Custom Injection Molding Services
From prototype and bridge tooling to full-scale production molds, SAMSHION manufactures custom plastic parts for low-volume launches and high-volume programs. Our engineers review part geometry, material, tolerance, surface finish and production requirements before tooling begins.
ISO 9001:2015 Certified
Full quality documentation including FAI reports, PPAP, dimensional inspection reports, and material certifications provided with every order.
15 Days
Mold Fabrication Lead Time
50% Savings
vs. US/EU Tooling Cost
±0.05mm
Standard Part Tolerance
No MOQ
Order From 1 to 1M+ Parts
- Accepts STEP, IGES, SolidWorks, Parasolid, AutoCAD · Free DFM Analysis Included
| Process Specifications at a Glance | |
| Mold Steel | P20, H13, S136, NAK80 |
| Mold Hardness | 28–52 HRC (depending on grade) |
| Cavity Count | 1 to 32 cavities |
| Shot Weight | 1g – 5,000g per shot |
| Clamping Force | 80 – 1,600 tons |
| Max Mold Size | 1,500 × 1,200 × 800 mm |
| Part Tolerance | ±0.05mm (standard) / ±0.02mm (tight) |
| Surface Roughness | Ra 0.4 – 3.2 μm |
| Mold Life (steel) | 500,000 – 1,000,000+ shots |
| Mold Life (aluminum) | 5,000 – 20,000 shots |
What Is Plastic Injection Molding?
Plastic injection molding is a manufacturing process in which thermoplastic resin is melted, injected into a precision-machined mold under controlled pressure, cooled until solid and then ejected as a finished component.
Because the same mold cavity is used repeatedly, the process can deliver consistent geometry, surface finish and mechanical performance across production runs. It also supports molded-in features such as ribs, bosses, snap fits, threads, textured surfaces and integrated fastening points.
Injection molding is generally most economical when the tooling investment can be distributed across a meaningful production quantity. Wall thickness, draft, shrinkage, gating, cooling and ejection must therefore be evaluated before the mold design is released.
SAMSHION supports prototype, bridge and production tooling together with material selection, mold design, trial molding, inspection and repeat production.
OVERMOLDING AND INSERT MOLDING
Overmolding
Overmolding combines two compatible materials in one component by molding a second polymer over a previously molded substrate or rigid base part. It is commonly used to create soft-touch grips, sealing surfaces, impact protection, insulation and improved ergonomics.
Successful overmolding depends on substrate compatibility, chemical or mechanical adhesion, part geometry, wall thickness and processing temperature. These factors should be confirmed during material selection and DFM review.
Insert Molding
Insert molding places a pre-manufactured metal or non-plastic component inside the mold before resin is injected around it. Typical inserts include threaded bushings, electrical terminals, pins, magnets and reinforcing components.
This process can reduce secondary assembly, improve pull-out strength and integrate multiple functions into one molded part. Insert location, retention features, thermal expansion and molding pressure must be considered during mold design.
Why Choose Injection Molding?
Injection molding becomes increasingly economical as production volume grows while providing repeatable geometry, broad material selection and the ability to integrate complex features directly into the molded part.
Lower Per-Part Cost at Suitable Volumes
Once the tooling investment is distributed across a larger production quantity, injection molding can achieve a lower per-part cost than many machining or manual assembly processes.
Consistent and Repeatable Production
A validated mold and controlled molding process help maintain dimensions, appearance and functional performance from batch to batch.
Broad Material and Color Options
Commodity, engineering and high-performance thermoplastics are available for different mechanical, thermal, chemical and cosmetic requirements. Color matching is subject to resin grade and supplier availability.
Molded-In Features
Ribs, bosses, snap fits, textures, logos and selected threads can be incorporated into the molded component, reducing secondary operations and assembly requirements.
Scalable Production
The same validated tooling can support pilot production, scheduled repeat orders and higher-volume manufacturing when the mold is designed for the required service life.
Material-Efficient Processing
Where material properties and quality requirements allow, runners and sprues may be reground or reused through a controlled production process.
Which Mold Type Is Right for You?
We help you select the most cost-effective tooling path based on your volume, timeline, and budget
Prototype / Soft Tooling
Aluminum molds for fast, low-cost validation of part design, fit, and function before investing in steel tooling. Ideal for design iterations and pre-launch samples.
