Electroplating Model Preparation

BY AL BACON, ASSOCIATED ELECTROPLATERS
AND JASON CHANNELL, ASSOCIATED ELECTROPLATERS

Supplies: 1. Zep Citrus Cleaner 2. Primer- Lacquer-based, sandable 3. Sandpaper- 220 & 320-grit dry; 600, 800, 1000 & 1200-grit wet 4. Body filler or sandable putty

Overview

For product demonstrations or functional applications, electroplating adds the look and characteristics of metal to a PolyJet™ model. With simple finishing techniques, models are ready for plating with chrome, nickel and even gold.

PolyJet's post-build surface characteristics minimize the preparation time need for electroplating. Unlike other rapid prototyping parts, your PolyJet model does not require tedious filling of build lines and extensive sanding. This reduces cost and expedites the delivery of the plated part.

Electroplating extends PolyJet applications. The breadth of plating materials offers the decorative properties of nickel; the wear properties of chrome; the conductive properties of copper; or the brilliance of precious metals like gold, silver and platinum. Electroplating thickness depends on several factors, including the plated metal, type of finish, part size and part shape. The thickness typically range from 0.0001 inch to 0.020 inch (2.5 micron to 508 micron), depending upon the plating material system.

Preparing models for electroplating requires no special equipment. Supplies are inexpensive and readily available from automotive supply retailers and hardware stores.

Process
1. Prepare model
Following support removal, clean the model to eliminate any wax, grease, oil or support residue that will impair adhesion of the primer coat. Soak the model in Zep Citrus Cleaner for 5 to 15 minutes (figure 1). Wash the model in water and allow it to dry.

Figure 1: Clean model For primer adhesion, clean and degrease model with Zep Citrus Cleaner.

 

2. Prime and fill surfaces
Primer provides an excellent bond coat for metal adhesion. It is also an aid in surface preparation since it highlights blemishes on the model. Using an acrylic lacquer or epoxy primer, spray the model with several thin coats. Allow the primer to dry between coats. The primer can be applied from an aerosol spray can or from a paint spray gun.

Following the manufacturer’s recommendation, let the primer dry. When dry, start sanding the model with 240-grit and progress to 320-grit sandpaper to remove any imperfections. Stop sanding a surface if the PolyJet model material shows through the primer.

Inspect the model for any remaining surface blemishes. If there are imperfections, either sand the model or fill in surface mars with Bondo body filler (figure 2). Other fillers and putties will also work, but avoid UV-hardened fillers. Allow the body putty to dry and follow with spot sanding using 320-grit sandpaper. Wash the model with Zep cleaner to degrease the surface, rinse in water and dry thoroughly.

Reapply primer and inspect model for surface quality. Repeat step two if necessary.

Figure 2: Prime surface Apply a primer coat and sand the model. If any surface pits remain, fill with sandable body filler.	Figure 3: Dry sand model Sand model surface until polished by stepping through 600, 800, 1000 and 1200-grit sandpaper

 

Sanding Tips: To preserve the accuracy of your model when sanding, apply a red or white primer as the base coat and follow with gray primer. The color difference gives a visual reference that you are getting close to the model's surface.

For flat surfaces, apply a dye and block sand the part. Dye that remains shows low spots that could go undetected.

3. Sand surfaces
Electroplating may show imperfections in the model surface, it is important to sand the model to a polished finish. For some applications, a mirror-like finish may be required. Starting with 600-grit wet sandpaper, lightly sand all surface of the model (figure 3). Since this is a smoothing and polishing process, always use a light touch when sanding the model to avoid cutting through the primer coat.

When needed, follow the 600-grit sanding with 800, 1000 and 1200-grit wet sanding of all surfaces.

It is important to maintain a solid primer coat for good adhesion of the metal plating and a consistent appearance of the plated surfaces. If you have sanded through the primer coat to the PolyJet material, apply another coat of primer and re-sand the area.

Complete the model preparation with a water rinse to remove dust and debris.

4. Plating
The PolyJet model is now ready for electroplating with your selected metal. The electroplated model (figure 4) has a nickel plating for aesthetics.

Figure 4: Finished model An electroplated model, now ready for demonstration.

 

Author Acknowledgement
Associated Electroplaters, Inc. is celebrated its 50th anniversary in 2005. Al Bacon, Jr. and Jason Channell now run the business that their fathers started in 1955. The company began electroplating rapid prototypes in the early years of the technology.

Al is entering his second decade in electroplating. Jason has over 20 years experience in the finishing and plating business.
www.associatedelectroplaters.com

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