What Is a Three-Plate Injection Mold? A three-plate injection mold is a versatile tooling system used to produce plastic parts with flexible gate locations and efficient part separation. Compared with a two-plate mold, it includes an additional plate that creates a separate runner system. This design can improve product appearance, simplify gate removal, and support more complex injection molding applications.
A complete engineering guide to structure, gating systems, opening sequence, applications, and design considerations for three-plate injection molds.
A three-plate injection mold is a mold configuration that adds a second parting line to the standard two-plate structure, creating three separating plate sections instead of two: a fixed plate, a floating runner-stripper plate, and a moving plate. This additional plate allows the runner system to separate from the molded part automatically during mold opening, which makes three-plate tooling the standard solution whenever a part requires center or multi-point pin gating but the production budget or part geometry does not justify a hot runner system.
Unlike a two-plate mold, where the parting line and the gate typically sit on the same plane, and the runner remains attached to the part until manually trimmed, a three-plate mold introduces an intermediate “runner plate” that opens on its own stroke. This lets the designer place the gate directly over the center of the part — a geometric freedom that a two-plate edge-gated tool simply cannot offer. For plastic parts with circular symmetry, multiple cavities fed from a single sprue, or cosmetic surfaces where an edge gate would leave a visible witness mark, the three-plate mold remains one of the most widely specified tooling architectures in the injection molding industry.
This guide walks through the full anatomy of a three-plate mold, how its two-stage opening sequence works, the runner and gate types associated with it, when engineers should specify it over a two-plate or hot-runner alternative, and the design, cost, and troubleshooting considerations that determine whether a three-plate program succeeds in production.
Three-Plate Mold vs. Two-Plate Mold: Structural Differences
The core distinction between a three-plate injection mold and a two-plate injection mold is the number of parting lines and, consequently, the number of independent opening strokes the mold performs. A two-plate mold has one parting line and separates into two halves — the cavity (A) side and the core (B) side. A three-plate mold has two parting lines: one between the runner-stripper plate and the cavity plate, and one between the cavity plate and the core plate, so the tool opens sequentially in two stages controlled by a timed opening mechanism such as pull rods, latch locks, or a pinion-and-rack system.
Structural Comparison: Two-Plate Mold vs. Three-Plate Mold
| Attribute | Two-Plate Mold | Three-Plate Mold |
|---|---|---|
| Number of parting lines | 1 | 2 (sequential) |
| Typical gate location | Edge, along the parting line | Center or pin gate, anywhere on the part surface |
| Runner separation | Manual trimming or degating required | Automatic separation on the second opening stroke |
| Tooling cost (relative) | Baseline | 15%–35% higher than an equivalent two-plate tool |
| Cycle time impact | Baseline | Slightly longer due to the extra opening stroke |
| Mold height (Z-dimension) | Compact | Taller, due to the added runner plate stack |
| Best suited for | Flat or shallow parts, simple gating | Round, symmetrical, or multi-cavity parts needing center gating |
The added complexity of a three-plate mold is not arbitrary — it exists to solve a specific gating problem. When a part’s geometry demands that molten plastic enter at or near its geometric center, an edge gate cannot reach that location without leaving a long, visible runner scar across the part’s cosmetic face. The three-plate structure resolves this by routing the runner through a separate plate that lifts away cleanly once the part has cooled, leaving only a small, easily trimmed pinpoint gate vestige.
Tip: When evaluating whether a part needs a three-plate mold, check the part’s symmetry first. Round, dome-shaped, or radially symmetric parts almost always benefit from a center pin gate — and a center pin gate is very difficult to achieve without a three-plate or hot-runner structure. If the part is flat with an accessible edge, a two-plate tool is nearly always the more economical choice.
Anatomy of a Three-Plate Mold: Core Components
A three-plate injection mold builds on the same fundamental A-side/B-side logic as a two-plate tool, but inserts an additional runner-stripper plate between the fixed clamping plate and the cavity plate. Understanding each component’s role is essential before evaluating gating options or troubleshooting production issues.
