Custom Cold Runner Injection Mold Manufacturer for Cost-Efficient Plastic Tooling
GBM designs and manufactures custom cold runner injection molds for prototype validation, low-to-medium volume production, multi-cavity parts, family molds, and material or color change projects.
- Custom 2-plate, 3-plate, multi-cavity, and family cold runner mold design
- Lower initial tooling investment compared with complex hot runner systems
- Runner, gate, cooling, venting, and ejection design based on part geometry
- T1 mold trial, sample inspection, CMM report, and mold trial video available
- Export-ready mold package with drawings, spare parts, and secure packaging
Quick Facts
- Mold Type: 2-plate / 3-plate / multi-cavity / family mold
- Runner System: Unheated cold runner
- Best For: Prototype, low-to-medium volume, color change projects
- Materials: ABS, PP, PC, POM, PMMA, PA, PBT, TPE, TPU, PEI, PPS, PEEK
- Support: DFM, moldflow, T1 samples, CMM reports
- Quote Data Needed: 2D/3D drawings, resin, annual volume, tolerance
Cold Runner Mold at a Glance
A practical runner system for lower upfront tooling cost, easier maintenance, material flexibility, and early-stage production validation.
What It Is
A cold runner injection mold uses unheated runner channels to transfer molten plastic from the machine nozzle to each cavity. The runner cools and is ejected together with the molded part.
How It Works
Molten resin flows through the sprue, runner, and gate into the cavity. After cooling, both the part and solidified runner are ejected, separated, trimmed, or reground.
Why Buyers Use It
Cold runner molds usually have lower initial tooling cost, simpler mold maintenance, easier color changes, and greater material flexibility.
What to Watch
Buyers should evaluate runner scrap, cycle time, trimming labor, resin cost, gate appearance, and whether a hot runner system would be better for high-volume production.
A cold runner mold is best when the project requires lower initial tooling cost, simpler maintenance, material flexibility, or early-stage production validation.
How a Cold Runner Injection Mold Works
In a cold runner mold, molten plastic flows through an unheated sprue and runner system before entering the cavity through the gate. The part and runner cool together, then both are ejected from the mold. This makes the mold structure simpler and more cost-effective, but buyers must consider runner scrap, trimming labor, cycle time, and regrind control.
Fig 1: Plastic flow path through sprue, cold runner, gate, and mold cavity.
01 | Plasticizing
Plastic resin is melted in the injection molding machine barrel.
02 | Injection Through Sprue
Molten plastic enters the mold through the sprue bushing and main sprue.
03 | Flow Through Cold Runner
The material flows through unheated runner channels inside the mold plate.
04 | Gate Into Cavity
Plastic enters the cavity through selected gate locations such as edge gate, submarine gate, pin gate, or tab gate.
05 | Cooling & Solidification
The molded part and runner cool together until they are solid enough for ejection.
06 | Ejection & Trimming
The part and solidified runner are ejected together. The runner is then trimmed, separated, or reground when allowed.