Mold Material
Aluminum (7075-T6)
Quantity
1-1,000 pcs
Mold Life
5,000 – 20,000 shots
Lead Time
7 – 10 days
Advantages
- Fastest mold delivery: 7–10 days
- Lowest upfront tooling investment
- Easy cavity modifications if design changes
- Real injection-molded material (not 3D printed)
- Perfect for investor demos and market testing
Limitations
- Limited mold life (up to 20K shots)
- Not suitable for abrasive glass-filled materials
Best for: Startups, design validation, pre-launch samples
Bridge / Pilot Tooling
Semi-hardened steel molds for production-quality parts while your production tooling is being built, or for products with uncertain long-term volumes.
Mold Material
P20 Steel (pre-hardened)
Quantity
1,000 – 50,000 pcs
Mold Life
100,000 – 500,000 shots
Lead Time
10 – 18 days
Advantages
- Production-quality surface finish
- Handles most engineering resins
- Good for market launch with real demand data
- Can be upgraded to full production spec
- Suitable for low to mid-volume production
Limitations
- Higher upfront cost than aluminum
- Not optimal for very high volumes
Best for: Market launch, bridge production, mid-volume
Production / Hard Tooling
Fully hardened, precision-machined steel molds built for millions of cycles with hot-runner systems, automated ejection, and full surface treatment.
Mold Material
H13 / S136 Hardened Steel
Quantity
50,000 – 10M+ pcs
Mold Life
500,000 – 2,000,000+ shots
Lead Time
18 – 35 days
Advantages
- Lowest per-part cost at high volumes
- Multi-cavity (4, 8, 16, 32 cavity options)
- Hot-runner systems eliminate sprue waste
- Automated ejection for lights-out production
- Compatible with all engineering resins incl. glass-filled
Limitations
- Higher upfront investment
- Longer lead time for mold build
Best for: Mass production, consumer goods, automotive
| Comparison Factor | Prototype Tooling | Bridge Tooling | Production Tooling |
| Upfront Tooling Cost | Low | Medium | High |
| Per-Part Cost (10K+) | Highest | Medium | Lowest |
| Mold Lead Time | 7–10 days | 10–18 days | 18–35 days |
| Part Quality | Good | Production Grade | Production Grade |
| Design Change Ease | Easy | Moderate | Difficult / Costly |
| Max Part Volume | ~20K pcs | ~500K pcs | Unlimited |
| Glass-Filled Resins | Limited | Yes | Yes |
| Multi-Cavity Support | No | 1–2 cavities | Up to 32 cavities |
Injection Molding Material
Material selection affects shrinkage, stiffness, impact resistance, heat performance, chemical resistance, appearance and regulatory requirements.
Our engineers review the intended operating environment, expected loads, cosmetic standards, assembly conditions and production volume before recommending a resin family.
The material values shown below are general reference ranges. Actual properties and molding behavior vary by grade, supplier, additives and processing conditions. Final approval should be based on the selected resin datasheet and project requirements.
For additional comparisons of commonly used plastics and metals, explore our manufacturing materials guide.
