Defective 11. Primer Not Dry

Description:

The primer is not completely dried in the curing process, and the position that is not dried after vacuum plating, and the paint will be scraped off by hand

Analysis of the causes:

1. UV energy is too weak

2. The product structure is special and there are too many dead corners

3. Fault of UV machine

Key points of quality control:

1.  Confirm whether the number of strong and weak lamps and light energy of UV furnace are consistent with the operation instructions
2. Try to confirm before production and fix production parameters before production
3. Regularly check whether the equipment is inspected and maintained as required, and confirm the maintenance records

Defective 12. Poor Etching

Description:

Poor etching occurs on the surface of products with etching. Compared with the standard vacuum plating sample, the etching effect is not obvious

Analysis of the causes:

1. Primer spraying is too thick

2. Inappropriate primer selection

3. The product design is too shallow in terms of etching

Key points of quality control:

1. During the production process, confirm whether the spraying times and spray gun distance are consistent with the operation instructions, and compare with the standard sample for confirmation during the production process.
2. The etched products are generally thin coated , which shall be tested and confirmed before production
3. Test and confirm before production, and ensure that the etching effect is consistent with the standard sample.

Defective 13. Primer Whitening

Description:

After the primer is cured by UV, the coating surface is dry, the interior is not completely dry, and the uncured part is milky white

Analysis of the causes:

1. The primer coating is too thick, and oil accumulations occur in some parts.

2. The standing time after the primer coating is too long

Key points of quality control:

1. During the production process, confirm whether the spraying times and spray gun distance are consistent with the operation instructions, and compare with the standard sample for confirmation during the production process.
2. Supervise the spraying of UV primer. UV curing is required within 6 minutes after spraying

Defective 14. Fingerprint

Description:

After spraying the UV base or coating the product, the fingerprints that are felt by hand and flow down cannot be wiped.

Analysis of the causes:

1. The product is not firmly clamped, and the hands touch the product after spraying the UV background

2. The handprints on the material surface are not wiped clean

Key points of quality control:

1. During fixture, confirm whether the operation method is consistent with the operation instruction. After clamping, confirm the product status and the rationality of the fixture.

2. During material pre-treatment, confirm whether the operation method is consistent with the operation instruction

Defective 15. Plating color

Description:

Some parts on the surface of the plating layer is white or blue, which is obviously different from that of the normal plating layer

Analysis of the causes:

1. Primer is not dry
2. The baking time of the top coat is too long

Key points of quality control:

1. Confirm whether the actual parameters of the UV furnace are consistent with the operation instructions before production, and confirm the product quality after UV curing
2. When baking the finish coat, confirm whether the parameters set by the oven are consistent with the requirements of the operation instructions

More in the next chapter. Follow LKKER SCM Linkedin Page for chapter updates. 

About LKKER SCM

LKKER SCM Co., Ltd is a member company of LKKdesign Group, 100% owned by LKKdesign Group which is founded in 2004. LKKER SCM is a one-stop product development and customized supply chain solution provider. We offer services from design to manufacturing covering industrial design, mechanical design, electronics engineering, rapid prototype, tooling, pilot production, and mass production. LKKER SCM has been recognized as Indiegogo Recommended Prototyping & Manufacturing Expert since 2019.

LKKdesign Group is a regular product design award winner worldwide. Being the largest and top-tier design house in China, LKK has won 521 design awards since company establishment. LKKdesign is recognized as the National Industrial Design Center by The Ministry of Technology since 2013. Key investors of LKKdesign include Fortune Capital, China Culture Industrial Investment Fund, and Green Pine Capital Partners.

LKKER SCM partners with you to develop your product and get it to market quickly, efficiently, and economically. We have the design expertise, engineering knowledge, and manufacturing know-how to tailor solutions that work for you and your product in these sectors:

Turnkey Designs Electronic Design Mechanical Design Assembly Process Design Metal & Plastic Enclosure DFM Certification Support Prototypes Builds NPI Project Management

Supply Chain Development Smart Product Development Alternatives Solution QC, QA, and Delivery Manufacturing Operation Supplier Management Presence in China Transfer to High Volume Manufacturing Ship Direct to Customers

 

Defective 5. Electroplating semi-transparent

Description:

The translucent and pinhole light transmission properties are similar, and they also occur on PC transparent or translucent materials that require cover mold plating. When illuminated with light, the light passes through the coating position.

