Introduction to Plastic Plating Process

1. There are many types of plastics for plastic parts: but not all plastics can be electroplated.

Some plastics and metal coatings have poor bonding strength and are of no practical value; some physical properties such as expansion coefficients of plastics and metal coatings are too different: it is difficult to guarantee their performance in a high temperature environment.

The plating layer is mostly a single metal or alloy, such as titanium target, zinc, cadmium, gold or brass, bronze, etc.; there are also dispersion layers, such as nickel-silicon carbide, nickel-graphite fluoride, etc.; there are also clad layers: Such as copper-nickel-chromium layer on steel, silver-indium layer on steel, etc. At present, the most used for electroplating is A BS: followed by PP. In addition, PS F, PC, PTFE, etc. also have successful electroplating methods: but it is more difficult.

ABS/PC plastic plating process process

Degreasing—hydrophilic—pre-roughening (PC≥50%)—roughening—neutralizing—whole surface—activating—deadhesive—electroless nickel—coking copper—acid copper—plating semi-bright nickel— High sulfur nickel plating—bright nickel plating—plating seal—chrome plating

2. Plastic parts modeling design should meet the following requirements as far as possible without affecting the appearance and use:

(1) The metallic luster will make the original shrinkage more obvious: Therefore, the uneven wall thickness of the product should be avoided: so as to avoid shrinkage: and the wall thickness should be moderate: so that the wall is too thin (less than 1.5 rn m): Otherwise it will cause poor rigidity: easy to deform during electroplating: poor adhesion of the coating: it is also easy to deform during use and 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 and dry; it will cause pollution in the next process, which will affect the quality of electroplating.

(3) The electroplating process has the phenomenon of thickening of sharp edges. The sharp edges in electroplating will cause tip discharge: cause the corner plating to bulge. Therefore, fillet transitions should be used as much as possible: the fillet radius should be at least 0.3 mm or more. Plate-shaped plastic parts are difficult to electroplating: the center part of the plated part is thinner, and the more the side is, the thicker the coating: the entire coating is in an uneven state: the flat shape should be changed to a slightly arc surface or a matte surface with orange peel . The larger the surface area of ​​electroplating: 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 [2].

(4) Minimize grooves and protrusions on plastic parts. Because deep concave parts are easy to expose plastic during electroplating, while protruding parts are easy to be scorched. The groove depth should not exceed 1/3 of the groove width: the bottom should be in 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: the contact surface with the hanging tool should be 2~3 times larger than the metal parts.

(6) The design of the plastic part should make the part easy to demold when it is sinking: otherwise, the surface of the plated part will be strained or sprained when forcibly demolding; or it will cause the internal stress of the plastic part to affect the adhesion of the coating.

(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 knurling 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 treatment.

(9) The surface of the plastic part should be guaranteed to have a certain surface roughness.

3. Mold design and manufacturing In order to ensure that the surface of plastic plating parts is free of defects, no obvious directional structure and internal stress: the following requirements should be met when designing and manufacturing molds.

(1) Do not use beryllium bronze alloy as the mold material: it should be made of high-quality vacuum cast steel: the surface of the cavity should be polished along the mold ejection direction to a mirror-bright surface: the surface with unevenness less than 0.2μm is best plated with hard chrome.

(2) The surface of the plastic part faithfully reflects the surface of the mold cavity: Therefore, 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 Xitong injection mold), and it is best to use a gate and runner with a circular cross section: the length of the runner should be shorter.

(5) There should be vent holes: 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.