Electroforming is a specialized electroplating process used to create metal parts and objects. By using electric current, a thin layer of metal can be deposited onto a model or mandrel to create an exact replica of its shape. Two of the most important parameters that determine the electroforming process are amps and volts.
What Are Amps and Volts?
Let’s first understand what amps and volts are and how they relate to electrical current flow.
Amps (Amperes)
Amps, short for amperes, measure the rate of electric current flow in a circuit. It indicates how many electrons pass through a point in the circuit per second. The higher the amperage, the greater the flow of electrons.
In electroforming, amps determine the amount of metal deposition onto the object being plated. Higher amps lead to faster deposition of metal ions onto the model surface. With lower amps, the metal deposition occurs more slowly.
Volts (Voltage)
Volts, or voltage, measure the electrical potential difference between two points in a circuit. It represents the “push” or “pressure” driving electrons to flow around the circuit.
In electroforming, volts determine the strength of the electric field that causes metal ions to deposit onto the model. Higher voltage creates a stronger electric field, resulting in faster plating. Lower voltage leads to a weaker electric field and slower deposition.
How Amps and Volts Relate in Electroforming
In electroforming, amps and volts are closely interrelated. Their relationship is governed by Ohm’s Law:
Current (Amps) = Voltage (Volts) / Resistance (Ohms)
The resistance in an electroforming circuit depends on factors like the conductivity of the plating solution and the surface area of the object being plated.
While voltage provides the driving force for metal deposition, amperage controls the actual plating rate. Finding the right balance of amps and volts is crucial for achieving uniform and quality electroformed parts.
Choosing Amps Settings
The amperage used in electroforming can range from a few amps to hundreds of amps, depending on the desired outcome. Here are some guidelines on selecting amp settings:
- Higher amps – Generally, higher amperage settings lead to faster deposition of metal. It is useful when a thick layer of plating is required in a short time. However, too high an amperage can cause issues like burning, pitting, and poor plating distribution.
- Lower amps – Low amp settings allow for slower and more controlled metal deposition. It provides time for the depositing ions to arrange themselves evenly. Lower amps may be required for plating intricate or delicate objects. However, the process takes more time.
- Size of object – Larger surface areas require higher amperages to maintain sufficient plating speed, while small objects need lower amperage to avoid excess buildup in certain areas.
- Plating thickness – Thicker coatings require higher amperages to plate faster. Thin layers need lower amperage for slow and even deposition.
- Metal used – The conductivity of the metal affects the amount of amps required. More conductive metals like copper allow higher amperages compared to less conductive metals like nickel.
- Solution conductivity – More conductive solutions allow higher amperage without overheating. Solutions can be made more conductive by adding compounds like sulfuric acid.
Selecting Voltage Settings
The voltage applied in electroforming ranges from 1 to 15 volts, once again depending on the process requirements:
- Higher voltage – Increases the plating speed by enhancing the electric field strength and metal ion movement. But excessively high voltages can cause rough deposits.
- Lower voltage – Allows for slower and more uniform plating. But the process takes longer and may not be suitable for bulk production.
- Distance between electrodes – Higher voltage is needed to drive metal deposition across larger distances between the anode and cathode.
- Plating thickness – Thicker coatings require higher voltage to sustain the electric field strength. For thin layers, lower voltages around 1-3 volts are used.
- Solution conductivity – Low conductivity solutions require higher voltage to overcome their natural resistance and enable plating. Higher conductivity reduces the voltage needs.
- Metal used – More noble metals like silver and gold need lower voltages compared to base metals like nickel and copper which need higher voltages to plate.
Balancing Amps and Volts
While amps primarily control the plating rate, both amperage and voltage settings need to be balanced to achieve quality electroformed objects.
Here are some tips on balancing amps and volts:
- Start with lower settings and gradually increase until optimal deposition is achieved. Drastic changes can ruin the plating quality.
- Higher voltages allow higher amperages while maintaining plating uniformity. But do not exceed the voltage capability of your rectifier.
- Monitor the solution temperature. Higher amps/volts generate more heat. Regulate settings to keep temperature in the optimal range.
- Use higher voltages with lower amps when plating large surface areas to get sufficient deposition without excess buildup.
- For intricate shapes, use lower voltages and amps to slowly fill in details without over-plating edges and corners.
- Adjust settings periodically as the plating thickness increases. Thicker coatings may require higher amps/volts to continue uniform deposition.
Advanced Control Methods
While manual adjustment of amp and volt settings allows reasonable control over the electroforming process, even better precision can be achieved through advanced methods like:
Pulse Plating
This involves turning current on and off at high frequencies, allowing periodic replenishment of metal ions which gives very uniform deposition.
Periodic Reverse Plating
Here the current is alternated between forward and reverse polarity. This minimizes solution concentration gradients and gives exceptionally smooth and even plating.
Computer-Controlled Power Supply
Sophisticated power supplies can be programmed to automatically adjust amperage and voltage continuously during the process based on plating parameters entered, eliminating manual intervention.
Conclusion
Properly controlling amps and volts is key to achieving high-quality, precision electroformed parts. While amperage mainly determines the plating rate, voltage provides the driving force for metal ion deposition. Finding the right balance of settings based on the object size, metal used, desired plating thickness, solution conductivity and other factors leads to optimal results. Advanced methods allow very fine control over the electroplating process. A clear understanding of the role of amps and volts enables electroformers to master this unique metal fabrication technique.