Analysis of the causes:

1. The amount of aluminum wire in the plating furnace is too small to form semi-permeability

2. The current through the tungsten wire is set too small in the plating furnace

3. The vacuum pressure in the electroplating furnace is too high

4. Air leakage in a vacuum furnace

5. Insufficient coating time

Key points of quality control:

1. The amount of aluminum wire in the plating furnace is too small to form semi-permeability 2. The current through the tungsten wire is set too small in the plating furnace
3. The vacuum pressure in the electroplating furnace is too high
4. Air leakage in the vacuum furnace
5. Insufficient coating time

Defective 6. Plating Burnt/Black Plating

Description:

The yellowing or whitening of the surface of the coating is obviously different from that of the standard plate.

Analysis of the causes:

1. There is air leakage in the vacuum furnace

2. The coating time is too long

3. The vacuum pressure of the vacuum furnace is too high

4. The current passing through the tungsten wire is too strong

5. There is a fault during the operation of the equipment

Key points of quality control:

1. Confirm whether the pressure gauge can reach the set standard pressure during the operation of the vacuum furnace.

2. Confirm whether the actual current parameters are consistent with the “Operation Instructions”, and require adjustment if they do not match.

3. Confirm whether the pressure gauge parameters are consistent with the “Operation Instructions”, and require adjustment if they do not match

4. Confirm whether the parameters in the benchmark book are consistent with the actual parameters, and require adjustment if they do not match.

5. Regularly check whether the equipment is inspected and maintained as required, and confirm the maintenance records

Defective 7. Accumulated oil

Description:

Oil deposits generally appear in the product； Edge or angular position, commonly known as runny oil. target； Depending on the hypertrophy, there is a feel.

Analysis of the causes:

1. Improper spraying technique, too thick spray film

2. Not drying in time after spraying, too long standing time

3. The viscosity of paint spraying is too low

4. The oil volume and air pressure of the spray gun are too high

Key points of quality control:

1. In the production process, confirm whether the spraying times and the distance of the spray gun are consistent with the “Operation Instructions”, and compare and confirm with the sample during the production process

2. Supervise the spraying of UV primer, and it needs to pass UV within 6 minutes after spraying

3. Confirm the paint before production, and deal with the bad paint in time

4. During the process inspection, confirm whether the spray pressure is within the standard range of the “Working Instructions”

Defective 8. Thin-oil

Description:

Contrary to oil accumulation, it is mainly caused by uneven local spraying, showing orange peel, dense pinholes and other phenomena.

Analysis of the causes:

1. Improper spraying technique, too thin spraying film thickness

2. Too high spraying viscosity, which is not conducive to operation

3. The fuel volume of the spray gun is too small / the air pressure is too small

Key points of quality control:

1. In the production process, confirm whether the spraying times and the distance of the spray gun are consistent with the “Operation Instructions”, and compare and confirm with the sample during the production process.
2. Confirm the paint test spray before production, and deal with the bad paint in time
3. During the production process, confirm whether the oil quantity and air pressure of the spray gun are within the standard range of the “Working Instructions”

Defective 9. Chromatic Aberration

Description:

Produces local or overall color differences on the surface of the coating. Generally, the overall color difference needs to take the standard sample as a reference, and the overall color is darker or lighter than the standard plate.

Analysis of the causes:

1. Improper spraying technique, a too thick or too thin topcoat

2. Too little or too much air pressure on the spray gun

3. Too little or too much fuel in the gun

4. The color difference of the paint itself

5. Color difference of electroplating coating

6. High humidity and moisture absorption

Key points of quality control:

1. In the production process, confirm whether the spraying times and the distance of the spray gun are consistent with the “Operation Instructions”, and compare and confirm with the sample during the production process

2. During the production process, confirm whether the air pressure of the spray gun is consistent with the parameters of the “Operation Instructions”

3. During the production process, confirm whether the oil quantity of the spray gun is consistent with the parameters of the “Operation Instruction”

4. After the paint is toned, the color of the first piece is the same as the standard sample when confirmed

5. Confirm that the parameters of the electroplating furnace are consistent with the parameters of the “Operation Instructions”

6. Regularly confirm and record the temperature and humidity of the workshop (standard: relative humidity 65%±10)

Defective 10. Crack

Description:

Linear cracks on the UV primer or on the surface of the material are more obvious under the reflection of light or through light transmission. Cracks tend to worsen over time.

