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Metal Coating
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Overview
“Metal
coating can be successfully performed on PolyJet models to provide a
decorative finish or a hard surface for wear in various applications”,
says Mr. Paul Willment, Director of Morganic Metal Ltd UK.
“Plating
can improve physical properties of the Objet parts, such as tensile and
flexural strength and the heat deflection temperature. Because of their
light weight and Nickel ease of design, RP parts have been used in many
applications to replace other alternatives”.
Product design of
parts to be plated is particularly critical in determining the success
of the plating operation, add Paul. Basic RP design practices should be
followed to achieve a good molding in the unplated product, and it is
advisable to have the design reviewed by the plater. Because the proper
choice of resin for products to be plated is of basic importance, the
resin supplier should be consulted while the product is in the design
stage.
Since PolyJet models are nonconductive, they must first
be processed through a preplate cycle, during which a metallic coating
is deposited by an electroless plating process to make the plastics
part conductive.
The preplate cycle consists of etching, neutralizing, catalyzing, acceleration, and electroless plating.
Etching
The
etch bath consists of a highly concentrated acid solution of chromic
and sulfuric acid. The solution oxidizes selective areas on the Objet
part. The holes produced by the oxidizing action are absorbing sites
that hold small metallic particles that serve as activators for
electroless plating.
The hole size influences adhesion and other physical properties. After etching, the plastic is thoroughly rinsed.
Neutralizing (sensitizing)
The neutralizing bath containing mild acids or alkaline solutions chemically neutralize the acids from the etching bath.
Catalyzing
In
this step, a catalytic film is put on the oxidized surface to prepare
for electroless metal disposition. It is done in two steps, in step 1
the liquid is immersed in a bath, step 2 involves another solution that
prepare the Objet model to be plated by nickel.
Acceleration
The
accelerator bath removes the entire chemicals that remain after the
Catalyzing procedure. It also accelerates the catalytic film, to ensure
a rapid coverage of electroless deposits.
Electroless Plating
The
plating bath is the final bath of the preplate cycle. A thin deposit of
metallic file is deposited on the Objet part. It can be made of nickel
or copper depending on the objects application. Electroless plating
helps electroplated parts in a corrosive environment.
Plating
There are many kind of ways to plate plastics. Some of the following are:
- Strike bath
- Acid copper bath
- Semi bright nickel bath
- Chromium plating bath
Solution Control
The process described above should be
done in the best of conditions possible. You should rinse the PolyJet
model being plated after every step taken. There should be careful
watch over different aspects of each constituent. pH levels,
temperature, or brightener level fluctuations may ruin the whole
process. The Hull cell is one of the most vital tools in
electroplating. It can show current ranges, the appearance of the
deposit, and check if there are impurities. If there are any changes in
the solution the Hull cell would know. Troubleshooting electroplating
is a long and lengthy process. There are hundreds and hundreds of
possible
explanations for why your bath is bad. You should be able
to know the most common troubleshooting tips if you were to start
electroplating for industry.
Applications
Metal
Plating is the method of applying a metallic coating to another
material. There are many reasons to plate objects. They can be applied
to almost any coarse material. Plating can be used for different
reasons.
Some models are plated to increase their sturdiness and
provide a hard shell for whatever it is plate on. Some are plated to
avoid corrosion, and a few are plated just to give off an attractive
finish.
As described above, metal plating can be used for a
number of reasons. Nickel plating is one of the most common used in
decoration. When combined with an under layer of chromium, it provides
a bright, shiny
surface that is corrosion-free, and resistant to
wear. These products can be found in car parts, metallic decorations
(like streamers). Nickel Plating is used for the following reasons:
- Provides a bright, shiny appearance.
- It can conduct electricity
- It can plate a large variety of materials
- Has high resiliance to wear and tear
- Is corrosion-resistant
- Long lasting
Automotive, appliance, military, marine, trucking, electrical and
construction are some of the markets in which metal coating is found.
Metal coating can be applied to parts such as fasteners, brackets,
clips, clamps, stampings, beams and rotors.
“As a technology
leader, says Mr. Paul Willment, we are continually developing and
experimenting with cutting-edge technologies and processes to meet the
customers’ changing metal finishing needs of the industries we serve”.
Morganic
Metal Ltd continually improves its electroless nickel process for Objet
models, our most popular coating process, to keep it at the forefront
of the electroless plating marketplace.
Disclaimer
Objet Geometries Ltd. is not responsible for misuse of our products or
their use in conjunction with unsafe or improperly maintained equipment
or for uses other than intended as specified in this application note.
Information and pictures in this applications note are curtsey of
Mr. Paul. S. Willment Director, Morganic Metal Ltd. www.morganicmetal.com
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Figure 1. Faucet Model design
using CAD.
Figure 2. Model orientation in
Objet Studio.
Figure 3. Objet model being
matellizing with a conductive
surface.
Figure 4. First coating of model
with Copper.
Figure 5. Final metal coating
with Nickel. |
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