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10 Problems with 3D Printing

I have really been enjoying this forum, and the excellent conversations with many of the folks here. There is so much talent and knowledge here – awesome (and a little intimidating!) As you may know if you have been reading my posts, I have been talking about 3D printing - and some of you have been saying that you are considering it. The interests of fair play, (and to show you that I am not completely fanatical!),  I thought I would make a posting giving voice to “the other side”. I am sorry if this evolved into more of an article than posting, but I wanted to capture some of the discussions I have been having with various members.

1.        Most 3D designers are not scale modelers- the ‘lump’ problem.

It is terribly important to remember that 3D files had their origins in the world of video games and CGI. Actual objects only came later, and even then, these were usually manufactured products designed to be used as printed. The idea that one would print accurately fitting model parts that assemble into a fine scale replica is only a most recent development. As such, you will find a lot of 3-D designers publish files designed to print an entire model as a ‘lump’. Or not scalable to 1/25. Or look like a crude toy. These are, unfortunately, of little value to us. It also needs to be clearly understood that, although your slicer program can shrink or magnify any file infinitely, it will not create greater detail as you enlarge. Scaling from 1/32 up to 1/25 is about the practical limit as the walls of things like cab start to get very thick. Going the other way scaling down from 1/14 to 1/25 is also the practical limit, caused by small parts getting excessively thin, and being too fragile to survive the print process.

2.        Most designers lack accurate source data – the “THAT’S not a Freightliner” problem.

We know how often large model companies, with their huge budgets and a team of engineers get some rather surprising details wrong. Imagine how much more difficult that is for a designer, who may never have seen the actual item he is modelling, to create a faithful replica. It is very much “buyer beware” out there, and what a designer may represent as being a replica of a particular truck, actually is not. I have found that moderate to radical scratch building is required to correct these deficiencies, and that is something that one should take into account before jumping into 3D printing with both feet.

3.        Straight lines sometimes aren’t.

Now we come to the limitations of the medium itself. For various technical reasons, 3D printers will sometimes struggle to produce straight lines. There are various settings that can be tweaked, and some tricks played with print angles, but the problem remains. The bottom edge of a cab may be slightly curved. Even if the object prints completely straight, resin is prone to warping, particularly in humidity shifts. This means sometimes reinforcing with brass shim or rod.

4.        Other technical problems – layer separation, unwanted lines, failed prints.

Just as with any modelling skill, 3D printing has some art associated with it. You can expect a fair number of failed prints and you will be surprised by some of the things that can happen along the way to maturing your skills. Layers printed flat to the print surface will sometime separate, and the fix for that is to print at about a twenty degrees angle. Large solid objects sometimes create so much suction that they stick to the print film (that cellophane-like stuff where all the action happens), and pull the entire print off build plate. I find this happens in our hobby a lot with fuel tanks. Hence, I always print fuel tanks hollow. There is a lot to learn.

5.        Just because you can doesn’t mean you should.

3D printing is well suited to producing complex shaped small parts, typical of what we work with an engine or suspension assembly, and large compound curves such as fenders or cabs. They are not very good at producing thin lines such as bolts or large flat surfaces which tend to warp or distort. Nothing will ever beat fabrication in sheet styrene, or brass rod/sheet. There are some truly awesome fabricators on this forum, and 3D printing will never produce anything better than what they are doing. Scratch building, IMHO, is still the gold standard.

6.        Cost.

Many of us on this forum are older and retired. We do not have limitless funds. A good 3D printer will cost in the vicinity of $350-$500, which is better than a lathe or milling machine, but it is still a lot of money. A bottle of resin which will print about 10 average truck bodies runs about twenty dollars. We need a few other sundry items such as an ultraviolet curing light and ultrasonic cleaner, so the whole setup is going to run you the better part of a thousand dollars. Not chump change.

7.        It’s messy and it smells

Well, yeah. But so do a lot of other things we do, like painting with lacquers or using acetone -based solvent. I think this part may have been a bit exaggerated. Water-soluble resins do not smell that bad and most modern printers now come with fans or attachment ports for venting them to the outside via a window. Resin needs to be handled with gloves, but clears up well with isopropyl alcohol or water as the case may be. It is no worse than many of the other materials we work with in scale modelling.

8.        Resin isn’t styrene – and clear isn’t clear

Happily, those of us that are seriously into scale modelling understand about aftermarket resin parts. You cannot treat them the same way you treat styrene. The same thing is true of 3D prints. They tend to be more brittle and prone to breaking if mishandled. They tend to warp, so construction has to take that into account. While many companies advertise that their brand of clear resin prints transparently, I have not found anything that actually does nearly as well as clear styrene or acetate. This is likely coming, and as the medium matures we will get better results. In the meantime, I would count on printing the “glass” in any model as a buck and using it with a vacuform machine to vacuform acetate windows.

9.        You need to learn a new skill – and have some basic computer chops.

While many writers, including myself, have stressed that anyone with very basic computer skills can do this, it still demands that you have a reasonably modern computer at your disposal, know how to download things off the Internet, can work your way around learning the slicer program, which is very user-friendly and simple, however still requires some knowledge, and is not intimidated by transferring print files onto a thumb drive to get them into your printer. It is not hard, but you may need a ten-year-old kid to help you!

10.   Did you get into modelling to build? Or make parts?

This is a profoundly philosophical issue which was vastly better discussed by Dr. Cranky in a YouTube video (https://www.youtube.com/@DoctorCrankysLabRATory/videos). I get that many of us, with very limited hobby time, want to spend it getting glue and putty under our fingernails, not 3D resin. Even if you decide not to print, you can still download files that intrigue you, and fairly economically have them printed by aftermarket printing companies that are set up to do small orders. Alternatively, there are some small companies on this forum that print 3D files and sell them as complete end products. The more you patronize them, the more files will become available for us.

 

So – I think the sum total is – 3D printing is just another modelling tool. Some will love it, some will hate it – and most will learn where it fits in their own approach to our wonderful hobby. Thanks for indulging me – as always – comments/brickbats are welcome.

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Posted

A timely, and very informative overview of the resin printing field as it currently stands. 

Thanks you for sharing with us. I'll be a consumer of 3D printed parts, but not making any of my own.

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Posted (edited)

I watched on You tube how to do 3D printing and I have a new found respect for guy's that do this , way pass my pay grade , so I'm a buy of this 3D stuff and I like it .

Edited by Mr mopar
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Posted

Mostly true, tho I'm sure I my setup was more like $600 - $700 with my Elegoo Mars 12k, as I didn't go with the clean & wash station.
I do very few body parts and almost exclusively design & print smaller parts.
I get to make stuff that will never be available commercially, but I really like or remember from when I was a hot rodder.
And yes, the mess can be a pain.

Posted
8 minutes ago, MeatMan said:

Mostly true, tho I'm sure I my setup was more like $600 - $700 with my Elegoo Mars 12k, as I didn't go with the clean & wash station.
I do very few body parts and almost exclusively design & print smaller parts.
I get to make stuff that will never be available commercially, but I really like or remember from when I was a hot rodder.
And yes, the mess can be a pain.

Exactly!3D printing excels at small parts - even things like wheels and tires. I use a Saturn ultra and find it excellent for bodies - with the provisos I gave above. I’m not skilled enough to design my own yet - but that’s coming. 

IMG_1318.jpeg

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