1. 2-Level Stack Mold
Engineered for shallow plastic parts where the buyer wants to double output per cycle without adding another injection molding machine. It optimizes existing clamping force for maximum productivity.
Room 101, Jiumo Technology Park, Gangsheng Road, Yabian Village, Shajing Street, Baoan District, Shenzhen City
Shenzhen City, China
Custom Stack Mold Manufacturer
for High-Volume Injection Molding
GBM designs and builds 2-level and multi-level stack molds for plastic parts that need higher output per injection cycle without adding another molding machine. Before mold cutting, our engineers review your CAD file, annual volume, material, part height, machine daylight, shot size, ejection method and hot runner balance.
2-Level & Multi-Level Stack Mold Design
Hot Runner Balance + Center Plate Review
DFM, T1 Trial and Export Mold Support
Mold Type
2-level stack mold / multi-level stack mold
Suitable Parts
Caps, lids, closures, thin-wall containers, shallow covers
Key Review
Machine daylight, shot size, shut height, ejection, hot runner balance
Support
DFM, mold design, machining, assembly, T1 trial, export packing
What Is a Stack Mold in Injection Molding?
Advanced Injection Technology
Redefining High-Volume Manufacturing
A stack mold is an injection mold with two or more parting lines arranged in a stacked structure. Instead of producing parts from only one molding face, a stack mold uses multiple molding faces in one injection molding machine, allowing more parts to be produced in the same cycle.
For suitable high-volume plastic parts, this helps increase output per machine without adding another press or taking more factory floor space. Stack molds are commonly used for shallow parts such as caps, lids, closures, thin-wall containers, medical disposables and packaging components.
x2
Production
Capacity
Increased Output
Double or even quadruple your production capacity within the exact same cycle time. Drastically lower your per-part manufacturing costs while meeting high-volume demands effortlessly.
Space Efficiency
Achieve massive production volumes without the need to invest in larger tonnage injection molding machines, saving valuable factory floor space and reducing capital expenditure.
When Should You Choose a Stack Mold?
Stack molds can double your production output without requiring larger injection machines, but they require specific part geometries and production conditions to be cost-effective.
Suitable for Stack Mold
- Annual demand is high and stable
- Part height is relatively low
- Same part needs higher output per cycle
- Machine has enough daylight and shot size
- Buyer wants lower unit cost at volume
- Caps, lids, closures, thin-wall containers
Better to Review Other Options
- Low-volume or uncertain demand
- Tall parts need long opening stroke
- Part structure has many side actions
- Existing machine has limited opening stroke
- Tooling budget is very limited
- Deep housings or complex undercuts
Not sure if your part is suitable?
Send your CAD file and machine model. GBM's engineering team will compare stack mold, multi-cavity mold, and standard mold options to find the most cost-effective solution before quotation.
Custom Stack Mold Design Options
As one of the premier suppliers of stack molds and among the top companies specializing in custom stack mold design, GBM Mold Technology Co., Ltd. provides industry-leading custom stack mold design and fabrication services. Explore our core design configurations tailored for high-volume precision injection molding.
2. Multi-Level Stack Mold Review
For projects with very high annual demand, GBM meticulously reviews part height, machine daylight, center plate weight, and ejection space before recommending robust 3-level or 4-level stack mold concepts.
3. Hot Runner Stack Mold
For projects requiring balanced melt delivery between front and rear parting lines. We specialize in configuring the stack mold hot runner manifold, back-to-back internal valve gate nozzles, and valve-to-valve melt transfer nozzles. GBM ensures precise manifold balance, advanced temperature control, and streamlined maintenance access.
4. Stack Mold for Caps & Closures
Tailored specifically for caps, lids, flip-top closures, over caps, and small packaging parts that demand extremely high cavitation output and a highly stable, repeatable cycle time.
5. Stack Mold for Thin-Wall Containers
Perfect for food containers, take-out boxes, cosmetic containers, and lightweight packaging parts. We apply strict flow length calculations, optimized conformal cooling, and superior warpage control.
6. Stack Mold for Medical & Labware
Designed for medical disposables, labware, diagnostic plastic parts, and small precision components where absolute part consistency, traceability, and clean ejection are critically important.
Is Your Injection Molding Machine Ready for a Stack Mold?
A stack mold project should not start from cavity count only. Before design, GBM checks whether your existing injection molding machine can support the mold thickness, opening stroke, shot volume, center plate weight and ejection method.
