3D Printing

If there is a Maker Faire (or similar show) coming up in your area, you might think about visiting. I went to the one in Kansas City a couple of months ago and there were a lot of different of 3D printers running there. Some of them were being displayed by vendors, and some of them just by their owners. Plus there was other fun tech stuff to look at and play with.

Some cities now have a "makerspace" or "hackerspace" - basically a club workshop, you join the club and then you can use their machines. They usually have at least one 3D printer. I think you usually have to join to actually use the printer, but there is sometimes an "open house" night where you can watch it running and ask questions.

Standard disclaimers apply; I don't get money or other consideration from any companies mentioned.

Matt Roberds

No, but you can make two parts that interlock to capture the metal, or design for the metal being a press-fit.

"build platform" I think.

most FDM printers run the extruder very close to the work, you're likely to have a collision

yeah.

you'd have to get the unfinished part part in exactly the right place,

but if the printer paused and moved its head aside you could reach in and insert the nut. Perhaps an electromagnet, or vacuum nozzle, could be added to the head and it could do pick-and-place and then continue with the print.

It can build them in-place, so you end up with a working device.

That's fine for a prototype -- but you wouldn't manufacture products that way.

The 3D printer will never be the equivalent of the Star Trek "matter synthesizer".

Dear Dave,

There are many videos on youtube of these type printers working that might interest you. There are also many service companies. Search for 3D printing service and you'll be inundated. If you want an inexpensive sample of printing from a modest machine, see ebay - some people are using these to make gee-gaws to sell.

Here's a close-up of the print nozzle for a Makerbot Replicator 1 with a mm scale:

and here's a photo of a part with a melted-in brass insert:

A couple of other mods, besides those I previously listed, needed to get my printer somewhat reliable were a foil shield to block the extruder fans from cooling the part and replacing the plastic build plate arms with machined aluminum arms.

Someone mentioned the possibility of removing a part from the build plate and then precisely replacing it to continue the build. I wouldn't say it's impossible, especially since someone here would then do it, but it would be very impractical. The part is basically melted onto the build plate as the first layer is printed, and this adhesion keeps the part registered during the build. Loss of adhesion is a major cause of failed builds.

Some printers offer the option to pause in mid-build and then re-start. The feature is intended to allow you to change filament, say to a different color. It might be possible to get close to what you want using a pause as long as you don't remove the part from the build plate. You'd need to make sure that any metal you placed did not extend above the previously printed surface - else your print head will crash into the metal. Another way to embed metal might be to print the part in two halves, place the metal piece, and then glue the halves together.

I think machines like the Makerbot can produce reasonable results, but you pay with your time. You can even get nice prototype cases if you are willing to do some filling, sanding and painting. Alternatively you can get pretty and reliable prints from a service or by purchasing a $20k Stratasys machine, then you pay with your wallet.

ChesterW

Another approach is to make a plaster mould and cast it. You have to make some jig to hold the metal part where you want it while the material cures, but that isn't a fundamental problem in most cases.

Devcon polyurethane is a good material for this.

Cheers

Phil Hobbs

Hobby stores have cool plastic casting supplies.

Hobby stores have cool plastic casting supplies.

Coming in late to the discussion -- got hit by the Win7(64) BSOD from the latest Black Patch Tuesday. &^$^%&# Microsoft

Embedding nuts and such like is quite possible. The print needs to stay in place on the build platform and the print paused just as it's starting the layer that covers the nut, which has to rest flush with or just below the last printed surface. But it's basically pause, pop it/them in, and hit continue.

For strength, parts are certainly weakest in the layer plane and thin walls or toothpick-sized risers normal to the layer plane can be fragile. On the other hand, I did some custom length hex standoffs in ABS, 1/4" on the flats and not quite 1.25 inches long, F-to-F for #4 machine screws that were too tough to break by hand. Also, no nuts needed, just size the holes right.