What GBM Controls in Cold Runner Mold Design
Runner Balance
Helps each cavity fill evenly
Gate Design
Controls filling, appearance, and trimming
Cooling Layout
Supports cycle time and part stability
Ejection Design
Reduces deformation and part damage
Cold Runner Mold Anatomy
| Component | Function | Why It Matters for Buyers |
|---|---|---|
| Sprue Bushing | Connects injection machine nozzle to mold | Affects material entry, pressure loss, and runner layout |
| Sprue | Main channel guiding molten plastic into runner | Affects initial material flow and total runner scrap |
| Runner | Unheated channels distributing plastic | Proper runner sizing balances filling and reduces pressure loss |
| Gate | Final entry point into the cavity | Determines cosmetic gate mark, trimming labor, and filling behavior |
| Gate Vestige | Remaining mark after gate trimming | Important for visible surfaces and assembly areas |
| Cavity & Core | Shape the external and internal part geometry | Directly affects tolerance, surface finish, and function |
| Cooling Channel | Regulates mold temperature | Critical for cycle time, warpage control, and part stability |
| Ejector System | Pushes parts and runners out | Helps avoid deformation, sticking, or runner separation issues |
| Parting Line | Mold split surface | Affects flash risk, appearance, and assembly fit |
| Slider / Lifter | Forms undercuts or side features | Increases mold complexity but enables complex geometry |
| Mold Base | Supports all mold components | Affects durability, standardization, and maintenance |
GBM Cold Runner Mold Specifications
| Parameter | GBM Support | Buyer Notes |
|---|---|---|
| Mold Category | Custom plastic injection mold tooling & manufacturing | Suitable for export molds or domestic molding production. |
| Runner System | Cold runner, or optimized runner system evaluation based on DFM | Recommended based on part design, resin cost, annual volume and quality. |
| Plate Structure | 2-plate mold, 3-plate mold (for specific gating requirements) | Selected according to gate location, part appearance and runner separation needs. |
| Cavity Options | Single-cavity, multi-cavity, family mold configurations | Based on annual quantity, part size, filling balance and tooling budget. |
| Gate Options | Edge, submarine, pinpoint, tab, fan, or direct sprue gating | Customized according to part geometry, cosmetic requirements and trimming method. |
| Suitable Plastics | ABS, PC, PP, POM, PMMA, PC/ABS, PBT, TPE, TPU, PEEK, PPS, PEI | Suitability depends on part geometry, resin behavior, runner size and volume. |
| Mold Base Standard | DME, HASCO, LKM, or customized to buyer specifications | Based on customer machine data, export market and maintenance preference. |
| Mold Steel | P20, H13, S136, NAK80, 718H, 1.2344 (Selected based on resin & volume) | Do not use one steel for all projects. Steel should match requirements. |
| Cooling System | Optimized conformal or standard cooling channels for fast cycle times | Important for cycle time, warpage control and part stability. |
| Ejection System | Ejector pins, stripper plates, sleeves, lifters, or sliders | Designed according to part shape, undercuts and demolding risk. |
| Mold Trial | T1 sampling in 15+ days, comprehensive trial pictures & videos | Helps buyers verify part quality before mold approval. |
| Inspection Reports | Sample QC report, full CMM dimension report, FAI / CPK capability | Useful for engineering approval and supplier qualification. |
| Delivery Documents | 2D/3D mold drawings, spare parts list, maintenance manual, QA certs | Especially important for export molds. |
| Packaging | Anti-rust coating, vacuum seal, secure export wooden case | Helps reduce mold damage risk during international shipment. |
Send your 2D/3D drawing, resin, annual quantity, tolerance, and surface requirements for a cold runner mold evaluation.
Cold Runner Mold Types We Manufacture
Two-Plate Cold Runner Mold
Best for: Simple parting line, standard plastic parts, cost-sensitive projects.
Design focus: Gate location, runner trimming, ejection stability.
Buyer benefit: Simple structure and lower initial mold cost.
Three-Plate Cold Runner Mold
Best for: Parts requiring more flexible gate location or automatic runner separation.
Design focus: Opening sequence, runner separation, gate size, mold complexity.
Buyer benefit: Better gate placement flexibility than standard two-plate mold.
Multi-Cavity Cold Runner Mold
Best for: Repeated output of the same part.
Design focus: Runner balance, cavity filling consistency, cooling balance.
Buyer benefit: Higher output while controlling tooling cost.
Family Cold Runner Mold
Best for: Multiple related plastic parts molded in one shot.
Design focus: Flow balance between different part sizes and weights.
Buyer benefit: Can reduce tooling cost for matched components when properly evaluated.
Prototype Cold Runner Mold
Best for: NPI, design validation, trial production, and market testing.
Design focus: Cost, manufacturability, quick design iteration.
Buyer benefit: Supports early-stage product validation before mass production tooling.
Cold Runner Mold for Engineering Plastics
Best for: ABS, PC, POM, PA, PBT, PPS, PEI, PEEK and other engineering materials.