| Material | Density | Heat Resistance | Shrinkage Rate | Typical Applications |
|---|---|---|---|---|
| ABS | 1.05 g/cm³ | 80–100°C | 0.4–0.7% | Consumer electronics housings, automotive interior, appliances |
| PP (Polypropylene) | 0.90–0.91 g/cm³ | 100–120°C | 1.0–2.5% | Packaging, automotive, living hinges, medical containers |
| PE (Polyethylene) | 0.94–0.96 g/cm³ | 80–90°C | 1.5–3.0% | Bottles, containers, pipes, consumer goods |
| PS (Polystyrene) | 1.05 g/cm³ | 60–80°C | 0.3–0.6% | Disposable packaging, toys, CD cases, medical disposables |
| Material | Density | Heat Resistance | Shrinkage Rate | Typical Applications |
|---|---|---|---|---|
| PC (Polycarbonate) | 1.20 g/cm³ | 120–130°C | 0.5–0.7% | Optical lenses, safety equipment, electronics, lighting |
| Nylon 6 / PA6 | 1.14 g/cm³ | 80–120°C | 0.6–1.4% | Gears, bearings, structural components, cable ties |
| Nylon 66 / PA66 | 1.14 g/cm³ | 90–120°C | 0.8–1.5% | Automotive under-hood, high-load mechanical parts |
| POM / Delrin | 1.41 g/cm³ | 90–100°C | 1.8–2.0% | Precision gears, pump parts, bearings, valve bodies |
| PC/ABS Blend | 1.14 g/cm³ | 90–110°C | 0.4–0.6% | Automotive dashboards, laptop shells, power tools |
| PBT | 1.30 g/cm³ | 120–150°C | 1.5–2.2% | Electrical connectors, automotive sensors, switches |
| Material | Density | Heat Resistance | Shrinkage Rate | Typical Applications |
|---|---|---|---|---|
| PEEK | 1.32 g/cm³ | 250°C continuous | 1.0–1.3% | Medical implants, aerospace brackets, semiconductor parts |
| PPS | 1.35 g/cm³ | 200–220°C | 0.6–1.4% | Chemical pumps, automotive fuel systems, electrical parts |
| LCP | 1.40 g/cm³ | 240–280°C | 0.1–0.3% | Ultra-thin connectors, 5G antenna parts, micro-components |
| PSU / PPSU | 1.24 g/cm³ | 150–190°C | 0.6–0.8% | Medical sterilizable parts, plumbing, aerospace |
| Material | Density | Heat Resistance | Shrinkage Rate | Typical Applications |
|---|---|---|---|---|
| TPU (Thermoplastic PU) | 1.12 g/cm³ | -40 to 80°C | 1.0–2.0% | Phone cases, footwear, cables, seals, medical tubing |
| TPE / SEBS | 0.90 g/cm³ | -50 to 120°C | 1.5–2.5% | Soft-touch grips, overmolding, baby products |
| Silicone (LSR) | 1.12 g/cm³ | -60 to 200°C | 2.5–3.5% | Medical seals, baby nipples, keypads, wearable gaskets |
Don’t see your material? Contact our material engineers → We source specialty resins on request.
Mold Surface Finish Standards
Choose the right finish for your application, from optical-grade polish to industrial texture
SPI Finish Standards
Society of the Plastics Industry standards for mold cavity finish
| SPI Grade | Method | Surface Roughness | Typical Application |
| SPI A-1 | Grade #3, 6000 Grit Diamond | Ra ≤0.025 μm | Optical lenses, mirrors, clear parts requiring maximum clarity |
| SPI A-2 | Grade #6, 3000 Grit Diamond | Ra ≤0.05 μm | High-gloss cosmetic parts, premium consumer products |
| SPI A-3 | Grade #15, 1200 Grit Diamond | Ra ≤0.1 μm | Semi-gloss, most cosmetic-grade consumer plastic parts |
| SPI B-1 | 600 Grit Paper | Ra 0.05–0.10 μm | General cosmetic surfaces, automotive interior trim |
| SPI B-2 | 400 Grit Paper | Ra 0.10–0.15 μm | Low-sheen surfaces, non-critical cosmetic parts |
| SPI B-3 | 320 Grit Paper | Ra 0.20–0.30 μm | Medium smooth finishes |
| SPI C-1 | 600 Stone | Ra 0.30–0.35 μm | Functional non-cosmetic parts, industrial components |
| SPI C-2 | 400 Stone | Ra 0.35–0.40 μm | Utility parts |
| SPI D-1 | Dry Blast Glass Bead | Ra 0.8–1.0 μm | Matte/textured appearance, hides surface defects |
| SPI D-3 | Dry Blast #24 Oxide | Ra 3.2 μm | Heavy matte, anti-glare, industrial use |
Selected molded parts can also receive painting, coating, printing and other secondary treatments. Explore our surface finishing options for additional processes.
