16. Wildcard Week
The objective of this wildcard week was to design and produce something utilizing a digital fabrication process that incorporates computer-aided design (CAD) and manufacturing (CAM) which has not been covered in any of the previous academic assignments.
To make the most of this week, I decided to broaden my hands-on skills by experimenting with three distinct industrial and prototyping processes: Sandblasting, Electroplating, and Thermoforming.
1. Sandblasting Process
What is it?
Sandblasting (abrasive blasting) is a surface-finishing technique where a high-pressure stream of abrasive material is forcibly propelled against a surface. It is commonly used to smooth rough surfaces, shape profiles, or etch patterns onto materials like metals, and plastics by wearing down the exposed areas.
For this process, I created custom masks by vectorizing artwork in Adobe Illustrator and cutting adhesive vinyl masks using the Roland VersaSTUDIO GS2-24 cutter combined with Cut Studio software. These vinyl stencils were carefully applied onto a painted metal bottle before placing them inside the sandblasting chamber to achieve a engraved effect. Additionally, I ran an experimental test to investigate how sandblasting can be utilized to post-process and smooth out the layer lines of a raw FDM 3D printed parts.
Vectorizing
To obtain clean cutting paths for the vinyl machine, the original raster images needed to be translated into crisp vector geometries.
Step 1: Import an image directly into Adobe Illustrator by creating a new document.
Step 2: Navigate into the tool bar, open the Object menu bar, open the Image Trace submenu, and click on 'Create' to begin processing the image into traces.
Step 3: Open the Advanced Image Trace Options panel to fine-tune the thresholds, paths, and corners until the preview lines match your target shape Once satisfied, click Expand to convert the live trace into editable vector vector paths and anchor points.
Step 4: Adjust the vector paths as needed and export the finalized graphic in a format compatible with your cutting software. In this case I inverted the color scheme to a negative version of the original, so when I sandblast the results is just like the original image.
2. Electroplating Process
What is it?
Electroplating is an electrochemical deposition process where metal ions in a chemical solution are reduced via an electrical current to form a thin, coherent metal coating over a conductive substrate. For non-conductive parts (like 3D prints), a specialized conductive coating must be applied before submersion to close the electrical circuit.
For this experiment, I downloaded and 3D printed a mockingjay model from Thingiverse. To make the 3D print surface electrically active, I applied a layer of conductive paint. Then formulated the electrolyte solution by measuring copper sulfate and dissolving it into distilled water until it achieved full saturation. Before applying the electrical current, I connected the conductive 3D printed piece to the negative terminal (Cathode) and a pure copper plate to the positive terminal (Anode). Once everything was secure, I applied voltage and current for approximately one hour, and some copper ions began bonding onto the print.
Electroplating Process Step by Step
Detailed workflow for preparing, calculating, and executing the electrodeposition process on a 3D printed model.
Step 1: I 3D printed a 4cm mockingjay model I found on Thingiverse with PLA.
Step 2: Then I applied three uniform coats of conductive paint. In this case, I used the MG Chemicals 838AR Total Ground carbon conductive paint. As indicated on its data sheet, I waited a 3 minute flash-off period between layers to ensure proper solvent evaporation and prevent the acrylic lacquer from softening the PLA fine details.
Step 3: Calculate and measure the required amount of dry copper sulfate crystals using a precision digital scale to achieve the correct concentration target for our electrodeposition tank.
The standard formulation requires a ratio of 200 grams of Copper Sulfate Pentahydrate (CuSO₄·5H₂O) per 1 Liter of distilled water to ensure an optimal concentration of copper ions.
Step 4: Mix the measured copper sulfate crystals thoroughly into a beaker of pure distilled water. Stir continuously until the crystalline solids are completely dissolved, yielding a clear, bright blue electrolyte fluid. For this exercise I used 1L of distilled water and dissolved exactly 200 grams of CuSO₄.
Step 6: Configure and document the finalized voltage, current, and time variables on the laboratory bench power supply unit. Maintain tight regulation to avoid scorching or burning the delicate deposited layer.
Electroplating is governed by Faraday's Laws of Electrolysis, which state that the mass of altered material is directly proportional to the electric current. To achieve a smooth, bright copper finish without burning the piece, we must balance the Total Surface Area (A) with a safe Current Density (J) limit before powering the system.