Design focus: Runner size, gate design, venting, cooling, and resin behavior.
Buyer benefit: More stable molding performance when material behavior is considered in mold design.
Application Scenarios for Cold Runner Injection Molds
Prototype & NPI Plastic Parts
- Typical buyer: Engineers, product developers, startups.
- Typical parts: Housings, covers, brackets, test parts.
- Why cold runner fits: Lower initial tooling cost and easier design iteration.
- GBM support: DFM review, prototype mold, T1 sample, sample QC report.
Low-to-Medium Volume Production
- Typical buyer: Industrial parts purchasers, OEM teams.
- Typical parts: Functional covers, small enclosures, brackets, components.
- Why cold runner fits: Cost-effective tooling for moderate quantities.
- GBM support: Runner balance, CMM inspection, mold trial video.
Automotive Functional Parts
- Typical buyer: Automotive component suppliers.
- Typical parts: Clips, brackets, interior functional parts.
- Why cold runner fits: Suitable for selected parts depending on resin and quantity.
- GBM support: DFM, CMM report, FAI report, material certificate when required.
Electronics Housings & Connectors
- Typical buyer: Electronics manufacturers.
- Typical parts: Connector housings, switch covers, enclosures.
- Why cold runner fits: Suitable where tooling cost and quality control must balance.
- GBM support: Precision insert support, CMM inspection, material compatibility review.
Medical Device Components
- Typical buyer: Medical device product teams.
- Typical parts: Non-implant housings, covers, holders.
- Why cold runner fits: Suitable depending on material and validation needs.
- GBM support: Sample QC report, full CMM report, traceable inspection.
Material or Color Change Projects
- Typical buyer: OEM product teams.
- Typical parts: Parts requiring multiple colors or resin trials.
- Why cold runner fits: Easier color and material change compared with complex hot runner systems.
- GBM support: Material trial, mold trial video, process feedback.
Common Cold Runner Risks & GBM Solutions
Runner Scrap Cost
Risk:
The runner solidifies and is ejected with each cycle.
Business Impact:
Higher material waste, especially when resin is expensive.
GBM Solution:
Evaluate runner size, part weight, resin cost, regrind feasibility, and production volume before mold approval.
Unbalanced Filling
Risk:
Cavities may fill unevenly in multi-cavity molds.
Business Impact:
Short shots, flash, weld lines, or inconsistent dimensions.
GBM Solution:
Optimize runner layout, gate size, venting, cooling, and cavity balance.
Visible Gate Marks
Risk:
Gate trimming can leave marks on the part surface.
Business Impact:
Cosmetic rejection or assembly interference.
GBM Solution:
Select suitable gate type and location based on appearance and function requirements.
Longer Cycle Time
Risk:
Part and runner cool together.
Business Impact:
Cycle time may increase when runner size is large.
GBM Solution:
Optimize runner diameter, cooling channels, and mold temperature control.
Regrind Quality Risk
Risk:
Reused runner material may affect performance or appearance.
Business Impact:
Color variation, weak areas, or unstable molding.
GBM Solution:
Help evaluate whether regrind is acceptable based on material type and product requirements.
Wrong Runner System Selection
Risk:
Choosing cold runner only for low tooling cost may increase total part cost.
Business Impact:
High waste or inefficient production.
GBM Solution:
Compare cold runner and hot runner based on resin cost, volume, cycle time, and maintenance needs.
Why Choose GBM Cold Runner Injection Molds
Lower Initial Tooling Investment
Capability: Custom 2-plate, 3-plate, multi-cavity and family cold runner molds.
Support: Simpler structure, fewer heated components, easier maintenance.
Benefit: Reduces upfront mold investment for prototype, NPI and low-to-medium volume projects.
Runner & Gate Design First
Capability: Runner, gate, cooling and ejection designed around part geometry.
Support: DFM review, Moldflow analysis, mold layout review before steel cutting.
Benefit: Reduces risk of short shot, weld line, sink mark, gate mark and filling imbalance.
