Improve the resistance or appearance of 3D printed parts by post processing?

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Improve the resistance or appearance of 3D printed parts by post processing?




by Christophe » 26/10/20, 14:44

Tutorial: how to strengthen the resistance or improve the surface of 3D printed parts with a post treatment?

I have been printing 3D parts for some time in molten wire and SLA / LCD photosensitive resin. This subject only concerns molten wire parts, (still the most widespread technology) ... although some techniques can certainly be applied to resin parts ... to see!

My pieces must be functional, that is to say not only to be beautiful in appearance but above all functional with resistance to mechanical resistance over time.

The majority of 3D prints by makers (users of 3D printers) concern knickknacks and for them, only the surface aspect and the finish.

The subject of 3D prints is therefore not often mentioned by the maker community (as long as the arm of his GI Joe or Sankogu stands alone and is beautiful, the maker is happy ... : Mrgreen: )

So I looked for some surface treatment avenues to post surface treatment of 3D printed parts in order to improve their resistance and / or appearance.

Indeed, the weak point of 3D printed parts is their anisotropy and a lack of mechanical cohesion: even if the part seems "perfectly well printed" to you, it will still present a HIGH risk of layer detachment in the direction in which it was printed.

Some have shown that the direction of printing (= the positioning of the part during printing) has a huge influence on the mechanical resistance of the part and thata 3D printed part did not have at all the mechanical properties of a plastic part injected or machined in the equivalent mass ... (but we suspected it ...):





Listing (dynamic) of the post processing techniques of the printed parts that I could find (for the moment) and that I will try to experiment for some

1. Treatment with fiberglass or carbon and epoxy or polyester resin

The solution certainly the heaviest but probably the most effective: we use the 3D part as a permanent "mold" by applying one or more layers of glass or carbon fibers

Disadvantages:
- it's heavy work,
- need to master the technique,
- incompatible or hardly compatible with small parts or parts with too small details or too complex a shape (the main purpose of 3D printing is to print "complexity")

2. Re-melt the plastic with acetone

Passing one or more layers of acetone on the ABS parts or soaking them will reshape the surface of the part and ensure better cohesion. It's quite easy, cheap and efficient.

Disadvantages:
- can only be used with ABS (and derivatives)
- removes any details from the room
- requires mastering the technique (quenching time / number of layers VS details to keep / thickness of the part)

3. The "ABS soup" or polystyrene: homemade resin

Close to technique 2 but which can be used on all plastic parts (a priori), it consists in melting ABS in acetone to obtain a resin applicable to any surface. Fairly easy to implement.

Some on this forum do the same thing with polystyrene it seems to me but I no longer remember the solvent?

Disadvantages:
- less homogeneous solution 2
- need ABS
- requires experience to know the number of layers
- almost free

I prepared a small pot yesterday (with a 3mm ABS coil from 2014 ...) that melted well overnight I added a few strands (at random) this morning.

soup_abs_2.jpg


Soup_abs_1.jpg
Soupe_abs_1.jpg (346.94 KiB) Viewed 7894 times



I will test the application on a carbon PLA part

4. "Conventional" two-component resin treatment

Between 1 and 3 with a resin (epoxy or polyester or other if you have any suggestions?) Which is not loaded with fiber or plastic.

Disadvantages:
- more expensive than 3
- resistance?
- held over time?
- must be applied in a short time (open time of the two-component resin)

5. Treatment with 405 nm photosensitive resin

Apply one (or more) layer (s) of resin dedicated to resin 3D printers and put the part in the sun. Very easy to set up. I will test.

Disadvantages:
- quite expensive (photosensitive resin is at best 35 € per kg)
- homogeneity with the unknown parts
- little known mechanical properties (we do not yet know what resins for the general public are)
- resin is brittle especially if overexposed to UV (use of the room outdoors)

6. Treatment with "glue"

Suggested by some internet users ... I don't really believe it but it's a solution. Use glue, neoprene, cyano ... to strengthen the surface ...

Disadvantages:
- probably quickly overpriced
- homogeneity?
- held over time?

7. Redesign of the part in the oven with an inert material

The technique consists of passing a part in the oven for a certain period of time in order to recast it. All in an inert powdery material. The idea seems good but my first experience was not that great in terms of results: 3d-printers / marvelous-technological-advancement-but-t16549-30.html # p412108

The technique is obviously limited to the parts entering your furnace ... and to massive parts ... (100% inflill filling ... which was not the case with my parts ... but the surface aspect was not improved anyway).

