3D Printing and Rapid Prototyping

Preparing ABS Parts for
Coating or Plating

Prepared By:
PPG Industries
One PPG Place
Pittsburg, PA 15272

Many users of 3D printers have found that, by coating or plating ABS models, they can use the actual model
for display and other purposes where production parts would not be feasible. This process is becoming very
popular for automotive mock-up applications, such as concept vehicles for shows. Preparing parts to be plated
or metalised is very similar to preparing them for painting, and the following finishing procedure should be
followed for both processes.
The first and most important step to take is to prime and smooth the models. A good acrylic-based automotive
primer, such as Kondar DZ3 Acrylic Primer Surfacer by PPG Industries, should be used in its original, thick
form to fill in gaps and “stepping” between layers. Once the primer is thoroughly dried it should then be fine
sanded until you begin to see the color of the ABS model through the primer. This step should be repeated
until all surfaces are smooth and all voids have been filled in.
Once all surfaces are smooth, another layer of primer, thinned to a consistency that can be sprayed
(approximately 4 parts thinner to 1 part primer), should then be applied and wet-sanded with a very fine
(minimum 1000 grit) sandpaper or emery cloth. This should also be repeated until the surface is very smooth
and no ABS is showing through. It is very important to have a solid coating of primer to ensure uniform
bonding of the plating. Also remember that any flaws in the finishing will be visible, and even magnified,
once the coating or plating is applied.
Once the part has been filled and smoothed, you will need to determine which plating process is best suited for
your application. The two most common processes are electroplating and vacuum metalising, and each
process will yield slightly different results. Following is a brief description of these two procedures and their
respective advantages and disadvantages to help with your decision.
Vacuum Metalising:
Also known as Vapor Deposition, this is a 3-step process that produces very good results. The part is first
coated with a lacquer base material to provide adhesion, and then the metal to be deposited, usually aluminum,
is converted into a vapor and is deposited onto the part in a vacuum chamber. A clear top coat is then applied
to the finished part to increase gloss and add durability. This clear coat can also be dyed to achieve different
colors or to produce the effect of gold, copper, brass or other types of metallic plating.
The metalising process is useful for applications where dimensional accuracy is needed, such as in an
assembly, because the total thickness of the coating only adds .002/.003” to the part. However, this type of
coating is not as hard or durable as a metal electroplate and can be worn off with repeated use or scratched off
with an abrasive.
Electroplating:
The plastic model needs to be made electrically conductive in order for the electroplating process to work, and
ABS plastic, the material that FDM models are made from, works very well with this process. The model is
chemically etched, which removes the butadiene molecules from the surface and improves bonding of the
subsequent layers. Once etched, the part is then coated with a layer of palladium, which acts as an
intermediate bonding agent, followed by a layer of nickel to provide the necessary conductivity. At this point,
the model is placed in a tank containing a solution of the metal to be deposited and given a negative electric
charge, which attracts the positively charged metal ions from the solution and becomes a solid metal again.
Hard chrome electroplating gives the plastic model a very durable coating, but it can have a tendency to make
the part somewhat brittle. It may be better to only plate surfaces or areas that will be visible and allow the
unplated areas to absorb and dissipate any possible impact stress. Also, if a part will need to bend or flex it
should not be plated at all because the thin layer of plating can crack.
Another thing to consider is that an electroplate will most likely be thicker than a metalised coating, so it may
not be suitable for use when dimensional accuracy of the finished part is critical. This process is much harder
to control and can add an average of .010”/.020” to the size of the part. If accuracy is an issue, it would be a
good idea to discuss this with your selected plating vendor; they may be able to control the process more
tightly to conform to a certain thickness. Otherwise, you may need to downsize the model, either through
overall scaling of the STL file before building or selectively removing material during the finishing process.

WHY WE DON’T USE AUTOMATIC WEB-BASED QUOTING

(find out even more here about why we don’t use automatic web-based quoting)

 One of our main goals at BSLA Paradigm/3dRapidParts.com is to be the premier low-cost provider of rapid plastic prototype parts via 3D Printing and FDM technology.  Low-cost does not mean lower quality, however.  We use the exact same processes as other bureaus, and we deliver just as quickly…..usually QUICKER in fact.

We simply keep our overhead low so that we can pass the savings on to you. It’s not hard….it’s common sense.  We treat our customers the way we like to be treated.  Rapid, quality service with lots of communication.  Simple.

Just take a look around at some of the “instant quotes” you get through other companies.  They are outrageous.

Try the instant quote features at xpress3d.com, redeyerpm.com or APproto.com.  Yikes.

We don’t use instant-quotes at BSLA Paradigm because there are too many variables in even the simplest project to give an accurate and economical quote without communicating with the customer.  Surface finish requirements, detail features such as snaps and determining what the part will be used for are only a few of the things that can drastically affect the cost of the part.  Instant-quotes orient the part in the way that is most economical for the PROTOTYPER.  At BSLA Paradigm we orient your parts in the way that is most economical and useful to you, the CUSTOMER. 