Analysis of the causes:

1. The UV energy is too strong

2. The UV primer is sprayed too thickly

3. Degreasing solvent is too strong

4. The UV primer is too strong, and the solvent penetrates into the material, causing cracking

5. The internal stress of the material is too large, and it is cracked by normal UV irradiation or solvent degreasing

Key points of quality control:

1. Confirm whether the number of strong and weak lamps in the UV furnace and the light energy are consistent with the “Operation Instructions”

2. In the production process, confirm whether the spraying times and the distance of the spray gun are consistent with the “Operation Instructions”, and compare and confirm with the sample during the production process.

3. Before using different batches of flux, make a trial to confirm, and then put into production

4. Different batches of primer should be tried and confirmed before use, and then put into production

5. When the material is inspected, it will be confirmed as a trial production according to the standard process

More in the next chapter. Follow LKKER SCM Linkedin Page for chapter updates. 

Introduction to Vacuum Plating:

Vacuum plating mainly includes vacuum evaporation, sputtering, and ion plating. They are all used to form various metal and non-metal films on the surface of the product by distillation or sputtering under vacuum conditions, so as to achieve the effect of electroplating.

LKKER SCM currently uses mainly vacuum evaporation. Vacuum evaporation (vacuum evaporation coating) is a technology in which the evaporated material is heated by an evaporator to vaporize it under vacuum conditions, and the evaporated particle stream is directly shot to the product and deposited to form a solid film on the product.

The film material (aluminum wire) is placed in the evaporation source (tungsten wire) in the vacuum chamber. Under high vacuum conditions, the evaporation source heats up to make it evaporate. After the atoms and molecules of the film material vapor escape from the surface of the evaporation source, they are directly When it reaches the surface of the product to be plated, due to the low temperature of the product, it condenses to form a film.

In terms of the production process, LKKER SCM has expanded from a single manual electroplating line in the original Shenzhen Guanlan factory to a vacuum electroplating department integrating automatic and manual lines in the current Tangxia factory.

Introduction to Electroplating process:

Material degreasing → cover mold → clamping → dust removal → UV spraying

→UV Curing → Coating → Finishing → Baking → Inspection → Packaging

A sketch of the effect of vacuum plating:

Vacuum plating process (1): manual production line process

Vacuum plating process (2): automate production line process

Defective 1. Lines/dust spots

Description: The raised granules or lines on the surface of the product are bad, and the distribution is irregular.

Analysis of the causes:

1. The surface of the material is not cleaned or cleaned in place
2. Invisible wool (plastic wire) produced at the corners of the product during the molding process
3. Too much dust in the air or on the floor
4. Dust from the workshop vents
5. Flying dust inside the equipment (such as UV machine, etc.)
6. Paint pollution or poor paint
7. Flying dust or fibers/hair on the human body falls on the product during operation

Key points of quality control:

1. When pre-processing materials, confirm whether the operator’s dust removal method is in accordance with the requirements of the “Operation Instructions”
2. When the materials are received, refer to the standard template and “Inspection Benchmarks” for confirmation
3. Regularly confirm the workshop “3S” during the inspection process
4. Confirm the use of the ventilation system during the process inspection, and confirm whether the ventilation equipment is regularly inspected and maintained
5. Regularly check the equipment maintenance records and “3S” to confirm whether the equipment is regularly inspected and maintained.
6. Before using the paint, test spray to confirm, and replace the bad paint in time.
7. Check whether the workshop workers wear electrostatic clothes/caps as required Wait

Defective 2. Oil stains/oil spots

Description: The concave shape on the surface of the product is not good, the shape is generally round or oval, and it is diffuse. Neat edges generally appear in the groove position of the product

Analysis of the causes:

1. The oil on the surface of the material has not been treated.
2. The material itself has too much oil and cannot be removed by normal degreasing.
3. There is water or oil in the air pipe of the spray gun. 4. The paint is bad or polluted.