Core Components of a Three-Plate Mold System
| Component | Location | Function |
|---|---|---|
| Top clamping plate | Fixed to the injection machine’s stationary platen | Anchors the sprue bushing and transfers clamp force |
| Runner (stripper) plate | Floats between the top clamping plate and the cavity plate | Carries the runner system; separates on the first opening stroke |
| Cavity plate (A-side) | Second parting line, above the core | Forms the external part surface; houses the pin gates |
| Core plate (B-side) | Moving half of the mold | Forms the internal part surface; carries the ejection system |
| Pull rods (puller bolts) | Connect the runner plate to the fixed platen | Control the timing and distance of the first opening stroke |
| Latch lock/ball catch | Between runner plate and cavity plate | Holds the runner plate closed until the pull rod stroke is exhausted |
| Sprue puller/undercut pin | At the sprue bushing outlet | Retains the sprue in the runner plate during the first opening |
| Ejector system | Core (B) side | Ejects the finished part on the main opening stroke |
The pull rod and latch lock system together form the “timing mechanism” of a three-plate mold. Without a controlled, sequenced opening, the mold would simply open at a single parting line, and the runner would never separate cleanly from the part. This is the single most mechanically distinctive feature of three-plate tooling compared to any other mold architecture, and it is also the component set most responsible for tooling cost, mold height, and long-term maintenance requirements.
How a Three-Plate Mold Opens: The Two-Stage Separation Sequence
The defining functional characteristic of a three-plate mold is its sequential, two-stage opening behavior. Rather than separating at a single plane like a two-plate tool, a three-plate mold performs two distinct movements in a controlled order every cycle.
Stage 1: Runner Plate Separation
When the injection molding machine begins its opening stroke, the pull rods engage first, holding the runner plate stationary relative to the machine’s stationary platen while the cavity plate begins to move away with the core side. This creates the first parting line gap — between the runner plate and the cavity plate — which is where the pinpoint gates shear and the runner system is exposed for removal. The latch lock (or ball catch mechanism) that normally clamps the runner plate to the cavity plate releases at a pre-set spring tension, allowing this first-stage separation to occur cleanly and repeatably.
Stage 2: Main Mold Opening and Part Ejection
Once the pull rod stroke is exhausted — typically after the runner plate has traveled far enough to allow the sprue and runner to drop free by gravity or be extracted mechanically — the mold continues opening at the second parting line, between the cavity plate and the core plate. This is the conventional mold-opening motion familiar from a two-plate tool, and it is where the ejector system engages to strip the finished part from the core.
Three-Plate Mold Opening Sequence Timeline
| Stroke Stage | Mechanism Active | Result |
|---|---|---|
| 1. Runner plate lift-off | Pull rods restrain runner plate; latch lock releases | Runner and sprue separate from the part at the pinpoint gate |
| 2. Runner/sprue drop | Gravity or a mechanical sweep arm | Runner system exits the mold, clearing the cavity for the next cycle |
| 3. Main mold opening | Core and cavity plates separate on the primary stroke | Part remains on the core, exposed for ejection |
| 4. Part ejection | Ejector plate and pins actuate | Finished part is released and removed by robot or gravity |
Tip: The pull rod stroke length must be calculated precisely — long enough to fully clear the sprue and runner from the cavity plate, but not so long that it interferes with the main mold-opening stroke or the safe operating envelope of the machine’s tie bars. Undersized pull rod strokes are one of the most common causes of runner-jam downtime on new three-plate tools during initial trials.
Runner and Gate Systems in Three-Plate Molds
The entire purpose of the three-plate architecture is to enable pin-gate designs that a two-plate mold cannot support. The runner system in a three-plate mold is machined into the runner (stripper) plate, and the gates connect that runner network down through the cavity plate to the part surface below.
Common Gate Types Used in Three-Plate Molds
| Gate Type | Typical Application | Advantage | Consideration |
|---|---|---|---|
| Pin gate (conventional) | Center-fed round or symmetrical parts | Minimal gate vestige; balanced radial fill | Requires draft on the gate land for clean shear |
| Sub-gate variant (three-plate) | Multi-cavity families needing hidden gates | Automatic degating on runner plate separation | Gate diameter must be tuned to the resin’s shear sensitivity |
| Multi-point pin gate | Large or thin-walled round parts | Reduces weld lines by filling from several points simultaneously | Requires balanced runner branching for even fill |
| Offset pin gate | Parts with a non-cosmetic zone off-center | Keeps the gate mark away from the visible face | May introduce asymmetric fill patterns |
Runner balance is especially critical in three-plate tooling because the runner system typically feeds multiple cavities from a single sprue, and any imbalance in flow length or cross-section between branches will cause uneven packing pressure — leading to short shots in the farthest cavity and flash in the nearest one. Naturally balanced (“H-pattern”) runner layouts are strongly preferred over artificially balanced layouts wherever cavity count and mold size allow.
Tip: Keep the runner cross-section in a three-plate mold as small as the resin’s flow properties allow. Because the entire runner system must separate cleanly and drop out of the tool every cycle, an oversized runner not only wastes material and extends cooling time, it also increases the mass that the pull rod and latch mechanism must handle on every opening stroke, accelerating wear on the timing components.
