On 8/14/14, 1:51 PM, Dave M wrote:
I'm starting to get interested in 3D printing. My primary purpose would be
to make parts for obsolete equipment, and other parts that are no longer
available. These parts often have imbedded metal parts, such as a metal
ferrule inside a knob, or an imbedded nut or mounting tab.
Can 3D printers make such parts? If so, is any additional equipment or
unique model of 3D printers required?
Monoprice has a model that appears to be a clone of a Makerbot printer at
about half the price. Reviews seem to indicate that it is an excellent
printer, although not perfect. I guess that 3D printers are relatively new
on the scene, and will improve in time.
Thanks for any insight,
Dave M
Hi Dave,
If you want to get your own 3D printer and make custom parts I can think
of 3 things you'll need:
First is a 3D drafting package, something that will make a .stl file
(stereo lithography file). I think Google sketchup might work and be
free, but haven't used it. Alibre design used to make a reasonable
SolidWorks clone for about $100 US that is good. SolidWorks is one of
the professional standard tools, but costs a lot.
Second is a program to prepare the .stl file for printing. These
programs are commonly called slicers. Makerbot has one for free. There
are other free ones available, but they may require tweaks to work with
a particular printer. One good one is called Replicator G.
Third is a printer. One decision you need to make is material type. The
two main choices for the class of printers you are considering is PLA (a
hard, biodegradable, brittle plastic) and ABS. Some printers print only
PLA, some print either. Each plastic has its merits. For me, the main
benefit of PLA is less part warping during printing and cooling, and the
main benefit of ABS is part workability for secondary operations after
printing.
There are many types of professional 3D printers. They come closest to
turn-key what-you-draw-is-what-you-get operation. There are many
services that will print your parts for a fee and have available
printers of various capabilities. Materials for these printers cover a
wide range from fused plastic powders to stainless steel. Most companies
use printing supplies as profit centers and so even after purchasing,
printing supplies can cost you. Using a professional service is the
surest way to get parts that are exactly as you've drawn the first try.
If you use an inexpensive home printer, prepare to spend a lot of time.
You'll need to become an expert in it's operation to produce reasonable
results. To my knowledge, there are two main types available. The first,
which I've seen but not operated, uses a photo-polymer and a light
projection system, and is best for small parts and high resolutions
(microns), but the finished material is kind of soft. The second melts a
plastic filament to print the part with resolutions down to about 100 um.
For the inexpensive route, here are some of the things you'll need to
get right for reasonable results:
- the build plate needs to be flat to within about 50 um. This means you
need a machined plate. The plates are typically removable and
adjustable, and it's useful to make tools to help you level the plate.
Too small a gap means the print nozzle will clog up, too large a gap
means the parts will not stick to the build plate. Look at
http://www.thingiverse.com for .stl files for various tooling. A very
inexpensive printer may not include a machined build plate.
- the build plate needs to be heated for using ABS.
- one main problem with this class of printer, and especially with ABS,
is that the parts will warp during printing due to differential cooling.
The best fix is a heated build chamber. Unfortunately, this is patented
and the working parts in a home-class printer are not up to residing
inside a heated build chamber anyhow. One thing you can do to help is to
enclose the printer to at least avoid cool outside air from circulating.
You can also help warping with part design, by minimizing long solid
runs of plastic for example, or putting relief slots into the part to
break up long runs, and later filling with epoxy. These printers work
best for parts with under a 4 inch span.
- The home-class additive printers (melted plastic) can't print much of
an overhang reliably (around 45 degrees or so). You need to take this
into account when designing your parts.
You mentioned embedding metal into the parts. Brass inserts are
available in various sizes and can be melted into holes in ABS parts
using a soldering iron (one you don't love anyhow). Printing ABS with
embedded metal parts, while not impossible, is IMHO, impractical in most
situations. JB weld epoxy has been useful for modifying parts after
printing.
To sum up, I think these printers can be a useful tool for prototyping,
making jigs and even for short run production, especially for internal
brackets that don't need the strength of metal and where surface finish
is not important. The home-class machines require a large investment of
time but not a lot of cash. The professional printing services are the
best bet if you need only a very occasional part or if you have a
reasonable budget for parts. I might compare using the home-class
machines to making pcbs at home vs using a professional service, say 20
years ago.
ChesterW