Getting started with 3D printing

[Raminator]

I've come to accept my limitations with regards to scratchbuilding; I have previously overestimated my resourcefulness, dexterity and (most critically) patience. Since I've done some 3D modelling while modding video games before, I thought I'd give 3D printing a go. I've spent the last two days playing around with DesignSpark and feel like I'm getting the hang of it, so now I'm wondering about the workflow for the whole process.

As far as I understand it, once I've made a model and exported an .stl it gets sent through slicing software and then printed. Since I don't have access to a printer (yet), would I be best off trying some of my designs through Shapeways to see how they translate from computer to real life? If I'm mostly interested in printing small, functional components and details (rather than large assemblies), what would be a good way to test the waters? I'm more than happy to muck around with the technical aspects of a printer, but I'd want something I can get reasonably high-fidelity prints with.

[Raminator]

Here's what I've come up with over the last two days.

Some of the large hinges for the SU-152; one each on the gunner's and commander's hatches, and two each for the two halves of the loader's hatch:

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The little indents would be drilled out to accommodate a steel torsion bar.

Half-spider roadwheels for the T-34 (the full-spider wheels were introduced in 1944, so my T-34/76 should have these as it's a 1943 production):

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All-steel roadwheels for the T-34:

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Something about DesignSpark's workflow really clicks with me, I could not get OpenSCAD to do what I wanted for love or money.

[Estnische]

Looks good. If you can print those, you will have a whole raft of bits you could tackle.

What video games did you mod?bive always admired the work modders did with rfactor.

[RobW]

Nice work. I'm just learning the sketch tools for the full version of DesignSpark (having been avoiding it for a few years - it's based on SpaceClaim). Hopefully the sketcher will see some significant upgrades in the new year.

Do you have the faceting toolkit on that version? This means you can improve the resolution where you need it.

[Woz]

Due to the limitations of printing you don't want to get too bogged down with the detail.

Here's a guide to SW's Frosted Detail plastic https://www.shapeways.com/materials/fro ... il-plastic

You can find yourself designing detail that won't print or would be too fragile to be practical.

My newest printer can print detail down to about 0.02mm thickness but it breaks as soon as you try and wash it.

[Raminator]

Thanks for the kind words, guys. I've quite enjoyed playing around with DesignSpark and getting a feel for the different tools they let you play with.

Do you have the faceting toolkit on that version? This means you can improve the resolution where you need it.

Yes, you can set the faceting in the version I'm using Rob. I've set the values to half of what they use in the "fine" preset, and the .STLs look nice and smooth in Cura.

Due to the limitations of printing you don't want to get too bogged down with the detail.

Cheers for the tips Woz, much appreciated. For reference, the ribs on the hinges are 1 mm thick, the spokes on the steel wheels are 0.8 mm thick, and the spokes on the half-spider wheels are 1.5 mm wide at the base. Would the frosted detail plastic be strong enough for functional hinges, do you think? The curved part is 3.5 mm in diameter, and should take a 2 mm axle through the centre.

[Woz]

Cheers for the tips Woz, much appreciated. For reference, the ribs on the hinges are 1 mm thick, the spokes on the steel wheels are 0.8 mm thick, and the spokes on the half-spider wheels are 1.5 mm wide at the base. Would the frosted detail plastic be strong enough for functional hinges, do you think? The curved part is 3.5 mm in diameter, and should take a 2 mm axle through the centre.

A 2mm hole through a 3.5mm part means it's only going to be 0.75mm thick which'll be very weak. I use paperclips which are 0.8mm in diameter. The plus side of using paperclips is that the ends of the clips are smooth which goes into the hole easier and the end you cut usually gets flattened by the cutters and when pushed into the hinge helps keep it in place.

If you upload to SW's it has an auto checker that'll tell you if it's prinable.

[wibblywobbly]

I can support everything that Woz has said. One thing to remember with domestic printers is that they are putting down layers, so the item has a grain much like wood. If you try and break it one way it is easier than breaking it the other.

Imagine an upright cylinder, with the layers going from top to bottom, it would be easy to snap it.
Imagine a horizontal cylinder, with the layers going from top to bottom, it would be more difficult to snap it.

The smaller the part, and the thinner the wall, the weaker the part becomes.

Horizontal cylinders rarely print as perfect uniform cylinders, the filament is hot when it is printed, and this inevitably causes sagging.
Vertical holes also tend to come out undersize, the filament gets squeezed slightly as it is laid onto the layer below, this reduces the diameter of the hole.
It is better to print an undersize hole and then drill it using the hole as a guide.

Overhangs require support material. The only slicing software that does this really well is Simplify 3D which is around $130. Cura and Slicr do it as well, but not to the same quality. I use an old version of Cura and live with it.