Easier Material/Color Change
Capability: Suitable for certain thermosensitive materials and color switching.
Support: Simpler runner path and easier cleaning compared with complex hot runner systems.
Benefit: Better flexibility for design validation and product variation projects.
T1 Mold Trial Before Shipment
Capability: GBM provides T1 samples, mold trial pictures and trial videos.
Support: Engineering review, sample checking and adjustment recommendations.
Benefit: Allows buyers to verify mold performance before final shipment.
CMM-Based Verification
Capability: 3D CMM testing, sample QC report, full dimension report, FAI / CPK.
Support: Incoming, in-process and final quality inspection.
Benefit: Helps engineering teams verify critical dimensions before approval.
Export-Ready Mold Package
Capability: Mold packing, shipment, spare parts list, drawings, maintenance support.
Support: Final fit/form/function inspection, water testing, packaging protection.
Benefit: Customers receive a mold easier to install and run in their own facility.
Cold Runner vs Hot Runner Injection Mold: Which One Should You Choose?
Cold runner and hot runner systems are not simply “good” or “bad”. The right choice depends on production volume, resin cost, part quality requirements, gate appearance, cycle time, maintenance preference, and tooling budget.
| Comparison Factor | Cold Runner Mold | Hot Runner Mold | Buyer Consideration |
|---|---|---|---|
| Initial Tooling Cost | Lower | Higher | Suitable when budget or validation cost is limited. |
| Mold Structure | Simpler, easier to maintain | Complex, requires heated manifold | Maintenance capability and local tech support matter. |
| Runner Scrap | Generated every cycle | Greatly reduced or eliminated | Affects material cost, regrind control and post-processing. |
| Material Efficiency | Less efficient if resin is expensive | Better for reducing material waste | Expensive engineering resins may justify hot runner investment. |
| Cycle Time | May be longer (runner must cool) | Often faster | Important for high-volume production. |
| Production Volume | Low-to-medium, prototype, NPI | High-volume production | Compare tooling cost and long-term part cost together. |
| Resin Cost | Better when cost is moderate | Better when resin is expensive | PEEK, PPS, PEI need careful cost evaluation. |
| Thermosensitive Materials | Suitable for selected materials | Needs careful residence time control | Material degradation risk should be evaluated. |
| Color Change | Easier to purge and clean | Harder, depending on manifold | Useful for multi-color product families and trial projects. |
| Gate Appearance | May require trimming, leaves vestige | Can improve gate control | Important for cosmetic surfaces. |
| Best For | Prototype, low-medium volume, lower budget, color change | High-volume, multi-cavity, expensive resin, lower waste | The best option depends on total project economics. |
Conclusion: A cold runner mold is not always the cheapest option in total cost. It usually reduces initial tooling investment, but creates runner scrap, trimming labor, and production volume limitations. GBM evaluates both cold runner and hot runner options through DFM to help buyers choose the most economical mold structure.
Not sure which runner system fits your part?
Buyer’s Guide: Choosing the Right Runner System
For early-stage projects, prototype tools and cost-sensitive production, a cold runner mold may be a practical choice. For high-volume production or expensive engineering resins, GBM may recommend a hot runner or optimized runner system after DFM review.
Optimized DFM & Runner Design by GBM
Annual Production
Check: Prototype, low, medium, or high volume?
Direction: Cold runner is often practical for prototype and low-to-medium volume production.
Resin Cost
Check: Is the resin expensive?
Direction: Expensive resin may make runner scrap less acceptable.
Heat Sensitivity
Check: Does the material degrade with long residence time?
Direction: Some thermosensitive materials may benefit from cold runner evaluation.
Part Size & Thickness
Check: Small, large, thin-wall, or thick-wall part?
Direction: Part size affects runner size, filling pressure, cooling time, and gate location.
Number of Cavities
Check: Single, multi-cavity, or family mold?
Direction: Multi-cavity molds need balanced runner and gate design.