Industry Insight: High-Performance Machine Requirements
Leading equipment manufacturers like Husky clearly stipulate that stack molds demand higher machine specifications. The clamping unit must bear a significantly heavier mold weight with ample opening stroke and shut height. The injection unit requires a larger shot size, higher recovery speed, and increased injection rates. Furthermore, the mold itself must integrate a highly engineered hot runner system to guarantee perfect flow and temperature balance across all levels.
| Machine Item | Why It Matters for Stack Mold |
|---|---|
| Clamp tonnage | Check projected area and cavity pressure, not just number of mold levels. |
| Machine daylight | The machine must open enough for two parting lines and safe part ejection. |
| Shut height / mold thickness | Stack molds are significantly thicker than standard single-face molds. |
| Shot size | The machine must inject enough melt for both mold faces in one single cycle. |
| Recovery speed | Screw recovery must be fast enough to match the target cycle time. |
| Injection rate | Thin-wall or high-cavity parts may need much faster filling capabilities. |
| Tie-bar spacing | The larger stack mold base must physically fit between the machine tie-bars. |
| Mold weight capacity | The clamp unit must carry the heavy center section safely without sagging. |
| Ejection system | Center plate ejection or special knockout designs may be required. |
| Robot clearance | Important for high-speed automated removal of lids, caps, containers, and packaging parts. |
Unsure if your current machinery can handle a stack mold upgrade?
Our Stack Mold Manufacturing Process
No jumping ahead and no guessing. From the moment we receive your CAD file until your plastic parts are boxed and ready to ship, here is exactly how we keep your project on track.
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Build Custom Injection Molds
Need to scale up production quickly or tackle tricky designs like internal threads? We manufacture the exact tooling your project requires right in our own facility, ensuring consistent quality and keeping your costs under control.
Multi-Cavity Molds
Need high volumes? We build molds with 32, 64, or 128 cavities so you can produce dozens of identical parts in a single machine cycle. It i...
2-Shot Molding
Mix hard and soft plastics (like PC and rubber) in one step. By molding both materials at the exact same time, you completely skip the...
Unscrewing Molds
Dealing with bottle caps or threaded pipes? We build molds with internal gears that automatically unscrew your parts before they drop. This...
Hot Runner Systems
Stop paying for wasted plastic. These systems keep the material melted right up until it reaches the part cavity. This eliminates scrap...
Applications for Stack Molds
Caps and Closures
Bottle caps, flip-top closures, over caps and small threaded closure parts.
Thin-Wall Containers
Food containers, take-out boxes, trays and lightweight packaging parts.
Lids and Covers
Shallow lids, appliance covers, cosmetic packaging covers and small protective covers.
Medical Disposables
Labware, diagnostic plastic parts, syringe-related components and disposable medical parts.
Consumer Packaging Parts
Cosmetic containers, household product packaging, small boxes and repeated plastic parts.
High-Volume Small Plastic Parts
Clips, small housings, compact covers and repeated plastic components with stable demand.
Why Choose GBM for Custom
Stack Mold Projects?
Partner with an industry leader committed to delivering high-precision, cost-effective, and durable stack mold solutions tailored to scale your production capabilities.
Feasibility Review Before Quotation
We check part structure, annual volume, material, machine daylight, shot size and ejection requirements before recommending a stack mold.
Stack Mold Engineering Support
Our mold team reviews center plate support, hot runner balance, cooling layout, guide structure, linkage system and part drop clearance.
In-House Manufacturing and T1 Trial
GBM supports mold design, CNC/EDM machining, mold fitting, assembly and T1 trial under one project team.
Export-Oriented Project Communication
For overseas buyers, we provide English DFM communication, trial photos, T1 videos, sample delivery, mold packing photos and export documents.
PRACTICAL INJECTION MOLDING TIPS
How to Boost Output with Multi-Level Injection Molds
Let's talk about getting more parts out of your machines without buying new ones. At GBM Mold Technology, we help production teams figure out the most practical multi-cavity setups to save time and reduce costs.
Stack Mold vs. Tandem Mold: Which One Should You Choose?
If you need to make a lot of parts fast, you're probably looking at stack molds or tandem molds. The main thing to consider is how they open—and what your current machines can actually handle.
Here’s the simple breakdown. A stack mold opens all its sections at the exact same time. It practically doubles your output in one go, but your machine needs enough space (daylight) and a powerful injection unit.
A tandem mold, on the other hand, opens one side while the other side is cooling down. It’s a bit slower than a stack mold, but it’s great if your machine has a lower injection capacity, or if you need to run two different parts during the same cycle.
Stack Mold: Opens all at once. Best for doubling output quickly, but requires a larger, stronger machine.
Tandem Mold: Opens one side at a time. Ideal for lower-pressure machines or running two different parts.
Keeping Things Aligned: How Our Linkage Systems Work
The secret to a reliable multi-level mold is making sure both halves open and close smoothly every single time. If the linkage system gets stuck, your whole process stops. That's why we focus heavily on building a mechanism you don't have to worry about.