Key points of quality control:

1. Confirm whether the operation method is consistent with the “Operation Instructions” during pre-processing
2. Regularly confirm the use of mold release agents at the molding site
3. Check whether there is water in the spray gun every day before production
4. Confirm the paint before production, and deal with the expired paint in time

Defective 3. Explosive tungsten wire

Description: The light transmission of tungsten filaments generally occurs on transparent or translucent PC materials that require cover mold plating. Light is irradiated, and the light passes through the coating position.

Analysis of the causes:

The electroplating tungsten wire is aging, and the undissolved part of the aluminum wire falls on the product after evaporation to form light transmission

Key points of quality control:

Check the appearance of the tungsten wire before going online, if there is obvious nodule or oxidation, it cannot be used, and regularly confirm the replacement record of the tungsten wire

Defective 4. Electroplating pinhole light transmission

Description: Pinhole light transmission generally occurs on PC transparent or translucent materials that require cover mold plating, illuminated with light, and the light passes through the coating position.

Analysis of the causes:

1. 1. The electroplating tungsten wire is aging, and the undissolved part of the aluminum wire falls on the product after evaporation to form pinhole-shaped light transmission
2. After the primer is cured, flying dust adheres to the surface, resulting in pinhole light transmission after electroplating
3. The purity of electroplated aluminum wire is too low and contains impurities
4. The thickness of the coating is too thick
5. Before the topcoat is sprayed, the dust removal pressure is too high
6. The spray pressure of the topcoat is too high

More in the next chapter. Follow LKKER SCM Linkedin Page for chapter updates. 

01 Mold appearance

1. The content of the mold nameplate is complete, the characters are clear, and the arrangement is neat.

2. The nameplate should be fixed on the mold foot near the template and the reference angle. The nameplate is reliable and not easy to peel off.

3. The cooling water nozzle should be made of plastic block water nozzle, if the customer requires otherwise, please follow the requirements.

4. The cooling water nozzle should not protrude from the surface of the mold base.

5. The cooling water nozzle needs to be processed with a counterbore. The counterbore diameter is 25mm, 30mm, and 35mm. The orifice is chamfered and the chamfering should be the same.

6. The cooling water nozzle should be marked for entry and exit.

7. Mark English characters and numbers should be greater than 5/6, and the position should be 10mm directly below the tap. The handwriting should be clear, beautiful, neat, and evenly spaced.

8. Mould accessories should not affect the hoisting and storage of the mold. During installation, there are exposed oil cylinders, faucets, pre-reset mechanisms, etc., which should be protected by supporting legs.

9. The mounting of the support leg should be fixed on the mold base with screws passing through the support leg, and the excessively long support leg can be fastened to the mold base with a machined external threaded column.

10. The size of the ejector hole of the mold should meet the requirements of the specified injection molding machine. Except for small molds, one center cannot be used for ejection.

11. The positioning ring should be fixed and reliable. The diameter of the ring is 100mm and 250mm. The positioning ring is 10-20mm higher than the bottom plate. Unless otherwise requested by customers.

12. The overall dimensions of the mold should meet the requirements of the designated injection molding machine.

13. For molds with orientation requirements, an arrow should be used to indicate the installation directly on the front template or the rear template, and there should be “UP” next to the arrow. The arrow and text are both yellow and the height of the font is 50 mm.

14. The surface of the mold base should not have pits, rust marks, redundant rings, water vapor in and out, oil holes, etc., and defects that affect the appearance.

15. Moulds should be easy to hoist and transport. Mould parts must not be disassembled during hoisting. Lifting rings must not interfere with faucets, cylinders, pre-reset rods, etc.

02 Mold material and hardness

1. The mold base should be a standard mold base that meets the standard.

2. The material of mold forming parts and gating system (core, movable and fixed mold insert, movable insert, diversion cone, pushrod, sprue sleeve) shall be made of materials with performance higher than 40Cr.
3. When molding plastics that are corrosive to the mold, the molded parts should be made of corrosion-resistant materials, or the molding surface should take anti-corrosion measures.
4. The hardness of the molded parts should not be lower than 50HRC, or the hardness of the surface hardening treatment should be higher than 600HV.