Gate Appearance
Check: Are visible gate marks acceptable?
Direction: If not, gate location and trimming method must be reviewed carefully.
Trimming Labor
Check: Manual, automatic, or separated during opening?
Direction: Three-plate or optimized gate design may reduce trimming difficulty.
Tolerance Requirement
Check: Are there critical dimensions?
Direction: CMM inspection and trial validation are recommended before approval.
Color Change Frequency
Check: Frequent color or material changes?
Direction: Cold runner molds may be easier to clean than complex hot runner systems.
Tooling Budget
Check: Is initial mold cost a key concern?
Direction: Cold runner can reduce initial cost, but total part cost should be evaluated.
Project Stage
Check: Prototype, NPI, validation, or mass production?
Direction: Cold runner is practical for early-stage validation and moderate production.
Local Production Machine
Check: What machine will run the mold after export?
Direction: Mold standard, platen size, machine tonnage, and tie-bar space must be confirmed.
Material Compatibility for Cold Runner Molds
Cold runner mold suitability depends on resin cost, heat sensitivity, flow behavior, regrind allowance, surface requirements, and production volume. GBM evaluates material compatibility before recommending cold runner or hot runner tooling.
| Material | Cold Runner Consideration | GBM Support |
|---|---|---|
| ABS | Generally suitable. Runner scrap and gate trimming should still be considered. | Runner size, gate location and surface requirement evaluation. |
| PC | Requires attention to mold temperature, gate design, internal stress and appearance. | PC mold design, cooling layout, gate review and CMM inspection support. |
| PP | Usually suitable depending on shrinkage, part size and wall thickness. | Runner balance, cooling design and shrinkage control. |
| POM | Needs attention to shrinkage, venting and dimensional stability. | Gate, venting and CMM checking support. |
| PMMA | Requires careful gate and surface control for transparent parts. | Transparent plastic molding experience and appearance review. |
| PC/ABS | Common for housings. Gate and cooling design affect appearance and stability. | Mold design review, material selection support and inspection. |
| PBT | Dimensional stability and filling behavior should be evaluated. | Runner balance, gate design and sample inspection. |
| TPE / TPU / TPV | Needs attention to flow behavior, material sticking, demolding and ejection. | Draft angle, ejection, gate design and trial support. |
| PEI / PPS / PEEK | Possible, but resin cost and processing risk may favor hot runner. | DFM and runner system evaluation before tooling, precise heating/cooling. |
| PA + GF | Glass-filled materials require attention to wear, gate shear, flow and shrinkage. | Mold steel selection, gate design and dimensional verification. |
Material selection affects runner size, gate type, mold temperature, cooling design, trimming method, and regrind policy. Please confirm resin grade and product requirements before mold design.
Engineering & Mold Design Support
We identify manufacturing risks before steel cutting to ensure your cold runner mold can be produced, tested, shipped, and operated smoothly.
1. DFM Review
What we check: Parting line, wall thickness, draft angle, undercuts, gate location, runner layout.
Why it matters: Identifies manufacturing risks before tooling begins.
Output: DFM feedback with manufacturability risks, gate suggestions, draft angle issues, and mold structure recommendations.
Buyer Benefit: Reduces tooling modification risk after steel cutting.
2. Runner & Gate Design
What we check: Sprue, runner size, gate type, gate location, cavity balance, and trimming method.
Why it matters: Improves filling balance and minimizes cosmetic gate marks.
Output: Runner layout, gate location proposal, and trimming consideration.
Buyer Benefit: Reduces short shot, weld line, sink mark, and gate vestige issues.
3. Cooling & Ejection Design
What we check: Water line layout, ejector pins, plates, sleeves, sliders, lifters, and demolding direction.
Why it matters: Cold runner molds must cool and eject together with the molded part.
Output: Cooling channel layout, ejection arrangement, and slider/lifter review.
Buyer Benefit: Helps reduce cycle time and prevent part deformation.
4. Moldflow Analysis When Required
What we check: Filling balance, weld lines, air traps, pressure drop, and warpage risk.
