Posts Tagged ‘Smooth-On

A Problem with a 3D Model Can Cause a Failed Print
Two of the most common issues with 3D models that are giving you problems to print, no matter if you designed them or somebody else did, are the presence of Non-Manifold Edges and Flipped Triangles. There are of course some more issues that may be present as well, but I’ll be talking about these two as they are the most common cause that may result in you 3D print looking not as it was supposed to be.

Non-Manifold Edges are parts of the model that have holes in them or unwanted faces, often this is referred to as the 3D model not being water tight as if you pour water in something with holes it will just get out.

Flipped Triangles are parts of the object geometry that is facing the wrong way, it is normal for connected triangles to be facing the same direction, however often when you design a 3D object you may end up with triangles that are facing different directions.

As a means of demonstration I’ll be using two cubes drawn with SketchUp (go back to Part 4 of the series to learn more about that software) and in these two I have intentionally created issues, so that you can easily see the problem and how it may affect your 3D print. The cube on the left is with a flipped triangle on the side and a surface on the top and the cube on the right is not watertight (has some holes on one of the sides). Notice how SketchUp uses different colors for the two triangles on the side, this is a hint for the user that there might be something wrong as they seem to be pointing at different directions. The large holes, intentionally left big, are clearly visible as well, though imagine if you have many of these and they are very small or the flipped triangles are small and you need to zoom in a lot to notice the color difference.

Depending on the 3D printing software you use the standard 3D model preview might or might not show any problems, often flipped triangles are not being shown in the default preview and as I said holes in the models might be too small to notice. When you generate the Print Preview however and the software actually slices the 3D model to a layer by layer structure you can see weird things happening to your models such as strange deformations or missing parts. This happens as while the slicer is working the problematic geometry actually confuses the software and it just gives weird results. Of course depending on the object and the issue sometimes even with a non-water tight model you can still get a good print without problems.

When you see that something is wrong the best thing to do is go back to the 3D modeling software and try to find the problem in your 3D model, then fix it and open it again in the 3D printer software. In case you noticed a flipped triangle somewhere it is very easy to fix it in SketchUp for example, just select the problematic face, right click with the mouse and choose Reverse Faces. If you found a hole somewhere you can just add some extra geometry to fill it in and make the 3D model solid again. Of course at times finding these issues can be a problem, especially if you have problems that are not easily visible from the outside of the 3D model.

Some 3D printer software like the Simplify3D slicer I talked about in the previous part of the series has additional tools for detecting problematic geometry in the 3D model that may be helpful in figuring out what is wrong. It even has some automated tools to help you try and fix the problem without having to edit the actual 3D model, though these may not work very well or as intended some of the time. There are also alternatives available for different software and even online services that offer to fix common issues in 3D models without you having to actually edit the 3D model.

Automatic Repair of Problematic 3D Models
Since there are quite a few options for automatic fixing of problems with 3D models that need to be repaired in order to be 3D printable I will not be covering them all. However I want to point your attention to a free online service for 3D model repair that in my experience has been giving some of the best results in successful repair of various issues after quite a lot of testing of different tools and methods. The service is being ran by a company called Trinckle that apart from offering to freely repair your models also provides 3D printing services, though you can just download the fixed model and print it yourself. So you might want to give it a try before going into manual fixing mode trying to figure out where the problems in the 3D model might be and how to fix them yourself, especially if you are new to the whole 3D printing and 3D modeling thing.

Sanding and Painting 3D Printed Models
One of the “problems” of the consumer 3D printers is the fact that when you get a 3D print ready you can usually see the lines that build up the object (these are the printing layers), though that is not actually a problem, but just the way these devices work. The higher the resolution you print with, the thinner the layers are and the visual quality is better, but that is achieved with more time needed for the printing. There are ways however that you can improve further the final quality of a 3D print with some additional post-processing work after it is made by the 3D printer. This is achieved by using sanding paper to take away some of the outer surface of the model and/or by using paint to fill in some of the gaps between the layers and make them less distinguishable.

The sanding process does require some effort and time and is not always applicable as some objects have way to complex form and many small details, making it very hard to sand by hand (a rotary tool with a fine tip could also be used at low RPM). Furthermore the sanding process requires you to use sandpaper with different grit size, starting from a rougher lower number and going in a few steps to a much finer higher number. This way you essentially start by taking more material from the object smoothing the differences between layers and then moving to a finer grit to actually smooth out and polish the surface. You may need a little practice for this to get the hang of things, but the final results could be well worth it.

The alternative option is to use paint to cover a sanded on non-sanded 3D printed object, it is a good idea to use paint that can provide thicker layers such as spray cans of paint for objects that are not going to be sanded as it covers better and gives better results. If you have sanded the object you may as well go with a thinner paint cover such as the one achieved with an airbrush for example as you already have a pretty smooth surface. Furthermore, depending on the paint used you can get either a matte or glossy look, this can be further strengthened if you decide to apply some clear coating on top of the paint. You can get creative here and the results can be quite nice with some paint. Using paint also gives you the option to overcome some of the limitations in terms of colors that the filament you use has. You can of course use some acrylic paint to hand paint a figure that you have 3 printed for example, that way you will get a better looking “full color”-like print from a 3D printer that can work with single color filaments only.

