Compression Molding Service
Compression molding is an ideal process for manufacturing thermosetting plastics, composites, and rubber parts. Compared to injection molding, compression molding offers lower mold costs and supports metal inserts. We provide a end to end service from material selection and mold design to volume production,ensure the rapid production of cost-effective components.
What Is Compression Molding?
Compression molding is a thermosetting plastic molding process that involves placing preheated material into a heated mold cavity, where it is allowed to flow and solidify under pressure and temperature. This process, over a century old, was initially used for phenolic resins processing and is now widely applied in the manufacture of various high-performance composite materials.
Key Characteristics and Advantages:
- Minimal material waste
- Low internal stress
- Precise fiber orientation control
- Products with excellent mechanical properties and dimensional stability
Compression Molding Process
Mold & Material Preparation
Prepare thermoset or composite materials as preforms (or use granules/sheets), and preheat the mold to 150–200°C.
Loading & Clamping
Place the preheated material into the lower cavity, then close the mold by lowering the upper half under 5–30 MPa pressure.
Curing
Maintain the set temperature and pressure for 5–30 minutes to complete cross-linking reaction.
Demolding & Processing
Open the mold, remove the cured part, and perform trimming, drilling, surface finishing, etc.
Compression Molding Tooling Solution
DESIGN & MANUFACTURING
MOLD TRIAL VERIFICATION
CUSTOM PLASTIC FABRICATION
Mold Design & Custom Manufacturing
We offer full-process engineering support from part analysis to mold delivery. Based on the specific requirements of compression molding (and injection molding), we design optimized mold structures including cavity layout, parting lines, heating/cooling channels, and ejection systems. We specialize in cost-effective tooling for high volumes, with flexible mold material options (P20, H13, stainless steel, etc.) to balance durability and investment. Whether for the type of molds, we can match your part complexity and volume targets.
Mold Trial & Process Verification
We conduct systematic mold trial and validation. By producing actual parts, we verify mold actions, material flow, curing parameters, and demolding performance. Key process windows such as temperature, pressure, and holding time are recorded and adjusted to eliminate defects like short shots, flash, and voids. After trials, we provide detailed inspection reports and process parameter sheets, ensuring every aspect is stable before production. For compression molding, we pay special attention to insert positioning and thickness consistency.
Plastic Material Selection & Processing
Material recommendation – Based on mechanical strength, temperature resistance, flame retardancy, insulation, or surface finish, we recommend the most suitable thermosets (BMC/SMC),or thermoplastics (PEEK,etc).
Custom compounding – We offer reinforcement (glass/ carbon fiber), toughening, anti-static, color matching, and other modifications to meet special service conditions.
Material testing – Melt flow index, HDT, UL flammability rating, etc. – to balance performance and cost, especially for high-end applications.
Materials Used for Compression Molding
We offer a broad range of thermoset and composite materials, each engineered for superior performance and tailored to suit a variety of applications.
Thermosetting Plastic
- Phenolic Resin (PF): The earliest material used for compression molding, offering excellent electrical insulation, heat resistance, and flame retardancy. Suitable for electrical switches, sockets, automotive brake pads, etc. Density 1.3-1.5g/cm³, tensile strength 50-70MPa.
- Epoxy Resin (EP): High bonding strength, low shrinkage rate, excellent chemical stability. Ideal for aerospace composites, electronic encapsulation, high-performance insulators. Can be enhanced with various fillers.
- Unsaturated Polyester (UP): Cost-effective, good flowability, easy to color. Widely used for automotive body panels, sanitary ware, construction components. Glass fiber reinforced strength can reach 120MPa.
- Melamine Formaldehyde (MF): High hardness, scratch resistance, good heat resistance, commonly used for tableware, decorative panels, electrical accessories.
- Silicone Resin (SI): Heat resistant, excellent weatherability, suitable for seals, medical devices, cookware handles.
Composite Materials
- Glass Fiber Reinforced Materials (GF): Most commonly used reinforcement, increases strength 2-3 times, cost-effective. Common content 20%-50%, suitable for structural parts, automotive components.
- Carbon Fiber Reinforced Materials (CF): Ultra-high strength, lightweight, good conductivity. Ideal for aerospace, high-end sports equipment, medical devices.
- Aramid Fiber Reinforced Materials (AF): High toughness, impact resistance, excellent insulation properties. Suitable for ballistic materials, electrical insulators materials.
Special Functional Materials
- Conductive Materials: Added carbon black, metal fibers, surface resistance 10²-10⁶Ω, suitable for EMI shielding, anti-static components.