Why it matters: Complex parts, multi-cavity molds, and family molds may require flow verification.
Output: Filling result, weld line review, air trap analysis, and design suggestions.
Buyer Benefit: Scientifically validates runner and gate design before cutting steel.
Quality Control & Inspection for Cold Runner Molds
For every export mold, GBM follows multiple quality checks, including steel hardness checking, 3D CMM inspection, water testing, mold trial, and final fit / form / function review before shipment.
Reports Available
- Steel hardness record
- Full 3D dimension report
- Trial pictures and videos
- CPK study when required
- Sample QC report
- Mold trial report
- FAI report when required
- Packing photos
Incoming Quality Control
Material check, mold base, components, hardness, and dimension review.
Machining Inspection
Electrode inspection, CNC / EDM / wire cutting process checking.
In-Process Mold Inspection
Steel dimension inspection during machining and assembly.
CMM Dimension Inspection
3D CMM check for samples, cores, cavities, sliders, and critical components.
Water Testing & Ejection
Cooling channel test, ejection action check, and mold movement review.
Final Fit / Form / Function
Confirm mold assembly, action, appearance, function, and trial status before shipping.
T1 Mold Trial Support Before Shipment
For export molds, T1 trial is especially important because runner balance, gate trimming, cooling time, ejection, and runner separation must be verified before shipment. GBM provides T1 samples and trial feedback to confirm whether the mold can meet part quality, appearance, and production requirements.
What Is a T1 Sample?
The first sample produced from a newly built injection mold during the first mold trial. It helps buyers verify filling behavior, appearance, dimensions, gate quality, ejection, and assembly performance before mass approval.
What GBM Checks
- Filling status and short shot risk
- Flash, burrs, and sink marks
- Gate mark and runner separation
- Runner balance in multi-cavity molds
- Trimming and ejection behavior
- Cooling and cycle stability
What Buyers Receive
- T1 samples
- Mold trial video
- Trial pictures
- Sample QC report
- CMM report if required
- Engineering feedback
- Adjustment plan if needed
Export-Ready Cold Runner Mold Packaging & Delivery
For export molds, packaging is not only about shipping protection. It also affects how easily the customer can install, validate, maintain, and restart production in their own facility.
Standardized Export Packaging for Seamless Global Delivery
Before Packing
- Final mold cleaning
- Anti-rust protection
- Water line check
- Ejection check
- Fit / form / function inspection
- Mold trial confirmation
Packing Process
- Anti-rust oil protection
- Protection film or wrapping
- Stable wooden case packaging
- Moisture protection when required
- Mold nameplate and shipping marks
- Spare parts packed separately
Documents Included
- Mold layout and 2D/3D drawings
- Spare parts list
- Mold trial video and QC report
- CMM report if required
- Maintenance instructions
- Water line and ejection check confirmation
Need an export mold ready for your local injection molding machine?
Send us your machine data, mold standard, and preferred documentation requirements.
From Inquiry to Delivery
-
1. RFQ Review
Buyer sends 2D/3D drawings, resin, annual quantity, tolerance, and surface requirements.
Upload Drawings
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2. DFM & Runner Evaluation
GBM checks whether cold runner, hot runner, or optimized runner design is more suitable.
Request DFM
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3. Mold Quotation
GBM provides quotation based on part structure, steel, cavity, gate, runner, and export requirements.
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4. Design Confirmation
Runner layout, gate location, cooling, ejection, and mold structure are confirmed.
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5. Manufacturing
CNC, EDM, wire cutting, grinding, fitting, and assembly work start.
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6. T1 Trial & Inspection
Parts, runner, gate, ejection, dimensions, and appearance are tested.
Review T1 Samples
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7. Adjustment & Approval
Mold is adjusted if needed. Customer confirms samples and performance.
Approve Shipment
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8. Packing & Shipment
Final check, anti-rust protection, documents, spare parts, and shipment.
