Reference for mechanical characteristic of 3D print process

Good luck. The current rule of thumb is that the accuracy of the printed item is at best the diameter of the plastic filament that is melted and applied. In some cases the surfaces are made smoother by melting the surface, this being the equivalent of flame-polishing of glass articles.

Joe

Resin prints can be pretty good, and the printers are nearly free.

Cheers

Phil Hobbs

It's true, but "pretty good" is not a number.

The heated nozzle is smaller than the feed filament, but cannot be that small or the printing speed suffers too much to be economical.

Joe, known to possess a biggish hot melt gun

Really? Whoda thunk? ;)

Resin printer resolution varies with the resolution of the LCD display it's based on, but can easily be 20 microns, which is a lot smaller than the nozzle you're going to be using with a filament printer.

Cheers

Phil Hobbs (Known to possess one of the first 3D printed objects, circa 1992 or

That would fall in the realm of dimensionality. One typically uses "plastic parts" for more than just cosmetics.

I'm concerned with *mechanical* aspects -- tensile strength, ability to withstand shear forces, ductility, behavior under compression, etc.

E.g., if I print a part and then expect it to support a mass (or, be supported by an aspect of its shape/design), will the layers delaminate if the force is orthogonal to the printing plane? If I "print" a mounting hole and a user uses a screw to secure the device to a surface THROUGH that hole, will the plastic crumble or splinter as force is applied to tighten the screw? If I print a boss with the intent of fastening to it with a self-tapping screw, will the penetration of the boss splinter (or delaminate) the boss (depending on print orientation)? If force is applied to printed surfaces, will their deformation be elastic or catastrophic?

How do materials and filament diameter effect each of these issues?

Or, should I just use 3D printing for non-functional *mockups* and not rely on them to perform comparably to molded/cast parts?

All of these things depend on a thousand details, far too complex for a few rules of thumb.

Well, save one rule: 3D printed components are far weaker et al than components made by the traditional methods. Maybe this matters, maybe not.

For making only a few units of each design, a 3D printer is very attractive.

What people do is to print a prototype and see if it works well enough. I have bought a number of such components, which have so far worked.

But it will be a long time before 3D printing can be used for automobile suspension components.

Joe

OP wanted numbers.

This sounds like a 3D printer that works like a Xerox printer with funny ink. Sounds very precise but very slow. Don't think OP was talking about this.

Heh. Back then I'd use a wood chisel driven by a 20-ounce urethane potato-masher mallet (Wood is Good, MA-20) for this.

My Mother had a real Ironwood potato-masher mallet, but I didn't inherit it. When the urethane mallets were introduced, there was a big debate, but the urethane was in fact better than traditional Ironwood - long push versus bang.

I also use the mallet in the kitchen to drive a Chinese Cleaver through recalcitrant gourds.

Joe

It’s massively parallel, and the printers are cheap.

I’ve never used a resin printer myself, but we’ve had protos made that way, and folk whom I trust have been singing their praises for awhile now—print speeds of several inches per hour, over the whole platen.

One link that might be useful is

Cheers

Phil Hobbs

I disagree. E.g., interlayer bonds seem to be less strong than the layers themselves -- suggesting how one could arrange for stresses to be distributed in the object. Nylon and PLA are more ductile than materials like SLA so expect less "catastrophic" (more plastic) deformation.

I wouldn't want to experiment with a material (or build orientation) only to discover these sorts of things would have been obvious on initial inspection.

It seems most suited to verifying form but likely not for actual

The problem is that those things depend on a thousand details, which could be different between each print.

For example, the slicer software sets how the path of the print head moves to draw the object. Suppose the slicer makes the head push down harder into the previous layer - result will be stronger interlayer bonds. Then the next version of the software comes out and changes the slicing algorithm

- changing all the properties.

Then you have the problem that the filament differs from manufacturer to manufacturer and sometimes batch to batch.

There are things you can do with that - eg orient the layers so they're parallel with the load, rather than perpendicular. Then you are applying force along the layer rather than between layers. Again that's a function of how the part is printed, which is a function of both the software and its hundreds of settings.

It's already happening:

PCBs are now roughly 80 years old. They are stiil made from a smallish number of parallel planes.

If 3D printiing could ever make decent conductors, we might have true

Parts inside?

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Well, Murata is shipping those DC-DC modules with the toroid core inside the board. Folk have been putting ceramic decaps inside PCBs for over 20 years that I know about.

Cheers

Phil Hobbs (Former member of the packaging research group at IBM Watson)

Yeah. Being pioneered by the aerospace community, who can afford such things. But it's largely research except for simple things. But they will get there.

Military aerospace are the folk that built the equipment to forge the F-22 fighter aircraft airframe of titanium.

Joe

There HAVE to be some "rules of thumb" otherwise if *a* print didn't meet your expectations, you wouldn't know what to tweek to close the gap; you could just as easily "spin the dials" and see what turns up for the NEXT instance.

Admittedly, these may not be known to non-professional printers. But, if there is no repeatable science involved, then no one will ever quote a job -- beyond making something that LOOKS like <whatever>

Then you need the equivalent of Good Manufacturing Practices (from pharma). Controlling the things that have significant impact on your product so they can't introduce unexpected changes.

So, you can never make two of the same thing! Sounds like a pretty useless technology!

And *a* version of a piece of software is infinitely repeatable. Presumably, settings are, as well. Ditto for materials.

As above, if there are NO rules of thumb, then the settings can be in bogounits as they don't matter, right?

SOMEONE understands these things -- even if there are dozens of caveats. Otherwise, the technology would just be a toy. I've found lots of anecdotes and guidelines for specific materials and specific types of constructions. What I was hoping for was a systematic reference that brought all of these together so comments made about X could be evaluated in the context of other comments about Y (if you accumulate anecdotes from a variety of sources, then the sources introduce variability in the quality of the data compiled)

They print *teeth*...

That's a cool part, but it's still a PC board.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Follow-up: Aviation Week follows 3D printing for manufacture of flight hardware. There are 3 articles in the February 23 to March 8

Joe