- Flame Retardant Materials: UL94 V-0 rating, oxygen index >30%, suitable for electrical equipment, rail transit components.
- High Temperature Resistant Materials: Long-term use temperature >200°C, suitable for engine surrounding parts, industrial equipment.
- Food Grade Materials: Compliant with FDA, EU10/2011 standards, suitable for cookware, food processing equipment.
Material Selection Guidelines
Performance Requirements First
Determine temperature resistance, strength, electrical requirements based on usage environment.
Cost-Benefit Balance
Choose the most cost-effective material while meeting performance requirements.
Process Adaptability
Consider material flowability, curing time, and equipment compatibility.
Regulatory Compliance
Ensure materials comply with industry standards and regulatory requirements.
Our Compression Molding Capabilities
Wontech’s compression molding capabilities enable the production of parts that meet diverse functional and aesthetic requirements. The following guidelines will help enhance part manufacturability, shorten lead times, and improve surface finish and structural integrity. You can refer to these standard design considerations for compression molded components.
Process Advantages
- Precise Temperature Control: Temperature fluctuations are controlled within ±3°C, ensuring uniform material curing.
- Precise Pressure Adjustment: Pressure adjustment range of 5-30MPa, adaptable to different materials and part requirements.
- Intelligent Curing Monitoring: Real-time monitoring of the curing process ensures optimal material performance.
- High-Efficiency Production: Over 15 years of experience in thermosetting material applications, providing professional material selection advice.
Standard
Description
Maximum Part Size
1000×800×400mm
39.4×31.5×15.8inch
Minimum Part Size
2×4×2mm
0.08×0.2×0.08 inch
The Range of Wall Thickness
From 0.5mm to 25mm
From 0.02 to 0.1 inch
Tolerance
+/- 0.05mm
+/- 0.002 inch
Volume Resistivity
≥1.0×10¹³ Ω·cm
Excellent electrical insulation properties
Mold Trial
T0, T1, and T2 verifications are conducted to confirm samples before mass production.
Quality Certification
ISO 9001, IATF 16949, ISO 13485, ISO14001
Mold Life and ROI Quantification
A well-designed, well-manufactured, long-life mold, while requiring a slightly higher initial investment, delivers lower amortized costs per unit, fewer production interruptions, and more consistent part quality in mass production of millions of units.We are committed to designing every mold with the goal of “optimal overall cost,” ensuring a longer-term return on your investment.
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Comparison
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Long-life molds
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Standard-life molds
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Initial Investment In Mold
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High(Made of high-quality steel, precision machined, and wear-resistant treated)
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Basic Standard
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Total investment in molds throughout their entire life cycle
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Low
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High(restarting or model repair)
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Production Interruption Risk
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Low(The mold is stable and can be used for continuous production)
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High(needs to be stopped for repair or replacement after wear and tear)
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Part Quality Stability
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High (uniform wear, long-term stable CPK dimensions)
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Medium → Low(Increased flash and dimensional deviation in later stages)
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Maintenance Costs And Spare Parts Pressure
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Low (Only requires routine maintenance, few easily damaged parts)
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Medium → High(Reserve spare parts or spare molds for major repairs)
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Controllability Of Project Schedule
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High(Stable production schedule)
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Low (Mold condition uncertain,easy to disrupt the production sequence.)
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Is Compression Molding Right for Your Part?
Ideal
- Large Size: Parts with length or width exceeding 300mm
- Relatively Simple Structure: No complex internal structures or deep cavities
- High Strength Requirements: Applications requiring high load-bearing or impact resistance
Challenging
FAQ
“What are the core factors determining the final cost of electric motor molds?”
The core factor is the comprehensive technical complexity. Besides steel, the real cost drivers are:
1. Design complexity (e.g., multi-station progressive machining, automated insert integration)
2. Materials technology (using powder metallurgy high-speed steel or cemented carbide can be several times more expensive than ordinary steel)
3. Precision level (for every micrometer-level improvement in tolerance, processing and inspection costs increase exponentially)
4. Lifespan standard (the design, material, and process investment required for a commitment of 100 million strokes is vastly different from that for 50 million strokes).
Therefore, purchasing molds is essentially a critical investment in the performance, efficiency, and long-term production costs of the final product, rather than simply comparing prices.
“What types of electric motor molds do you primarily manufacture? What are the differences between BMC and plastic bonded magnet motor molds?”
We specialize in injection molds for all types of motors, particularly BMC thermoset motor molds and plastic bonded magnet motor molds.