Ask for Photos
GBM Mold Manufacturing Strength
Company Snapshot
GBM Mold has developed mold and molding capability since 2006, supporting export mold projects for automotive, electronics, medical device, aerospace, and industrial applications.
- • Since 2006
- • Export project experience
- • Multiple industry applications
Highlights: 1,800㎡ mold workshop, experienced engineering team, export project experience.
Engineering Team
Our team supports part analysis, DFM review, mold layout, runner and gate design, project communication, and drawing modification.
- • Part analysis & DFM review
- • Mold layout, runner & gate
- • Project communication
Benefit: Engineering risks are identified before steel cutting.
Mold Workshop
CNC machining, EDM, wire cutting, grinding, fitting, assembly, mold trial, and inspection equipment support mold quality control.
- • CNC, EDM, wire cutting
- • Grinding, fitting, assembly
- • Mold trial & inspection
Benefit: In-house control supports lead time and delivery stability.
Injection Molding Support
GBM supports mold trial, T1 samples, low-volume molding, and material testing with Haitian and Fanuc injection molding machines.
- • Mold trial & T1 samples
- • Low-volume molding
- • Haitian & Fanuc machines
Benefit: Seamless transition from trial to production.
Quality Control & Reports
CMM inspection, sample QC report, steel hardness checking, water testing, FAI, and CPK reports are available based on project requirements.
- • CMM & hardness checking
- • Water testing
- • FAI, CPK & sample QC
Benefit: Lower approval risk for strict industrial projects.
Export Project Support
GBM provides mold drawings, spare parts, maintenance notes, trial video, packaging photos, and shipping support.
- • Mold drawings & spare parts
- • Maintenance notes & videos
- • Packaging & shipping support
Benefit: Easier mold installation and production restart after delivery.
What Is a Cold Runner Injection Mold?
Definition
A cold runner injection mold is a plastic injection mold that uses unheated runner channels to transfer molten plastic from the injection machine nozzle, through the sprue and runner, and into the part cavity through the gate. Unlike a hot runner system, the plastic inside the runner cools and solidifies together with the molded part.
When Is a Cold Runner Mold Suitable?
A cold runner mold is commonly used for prototype tooling, low-to-medium volume production, cost-sensitive projects, material or color change projects, and selected thermosensitive materials. It is also useful when the buyer wants simpler mold structure, easier maintenance, and more flexible material changes.
What Should Buyers Consider?
Buyers should evaluate runner scrap, trimming labor, resin cost, cycle time, gate appearance, production volume, regrind policy, tolerance, and whether a hot runner system may reduce total part cost in high-volume production.
Frequently Asked Questions
1. What is the difference between a cold runner and a hot runner injection mold?
A cold runner mold uses unheated runner channels, while a hot runner mold keeps the plastic molten inside a heated runner system.
Cold runner molds usually have lower initial tooling cost but generate runner scrap, while hot runner molds reduce material waste and are often better for high-volume production.
Send us your part drawings, resin, annual quantity, part size, and tolerance requirements so GBM can help compare both runner options.
2. When should I choose a cold runner injection mold?
You should choose a cold runner injection mold when your project needs lower upfront tooling cost, prototype validation, low-to-medium volume production, or easier material/color changes.
Cold runner molds have a simpler structure and are easier to maintain, but runner scrap and trimming should be considered before final selection.
Please provide your 2D/3D drawings, plastic material, estimated production volume, part dimensions, and surface requirements for evaluation.
3. Is a cold runner mold cheaper than a hot runner mold?
A cold runner mold is usually cheaper in initial tooling cost than a hot runner mold.
However, the total project cost also depends on runner scrap, resin price, cycle time, trimming labor, and annual production volume.
Share your drawings, material grade, quantity, part weight, and dimensional requirements so GBM can calculate whether cold runner is truly more economical.
4. What are the disadvantages of cold runner injection molding?
The main disadvantages are runner scrap, gate trimming, possible longer cycle time, visible gate marks, and regrind control.