Give us a try. We are different and we are better.  Oh yeah, we are less expensive with better quality and better material as well!

Simply contact us directly or send your files for a rapid (but not instant!) quote at:

QUOTES@PROTOZ.COM

It is convenient, no question about it.  And quick.  But do online quoting engines really serve the needs of rapid prototyping customers better than manual quotes?  When it comes to 3D printing and FDM (fused deposition modeling) the answer just may be “no”.  Sure it’s nice to be able to quickly get a price, place your order and pay immediately all at one time, but if the parts are not what you need when you get them, what is the benefit?

Part Orientation:  A Huge Factor in Part Quality and Price

Obviously there are parameters built into the code that runs the quoting engines that analyze the part and orient it in the build chamber based upon these parameters.  For the purposes of this article, those parameters don’t even need to be discussed.  Why?  Because no matter what the parameters are, they simply cannot take into account all of the things that an experienced rapid prototyping professional automatically applies when programming parts to be built.

For exaample, snap features are very common for 3d printed parts, and since the whole point of rapid prototyping is to apply form, fit and function testing to the parts to prove out design, these snap features need to actually work!  As is common knowledge to anyone familiar with the process, if these features are not built in an orientation that optimizes strength and flexibility they are useless.  For instance, who hasn’t seen snap features break off when hardly any force is applied to them because they were built in such a way that they were subject to the weakness inherent in the layers that make up 3d printed parts? What good is that?  And since it is such an important consideration, how can we be confident that “dumb” automatic quoting engines can even recognize a snap feature, much less orient for maximum strength and flexibilty of the feature?

And of course, snap features are only one consideration.  Others are dimensional accuracy, part surface finish, and part strength.  In short, all of these things require human eyes and decision-making when orienting the parts for rapid prototyping / 3d printing / fused deposition modeling (FDM).

A Happy Medium

This does not mean, however, that there has to be a long wait, multiple phone calls and hassle when getting quotes for your RP needs.  At 3dRapidParts.com we apply a happy medium in that we allow the customer to supply minimal information and quickly upload part files via our website athttp://www.3drapidparts.com/quote.htm.  We personally take a look at the parts, read any comments that the customer has attached, and quote the parts accordingly.  In this we we can make suggestions, or provide multiple quotes with different options depending upon what we think may be important to the customer. In this way we can optimize customer satisfaction, part surface finish and usability of the parts.  Quotes are always returned via email within an hour, usually much quicker, and convenient payment via of Paypal is offered at that point, as well as credit card.

Our philosophy lends itself to hassle-free and quick quoting / order placing that ensures customer satisfaction.  No one can write code that gives you ALL of that!!

It may surprise some to learn that FDM parts are accurate and robust enough to be used as fixtures and jigs for assembly and machining. Also, FDM parts themselves can be machined to achieve a very nice result. Because of these things, more and more FDM parts are being used as fixtures and jigs. For machining fixtures, the FDM part is simply designed to conform to the CAD model of the desired finish part. This is especially nice for parts with complex surfaces that will be difficult or impossible to hold without a fixture. It can then be drilled, tapped, machined etc. in order to achieve a cost effective and quick fixturing method. And, you can use your machining center to work on your part, and not to make a fixture; let the FDM machine do that for you!

The same holds true for assembly; the FDM part can be designed to hold two or more parts in position for assembly and fastener applications, or for gluing/bonding, etc.

Also, with FDM, complex fixtures can be created with undercuts and cavities that may be extremely difficult or impossible to create with traditional methods of machining etc. If you can conceive it, FDM can do it!! And it’s done while you sleep or while you are working on something else. Now THAT is a benefit.

For more on this, and our Rapid Prototyping Service please go to www.3dRapidParts.com

Many customers and potential customers may not realize that we are not limited as to the size of parts we can build with FDM.

Because the properties of the plastic that we use (ABSplus, 40% stronger than standard ABS plastic) are such that it is perfect for “solvent-welding” (utilizing chemicals to join/weld one segment to another) we can “puzzle cut” (see pics) larger parts, utilizing our special software, and build them in sections.  We then join the parts together as a post-process, thus creating the larger part required. 

Please see the pictures for details and for examples of large parts that we have utilized this method to manufacture here:   http://www.3drapidparts.com/largepics.html

This is currently the most common use for FDM parts. During the development cycle parts are needed to validate form, fit and function and the workability of the design before the expense and time to design and create a mold are undertaken. By using FDM you can test a design, make the necessary tweaks and make another to completely prove out the concept before going any further. Our FDM parts are robust and strong enough to snap into a working assembly to verify a design or to highlight problem areas. We routinely make FDM parts with snapp features and other small features that are usable for this purpose.Go to our homepage at www.3dRapidParts.com to learn more about our service and to get a FREE, RAPID QUOTE!