03 Eject, reset, pull out the core, take out

1. The ejection should be smooth, free of jamming, and no abnormal sound.

2. The inclined top surface should be polished, and the inclined top surface is lower than the core surface.

3. The sliding parts should be provided with an oil groove, and the surface needs to be nitrided, and the surface hardness after treatment is HV700 or higher.

4. All ejector rods should have stop-rotation positioning, and each ejector rod should be numbered.

5. The ejection distance should be limited by a limit block

6. Standard parts should be used for the return spring, and both ends of the spring should not be polished or cut off.

7. Slider and core-pulling should have stroke limit, small slide is limited by spring, if spring is inconvenient to install, corrugated screw can be used; cylinder core-pulling must have a stroke switch.

8. Generally, inclined guide posts are used for core pulling of the slider, and the angle of the inclined guide post should be 2°~3° smaller than the angle of the locking surface of the slider. If the stroke of the slider is too long, the oil cylinder should be used for drawing.

9. When the end surface of the core-pulling forming part of the cylinder is covered, the cylinder should be equipped with a self-locking mechanism.

10. There should be a wear plate under the large sliding block with a width of more than 150 mm. The material of the wear plate should be T8A. The hardness after heat treatment is HRC50~55. The wear plate is 0.05~0.1 mm higher than the large surface. Open the oil tank.

11. The ejector rod should not move up and down.

12. Add barbs to the top rod, and the direction of the barbs should be consistent, so that the barbs are easy to remove from the product.

13. The clearance between the ejector pin hole and the ejector pin, the length of the sealing section, and the surface roughness of the ejector pin hole should be in accordance with the requirements of the relevant enterprise standards.

14. The product should be convenient for the operator to remove it.

15. When the product is ejected, it is easy to follow the inclined top, and the top rod should be grooved or etched.

16. The top block fixed on the top rod should be firm and reliable, the non-formed parts around the circumference should be processed with a 3°~5° slope, and the lower periphery should be chamfered.

17. There should be no iron filings in the oil passage hole on the mold base.

18. The end face of the return rod is flat and there is no spot welding. No gasket at the bottom of the embryo head, spot welding.

19. The gate plate of the three-plate mold slides smoothly, and the gate plate is easy to open.

20. Three-plate mold limit rods should be arranged on both sides of the mold installation direction, or pull plates should be added to the mold base to prevent the limit rods from interfering with the operator.

21. The oil circuit and air passage should be smooth, and the hydraulic ejector reset should be in place.

22. An exhaust port should be opened at the bottom of the guide sleeve.

23. There should be no clearance for the positioning pin installation.

04 Cooling and heating system

1. The cooling or heating system should be fully unblocked.

2. The seal should be reliable, the system should not leak under the pressure of 0.5MPa, and it is easy to check and repair.

3. The size and shape of the sealing groove opened on the mold base should meet the requirements of relevant standards.

4. Grease should be applied to the sealing ring when it is placed, and it should be higher than the surface of the mold base after it is placed.

5. Water and oil flow channel separators should be made of materials that are not easily corroded.

6. The front and back molds should use a centralized water supply.

05 Gating system

1. The gate setting should not affect the appearance of the product and satisfy the product assembly.

2. The runner section and length should be designed reasonably, and the process should be shortened as much as possible under the premise of ensuring the forming quality, and the cross-sectional area should be reduced to shorten the filling and cooling time. At the same time, the plastic loss of the pouring system should be the least.

3. The partial cross-section of the three-plate mold runner at the back of the front mold plate should be trapezoidal or semicircular.

4. The three-plate mold has a material breaker on the gate plate, the diameter of the gate entrance should be less than 3 mm, and the ball head has a 3 mm deep step recessed into the gate plate.

5. The ball end pull rod should be reliably fixed, can be pressed under the positioning ring, can be fixed with headless screws, or can be pressed with a pressure plate.

6. Gates and runners should be machined according to the size requirements of the drawings, and manual grinding and polishing machines are not allowed.

