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Rapid prototype -- Common Surface Treatment knowledge (Spraying)

Oct 14,20

Rapid prototype -- Common Surface Treatment knowledge (Spraying)
Spraying
Spraying is the most common type of rapid prototyping surface treatment, whether plastic parts or hardware parts are so, spraying generally includes oil spraying, powder spraying, etc., common is oil spraying

1. Coating
Spray coating commonly known as paint, paint is made up of resin pigment solvent other additives have the following effect
1)The function of resin is to connect pigments with pigments and give the film gloss and hardness. The powder is natural resin and synthetic resin,
2)The purpose of pigments is to show the desired color of the coating. They are divided into body pigments, pigments and special pigments,
3)The solvent is used to dissolve the resin and make the paint flow easily. It is divided into true solvents and cosolvent fillers,
4)Other additives main role is to enhance the stability of the coating, divided into stabilizer dispersant anti-settling agent and other additives.
Diluent can also be added, its main role is to practice paint, paint is diluted to the concentration that can work and can reduce the cost of paint.
 
  1. Spraying process flow is introduced
 
  1. Most of the plastic spraying generally have two paints, the color of the surface is the top paint, the most surface transparent coating called protective paint its process is as follows
1)Early cleaning, such as electrostatic dust removal.
2)Spray a finish coat, which is usually a visible color on the surface;
3)Baking finish paint, divided into room temperature natural drying oven drying;
4)Cooling topcoat, special oven drying needs cooling;
5)Spray protection paint, protection paint is generally used to protect the top paint, most of the transparent paint;
6)Fixed line protection paint;
7)QC check, check whether meet the requirements.

3.Spraying method
Spraying methods are divided into manual spraying and automatic spraying.
1)Manual spraying is not easy to control the coating thickness and quality due to human factors. It is mainly used in small batch production and the production of color sample.
2)Automatic spraying is realized by automatic coating line, there are automatic and semi-automatic, automatic has multiple nozzle, through adjusting different angles to achieve uniform coating thickness, automatic spraying quality reliable, uniform color and thickness, suitable for mass production.

4.The thickness of the coating
The coating thickness mainly affects the following aspects:
1)The quality of color is influenced by the difference of color on the surface with different thickness
2)Coating thickness affects wear resistance and adhesion;
3)The coating thickness affects the structure, in some places where the rubber parts fit, such as the key, too thick affect the assembly, too thin easy to wear out;
4)Affect the cost, too thick will increase the amount of paint, thus increasing the cost, too thick will also affect the spraying time, indirectly increase the production cost.
Therefore, when spraying, the thickness of the coating must be controlled.
1)Spray two coats of paint, usually 8.0~12 μm coat thickness.
2)The thickness of protective paint atlas is generally 8.0~15μm
3)If three coats of paint are applied, one coat in front of the finish is called a primer. The primer is used to enhance the metallic luster of the finish, such as silver.Can also be used to mask plastic injection molding color, enhanced finish, usually similar to the finish color, primer thickness is generally 3.0~6.0 μm.

5.Oil injection quality inspection
Products finished with oil injection shall pass the inspection, and the requirements are as follows:
1)Appearance requirements: the spray layer should be uniform, and no defects such as lack of oil, flow oil, sharp point, scratch and rust are allowed.
2)Adhesion test: on the surface of the spraying layer, use a blade to delimit the squares with row spacing and column spacing of 1.0cm, which are 10 rows and 10 columns, scratch the coating, and then stick it on the surface with 3M adhesive paper to tear it vertically for once, and the spraying layer shall not fall off.
3)Anti-rust experiment: put the sprayed parts into a test box (45±5) with a pH value of 7~8. After 24H, take it out, no obvious rust occurs on the outer surface and inside of the workpiece.
4)Spray layer hardness test: spray oil with HB pencil, do not cut sharp, with general handwritten strength to test surface at an Angle of about 45° on the spray layer, and then wipe clean with cloth glue water, the surface only allow slight scratches, but can not be cut, exposed.
6.Rubber oil
Rubber oil is also known as elastic paint and feel paint. Rubber oil is a two-component paint with high elasticity. After being sprayed with the paint, the product has a special soft touch and high elastic surface feel.Impact resistance, recoverability, soft handle, even smooth film and strong chemical resistance are the best characteristics of the product.Rubber oil drying fast, convenient construction, all spraying product appearance mist surface transparent, comfortable high-grade, make the decorated product surface effect noble and elegant.
The disadvantages of rubber oil are high cost, general durability and permanent ease of shedding.
Rubber oil is widely used in communication tea farmers, audio-visual products, MP3, mobile phone shell, decorations, decorative boxes, leisure and entertainment products, game console, craft gifts, beauty equipment and so on.

7.UV paint
UV is the English abbreviation of ultraviolet ray, commonly used UV wavelength application range is 200~450nm.
UV paint needs to be cured in ultraviolet light exposure table.
UV paint features:
1)Transparent bright, UV paint brightness through additives to adjust.
2)High hardness.
3)Fast fixed speed and high production efficiency.
4)Temperature curing, no thermal deformation, and environmental protection.
The function of UV paint:
1)Protect the finish from scratch and abrasion.
2)Stiffen the surface.
3)Brighten the surface.