com/ if it were tunable. 

[gr5 2,173]

Well this puts gyroid on the outside.  Or you could remove the walls altogether:

 

[ShuttleSpace 0]

https://www.thingiverse.com/thing:3396739

A good recent discovery here