Whether we use a rack-and-pinion gear system or mechanical linkage arms, our goal is simple: keep the mold balanced. We use tough, wear-resistant steel and machine everything to tight tolerances (±0.002mm) to prevent parts from grinding against each other. This keeps the center block right where it belongs and helps the mold run longer without constant maintenance.
WHAT THIS MEANS FOR YOU
We don't use a one-size-fits-all approach. We customize the gears or lever arms to fit your exact machine daylight specifications and how your parts need to eject.
Do You Need a Bigger Machine to Run a Stack Mold?
Building a 2-level stack mold doesn't require a machine twice as big. Here's how clamping force works to avoid overspending on equipment.
Why the Forces Cancel Out
The clamping force you need is based on the projected area of only one parting line, not both. When the melted plastic is injected, it pushes against the center block from both sides at the exact same time. Because these pressures push in opposite directions, they cancel each other out internally. You basically only need enough force to keep one half of the mold closed.
THE SIMPLE FORMULA
Tonnage = (Projected Area of ONE Side × Cavity Pressure) × 1.15
Why the 1.15? That is a 15% buffer we add to handle the runner system and any sudden pressure spikes during injection.
Let's Look at a Real Example
- Force needed for a standard 1-face mold: 300 Tons
- Levels in the stack mold: 2 Levels
- What most people think they need: 600 Tons
- Actual Required Tonnage: ~345 Tons
The Takeaway: You get twice as many parts per cycle using a standard 350T machine. You save money by completely avoiding the need to buy and run a massive, expensive 600T press.
Need DFM or Technical Support?
Our senior engineering team at GBM Mold Technology is ready to review your part design and recommend the optimal stack or tandem mold configuration. Connect with us directly.
Email Engineering Team
Annie@gbminjection.com
Direct Phone Line
+86 13632611848
Headquarters
Room 101, Jiumo Technology Park, Gangsheng Road, Yabian Village, Shajing Street, Baoan District, Shenzhen City
We Build and Test Your Molds Entirely Under One Roof
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Measuring Every Detail
We don't just assume the machines did it right. Our quality team uses CMM tools to actually measure the steel at every step, making sure your parts meet ISO standards before moving forward.
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Stable Machines for Clean Cuts
A good mold relies on good cutting. We use heavy-duty, imported CNCs and EDM machines so the metal surfaces come out perfectly smooth and accurate without needing manual grinding.
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Engineers You Can Actually Talk To
You won’t get lost in a corporate maze. With over 30 experienced mold designers and project managers in our shop, you get straight answers and regular updates from people who understand your project.
| What Machine We Use | Brand / Origin | How Many | What It Achieves |
|---|---|---|---|
| CNC Milling Machines(For cutting the main steel blocks) | Makino (Japan) | 5 | ±0.005 mm |
| Spark EDM Sinkers(For fine details and mirror finishes) | Sodick (Japan) | 8 | Ra 0.1 / ±0.003 mm |
| Wire EDM(For exact straight cuts and tiny holes) | Seibu (Japan) | 6 | ±0.002 mm |
| CMM Measuring Tools(For double-checking our dimensions) | Hexagon (Sweden) | 2 | ±0.0018 mm |
| Injection Presses(For mold testing and mass production) | Haitian / Engel | 25 | 90T - 1200T |
Trusted by Global Industry Leaders
Global Presence
Connecting with partners worldwide at major industry exhibitions.
Certified Quality Systems
Our commitment to excellence is backed by international standards.
Stack Molds Boost Production Without Bigger Machines
Getting More Parts From the Same Machine
Instead of running one standard layer of parts, a stack mold essentially puts two molds "back-to-back." When the injection machine opens, both layers eject parts at the exact same time.
This means you can double or even quadruple your daily output without needing to rent floor space for a massive, expensive injection press. We carefully balance the hot plastic flow across all levels so every single piece comes out identical.
Keeping the Mold Opening Smooth and Balanced
The trickiest part of building a stack mold is making sure both layers open exactly at the same time without jamming. If the timing is off, the mold gets damaged. We use heavy-duty mechanical gears (like rack and pinion systems) to physically link the mold halves, forcing them to open and close smoothly together.
- Custom hot runners so the melted plastic reaches every cavity at the exact same time.
- A solid center block that won't bend or flex under high injection pressure.
- Smart water cooling lines to harden the plastic faster and shorten your cycle times.
Why Do So Many Stack Molds Fail During Production?
Building a stack mold is more than combining two molds. Their weight and complexity mean even minor errors can ruin the tool or harm your machine. Our engineering team ensures your mold works perfectly from the first trial.