To be continued...
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Re: Improve the strength or appearance of 3D printed parts by post processing?




by Christophe » 26/10/20, 14:53

Christophe wrote:7. Redesign of the part in the oven with an inert material

The technique consists of passing a part in the oven for a certain period of time in order to recast it. All in an inert powdery material. The idea seems good but my first experience was not that great in terms of results: 3d-printers / marvelous-technological-advancement-but-t16549-30.html # p412108

The technique is obviously limited to the parts entering your furnace ... and to massive parts ... (100% inflill filling ... which was not the case with my parts ... but the surface aspect was not improved anyway).


Here is a video which details the technique (recent, it is 1 month old):



Apparently he shows that you can triple the resistance with this technique.
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Re: Improve the strength or appearance of 3D printed parts by post processing?




by Petrus » 27/10/20, 19:52

During my experiments, I had good results regarding the appearance of ABS parts using acetone steam treatment.
The piece is placed on a plinth in a glass container in which I put a few ml of acetone and that I heat on a hot plate, the level of smoothing is adjusted by varying the amount of acetone:
acetone_test.jpg
acetone_test.jpg (71.97 KiB) Viewed 7820 times

Parts are printed in 0,1mm layers except the last one printed in 0,2mm
The first part is not treated, the others are from memory treated with 2, 4 and 6ml of acetone
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Re: Improve the strength or appearance of 3D printed parts by post processing?




by Christophe » 27/10/20, 20:16

Nice steam technique and not stupid, it solves the concerns of equalizing layers and the complexity of some parts!

So, you put them in a big closed jar, right? And for what duration / temperature of heating and treatment?

In fact if I follow you you need a very small amount of acetone! Is it mls or cls?

Too bad I don't print with ABS there! : Cheesy:

Otherwise I did my first test of "ABS soup" on PLA .. it seems to work but I made my soup at random, it is way too thick and I have lots of "lumps" ... I can't show you that!

On the other hand; I applied to a completely intentionally broken part (layers peeled off) and it seems to hold up well! So it's ugly for the moment but it repairs well! : Cheesy:
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Re: Improve the strength or appearance of 3D printed parts by post processing?




by Petrus » 27/10/20, 20:27

Yes, it is fine ml, the part is small so that is enough. I used a coffee maker carafe closed with a latex glove for sealing, the plate was heated to 90 ° C for 15min.
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Re: Improve the strength or appearance of 3D printed parts by post processing?




by Christophe » 27/10/20, 20:30

Ok thank you and you were leaving the room right after the 15 minutes then?
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Re: Improve the strength or appearance of 3D printed parts by post processing?




by perplex » 28/10/20, 08:33

I haven't tried it yet, but it seems effective. The technique of fine salt in the oven ...


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Re: Improve the strength or appearance of 3D printed parts by post processing?




by Christophe » 28/10/20, 09:24

Uh I tried talking about it above (must read lol ... : Shock: )

It works with baking soda, finer naturally, no need to grind the salt ...

I tried with an unfilled room, poor results (maybe my oven does not heat up enough? Next test I will put it "all the way" ...)

Christophe wrote:7. Redesign of the part in the oven with an inert material

The technique consists of passing a part in the oven for a certain period of time in order to recast it. All in an inert powdery material. The idea seems good but my first experience was not that great in terms of results: 3d-printers / marvelous-technological-advancement-but-t16549-30.html # p412108

The technique is obviously limited to the parts entering your furnace ... and to massive parts ... (100% inflill filling ... which was not the case with my parts ... but the surface aspect was not improved anyway).
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Re: Improve the strength or appearance of 3D printed parts by post processing?




by Christophe » 28/10/20, 12:52

Good news: ABS soup works SUPER well on a PLA printed part!

Despite a soup full of lumps, once very dry, it is impossible to peel off the layers by hand from the PLA test piece (from which I had voluntarily peeled off the layers)! It's even more resistant than I thought! It is an inexpensive "super glue resin" in fact, usable for a lot of repairs in fact!

Without treatment peeling off layers of this untreated "soup" piece was pretty easy! : Cry:

I'll post pictures when I have a new, better-prepared soup : Cheesy:
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Re: Improve the strength or appearance of 3D printed parts by post processing?




by Petrus » 28/10/20, 21:27

The method of cooking in salt, in detail with measurements by CNC Kitchen:
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