7. The pointed gate should be in accordance with the requirements of the specification.

8. There should be an extension at the front end of the runner as a cold slug hole.

9. The Z-shaped inverted buckle of the pulling rod should have a smooth transition.

10. The runner on the parting surface should be round, and the front and rear molds cannot be misaligned.

11. The latent gate on the ejector rod should have no surface shrinkage.

12. The diameter and depth of the cold slug hole for transparent products should meet the design standards.

13. The handle is easy to remove, there is no gate mark on the appearance of the product, and there is no residual handle at the product assembly.

14. For the curved hook latent gate, the two parts of the insert should be nitrided, and the surface hardness can reach HV700.

06 Hot runner system

1. The wiring layout of the hot runner should be reasonable for easy maintenance, and the wiring numbers should be a one-to-one correspondence.

2. The hot runner should be tested for safety, and the insulation resistance to the ground should be greater than 2MW.

3. Standard parts should be adopted for temperature control cabinets, hot nozzle, and hot runner.

4. The main flow port sleeve is connected with the hot runner with threads, and the bottom surface is in contact with the hot runner for sealing.

5. The hot runner is in good contact with the heating plate or heating rod, and the heating plate is fixed with screws or studs, and the surface fits well.

6. The J-type thermocouple should be used and matched with the temperature control meter.

7. Each group of heating elements should be controlled by thermocouples, and the position of the thermocouples should be reasonably arranged.

8. The nozzle should meet the design requirements.

9. The hot runner should be reliably positioned, at least two positioning pins, or fixed with screws.

10. There should be an insulation pad between the hot runner and the template.

11. The error between the set temperature of the temperature control meter and the actual display temperature should be less than ±5°C, and the temperature control should be sensitive.

12. The cavity and nozzle installation hole should pass through.

13. The hot runner wiring should be bundled and covered with a pressure plate.

14. There are two sockets of the same specification, which should be clearly marked.

15. The control line should be sheathed and not damaged.

16. The structure of the temperature control cabinet is reliable, and the screws are not loose.

17. The socket is installed on the bakelite and cannot exceed the maximum size of the template.

18. The wires must not be exposed outside the mold.

19. There should be rounded transitions at all the places where the hot runner or template is in contact with the wires.

20. Before the template is assembled, there is no open circuit or short circuit in all circuits.

21. All wiring should be connected correctly, with good insulation performance.

22. After the template is installed and clamped, all circuits should be checked again with a multimeter.

08 Injection molding production process

1. The mold should have the stability of injection molding production and the repeatability of process parameter adjustment within the range of normal injection molding process conditions.

2. The injection pressure during mold injection production should generally be less than 85% of the injection molding machine’s rated maximum injection pressure.

3. The injection speed during the injection molding production of the mold, the injection speed of the three-quarter stroke is not less than 10% of the rated maximum injection speed or more than 90% of the rated maximum injection speed.

4. The holding pressure during mold injection production should generally be less than 85% of the actual maximum injection pressure.

5. The clamping force of the mold during injection molding production should be less than 90% of the rated clamping force of the applicable model.

6. During the injection molding production process, the product and nozzle material should be taken out easily and safely (the time is generally not more than 2 seconds each).

7. For molds with inserts, the inserts are easy to install and the inserts are fixed reliably during production.

09 Packing and shipping

1. The mold cavity should be cleaned and sprayed with anti-rust oil.

2. The sliding parts should be lubricated.

3. The inlet of the sprue bushing should be sealed with grease.

4. The mold should be equipped with a clamping piece, and the specifications meet the design requirements.

5. Spare parts and wearing parts should be complete, with a detailed list and the name of the supplier.

6. Sealing measures should be taken to prevent foreign matter from entering the mold water, liquid, gas, and electrical inlets and outlets.

7. Spray paint on the outer surface of the mold, as required by the customer.

8. Moulds should be packaged in moisture-proof, waterproof, and bump-proof packaging, as required by customers.

9. Mold product drawings, structural drawings, cooling, and heating system drawings, hot runner drawings, spare parts, and mold material supplier details, operating instructions, mold test report, factory inspection certificate, and electronic documents should all be complete.

Learn More:

1. LKK Mold Making Service

2. Mold Assembly Process Video

3. Mold Making Process Video 

4. Mold T0 Sample, T1 Sample Video -Sweeping Robot