BMC molds are used to produce structural components such as motor housings, insulating frames, and end caps. BMC material offers excellent high-temperature resistance, corrosion resistance, and dimensional stability, making it suitable as a replacement for metal parts.
Plastic bonded magnet motor molds are used to produce functional components such as rotor magnetic rings and sensor magnets. Plastic magnetic materials allow for integrated molding of the magnetic circuit, reducing assembly steps and improving the consistency of magnetic properties.
The two differ in material properties, mold design considerations, and application scenarios. We can recommend the most suitable mold solution based on your motor type and performance requirements.
"What are the fundamental differences between servo motor core molds and ordinary household appliance electric motor molds?"
The core difference between servo motor core molds and ordinary household appliance motor molds lies in their performance and precision orientation.
Servo motors prioritize extreme dynamic response and positioning accuracy. Therefore, their molds must ensure extremely low cogging torque in the core and high symmetry in the magnet slots. Slot dimensions and indexing accuracy typically need to be controlled within ±0.002mm, and a special unloading structure is required to prevent deformation of the silicon steel sheet.
In contrast, household appliance motor molds prioritize stability and cost-effectiveness in large-scale production. Manufacturing servo motor molds to the latter’s standards will directly lead to motor torque fluctuations and increased noise, completely failing to meet the performance requirements of high-precision servo systems and affecting the overall reliability and lifespan of motion control.
“What is the difference between electric motor molds for plastic encapsulation and ordinary injection molds?”
Molds for plastic-encapsulated motor components fundamentally differ from standard injection molds in design philosophy, material processing, and functional specifications. Electric motor molds are specifically engineered for electrical applications (e.g., housings, insulation end caps, stator encapsulation), utilizing thermoset materials like BMC (Bulk Molding Compound) processed via compression or overmolding to achieve superior electrical insulation, heat resistance, and mechanical integrity. Their design incorporates critical features such as thermal management channels, electrical isolation grooves, and micron-level dimensional tolerances to comply with stringent motor safety standards (e.g., IEC 60034).
In contrast, standard injection molds target general-purpose thermoplastics (e.g., PP, ABS) using conventional injection molding, prioritizing high-volume production efficiency, surface finish, and cost-effectiveness without specialized electrical or thermal requirements.
For instance, electric motor molds require precise temperature control (150–200°C) for BMC curing, while standard molds operate at lower ranges (80–120°C); electric motor molds also demand higher mold steel hardness (HRC 50+) to withstand abrasive thermoset materials, versus standard molds (HRC 35–45) focused on affordability. This distinction elevates electric motor mold reliability by over 40% compared to generic molds, making them indispensable for precision applications like servo and HVAC motors.
“What are the key indicators and methods for precision inspection of electric motor molds?”
The core indicators for precision inspection of motor molds fall into three main categories: geometric accuracy, functional accuracy, and process stability. For geometric accuracy, the primary focus is on the stator/rotor slot dimensions. A coordinate measuring machine (CMM) is used to measure slot width, slot spacing, and concentricity, with an accuracy requirement of ±0.005mm. The flatness and perpendicularity of the stacked iron core are also crucial; a laser scanner can quickly acquire three-dimensional data.
Functional accuracy inspection is more complex, including magnetic performance verification: iron loss, magnetic flux density, and stacking factor are measured using a dedicated test bench. A high-quality mold should achieve a stacking factor of over 95%.
Dynamic balancing is critical for rotor molds; the imbalance must be controlled below 0.5 g·cm. Process stability is achieved through SPC (Statistical Process Control), with the critical dimension CPK value greater than 1.67.
In terms of inspection methods, we adopt a hierarchical strategy: first-piece full-size inspection (using a CMM and optical comparator); automated online inspection during production (sensors installed inside the mold monitor key points in real time); and periodic downtime depth inspection (once a week). For BMC motor components, additional electrical performance tests are required, such as withstand voltage testing (2500V/1min) and insulation resistance measurement (>100MΩ).
Furthermore, we establish a “mold file” to record data from each test, analyze it promptly, and predict future needs. While this comprehensive testing system increases upfront costs, it significantly reduces production risks for our customers.
“How long does the development cycle for electric motor molds typically take?”
The development cycle for motor molds varies depending on complexity. Standard motor stator molds typically take 8-10 weeks, high-precision BMC motor component molds take 10-12 weeks, while complex multi-station progressive dies can take as long as 14-16 weeks.
This timeline includes requirements analysis (1 week), 3D design (1.5-2 weeks), CAE simulation (3-5 days), machining and manufacturing (3-4 weeks), assembly and debugging (1-1.5 weeks), and trial molding verification (1-2 weeks).
