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Common surface treatment knowledge of rapid prototyping -- water plating

Oct 13,20

Common surface treatment knowledge of rapid prototyping -- water plating

Water plating is an electrochemical process, the popular understanding is the need for electroplating product parts soaked in electrolyte, and then pass the current, electrolytic way to make metal deposition on the surface of the parts to form uniform, compact, good adhesion of the metal layer surface processing method.

1.The action of electroplating

Whether water plating or vacuum plating, the main role of electroplating is described below
1Decorative surface, plastic parts electroplating can make the surface of plastic parts produce metallic luster.
2Anti-corrosion, such as electroplating on the surface of screws to prevent rust.
3Anti-wear, such as electroplating hard chromium can be added to the surface of electroplating parts, so that electroplating parts more wear.
4Improve electrical properties, such as copper plating and gold plating can improve electrical conductivity.
2.Process flow of water plating

The technological process of water plating includes three processes: pre-plating, electroplating and post-plating.The main function is to clean the surface of parts before plating, to prepare for electroplating.
  1. The process flow before plating is generally destress - degreasing, washing - roughening, washing - neutralization, reduction - acid leaching, washing - sensitization, washing - activation, washing - electroless plating, washing - electroplating.
2Electroplating process flow is generally before plating products -- activation -- plating bottom -- plating surface layer -- washing -- drying.
3The post-plating treatment is passivation treatment and hydrogen removal treatment.
3.Introduction of suitable materials and coatings for water plating

There are not many commonly used plastic materials for water plating, the most common is ABS, and the ABS of electroplating level is good. Other commonly used plastics, such as PP, PC and PE, are difficult to water plating.
1Common coatings include copper, nickel, and chromium.
Copper: generally used for plating bottom, commonly known as playing copper bottom.Nickel: Silver, mainly used on ordinary surfaces or as a precursor to chrome plating.
Chrome: Bright silver, used for highlighting surfaces.

2Common surface colors are gold, silver, black, gun color.
Gold: it can be achieved by plating real gold and plating hexavalent chromium (false gold).
Silver: can be achieved by nickel,  chromium, silver.
Black: can be achieved by black chrome, black zinc.
Gun color: can be achieved by alloy plating.

3Common electroplating effect highlights, matte, mist surface, mixing, etc.
The surface of the product forms a highlight effect, usually silver.The premise is that the plastic mold needs to be highly polished, and the plastic parts processed by CNC machine can achieve the effect by chrome plating.
Matte: The product surface forms the general bright effect. On the premise of general polishing treatment of plastic mold, CNC machining parts through chromium plating to achieve the processing effect

Foggy surface: The surface of the tea farmer forms a hazy effect.The realization premise is the plastic mold surface etching or sandblasting treatment, injection molding parts through chromethylene plating to achieve the effect.
Mixing: To achieve two different effects on the same piece of glue, such as the coexistence of highlights and matte.These adhesive parts are generally processed by CNC machine or laminating adhesive parts, and then electroplated to achieve the effect.
4Can you make color plating by water plating?Can be achieved, but the process is complex, high defect rate, so less to do color plating.
Color roughly process water plating process for plating products - activation - water - water sealing hole, color plating, spray cleaning, washing, drying, quality inspection, packaging, warehousing.

4.The thickness of the coating

There are many factors affecting the coating, water coating thickness is less than 1.0 m, greater than 0.1 m, the plating manufacturer's technical level affects the thickness of the coating, in the structural design, the coating is generally calculated by 0.03mm.
If the structure of the coating has special requirements, before the plating should be clear to the plating manufacturer, so as not to affect the structure of the coating too thick.

5.The realization of local electroplating

Why do we need partial electroplating?The reasons are as follows:
  1. Water plating changes the material properties of plastic products by making them hard and brittle, while some structural parts of the products do not require water plating.Such as screw column, buckle position, hot melt column, etc., need local electroplating.
2)Product appearance process requirements, some places do not need electroplating treatment.
3)For special applications, because electroplating will conduct electricity, some places do not need to conduct electricity, so local electroplating is needed.
The realization of local electroplating is as follows: 

1)Apply insulating ink where electroplating is not required.
2)Remove plating where it is not needed.
3)Second cladding, first cladding part of the membrane electroplating treatment, and then put the electroplated plastic parts into the mold for the second cladding.
4)If the appearance process is acceptable, the parts to be electroplated and the parts not to be electroplated shall be disassembled into two different parts.
6.Requirements for structural design of electroplated plastic parts

Whether water plating or vacuum plating, the premise of good electroplating for plastic parts design to be reasonable, to meet the basic requirements of electroplating process.
1)Choice of materials.Vacuum electroplating plastic materials can be many, generally no special requirements.In case of water plating, electroplated ABS shall be selected as the plastic material.
2)The surface of plastic parts should not have defects, because electroplating can not cover up the defects, only make the defects magnified.If there is shrinkage on the surface of plastic parts, it is not obvious before electroplating, but it will be very clear after electroplating.
3)Do not have sharp edges on the surface of plastic parts. Sharp edges are easy to cause the coating to fall off due to weak adhesion. The transition edge should be rounded.
4)It is better not to have a boss more than 0.50mm high and a groove 0.30mm deep on the surface of the plastic parts, and the transition edge should be rounded.
5)If the plastic parts have blind holes, the depth of the blind hole should not exceed 1/2 of the diameter, in order to avoid the blind hole too deep bottom plating effect is poor or plating is not in place.
6)Plastic parts good structural strength, not easy deformation, because of water plating, the working temperature is higher, if the structural strength is poor, deformation is inevitable.
7)For plastic parts with poor structural strength and easy deformation, the product should be designed with reliable fixed structure so as to correct the deformation defects after water plating.
8)Small plastic products pay attention to the design of the platform.Because water plating is directly soaked in water, if the nozzle cannot be used as a platform, it is difficult to locate the product without designing the platform.