Mathematical Target: I = A × J
Estimated Area (A): ~50.26 cm² (0.5026 dm²). Calculated treating the 4 cm model as a bounding sphere (4 × π × r²) to establish an upper geometric framework.
Target Current Density (J): 0.015 A/cm². Standard conservative limit recommended for carbon-coated substrates to prevent localized hotspots.
Ohmic Analysis: The massive divergence between theory and reality is governed by Ohm's Law (I = V/R). According to the product's Technical Data Sheet (TDS), the MG Chemicals 838AR carbon paint has a high surface resistance of 100 Ω/sq at a 50 μm thickness. This initial resistance bottleneck forced the power supply to scale up to 32.3V just to drive a minimal functional current of 5 mA through the piece.
Analysis of Plating Failures & Boundary Parameters
An examination of deposition irregularities, electrical constraints, and the analytical logic used to solve operational bottleneck problems.
Close-up Analysis: The plating was only partially successful. Copper deposition occurred predominantly on the localized boundaries where the cathode wire made direct contact and at the fluid line interface, leaving the deeper surfaces bare.
Error 1 (Substrate Resistance Bottleneck): The primary failure mode was governed by the electrical constraints of our conductive layer. Unlike silver or copper-filled coatings, the carbon-pigmented acrylic lacquer introduces a substantial initial resistance across complex organic geometries. This caused an immediate voltage drop away from the contact clip, restricting ionic bonding to the nearest low-resistance paths.
| Property | Value / Specification |
|---|---|
| Surface Resistance | 100 Ω/sq (50 μm) |
| Volume Resistivity | 0.63 Ω·cm |
| Adhesion Rating (PLA) | 5B (Excellent Cross-Hatch) |
| Full Cure Parameters | 24 hours Room Temp |
*Optimization Lesson:* For future trials using carbon lacquers, burnishing the completely cured surface with a micro-abrasive cloth or graphite powder can mechanically align the carbon atoms, dropping the initial surface resistance significantly before immersion.
2. Thermoforming Process
What is it?
Thermoforming is a manufacturing technique where a plastic sheet is heated to a pliable forming temperature, stretched over or into a single-surface mold, and held against the mold by applying vacuum pressure. Once cooled, the plastic retains the details of the master mold shape and can be trimmed for final assembly.
For this process, I experimented with creating custom molds using 3D printing parameters to test the precision limits and geometrical constraints of vacuum forming over rigid plastics. I used a polystyrene sheet cut precisely to match the machine's dimensions and evaluated how different shape factors ranging from strict geometric configurations to low-profile relief silhouettes behave during the critical cooling and demolding release phases.
Thermoforming Process Step by Step
Creating solid master tooling geometries capable of withstanding both the temperature shifts and the intense directional suction forces of the vacuum cell. Securing raw material stocks, dialing thermal boundaries, and coordinating mechanical controls to guarantee optimal plastic deformation.
Step 1: I 3D modeled a figure similar to a LEGO brick on Onshape, I decided use this shape to analyze interlocking tolerances and vertical wall restrictions.
Step 2: The master piece was 3D printed with translucent PLA filament, keeping solid perimeter structures to prevent shell collapse under thermal stress.
Step 3: Measure the raw styrene material sheet stock and cut it directly down to 54 cm x 75 cm, which matches the exact dimensions of the thermoformer clamp bed framing workspace.
Step 4: Position the prepared plastic sheet directly onto the structural perimeter frame and clamp it down safely over the bed to seal the pressure zone.
Step 5: Connect the pneumatic high-pressure air line manifold to the machine input valves and elevate the main workspace bed frame upward.
Step 6: Arrange and position the target 3D printed master molds over the thermoformer lower tooling baseplate array with adequate separating clearances.
Step 7: Turn on the primary temperature controller instrumentation and ramp the thermal setting window up to 200°C to heat the sheet to its soft transition point.
Step 8: Once the sheet stretches into its pliable state, engage the pump startup button (arranque de bomba), drive the piston assembly downward, and actuate the main pneumatic air valve to form the part.
