Pen cover inserts are key components in pen cover molds. They are mainly used to form complex structures of pen covers (such as snaps, threads, decorative patterns, etc.). Their design, materials and processing accuracy directly affect the functionality of pen covers (such as smoothness of opening and closing) and appearance quality. The following is a technical analysis of pen cover inserts, covering functional design, material selection, processing technology and common questions:

1. Function and structural characteristics of pen cover insert

Core role:

Functional structural molding: snap groove (matching tolerance ±0.03mm), thread (pitch 0.5~1mm), anti-slip mark, etc. 

Decorative details: LOGO relief (depth 0.1~0.3mm), gradient texture (such as CD patterns), light-transmitting window (for LED pens).

Enhanced durability: High wear areas (such as snap contacts) are individually formed with inserts for easy replacement and maintenance. 

Typical structure: Modular design: combined installation of split inserts (such as snap inserts, threaded inserts) to reduce the overall mold cost. 

Special-shaped surface: curved chewy (VDI 3400 standard texture), micropore array (breathable and anti-slip design). 

Cooling and exhaust: Built-in micro cooling water circuit or exhaust tank (width ≤0.02mm).

2. Design Points and Challenges

(1) Snap structure design

Strength and lifespan:

The number of repeated openings and closings of the snaps must be ≥100,000 times (refer to ISO 8442 durability standard). 

Material selection: cemented carbide (such as SKD11, HRC 58~62) or powdered metallurgical steel (such as ASP-23).

Demolding angle: The inclination of the snap barb is ≥3° to avoid plastic deformation or breaking during demoulding.

 Case: A certain brand of pen cover snap inserts adopt double slope + root rounded corner (R0.2mm), and the life span is increased by 50%.

2) Decorative texture processing

High-precision texture: laser nipples (accuracy ±0.01mm) or chemical etching (depth consistency ±5%). 

Gradient texture requires five-axis linkage processing (such as a ball-headed knife with a diameter of 0.2mm). 

Light-transmitting structure: The light-transmitting window insert needs to be injection-molded with high transparency materials (such as PMMA) and metal inserts.

(3) Heat balance and cooling

Cooling in a shape: 3D printed special-shaped waterway (section 1mm×1mm) is embedded in inserts, and the cooling efficiency is improved by 30%. 

Case: A metal insert uses copper alloy + stainless steel composite waterway, and the cooling cycle is shortened to 8 seconds.

3. Material selection and surface treatment

(1) Common materials

Tool steel: 

SKD61 (HRC 48~52): High toughness, suitable for complex snap-on structures. 

NAK80 (pre-hard HRC 40~43): Excellent mirror polishing performance, used for high-gloss inserts. 

Carbide: Tungsten steel (YG15): Excellent wear resistance and is used in high friction areas (such as threaded inserts). 

Special material: Beryllium copper alloy (thermal conductivity 330 W/m·K): Quickly cool the insert to reduce thermal deformation.

(2) Surface treatment technology

Wear-resistant coating: 

TiCN coating (hardness HV3000): reduces wear on the contact surface of the snap. Diamond-like (DLC) 

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spraying: avoid plastic sticking molds (such as TPU material pen cover).

4. Processing difficulties and process plans

(1) Microstructure processing

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Width 0.1mm Anti-slip mark: Five-axis high-speed milling (speed 30,000rpm, feed 1m/min).

Case: 0.15mm deep relief of a certain pen cover LOGO insert, using laser engraving + electrolytic polishing, Ra≤0.05μm.

(2) Multi-material composite insert metal-plastic 

composite insert: Metal insert pre-embedded injection 

molding: positioning accuracy ±0.02mm (such as pen cover metal decorative ring). 

Process Difficulty: Interface stress caused by temperature difference (mode temperature control ±1℃ is required).

(3) High-gloss surface treatment

Mirror polishing:

Diamond grinding (grain size 0.5~5μm) + ultrasonic polishing, Ra≤0.02μm. 

Avoid polishing traces: Use a vibration polishing machine + ceramic medium.

5. Frequently Asked Questions and Countermeasures

1) The snap failed

Cause: The insert wear causes excessive buckle size (such as width deviation >0.05mm). 

Uneven shrinkage of plastic causes the buckle to deform.

Countermeasures: The surface of the insert is coated with a hard coating (such as CrN). 

Optimize the pressure holding curve (multi-stage pressure holding compensation shrinkage).

(2) Blast and Flying

Cause: The matching gap between the insert and the mold core is >0.01mm. 

The injection molding pressure is too high (>120MPa) or the clamping force is insufficient.

Countermeasures: 

The insert adopts interference fit (interference amount 0.003~0.005mm).

Reduce injection molding pressure and increase the clamping force (≥300 tons).

(3) The texture is unclear

Cause: 

The mold temperature is too low, resulting in the melt being insufficiently filled with texture. 

Residual release agent or oxide layer remains on the surface of the insert. Countermeasures: 

Increase the mold temperature to 80~100℃ (depending on the material). 

Regularly plasma-clean the surface of the insert (remove organic contamination).

6. Innovative technologies and trends

Smart Instruments: Integrated micro sensors (such as pressure sensing inserts) to monitor injection molding status in real time. 

Application case: Inserts embedded with RFID chips to realize production traceability.

Additive Manufacturing: 3D printed follow-up cooling inserts (material: H13 tool steel + internal honeycomb structure). 

Advantages: The cooling efficiency is increased by 40%, and the mold life is increased by 2 times.

Eco-material adaptation: Degradable plastics (such as PLA) for special inserts: increase the release slope to 3°, surface Teflon treatment.

Our Services

1. Specialized in precision mold part ,inquiries will get highly attention and be prompt response.(within 24 hours).

2. Advanced facilities and experienced engineers, rich experience in mold parts.

3. Guaranteed quality, superior material quality compared to all other.

4. Customer oriented, efficient solution to control the cost for our client.

5. One-stop service, any questions can be solved at the first time by us.

6. Each part has been got 100% inspection before shipment.

Our adavanges

1. Clean and tidy workshop.

2.Strick and serious manangement, skilled and expericenced technicians.

3. Various raw material(imported and Chinese) to meet different needs of customers.

4.Equipment of high pricision.( Surface grinding,Sodick Wire-cutting.drilling machine).

5.The QC go along with all the production processes in our factory.

6. You can use English or Japanese for cummunication

Payment Terms

T/T,Paypal,Western Union,50% deposit, balance before shipment is available

Package:PE bag with anticorrosive oil,foaming film with carton,or wooden box according to customer's requirement.

Delivery:Delivery time is usually 7-15 working days for type of ejector pin,specific time is according to quantity.

Shipping:We ship using express such as DHL, UPS, FEDEX etc. or according

to customer's requirement . It takes about 3-5 days to arrive your front

door, and proof of shippments are provided with a shipping or tracking

number. And we ship by occean shippment for larger quantity items,

it will be economic for customers.