When NOT to use a 3D printer

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When NOT to use a 3D printer

Postby fruzzetti » June 3rd, 2015, 3:03 pm

Hi, readers everywhere! I'm glad to be able to work with such a large and highly skilled group. In this thread I hope to clarify some "don't"s for the less experienced among us who are getting in to 3D printing.

I am an AP Calculus BC instructor and the local guru for 3D printing in education. When I work with young people who are first starting out at 3D printing, they have two major misunderstandings: first, that the 3D printer can do anything (even violating the laws of physics); and second, that even after watching it move they don't quite understand how it fabricates. To combat that, I'm investigating just how deeply this "not knowing" runs in them. Eleven years into this profession I can tell you many of our brightest youth have zero experience with anything that isn't a touch-screen -- our Principles of Engineering class has a mix of highly competent students and students who understand the theory but in the lab setting tend to pick up the wrong end of a screwdriver, if you get my drift. There's nothing wrong with them; they're just VERY inexperienced in the non-academic world and in most cases parents are not doing any hacking / making / fixing with their kids anymore; it's like they don't even understand how vital it is.

So let's catalog some stuff that will help noobs get fewer blobs and more good parts. In this thread let's avoid getting technical about G-code and let's avoid arguing about subtle things -- our noobs need to start with good basic 'rules' and then grow from there.

DON'T EXPECT TO MAKE HOLLOW CAVITIES. While you may wish to create a hollow cube in a single print, and it may be possible to do so, you wont be able to do it without building in some support material. Modern slicing software is usually able to do this, crafting good support material that still breaks away easily when the part is cooled. Until you really understand the limitations of YOUR printer and feedstock, play it cool on slopes (stay within about 45 degrees with the vertical). Once you have more experience and you really understand your 3D printer, you'll be able to fine-tune its performance and get some really advanced shapes.

DON'T 3D PRINT ANYTHING THAT'S EASIER TO FABRICATE BY OTHER MEANS. This is one of my biggest pet peeves. If you require a part that's extremely simple, 3D printing pales in comparison to hand fabrication. I've seen people 3D print little solid cubes with a single hole through two faces. Seriously, that will take seconds to make out of a wood furring strip but it will still take the better of a day to design, slice and then dial in performance. And it still won't be nearly as precise as the one you made with wood using 10 minutes of your time. This rule is generally respected by individuals with experience working the big three stock materials (wood, plastic, and metal for simplicity), but for people with little fabrication experience they will commonly not even think about constructing their parts by a non-3D printing means. Look into what you can do with the tools and materials you have on hand for all your simple part needs.

DON'T FORGET TO SIMULATE. Simulation is the 3D printing version of "measure twice, cut once." You can simulate as many prints as you like very very quickly using any number of free software packages. Simulation will save you time, material, and frustration by allowing you to rapidly correct mistakes without having to wait for the 3D printer to draw those mistakes for you.

DON'T GIVE UP IF YOU DON'T LIKE WHAT YOU GET. Just do it again. One of the most important philosophies in engineering is, "There is no such thing as failure; there are only 'complete' and 'I'm not done yet'." In engineering, if we have something to make, we would never give a status report to our bosses that says "I couldn't do it; sorry." Unless the demand violates the laws of physics, we give a status report that says, "I'm still working on it; I'm not done yet." Keep that idea in mind when your print doesn't work out.

Here's one for those of you who are, like me, interested in using G-code directly rather than always importing models and machine-slicing. It's more efficient and you can squeeze the very best performance and quality out of your 3D printer by generating and then refining the G-code manually.

DON'T TRY TO 3D PRINT ANY STRUCTURE OTHER THAN LAYERS. This is more common among students in the classroom setting. They use calculus to derive the formulae they need, and then they write code that traces their formulae like a graphing calculator would: complete with constantly-varying X, Y, **and Z**. You need to remember the extruder nozzle doesn't have negligible geometry and will destroy what you've printed if you bring it down below the highest level printed. So to address this, firstly you should just use slicing software until you get good at direct-to-G-code. Secondly, you need to remember as you advance and learn G-code directly that even when you're not using slicing software, you still need to think about your part in terms of layers, one at a time, from bottom to top without direction reversal.

PLEASE help add to this list. I hope you'll provide a single-sentence synopsis and then a brief justification for why NOT to do whatever it is along with a decent idea for alternatives. For example, talk about print bed contact area!

I'll be providing pictures of this year's 3D printing project parts AND some of their blobs and other errors.

Happy fabricating, and may you endure few to no blobs,

~ dan ~
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