Based on customer needs, we optimize the timeline through process reengineering and technological innovation.
“What parameters should be focused on during the trial molding stage of electric motor molds, and how to determine whether the mold is qualified?”
The primary concern is dimensional accuracy, especially stator slot width, slot spacing, and inner diameter. At least 20 consecutive samples should be inspected using high-precision measuring equipment (such as a coordinate measuring machine) to calculate the CPK value (≥1.67) and ensure dimensional stability.
The core stacking factor is a core indicator of motor performance. Through precise weighing and volume measurement, a qualified core stacking factor should reach 95% or higher. A factor below 92% indicates excessive burrs or insufficient flatness. Electromagnetic performance testing is crucial. Iron loss (W/kg) and magnetic induction intensity should be measured using a professional testing platform, with deviations from design values less than 5%. For permanent magnet motor rotors, the uniformity of magnetic flux distribution must also be tested.
Regarding surface quality, the stamped surface of silicon steel sheets should exhibit an ideal “bright band/fracture band” ratio (60:40). A 50x magnifying glass should be used to inspect burr height (≤0.005mm) and the quality of the stamped surface.
For BMC motor components, attention must be paid to air marks, exposed fiberglass, and shrinkage deformation, especially in areas with electrical clearances, which must be 100% defect-free. Process stability is verified through 8 consecutive hours of production testing, collecting data such as mold temperature, stamping pressure, and product weight. The fluctuation range should be less than ±3%.
To determine mold qualification, we use a scoring system: key performance (dimensions, electromagnetic characteristics) accounts for 60%, process stability for 25%, and ease of maintenance for 15%, with a total score exceeding 85 points.
Mold trials are not only an acceptance process but also an opportunity for optimization. We meticulously record every data point, creating a “mold file” to provide a benchmark for subsequent production.
FAQ
“What are the core factors determining the final cost of motor molds?”
The core factor is the comprehensive technical complexity. Besides steel, the real cost drivers are:
1. Design complexity (e.g., multi-station progressive machining, automated insert integration)
2. Materials technology (using powder metallurgy high-speed steel or cemented carbide can be several times more expensive than ordinary steel)
3. Precision level (for every micrometer-level improvement in tolerance, processing and inspection costs increase exponentially)
4. Lifespan standard (the design, material, and process investment required for a commitment of 100 million strokes is vastly different from that for 50 million strokes).
Therefore, purchasing molds is essentially a critical investment in the performance, efficiency, and long-term production costs of the final product, rather than simply comparing prices.
“How to improve motor energy efficiency from a die-cutting perspective?”
The molds directly determines the geometric accuracy and material condition of the iron core.
Through high-precision blanking, the burrs on silicon steel sheets can be controlled below 0.01mm, significantly reducing eddy current losses caused by burrs.
Through optimized riveting design, the core stacking coefficient can be increased to over 98.5%, effectively reducing air gap reluctance in the magnetic circuit.
We have previously helped a customer reduce the iron loss of a permanent magnet motor by approximately 12% by optimizing the blanking clearance and cross-sectional quality of the stator slot die, directly improving the overall energy efficiency of the motor.
"What are the fundamental differences between servo motor core molds and ordinary household appliance motor molds?"
The core difference between servo motor core molds and ordinary household appliance motor molds lies in their performance and precision orientation.
Servo motors prioritize extreme dynamic response and positioning accuracy. Therefore, their molds must ensure extremely low cogging torque in the core and high symmetry in the magnet slots. Slot dimensions and indexing accuracy typically need to be controlled within ±0.002mm, and a special unloading structure is required to prevent deformation of the silicon steel sheet.
In contrast, household appliance motor molds prioritize stability and cost-effectiveness in large-scale production. Manufacturing servo motor molds to the latter’s standards will directly lead to motor torque fluctuations and increased noise, completely failing to meet the performance requirements of high-precision servo systems and affecting the overall reliability and lifespan of motion control.
“What are the main differences between motor molds and ordinary injection molds?”
Motor molds and ordinary injection molds differ fundamentally in design principles, precision requirements, and material selection. Motor molds primarily include stamping dies for the stator and rotor cores, rather than traditional injection molds.
The core differences are: motor stamping dies must handle the high-precision stacking of special electromagnetic materials such as silicon steel sheets, with tolerances typically controlled at ±0.005mm, far exceeding those of ordinary molds; the mold structure must consider electromagnetic performance optimization, such as the slot design directly affecting motor efficiency and noise; the working environment is more demanding, with high-speed stamping (typically 150-300 SPM) posing significant wear challenges.