Because the runner cools and ejects with the part, material waste and post-processing may increase if the mold is not designed properly.
Send us your part design, resin, expected quantity, gate appearance requirements, and tolerance needs so we can reduce these risks during mold design.
5. What is the difference between a two-plate and three-plate cold runner mold?
A two-plate cold runner mold is simpler, while a three-plate cold runner mold allows more flexible gate placement and runner separation.
Two-plate molds are usually more cost-effective, but three-plate molds may be better when the part needs a specific gate location or improved runner removal.
Please provide your drawings, material, cavity requirement, part dimensions, and appearance requirements so GBM can recommend the right mold structure.
6. Can GBM design multi-cavity or family cold runner molds?
Yes, GBM can design multi-cavity and family cold runner molds based on your part structure, material, and production requirements.
These molds require careful runner balance, cavity filling control, cooling design, and Moldflow evaluation when needed to avoid short shots, flash, or inconsistent dimensions.
Send us all related part drawings, material, annual quantity, cavity target, and critical dimensions so we can review the mold feasibility.
7. Can runner scrap be reused or reground?
Runner scrap can sometimes be reground and reused, but it depends on the resin, product function, surface requirements, and quality standards.
Uncontrolled regrind may affect color stability, mechanical strength, appearance, and dimensional consistency, especially for precision or high-performance parts.
Please provide your material grade, product application, quality requirements, production quantity, and part specifications so GBM can evaluate regrind suitability.
8. What gate types can be used in a cold runner mold?
Common gate types include edge gate, submarine gate, pinpoint gate, tab gate, fan gate, and direct sprue gate.
The best gate type depends on part geometry, resin flow, cosmetic surface, trimming method, wall thickness, and assembly requirements.
Send your 2D/3D drawings, material, part size, surface finish requirements, and tolerance details so GBM can suggest a suitable gate design.
9. Can a cold runner mold be used for high-temperature plastics like PEEK, PPS, or PEI?
Yes, a cold runner mold can be used for some high-temperature plastics, but it must be evaluated carefully.
Materials like PEEK, PPS, and PEI are expensive and sensitive to processing conditions, so runner waste, mold temperature, gate design, and cycle stability must be considered.
Please provide your resin grade, drawings, production volume, part dimensions, and quality requirements so GBM can judge whether cold runner or hot runner is better.
10. What documents can GBM provide before mold shipment?
GBM can provide mold trial videos, T1 sample feedback, sample QC reports, CMM reports if required, spare parts lists, maintenance notes, and packing photos.
These documents help buyers verify mold performance, part quality, shipment readiness, and future maintenance before the mold arrives at their facility.
Tell us your required documents, drawing specifications, material, quantity, and inspection requirements so we can prepare the right delivery package.
11. What information do I need to provide for a cold runner mold quotation?
You need to provide 2D/3D drawings, material, annual quantity, cavity number, surface finish, tolerance requirements, and product application.
This information helps GBM evaluate mold structure, runner design, gate type, steel selection, inspection needs, and whether cold runner is suitable.
Please send your drawings, resin grade, production volume, part dimensions, and special quality requirements to receive a more accurate quotation.
12. Can GBM help decide whether my part needs a cold runner or hot runner mold?
Yes, GBM can help evaluate whether your part is better suited for a cold runner mold, hot runner mold, or another optimized runner solution.
The decision depends on resin cost, annual volume, part size, gate appearance, tolerance, cycle time, regrind policy, and tooling budget.
Send your drawings, material, quantity, part dimensions, and quality requirements, and GBM engineers can recommend the most practical runner system.
Get a Cold Runner Injection Mold Quote with Engineering Review
Send your 2D/3D drawings, resin, annual quantity and part requirements. GBM engineers will evaluate whether a cold runner mold, hot runner mold or optimized runner system is more suitable for your project.
What to Send for a Faster Quote
- 2D / 3D drawings
- Material or resin grade
- Annual quantity
- Surface finish & Tolerance
- Target market & Machine data
- Mold standard requirement