Mold Texture Options
EDM and chemical texturing for branded surface appearances
VDI 3400 Texture
EDM spark erosion texture scale 0–45
Mold-Tech Texture
Industry-standard leather & fine grain patterns
Custom Logo / Text
Molded-in branding on A-surface
Lifter Line Minimization
Precision alignment to hide parting lines
Post-Processing Options
- Painting & Coating
- Insert Threading (heat-set)
- Pad Printing
- Chrome / Metallic Plating
- Hot Stamping / Foiling
- Ultrasonic Welding
- Assembly & Packaging
- Full Dimensional Inspection
From CAD File to Production Parts
A proven, transparent process with clear milestones at every stage
Submit CAD Files & Requirements
Upload your 3D CAD files (STEP, IGES, Parasolid, SolidWorks, or AutoCAD format) along with your material preference, quantity, tolerance requirements, and surface finish specification. Our engineers begin review immediately upon receipt.
DFM Analysis & Quotation
Our mold engineers perform a full Design for Manufacturability (DFM) review, checking for moldability issues including draft angles, wall thickness, undercuts, and gate locations. You receive a detailed DFM report highlighting any concerns and recommended design changes, plus a complete quote covering tooling cost and per-part pricing.
Design Approval & PO Confirmation
Review the DFM report and quotation. Our engineers are available to discuss any design modifications that could improve quality or reduce cost. Once you approve the DFM and confirm the purchase order, mold fabrication begins immediately.
Mold Design & Engineering
Our mold design team creates detailed 3D mold designs including cavity & core layout, parting line definition, runner system, gate design, cooling channel layout, ejection system, and side action design. All designs undergo internal review before machining begins.
Mold Fabrication
CNC machining, EDM (sinker and wire), high-speed milling, and grinding operations produce the mold components. Critical dimensions are verified with CMM inspection at each manufacturing stage. Surface finish operations (polishing, texturing, coating) are completed to specification.
T1 Trial Shot & Inspection
First article trial shots (T1) are produced and subjected to a comprehensive dimensional inspection. A full First Article Inspection (FAI) report is generated documenting all critical dimensions against the nominal drawing. Any required adjustments are made to the mold before production approval.
Production & Quality Control
Approved production runs proceed with in-process SPC monitoring for critical dimensions. Finished parts receive visual inspection, dimensional sampling, and function testing as specified. All parts are cleaned, packaged, and labeled per your requirements before shipment.
How The Injection Molding Cycle Works
After the mold is installed and the process parameters are established, each molding cycle follows a controlled sequence.
Preparation before injection molding
- Raw material preparation: including plastic particle , plastic drying, pigment mixing.
- Tooling preparation: set up the tooling on the machine and do the inspection and maintainence to ensure the tooling quality and performance so as to meet the production requirements.
- The dry particles are poured into the hopper of the injection molding machine,when the particles are fed into the barrel,they are heated and melted at the same time.
Step 1 : Mold Closing and Clamping
The mold closes and the clamping system applies sufficient force to keep the parting line sealed during injection.
Step 2 : Plasticizing and Injection
Resin pellets are dried when required and melted inside the injection barrel. The screw then injects the molten material into the mold cavity.
Step 3 : Packing and Holding
Additional pressure is applied after the cavity fills to compensate for material shrinkage and improve dimensional stability.
Step 4 : Cooling
The part remains inside the closed mold until it has cooled sufficiently to retain its geometry during ejection.
Step 5 : Mold Opening
The clamping system releases and separates the mold halves after the cooling stage is complete.
Step 6 : Ejection and Part Removal
Ejector pins, sleeves or other ejection mechanisms release the molded component. The part is then inspected, trimmed or transferred to any required secondary operation.
Cycle parameters are established during mold trials and controlled during production to reduce short shots, flash, sink marks, warpage and dimensional variation.
Quality Assurance
Supplier certificates and material documentation are reviewed against the project requirements. XRF screening may be used to detect regulated elements associated with RoHS compliance.
When a restricted substance or material characteristic cannot be verified by XRF alone, additional documentation or laboratory testing should be arranged according to the applicable requirement.
Learn more about our quality assurance and inspection systems for prototype and production parts.
