Plastic plating advantages:
1. Easy to shape and good shape.
2. Light weight.
3. Good corrosion resistance.
4. Good drug resistance.
5. Excellent electrical insulation.
6. Low price.
7. Can be mass produced.
Plastic plating Quality influencing factors:
Injection machine selection:
Improper selection of the injection machine may sometimes cause large internal stress on the part due to excessive pressure, improper nozzle structure or mixing, which affects the bonding force of the coating.
Plastic plating parts selection:
There are many types of plastics, but not all plastics can be electroplated. Some plastics and metal coatings have poor bonding strength and have no practical value; some physical properties of plastics and metal coatings, such as expansion coefficients, are too different, and it is difficult to ensure their performance in a high temperature difference environment. At present, ABS is the most used for electroplating, followed by PP. In addition, PSF, PC, PTFE, etc. also have successful electroplating methods, but they are more difficult. [2]
Plastic part modeling:
On the premise of not affecting the appearance and use, the plastic part shape design should meet the following requirements as much as possible.
1) The metallic luster will make the original shrinkage more obvious, so the uneven wall thickness of the product should be avoided to avoid shrinkage, and the wall thickness should be moderate to avoid the wall being too thin (less than 1.5 mm), otherwise It will cause poor rigidity, easy deformation during electroplating, poor adhesion of the coating, and deformation during use to cause the coating to fall off.
2) Avoid blind holes, otherwise the treatment liquid remaining in the blind holes will not be easy to clean, which will cause pollution in the next process and affect the quality of electroplating.
3) The electroplating process has the phenomenon of thickening of sharp edges. The sharp edges in electroplating will cause the tip discharge, causing the corner plating to bulge. Therefore, round corners should be used as far as possible to transition, and the corner radius should be at least 0.3 mm. Flat-shaped plastic parts are difficult to electroplate. The center part of the plated parts has a thin coating. The more the edge is, the thicker the coating will be. The entire coating is uneven. Change the flat surface to a slightly rounded surface or use an orange peel pattern to make a matte surface. . The greater the surface area of the plating, the greater the difference in gloss between the center and the edge. A slightly parabolic surface can improve the gloss uniformity of the plating surface.
4) Minimize grooves and protrusions on plastic parts. Because the deep concave part is easy to expose plastic during electroplating, and the protruding part is easy to be scorched. The depth of the groove should not exceed 1/3 of the groove width, and the bottom should be a circular arc. When there is a grid, the hole width should be equal to the beam width and less than 1/2 of the thickness.
5) The plated parts should be designed with enough mounting positions, and the contact surface with the hanging tools should be 2 to 3 times larger than the metal parts.
6) The design of the plastic part should make the part easy to demould when it is sinking, otherwise the surface of the plated part will be strained or sprained during the forced demolding, or the internal stress of the plastic part will be affected and the coating bonding force will be affected.
7) When knurling is required, the knurling direction should be consistent with the demolding direction and be in a straight line. The distance between the knurled stripes and the stripes should be as large as possible.
8) Try not to use metal inserts for plastic parts, otherwise the inserts will be easily corroded during pre-plating.
9) The surface of the plastic part should be guaranteed to have a certain surface roughness.
Mold design:
In order to ensure that there is no defect on the surface of the plastic plating part, no obvious directional structure and internal stress, the following requirements should be met when designing and manufacturing the mold:
1) Do not use beryllium bronze alloy as the mold material, but should be made of high-quality vacuum cast steel. The surface of the cavity should be polished to a mirror-brightness along the mold ejection direction, and the unevenness should be less than 0.2mm. The surface is best plated with hard chrome.
2) The surface of the plastic part faithfully reflects the surface of the mold cavity, so the mold cavity of the electroplated plastic part should be very smooth, and the surface roughness of the mold cavity should be 1 to 2 levels higher than the surface roughness of the part.
3) Parting surface, weld line and core inlay line cannot be designed on the plating surface.
4) The gate should be designed at the thickest part of the part. In order to prevent the melt from cooling too fast when filling the mold cavity, the gate should be as large as possible (about 10% larger than the ordinary injection mold). It is best to use the gate and runner with circular cross section, and the runner length should be shorter.
5) Exhaust holes should be reserved to avoid defects such as air filaments and air bubbles on the surface of the workpiece.
6) When selecting the ejector mechanism, ensure the smooth demolding of the part.