Furthermore, motor molds need to integrate special functions such as automatic stacking and deburring systems to ensure a core stacking coefficient of over 95%. In terms of material selection, core components of motor molds often use powder metallurgy steel instead of ordinary mold steel to resist the continuous wear of the silicon steel sheets.
The testing and verification also differ; motor molds must undergo rigorous electromagnetic performance testing, not just dimensional inspection. This specialization requires a deep background in electrical engineering, rather than just mold manufacturing experience, to develop motor molds. This is also the core value of professional motor mold manufacturers.
“What are the key indicators and methods for precision inspection of motor molds?”
The core indicators for precision inspection of motor molds fall into three main categories: geometric accuracy, functional accuracy, and process stability. For geometric accuracy, the primary focus is on the stator/rotor slot dimensions. A coordinate measuring machine (CMM) is used to measure slot width, slot spacing, and concentricity, with an accuracy requirement of ±0.005mm. The flatness and perpendicularity of the stacked iron core are also crucial; a laser scanner can quickly acquire three-dimensional data.
Functional accuracy inspection is more complex, including magnetic performance verification: iron loss, magnetic flux density, and stacking factor are measured using a dedicated test bench. A high-quality mold should achieve a stacking factor of over 95%.
Dynamic balancing is critical for rotor molds; the imbalance must be controlled below 0.5 g·cm. Process stability is achieved through SPC (Statistical Process Control), with the critical dimension CPK value greater than 1.67.
In terms of inspection methods, we adopt a hierarchical strategy: first-piece full-size inspection (using a CMM and optical comparator); automated online inspection during production (sensors installed inside the mold monitor key points in real time); and periodic downtime depth inspection (once a week). For BMC motor components, additional electrical performance tests are required, such as withstand voltage testing (2500V/1min) and insulation resistance measurement (>100MΩ).
Furthermore, we establish a “mold file” to record data from each test, analyze it promptly, and predict future needs. While this comprehensive testing system increases upfront costs, it significantly reduces production risks for our customers.
“How long does the development cycle for motor molds typically take?”
The development cycle for motor molds varies depending on complexity. Standard motor stator molds typically take 8-10 weeks, high-precision BMC motor component molds take 10-12 weeks, while complex multi-station progressive dies can take as long as 14-16 weeks.
This timeline includes requirements analysis (1 week), 3D design (1.5-2 weeks), CAE simulation (3-5 days), machining and manufacturing (3-4 weeks), assembly and debugging (1-1.5 weeks), and trial molding verification (1-2 weeks).
Based on customer needs, we optimize the timeline through process reengineering and technological innovation.
“What parameters should be focused on during the trial molding stage of motor molds, and how to determine whether the mold is qualified?”
The primary concern is dimensional accuracy, especially stator slot width, slot spacing, and inner diameter. At least 20 consecutive samples should be inspected using high-precision measuring equipment (such as a coordinate measuring machine) to calculate the CPK value (≥1.67) and ensure dimensional stability.
The core stacking factor is a core indicator of motor performance. Through precise weighing and volume measurement, a qualified core stacking factor should reach 95% or higher. A factor below 92% indicates excessive burrs or insufficient flatness. Electromagnetic performance testing is crucial. Iron loss (W/kg) and magnetic induction intensity should be measured using a professional testing platform, with deviations from design values less than 5%. For permanent magnet motor rotors, the uniformity of magnetic flux distribution must also be tested.
Regarding surface quality, the stamped surface of silicon steel sheets should exhibit an ideal “bright band/fracture band” ratio (60:40). A 50x magnifying glass should be used to inspect burr height (≤0.005mm) and the quality of the stamped surface.
For BMC motor components, attention must be paid to air marks, exposed fiberglass, and shrinkage deformation, especially in areas with electrical clearances, which must be 100% defect-free. Process stability is verified through 8 consecutive hours of production testing, collecting data such as mold temperature, stamping pressure, and product weight. The fluctuation range should be less than ±3%.
To determine mold qualification, we use a scoring system: key performance (dimensions, electromagnetic characteristics) accounts for 60%, process stability for 25%, and ease of maintenance for 15%, with a total score exceeding 85 points.
Mold trials are not only an acceptance process but also an opportunity for optimization. We meticulously record every data point, creating a “mold file” to provide a benchmark for subsequent production.
Partner with Us. Engineer Your Success.
- Get Your Motor Efficiency Analysis Report
- Download Motor Mold Guide
- Talk to a Molding Expert
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