CMM Inspection
Renishaw coordinate measuring machines for 100% first-article dimensional verification
XRF Analysis
Fluorescence spectroscopy verifies resin composition and ensures RoHS/REACH compliance
SPC Monitoring
Statistical Process Control tracks key dimensions in real-time across production runs
Full Documentation
FAI reports, material certs, PPAP packages, inspection reports, all digitally archived
Documents We Provide
- First Article Inspection (FAI) Report
- Production Part Approval (PPAP)
- Material Certificates / Mill Certs
- Dimensional Inspection Report
- Process Capability Study (Cp/Cpk)
- RoHS / REACH Compliance
- Packing List & COC
- MSDS / SDS Sheets
Quality Certifications
ISO 9001:2015
Quality Management System, full facility and all processes
RoHS 3 Compliant
Verified via XRF spectroscopy for all plastics and metal inserts
REACH Compliant
SVHCs screened in all materials per EU regulation
PPAP Capable
Level 1–3 PPAP packages available for automotive customers
Injection Molding Design Guidelines
Following these guidelines reduces tooling cost, improves part quality, and avoids the most common DFM issues we see in submitted designs
Wall Thickness
Recommended: 1.5 – 4.0mm (uniform throughout part)
- Uniform walls reduce warpage, sink marks, and cycle time. Design ribs to 50–60% of wall thickness.
- Thick sections cause sink marks, warpage, and extended cycle time. Thin sections cause incomplete fill and surface defects.
If you need structural rigidity, use ribs instead of thicker walls. Ribs should be 50–60% of nominal wall thickness.
Draft Angles
Minimum: 0.5° · Recommended: 1–3° per side
- Adequate draft allows clean ejection, preserves surface finish, and extends mold life significantly.
- Zero-draft walls cause drag marks, galling, and part sticking, leading to ejection damage and shortened tool life.
Textured surfaces require additional draft, typically 1° per 0.025mm (0.001″) of texture depth.
Undercuts & Side Actions
Design undercuts only where functionally necessary
- External undercuts can often be handled with side actions. Internal undercuts may require lifters or collapsible cores.
- Excessive or deep undercuts increase mold complexity, cost, and cycle time significantly.
Share your design intent early, our DFM team can often redesign features to eliminate costly side actions.
Gate Location
Gates should be placed at thickest section of part
- Proper gate placement ensures complete fill, minimizes weld lines, and puts gate witness marks in non-cosmetic areas.
- Poor gate location causes short shots, weld lines in visible areas, and jetting defects on cosmetic surfaces.
For transparent parts, gate location is critical to avoid visible flow marks. Our engineers will advise during DFM review.
Radii & Sharp Corners
Minimum inside radius: 50% of wall thickness
- Generous radii distribute stress, improve material flow, and reduce stress concentration in finished parts.
- Sharp internal corners create stress risers, poor flow, and mold wear, leading to cracks in service.
Standard recommendation: R = 0.5T for inside radii and R = 1.5T for outside radii (T = wall thickness).
Sink Marks & Ribs
Rib thickness: 50–60% of nominal wall · Rib height: max 3x wall thickness
- Correctly proportioned ribs add rigidity without causing sink marks on the opposite surface.
- Ribs that are too thick create visible sink marks on the A-surface (cosmetic side) of parts.
For high-gloss cosmetic surfaces, reduce rib thickness to 40% of wall and polish the A-side cavity to SPI A2.
WHY CHOOSE SAMSHION FOR INJECTION MOLDING?
A successful injection molding program requires coordinated DFM, mold design, toolmaking, process validation and documented quality control. SAMSHION manages these stages as one connected manufacturing workflow.
Engineering-Led DFM
Our engineers review wall thickness, draft, ribs, bosses, undercuts, gates, parting lines, ejection and tolerance requirements before tooling begins.
Tooling for Each Production Stage
Prototype, bridge and production tooling options allow the mold material and service life to be matched to the expected production quantity.
Controlled Mold Trials
Trial molding is used to evaluate filling, packing, cooling, ejection, dimensions and cosmetic requirements before production approval.
Documented Quality Control
Inspection plans, dimensional reports, material certificates, FAI and PPAP documentation can be provided according to the agreed quality requirements.
Material and Finish Support
Our team helps evaluate resin performance, color, texture, surface finish and secondary operations according to the component’s intended use.
Production and Repeat-Order Support
Approved process information and project requirements are maintained to support repeat production, engineering changes and future volume increases.
Approved process information and project requirements are maintained to support repeat production, engineering changes and future volume increases.