Cosmetically, they're always recognizable as printed parts. Any good consumer grade machine should be able to do 0.1 mm layers ("normal" layer thickness nowadays is 0.2 mm) but 0.1mm ups the build time and it's still recognizably "printed." ABS, but not PLA, can be vapor smoothed with acetone.

PLA prints at a lower temperature (about 200C), doesn't require a headed build plate (although it helps for sticking the all important first layer), and shrinks about 0.2% as it cools. It has a harder surface than ABS but it tends to break rather than yield. Glass transition temperature is about 65C, so leaving PLA parts in a hot car is a bad idea. Smells like waffles when printing.

ABS prints at around 230C but does need a hot build plate (I use 110C for the first layer, 85C for subsequent) and an enclosed, draft-free chamber. Shrinks about 0.7% and can delaminate or curl during printing if conditions aren't right. Tougher than PLA and bends rather than snap. Higher glass transition temp (abt 105C). Smells like burning plastic when printing, though, so a filtered exhaust is suggested.

There are some "exotic" filaments (nylon, PVA, etc.) but PLA and ABS are the bulk of the raw materials used in consumer machines.

It's not (yet?) a point'n'click technology. Leveling (tramming) the build plate and preparing the build surface (AquaNet hair spray is actually a favorite for this ;-), tweaking filament feed rates and melt pool ooze compensation, extra cooling fans or not, etc. are all part of the fun.

The Monoprice printer looks like a rebadged FlashForge Creator X, which is indeed one of the MakerBot Replicator 1 clones. It will do PLA just fine as-is (hint: cover the build platform with 3M blue painter's tape that has been wiped with isopropyl alcohol for a good surface for PLA) and ABS if the top and front are covered to exclude drafts. Hairspray (AquaNet unscented extra hold) on either Kapton or glass as a surface for ABS. Should be a good, decent machine. Do give it a once over for loose screws. Also flip it over to expose the main PCB and check that the connectors there are all tight. There's also a bad habit on some of these of tinning leads going to screw compression connections, which IMHO is A Bad Thing, especially for the main 24V power connections. I'd clip off the tinning and either go commando or, better, crimp on ferrules if you've got some.

Do not dive in and try printing giant skulls (or whatever) right off. Start with the 20x20x10mm calibration boxes until you've got leveling and surface prep down and your extrusion multipliers are tweaked in.

Your main board will be similar to the MightyBoard Rev E. Schematics over at

There's a FlashForge group over at

I know someone who has one of these guys' 4th Gen printers:

It needed some minor mechanical retrofit--axes were racking & binding, but otherwise works. $600.

It's basically the same RepRap core, bits of MakerBot, all bundled together.

They've sure sold a lot of them. They claim 10,000+.

Cheers, James Arthur

Last weekend was the Bristol Model Engineering exhibition, and the commercial offshoot

Very impressive indeed.

This is the 'interrupted printing' issue, and it is a big problem, because the print head has to have a flat, aligned surface under it. This is also a problem when you start the print---the build platform has to be aligned, even though it's easier because at least it's know to be flat.

There are printers that have a THC-like height detection on the printhead and can compensate for flatness---the main motivation being multi-material printing.

As far as dropping an occasional nut into a hex pocket, it seems to me that this should work well---just make the pocket a little deeper. It's OK for the nut to wobble in the pocket a little bit---it doesn't need to be fully constrained, and it may even help in the assembly if it can move a bit.

^ ^^^ ^^^^^ Yep, that's what I had in mind. I guess the critical factor would be the ability to open the doors, and drop the nut in without disturbing the position of the part. Am I correct in assuming that the part is stuck securely to the build platform when the process starts?

Dave M

Yes, having the piece stuck securely to the build plate is critical to getting a successful print. It's somewhat of a black art. One wants the piece absolutely nailed to the platform during printing but able to release easily afterwards, without damage to the platform, the piece, or to the operator's cheery good mood.

The nut doesn't have to be fully encased. Lots of parts are made with hex cavities, and the nuts are dropped in later.

(I haven't tried it)

Cheers, James Arthur