Other Ways to Improve Visual Quality
The commonly used 3D printer filaments such as ABS and PLA have a hidden weakness, they can very easily be dissolved by some strong chemicals, but you can use that fact to your advantage. Some people are using the vapors of strong chemicals such as Acetone and THF to actually smooth the outer surface of 3D prints as these are essentially melting the outer perimeter of the layers and are giving them nicer and smoother look and feel. A word of serious warning here, these chemicals can be dangerous to your health and should you decide to use them you should be very careful not to get them on a bare part of your body or to inhale any of the fumes from them. Because of the possible danger to your health these methods are not that popular as for example using sandpaper or painting your 3D printed object.

Anyway, if you want to try, then you should go for Acetone for ABS plastic as it melts it and creates a smoother and glossy looking surface. As alternative to Acetone you might try smoothing ABS 3D printed objects with the use of Methyl ethyl ketone (MEK) with good results. Have in mind that Acetone and MEK are not suitable for PLA 3D prints like with ABS ones, so do not try them for smoothing PLA 3D prints. For PLA plastic smoothing you need to go for Tetrahydrofuran (THF) instead. Another dangerous solvent that needs to be extra carefully handled and also very flammable like the other two chemicals also mentioned already!

Another, much more safer alternative that could be used for smoothing of all kinds of 3D printed objects is the Smooth-On XTC-3D coating.

Protective coating for smoothing and finishing 3D printed parts that does not melt plastic. XTC 3D fills in 3D print striations and creates a smooth, high gloss finish. The need to post finish is almost eliminated. XTC 3D can be applied to both SLA and SLS prints. It works with PLA, ABS, Laywoo, Powder Printed Parts and other rigid media such as EPS, EPDM and urethane foam as well as wood, plaster, fabric, cardboard and paper.

I have tried this solution where you mix two components and then apply a thin coat of the material over the 3D printed object, then wait for it to cure and you get pretty good results. So it works pretty good, though you may need some getting used to working with the coating in order to be able to achieve consistently satisfying smoothing of different objects.

In the end you have multiple different variants for additionally improving the look and feel of your 3D printed parts, it is up to you to choose what works for you should you even need to do this extra work at all.

smooth-on-xtc-3d-package-contents

We continue experimenting with the use of the Smooth-On XTC-3D after we recently shared our first experience using it. This time we used Natural PLA filament for our tests as we wanted to see will the use of the XTC-3D help in improving the transparency of the printed parts. Last month there was an interesting article about using the XTC-3D for improving the clarity of the Taulman T-glase, so we wanted to see if there will be a similar effect on parts using the semi-transparent Natural PLA filament. The initial results that we’ve had with parts that we have already printed and decided to use for tests were not very good as apparently the 3D printed part with that you want to be more transparent will need to be specifically printed with thin walls. So we gave up on experimenting with improving the transparency on already 3D printed parts with Natural PLA, and while we also wanted to try out the Taulman’s tutorial for T-glase filament we had trouble with the filament sticking properly to our build plate covered with standard 3M ScotchBlue tape on the MakerBot Replicator 2 3D printer that we are using, so we have postponed testing with that material and XTC-3D for a later time as well.

batman-sign-natural-pla-xtc-3d-painted

What we have decided to do instead was to coat the 3D printed parts with XTC-3D, then sand them and paint them with a standard spray paint used for coloring plastic materials. We have started with a Batman logo that we have printed with Natural PLA filament, left to right on the photo: the 3D printed logo, the logo sanded with fine sanding paper getting a more matte look and then painted with black metallic spray paint. The end result is really nice and smooth surface after the sanding and painting, though we did not do great with the painting part, but we did it in a bit of a hurry. As we have mentioned the 3D printed parts that we have used here for testing are not good for testing to improve the transparency of Natural PLA filament as they are tick objects with infill like is the case of the Batman logo, but even with multiple shells and without infill it is hard to improve transparency. You would probably need to use less shells with no infill and maybe larger layer height to get better results with improved transparency on Natural PLA as the recommended setting for T-glase suggest.

trophy-cup-natural-pla-xtc-3d-painted

The Batman logo is easier to coat with XTC-3D and sand and paint, so we decided to also try a bit more complex 3D print – a small trophy cup. We have already had a few of these printed, so it was easy to compare before and after. On the photo above you can see the 3D printed cup on the left and the same cup coated with XTC-3D and sanded on the black background. You may notice that the coated and sanded cup still does show some noticeable lines for the layers, even though the surface is actually smooth – this is a result f the transparency of the material. On the right part of the image above you can see the already painted cups, the one that is coated with XTC-3D and sanded (inside and outside) on the left part and the one that is directly painted after being printed. Again not perfect painting on our side with some dust particles getting caught by the paint, but you can clearly the very smooth surface of the coated and sanded part. Even without sanding the 3D printed parts that are coated with XTC-3D that are painted after that may look great, but sanding may help in getting the paint to stick better and be more durable on the long run. We are going to continue experimenting with the Smooth-On XTC-3D coating as we like the results so far, though it does need to getting used to and trying out different with settings for the 3D printed parts depending on what are the final results that you want to achieve.

