1. Definition of electroplating
Electroplating is defined as an electrodeposition process (electrodeposition process), which uses electrolysis to attach metal to the surface of an object to form a uniform, dense, and well-bonded metal layer. Simply understood, it is a change or combination of physics and chemistry. Its purpose is to change the characteristics or dimensions of the surface of the object. For example, giving the product a metallic luster and a beautiful appearance.
2. Purpose of electroplating
The purpose of electroplating is to deposit a metal coating (deposit) on the substrate to change the surface properties or dimensions of the substrate. Such as endowing metal luster and beauty, rust prevention of articles, prevention of wear, improvement of electrical conductivity, lubricity, strength, heat resistance, weather resistance, heat treatment to prevent carburization, nitriding, size error, or repair of other parts.
3. Points Need To Be Attention To In the Structural Design Of Electroplating Parts
1) The base material is best to use electroplating grade ABS material. After ABS electroplating, the adhesion of the film is better, and the price is relatively low.
2) The surface quality of plastic parts must be very good. Electroplating cannot cover up some defects of injection, and usually makes these defects more obvious.
3) Effect of coating thickness of electroplated parts on matching dimensions
The thickness of electroplated parts will be controlled at about 0.02mm according to ideal conditions, but in actual production, there may be a thickness of at most 0.08mm, so at the position with sliding fit, the gap on one side should be controlled at more than 0.3mm, in order to achieve a satisfactory effect, this is what we need to pay attention to when we cooperate with electroplating parts.
4) The surface protrusion should be controlled within 0.1~0.15mm/cm, and there should be no sharp edges as much as possible.
5) If there is a blind hole design, the depth of the blind hole is best not to exceed half of the hole diameter, and it is responsible not to make requirements on the color of the bottom of the hole.
6) Appropriate wall thickness should be used to prevent deformation, preferably at least 1.5mm and below 4mm. If it needs to be made very thin, a reinforced structure should be made at the corresponding position to ensure that the deformation of the plating is within a controllable range.
7) The deformation of electroplating parts should be considered in the design. Since the working conditions of electroplating are generally in the temperature range of 60 degrees to 70 degrees, under the condition of hanging, the structure is unreasonable, and deformation is unavoidable. Therefore, in plastic parts In the design of the nozzle, attention should be paid to the position of the nozzle, and at the same time, there must be a suitable hanging position to prevent damage to the required surface during hanging. In addition, it is best not to have metal inserts in the plastic parts, because the expansion coefficients of the two are different, when the temperature rises, the electroplating liquid will seep into the gaps, which will have a certain impact on the structure of the plastic parts.
8) To avoid using a large plane.
After electroplating, the reflectivity of plastic parts increases, and the pits on the plane and local slight unevenness become very sensitive, which ultimately affects the product effect. This part can adopt a slightly curved shape.
9) Avoid right and sharp corners.
Designers who first make shapes and structures often design angular shapes. However, such corners are prone to stress concentration and affect the bonding force of the coating. Moreover, such a site can cause modulation. Therefore, try to change the square outline to a curved outline, or use rounded corners for transition. The shape must require a square place, and all corners and edges must be rounded R=0.2~0.3 mm.
10) Do not have too deep recesses,
Do not have small holes and blind holes. These parts are not only difficult to electroplate, but also easy to cause the residual solution to pollute the solution in the next process. Unavoidable blind holes like knobs and buttons should be seamed from the middle.
11) It is necessary to consider leaving the node parts for fashion hanging.
Nodes should be placed in an inconspicuous position. You can use hooks, slots, seams, and bosses as joints.
12) The thickness should not be too thin, and there should be no abrupt changes.
Parts that are too thin are easily deformed by heat or coating stress during the electroplating process. Sudden changes in thickness are likely to cause stress concentration. Generally speaking, the difference in thickness should not exceed twice.
13) Signs and symbols should use smooth fonts, such as round body, amber, colorful clouds, etc. It is not suitable for electroplating because of its many edges and corners. Smooth fonts are easy to form and have a good appearance after electroplating. The height of the raised text is preferably 0.3~0.5, and the slope is 65 degrees.
14) If decorative effects such as skin texture and knurling can be used, they should be used as much as possible because reducing the reflectivity of electroplated parts will help cover up possible appearance defects.
15) Try not to use threads and metal inserts, so as not to increase the process of protecting threads and inserts during electroplating.
4. Realization Of Partial Electroplating Requirements
In our design, it is often required to achieve different effects on different parts of the surface of the plastic part. We usually use the following four methods to achieve this effect:
1). Break down into small pieces. Different effect parts are made into small parts and finally assembled together. Under the condition that the shape is not too complicated and the components are in batches, the cost of opening a small set of mold injections will form a more obvious price advantage.
2). Add insulating ink. If it is not required to be electroplated in parts that do not affect the appearance, it can usually be processed by adding insulating ink and then electroplating, so that the parts sprayed with insulating ink will have no metal coating and meet the requirements. In fact, this is a part we often involve in the design, because the parts after electroplating will become hard and brittle, which is the result we don’t want to get, especially on parts such as buttons, its crank arm is The part that does not want to be electroplated is because we need it to have sufficient elasticity, and local electroplating is very necessary at this time. It is also commonly used in other cases. For lightweight products like PDAs, the general circuit board is directly fixed on the plastic shell. In order to prevent the influence on the circuit, the parts that are in contact with the circuit are usually insulated. At this time, ink is often used for partial treatment before electroplating.
3). Similar to the process of two-color injection molding. Generally, if there is a two-color injection machine, ABS and PC can be injected in different stages, and then electroplated after being made into plastic parts. Under such conditions, due to the different adhesion of the two plastics to the electroplating solution, the part of ABS will be electroplated. The effect of PC part does not have the effect of electroplating, which meets the requirements.
4). the Second injection. It is to divide the workpiece into two parts. First, one part is injected and then electroplated. The processed product is then put into another set of molds for a second injection to obtain the final sample.
5. Requirements For Mixed Plating Effect On Design
In the design, we often use the effects of high-gloss plating and etching plating to work together to obtain a special design effect on a product. Usually, it is recommended to use a smaller etching pattern in the design, so that the effect will be better, but in such a design, In order not to cover up the effect of the etching pattern by electroplating, sometimes electroplating is not performed after two layers of electroplating. The consequence of this is that the nickel on the second layer of electroplating will be easier to oxidize and change color, which will affect the effect of the design.
6. Introduction Of Electroplating Effect
High-gloss plating
The realization of the effect of high-gloss plating usually requires good polishing of the mold surface, and the effect is obtained after the injected plastic parts are treated with light chrome.
Matt plating
The realization of the effect of matte plating usually requires the surface of the mold to be well polished, and the injected plastic parts are treated with chromite to obtain the effect.
Pearl chrome
The realization of the effect of pearl chrome plating usually requires good polishing of the mold surface, and the effect obtained after the injection of plastic parts is treated with pearl chrome.
Etching plating
The realization of the effect of etching and electroplating usually requires that after the surface of the mold is treated with different effects of etching, the injected plastic parts are treated with light chrome to obtain the effect.
Partial plating
By adopting different methods, the surface of the finished part has no electroplating effect, forming a contrast with the electroplated part, forming a unique design style.
Color plating
By using different electroplating solutions, the metal deposited on the surface of the plastic part after electroplating will reflect different luster, forming a unique effect.