Injection Molding Applications by Industry
Injection molding supports repeatable plastic components across industries that require consistent dimensions, functional performance and scalable production.
The examples below illustrate common applications. Material selection, testing, traceability and documentation requirements must be confirmed separately for each project and end-use environment.
Automotive
- Dashboard panels & trim
- Door handle mechanisms
- HVAC duct components
- Sensor housings & brackets
- Fluid reservoir caps
Common Materials: ABS, PP, PA66, POM, PC/ABS
Medical & Healthcare
- Syringe bodies & plungers
- Diagnostic device housings
- Surgical instrument handles
- Drug delivery device components
- Laboratory consumables
Common Materials: PP, PC, ABS, Ultem, PEEK, LSR
Consumer Electronics
- Phone cases & bezels
- Laptop keyboard frames
- Remote control housings
- USB/charging port covers
- Wearable device enclosures
Common Materials: ABS, PC/ABS, PP, TPU
Industrial Equipment
- Valve bodies & actuators
- Pump housings
- Cable management components
- Safety guard panels
- Machine operator interfaces
Common Materials: POM, PA, PBT, GF-PA, PPS
Aerospace & Defense
- Interior cabin components
- Connector housings
- Environmental seals
- Structural brackets (non-load bearing)
- Ground support equipment
Common Materials: PEEK, PSU, PPSU, Ultem, LCP
Consumer Goods
- Appliance housings & knobs
- Toy components & assemblies
- Sports equipment parts
- Personal care device bodies
- Storage & organization products
Common Materials: PP, ABS, PE, TPE, Nylon
Frequently Asked Questions
What is the minimum order quantity (MOQ) for injection molding?
There is no minimum order quantity. We can produce as few as 1 part from a prototype mold. However, injection molding becomes most cost-competitive at volumes of 500+ parts, where the tooling cost is amortized across enough parts. For very small quantities (1–50 pcs), we often recommend vacuum casting or CNC machining instead, our engineers will advise you on the most cost-effective process for your volume.
How much does injection mold tooling cost?
Tooling cost depends on part size, complexity, and mold type. As a rough guide: simple prototype aluminum molds start around $300–$1,500; bridge steel molds range from $2,000–$15,000; production hardened steel molds typically run $8,000–$80,000+. All quotes include a detailed DFM analysis at no charge. We’re typically 40–60% less expensive than US/EU mold shops for equivalent quality.
How long does it take from CAD file to first parts?
For prototype/aluminum tooling: 7–10 days from PO to T1 samples. For bridge steel tooling: 10–18 days. For production hardened steel tooling: 18–35 days. After T1 approval, production runs can begin within 1–3 business days. Expedited tooling is available on request, contact us to discuss your deadline.
Can you match a specific color (Pantone or RAL)?
Yes. We can color-match to any Pantone, RAL, or customer-supplied color chip. Colors are achieved through master-batch color concentrate blending. For critical color matches, we produce color-match trial shots and send samples for approval before full production begins. Note that some resins have limited color options (e.g., natural-colored PEEK and PPS).
Do you offer overmolding and insert molding?
Yes, both processes are available. Overmolding allows us to mold a second material (often TPE/TPU) over a rigid substrate, commonly used for soft-grip handles, waterproof seals, and aesthetic accents. Insert molding involves placing metal inserts (threaded brass, stainless, or aluminum) into the mold before injection, producing parts with permanently integrated fasteners. Please mention overmolding or insert molding requirements in your initial inquiry.
What CAD file formats do you accept?
We accept STEP (.stp, .step), IGES (.igs, .iges), Parasolid (.x_t, .x_b), SolidWorks (.sldprt, .sldasm), AutoCAD (.dwg, .dxf), Catia V5 (.CATPart), and STL (.stl). STEP format is recommended for best geometric accuracy. We can also work from 2D engineering drawings (PDF or DWG) if you don’t have 3D CAD files available.
Do you provide design assistance if my part has DFM issues?
Absolutely. Our DFM review is not just a pass/fail check, we provide specific recommendations to improve moldability, reduce tooling cost, and enhance part quality. For complex projects, we offer Engineering Change Order (ECO) support to revise your design before tooling commences. This service is included free of charge with every project.