smooth-on-xtc-3d-package-contents

We finally got our hands on a XTC-3D 3D print coating from Smooth-On, though it was not very easy to find it as most companies selling 3D printers and accessories for them still do not offer that product – we had to find Smooth-On partner in Europe and order it from them. We got the larger 24 oz (644 grams) package as the smaller one turned out to be cheaper than what we’ve had to pay for the shipment costs, and anyway if we liked the result after testing the coating we would want to have some more to play with. Once you get the package it is very wise to read the manual very carefully and do try the use the XTC-3D coating a few times on test prints, before actually trying to apply it to 3D printed parts that are more important. Also you would probably want to get some small size paint brushes for applying the coating to smaller 3D printed objects with more details, as using a large size brush on small 3D models is not a wise idea if you want to get good quality. Interestingly enough the XTC-3D 3D print coating can be used in multiple ways – to coat models providing a glossy and smooth surface effect, to coat them, then sand them and paint, or to apply color to the coating and coat the model with color. It all depends on what is the end result that you want to achieve in the end, what you need to be well aware of however is that properly using the XTC-3D coating does take some getting used to in order to achieve best results and it also takes some time for the coating to cure and additional time if you want to further process the 3D printed part.

yoda-pla-3d-print-xtc-3d

We have started our testing with a 3D printed Yoda bust using PLA filament with a 0.3mm layer resolution, so the resulting print was with very easily distinguishable layers and not very smooth. The initial coating of the 3Dpritned part with the XTC-3D did make the layers of the print less apparent and the Yoda bust having a more glossy finish than what the original print had. We needed a second layer of coating with XTC-3D however in order to make the surface of the Yoda bust seem really smooth to the touch, although if looking up close you could still distinguish the texture of the different layers. The reason that you might still get to see very faint lines from the different players with a lower printing quality is that the XTC-3D coating is transparent, so even if ti makes the surface really smooth and glossy you may still need to apply some paint for 3D printed parts that use lower quality for the printing. The end results with 2 layers of XTC-3D coating to our roughly printed Yoda bust was really nice, smooth and glossy surface, though a bit of sanding on the ears and applying green paint could produce even better results after that.

exotic-materials-xtc-3d-coating

Next up was trying out the Smooth-On XTC-3D coating on a few more exotic filament types – Carbon PLA from Proto-pasta, Laywoo-D3 and LayBrick from Orbi-Tech. using a 0.2mm resolution for the test prints we have applied 1 layer of XTC-3D coating to each of the objects – on the left is the normal print and on the right you can see the same 3D model with 1 layer of coating applied. The result with just a single layer was not that good, the coated 3D models got slightly more smoother, but with the layers still easily distinguishable and more noticeable was the fact that they became glossies as the normal results when printing with the filaments produce more matte look. Adding a second layer may improve things, but the highly glossy end result might not be to your liking that much and sanding and painting on top of 3D printed parts when using materials that produce carbon, wood or stone look is not the best idea as it will ruing the realistic look that they do provide.

ninjaflex-xtc-3d-coating

We have also tried applying XTC-3D coating on NinjaFlex 3D printed keychain with the Nvidia logo, even though that might not be a very wise idea as this is a flexible filament. When you apply XTC-3D coating it hardens a bit the 3D printed part and make it less flexible, so this makes it unsuitable for flexible filaments as it will reduce their flexibility. After applying a single layer of coating to the 3D printed part with NinjaFlex filament we have observed the expected slight improvement in the surface feel – smoother as well as the keychain becoming glossier. Although the surface felt smooth, the topmost layer having a large surface area did not not look much more smoother tan before coating it, so XTC-3D might not work that well on flexible filaments such as NinjaFlex. The more interesting thing that we have observed is that after applying the XTC-3D on the NinjaFlex 3D printed keychain it has remained quite flexible, but stiffer than it was before the coating. You should however avoid flexing too much NinjaFlex printed parts if you have coated them with XTC-3D and also that if you apply multiple layers of coating their flexibility will most likely be reduced significantly.

So what ware our first impressions from using the Smooth-On XTC-3D coating? We are pretty satisfied with the results we got, although our first tries were not perfect we quickly got the hand of using the coating and the results started improving. When you get used to take advantages that the XTC-3D coating provides and you properly use it on 3D printed parts you can achieve really nice results in terms of final quality of the things you 3D print. The coating however is not perfect and suitable in all cases and for all kinds of materials, so you should be careful how and when you use it. You should also be prepared to spend some time for the extra finishing if coating 3D prints with XTC-3D as it does take some time to do it and then a few hours for the coating to fully cure. If you then plan on sanding and painting the coated part it could easily take a whole day, but if properly done the end result might be something that you can hardly believe was something that was 3D printed. We are going to keep experimenting with the XTC-3D coating, so expect more of our feedback pretty soon – next up is to get more experience with sanding and painting some 3D prints after getting them coated with XTC 3D.


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