3 Common Design Traps We Help You Avoid
Error 01
01 The Middle Plate Sagging
The center section of a stack mold is extremely heavy. If it isn't supported properly with sturdy guides or rollers, it will start to sag downward when the mold opens. This bends the pins, ruins your dimensional accuracy, and wears out the mold fast.
Error 02
02 Plastic Flowing Unevenly
The hot plastic has to travel different distances to reach both layers. If we don't balance the hot runner system perfectly, one side fills up before the other. This causes ugly flash on some parts and half-empty (short) shots on others.
Error 03
03 Trapped Heat and Warping
With two layers of hot plastic, a stack mold generates twice as much heat as a normal mold. If the water cooling lines aren't planned correctly, the center plate gets too hot. Uneven cooling means your parts will shrink unpredictably and warp out of shape.
Is Your Injection Machine Actually Big Enough for a Stack Mold?
A stack mold needs more than just clamping force. Run through this quick checklist to make sure your current factory machines can physically handle the mold before you commit to a design.
1
Can the machine open wide enough?
(It needs to open far enough to drop parts from TWO parting lines, not just one.)
2
Can it melt enough plastic at once?
(You are shooting double the amount of plastic per cycle, so your shot size needs to be large enough.)
3
Do you have enough clamping force?
(Remember, you only calculate the force for one layer, plus a 15% safety margin.)
4
Can the machine eject from the middle?
(Standard machines push from the back. Stack molds need a specialized knockout system to push parts off the center plate too.)
5
Can the machine hold the heavy weight?
(Stack molds are massive. Your machine's tie bars and platens must be rigid enough to hold it without tilting.)
Let's Review Your Stack Mold Idea
Not sure if your part can be turned into a stack mold? Send us your 3D CAD files and machine specs. Our engineers will take a look and give you honest feedback on how to make it work, helping you get reliable T1 samples in just 15 days.
Annie@gbminjection.com
+86 13632611848
Frequently Asked Questions
Have technical questions about implementing a stack mold for your next project? Our engineering team is ready to assist.
What is a stack mold in injection molding?
A stack mold is an injection mold with two or more parting lines arranged in a stacked structure. It allows one injection molding machine to produce parts from multiple mold faces during the same molding cycle.
How does a stack mold increase production efficiency?
A stack mold increases production efficiency by producing more parts per injection cycle. For suitable shallow and high-volume parts, filling, cooling and ejection happen across multiple mold faces with only a limited increase in cycle time.
What are the advantages of using a stack mold?
The main advantages are higher output per machine, better factory floor space utilization, lower unit cost at high volume and reduced need to buy another injection molding machine.
Is a stack mold the same as a multi-cavity mold?
No. A multi-cavity mold usually has multiple cavities on one parting line. A stack mold has two or more parting lines. Some stack molds can also be multi-cavity, but the mold structure is different.
What is the difference between a stack mold and a tandem mold?
A stack mold usually opens multiple parting lines together and ejects parts from multiple levels in one cycle. A tandem mold uses alternating mold actions, often allowing one side to cool while the other side opens or fills.
What parts are suitable for stack molds?
Stack molds are suitable for high-volume, relatively shallow plastic parts such as caps, closures, lids, thin-wall containers, cosmetic packaging, food containers, medical disposables and small repeated components.
What parts are not suitable for stack molds?
Very tall parts, deep housings, parts with long ejection strokes, low-volume projects, unstable part demand or parts with many side actions may not be ideal for stack mold tooling.
Do I need a larger injection molding machine for a stack mold?
Not always for clamp tonnage, but the machine must have enough daylight, shut height, shot size, recovery speed, mold weight capacity, tie-bar spacing and ejection capability.
Why is hot runner balance important in a stack mold?
A stack mold must deliver plastic melt evenly to different mold faces. Poor hot runner balance can cause short shots, flash, part weight difference, color variation and inconsistent dimensions between levels.
How much does a stack mold cost?
Stack mold cost depends on stack level, cavity count, part size, material, hot runner system, cooling design, ejection method, steel selection, surface requirement and tolerance requirement. A reliable quote needs CAD files and machine specifications.
Is a stack mold worth the higher upfront cost?
A stack mold is worth considering when production volume is high and the part is suitable for multi-level molding. For low-volume or uncertain projects, a standard mold or multi-cavity mold may be safer.
What information should I send for a stack mold quotation?
Please send 2D/3D drawings, material, part weight if available, annual quantity, target cycle time, surface requirement, tolerance requirement and injection molding machine specifications.
Get In Touch
Contact Our Engineering Team
Send us your 2D/3D drawings for a comprehensive DFM and quotation within 24 hours.
Email Us
Annie@gbminjection.comCall Us
+86 13632611848Factory Address
Room 101, Jiumo Technology Park, Gangsheng Road, Yabian Village, Shajing Street, Baoan District, Shenzhen City
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