I'm baffled by 3D printers/printing
 

I'm either too old or too stupid.

Does one just feed welding rods and tin cans into these contraptions instead of ink?

Discuss.

(PS there's no question about me being stupid, so we wont need to discuss that.)

Well then....how old are ya ;)?

Consumer grade printers use plastic on rolls. I typically use ABS plastic. Kind of like a computer controlled caulk gun, but with melted plastic.

so it places a layer, then the print head raises a little bit, and it prints another layer.

I'm thinking of picking up a cheap 3d printer (like $150). I'll just use it for miscellaneous stuff (like fixing kids toys) and prototyping for my CNC machine. I don't expect what it produces to be as robust as cast plastic, and I know they are limited in the kinds of plastics they can work with.

I built mine about 5 years ago, to make parts for a HS robotics team.

Great for prototyping. Also made drilling templates, spacers, hubs and adapters, etc.

Use ABS and crank the heat, the parts are pretty strong. Especially if used in compression (like bolting between plates/washers).

yes there are several methods of metal 3d prining. A few of which aren't far from what you describe, but with a touch more sophistication for course

Lets suppose you take an apple, and slice it sideways into 10,000 very thin layers.

The printer lays down a thin layer of melted plastic that represents the first layer, then the head moves up 1/10,000 of the total depth, and lays down the next layer. Layer by layer, you get an apple.

my idea for strong metal parts from a cheap 3d printer

wax or other low temp melting substance that flows eazy
do the part in wax with funnel shape to allow the wax out and metal in
make a plaster casting mold around the part
heat the wax and let it run out or very high heat to burn the stuff out
the pour in molten metal at a foundry
cool and break the plaster mold
trim off the funnel shape [ call a riser ]
if a complex shape more risers maybe needed or rotating the mold needed to get air out

called lost wax casting
works for most metals

Ours at work uses 2 reels of plastic line. One roll is the modeling material, while the other is for filling in gaps which we call the "support material". These reels (picture thick fishing line) unwind, and go through a heated head in a specific pattern, layer after layer. When the peice is complete, we soak it in a heated bath, which melts away the support material to reveal the part.

This must be hooked to a C.A.D. program on a computer for directions to build.

I though there were sputtered metallic printers.

Direct Metal Laser Sintering makes some relatively strong, for 3D printing, parts.

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More on the plastic ones.

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Its like a high tech hot glue gun. 😀

If you do some upgrades you can 3dprint polycarbonate.

sure but they are NOT the cheap home versions

and are the high end powdered and sinister-ed that need real power to melt/fuse the metal powder
so think many thousands not a few hundreds or rent time on not buy for most of us

while a cheap one should eazy to adapt for wax to do lost wax at a foundry

First designed parts using 3D printing manufacturing processes over 20 yrs ago, very primitive back then, molten wax was laid down in thin layers.

A few years later the process started being very cool, a moving platen plate would move vertically in a bath of resin, allowing a thin layer to be cured with each pass of a laser that was moved/positioned using a tilting optical mirror, real James Bond stuff

More recently for the last 10yrs I've designed racing car parts in titanium and aluminium. Metal parts are made using fine powder with a high powered laser melting one thin layer of powder at a time, nearly any shape can be made but there size limitations.

Metal parts are not quite there with regards to fatigue properties but the material properties are getting close to wrought bar stock.

The home 3D printers usually use a spool of plastic (like a MIG welder) that melts as it's fed through a heated nozzle.

We have one of the plastic ones here at work, fascinating and I'm very interested in the newer heavy duty models.

I first saw a 3D printed plastic set of captured gears at Airventure back in the early 90s.

Needless to say, we have some really neat 3D printers here at work. I watched one of them printing with concrete. We also printed a car and a house. We are actually using 3D printing ("additive manufacturing") to fabricate metallic parts that are too complex to machine conventionally.

https://www.ornl.gov/blog/eesd-review/moving-future-3d-printing

https://web.ornl.gov/sci/manufacturing/shelby/

Needless to say, you have LOTS of neat toys at your work.

Lucky guy, in that you still get to play with this stuff. We had pretty much just started using it, maybe for four or five years, when I retired.

What a godsend for AOG tooling. We could make all kinds of little widgets to perform task-specific functions during the course of a repair or mod. We could "grow" these things overnight, where they would often require days or weeks of machining, fabrication, welding, etc. Boy did we save time and effort.

Kind of one of the unfortunate downsides, however (and maybe you have seen this as well) comes from one of its greatest advantages - if you can model it (we used CATIA V5), they can make it. No more worries about backdrafts in pockets, areas unreachable with conventional machining, etc. Us old farts who are constantly aware of such things kind of intuitively avoid those traps. The young guys feel they don't have to anymore. Then, one day, in designing something too big to grow in a vat, they do the inevitable - they design the part that cannot be machined. Backdrafts, no cutter access, etc. Boy do things go sideways then - some old fart (usually me) gets to spend his Sunday night sorting it out... Fun stuff, though, at any rate. Kinda miss it sometimes...