On top of all of this, when you load the stl into Cura, you have to decide on outer wall thickness, infill density, print speed, print orientation etc all of which will affect the finished object, its trial and error initially but you soon get the hang of it.

After all that is done, the printer itself needs setting up, and maintaining. Bed levelling, nozzles, filament feed etc. You can add to that slight differences in print temperature each time you load a new reel in.

If you want to see what your parts would look like without paying Shapeways prices, check out local printers on PrintHub. They will be using printers that are shown in their profiles, and what they produce will be far closer to what you can expect on a domestic printer and at a much cheaper price. You can choose filament material from what they show. The part is analysed for printability online, and they will advise you if there are problems with it.

[Raminator]

Thank you for the advice, lads. This is all new to me and I appreciate the help and feedback!

A 2mm hole through a 3.5mm part means it's only going to be 0.75mm thick which'll be very weak. I use paperclips which are 0.8mm in diameter. The plus side of using paperclips is that the ends of the clips are smooth which goes into the hole easier and the end you cut usually gets flattened by the cutters and when pushed into the hinge helps keep it in place.

I've modified the hinge design with a smaller hole, I'll use a 1 mm axle (I've only got big paperclips here!) and cover it with a hollow styrene tube on the visible bits. I've also thickened some parts, simplified some of the detail and added some sprues (1 x 1 x 2 mm) to make it printable in one go:

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Shapeways are quoting me US$5 to print these in frosted extreme detail, so I thought I'd give them a go. As near as I can tell, the .stl looks okay and it's passed all of their automated checks, so I'll let you know how I go. I figured this will help let me know if I'm going in the right direction before I consider splashing out for a printer of my own.

One thing to remember with domestic printers is that they are putting down layers, so the item has a grain much like wood. If you try and break it one way it is easier than breaking it the other.

Imagine an upright cylinder, with the layers going from top to bottom, it would be easy to snap it.
Imagine a horizontal cylinder, with the layers going from top to bottom, it would be more difficult to snap it.

I'd been assuming that the final product would be fairly homogeneous, but in hindsight it's kind of obvious that that wouldn't be the case. I'll take the "grain" into consideration; does it make sense to orient the model to get larger, flatter areas for strength then?

Horizontal cylinders rarely print as perfect uniform cylinders, the filament is hot when it is printed, and this inevitably causes sagging.
Vertical holes also tend to come out undersize, the filament gets squeezed slightly as it is laid onto the layer below, this reduces the diameter of the hole.
It is better to print an undersize hole and then drill it using the hole as a guide.

Would a resin printer like Woz's be less prone to this kind of sagging, since it's being polymerised in a liquid bath? I'm just curious about the different technologies and approaches out there, it's a lot to take in. I should have got into this ages ago!

[wibblywobbly]

$5 for one track link? If I tell you that I can print 16 for £0.25p in an hour, using PLA, you will see where Shapeways make their money.

Orientating the model becomes important when using a domestic printer, Cura makes this easy, just rotate it any way you want, but I have a feeling that Slicr doesn't allow this, so you have to save the STL file in the orientation that you want it before loading it. The key is rotating it so that it has the minimum support material, and all cylinders and tubes are vertical where possible. This is what I always bear in mind when designing a part...how is it going to sit on the bed, and would it be better to print two parts instead of one etc.

Taking a track link as an example. Ideally a totally flat surface needs to be on the bed. A printer has problems if there are cavities on the underside of the part, especially if they are only a mm or two, as it will try and print 1-2mm of support material, and then that has to be removed. This will leave a rough surface.

I am going to try printing links in two halves and then gluing them together.

Woz will know how strong resin parts are, the drawback for me at any rate with using resin is the maximum print area currently available with domestic ones. Most home printers are 200x200, the Creality CR10 is 300x300 with a 500mm version available. All reports on them are good. They didn't exist when I bought my printers, but if I was buying one now then that is what I would get. Box section extrusions, solid as a rock, and all of the bells and whistles. Delivered in two prebuilt sections, just bolt them together, check all of the screws are tight, level the bed, and print?

Delta printers are whizzy and print very fast, I have one, but the drawback is that they are very complex to set up as accurately as a Cartesian printer.

I would avoid anything that you see on Kickstarter, it is full of people with zero business experience getting a load of cash, sending out prototypes that don't work, and then disappearing into the sunset.

The 'good' printers from China at bargain prices seem to be:

Creality CR10.
Anet A8
Sintron Prusa derivative

The best non Chinese printer is the original Prusa i3, on which most Chinese printers are based, but that is not cheap. It is however exceptionally good.