When to Choose a Three-Plate Mold: Application Scenarios
Selecting a three-plate mold over a two-plate or hot-runner alternative is a decision driven by part geometry, cosmetic requirements, production volume, and budget. The following scenarios represent the situations where three-plate tooling is most commonly specified.
Application Scenarios Favoring Three-Plate Mold Design
| Scenario | Why a Three-Plate Mold Fits |
|---|---|
| Round or radially symmetric parts (caps, lids, gears, knobs) | Center pin gating produces balanced, weld-line-free filling |
| Cosmetically sensitive surfaces | Small pinpoint gate vestige is easier to hide or trim than an edge gate scar |
| Multi-cavity family tools with symmetrical parts | A single sprue can feed several center-gated cavities through a balanced runner |
| Mid-volume production (moderate order quantities) | Avoids the higher upfront tooling and maintenance cost of a hot runner system |
| Materials sensitive to prolonged heat exposure | Cold runner in a three-plate tool avoids the extended residence time of some hot runner designs |
| Frequent color or material changes | Cold runner systems purge faster and more completely than hot runner manifolds |
Conversely, a three-plate mold is generally not the right choice for very high-volume production programs where the added material cost of a scrap runner every cycle becomes economically significant over millions of shots — in that scenario, a hot runner system typically offers a faster payback despite its higher initial tooling investment. Three-plate tooling is also a poor fit for very large parts, where the mass and travel distance of a separately opening runner plate becomes mechanically impractical.
Advantages and Limitations of Three-Plate Molds
Like any tooling architecture, the three-plate mold represents a deliberate set of trade-offs rather than a universally superior solution. Weighing these trade-offs against the specific part and program requirements is the core of sound mold design decision-making. A program manager evaluating a new part should treat the three-plate decision as a total-cost-of-ownership question rather than a simple tooling-quote comparison: the modest upfront premium over a two-plate design is frequently offset within the first production run by reduced labor for manual degating, fewer cosmetic rejects from visible edge-gate scarring, and more consistent cavity-to-cavity fill on multi-cavity family tools.
Advantages and Limitations of Three-Plate Mold Design
| Category | Detail |
|---|---|
| Advantage | Enables center or multi-point gating unavailable to a standard two-plate tool |
| Advantage | Automatic runner separation reduces manual labor and cycle-to-cycle variability |
| Advantage | Lower tooling investment than an equivalent hot runner system |
| Advantage | Faster color and material changeover than hot runner tooling |
| Limitation | Generates runner scrap every cycle, unlike a hot runner system |
| Limitation | Taller mold stack (added plate) increases mold weight and machine daylight requirements |
| Limitation | Slightly longer dry cycle time due to the added opening stroke |
| Limitation | Pull rod and latch mechanisms require periodic maintenance and add design complexity |
Tip: Ask your tooling partner for the projected dry cycle time difference between a three-plate design and a comparable two-plate or hot-runner design before finalizing the concept. On high-cavitation tools, even a half-second increase in dry cycle time compounds significantly across a multi-year production run and should be weighed against the tooling cost savings up front.
Three-Plate Mold vs. Hot Runner System: Cost and Performance Comparison
The most common architectural alternative to a three-plate mold is a hot runner system, which eliminates the runner entirely by keeping the melt channel heated between the machine nozzle and the gate. Both approaches can achieve center or multi-point gating; the choice between them is primarily an economic and process one.
Three-Plate Cold Runner vs. Hot Runner System
| Factor | Three-Plate Cold Runner | Hot Runner System |
|---|---|---|
| Upfront tooling cost | Moderate | High (manifold, heaters, temperature controller) |
| Per-cycle material waste | Runner scrap generated every shot | None; melt stays molten between shots |
| Cycle time | Slightly longer (extra opening stroke) | Shorter (no runner ejection stage) |
| Maintenance complexity | Mechanical (pull rods, latch locks) | Electrical and thermal (heater bands, controllers, sensors) |
| Color/material changeover | Fast; runner purges completely each cycle | Slower; manifold retains residual melt |
| Best production volume range | Low to mid volume | Mid to very high volume |
| Gate vestige | Small pinpoint mark, may need trimming | Minimal to none, depending on valve gate use |
For programs where annual volume is uncertain, material cost is low, or frequent color changes are expected, the three-plate mold’s lower upfront investment and faster purge characteristics generally outweigh the per-cycle material waste. For established high-volume programs with a stable resin and color specification, the amortized savings from a hot runner system typically overtake the three-plate mold’s cost advantage well before the tool reaches end of life.
Design Considerations for Three-Plate Molds
Successful three-plate mold design requires attention to several details that do not arise in simpler two-plate tooling. Getting these wrong is the most common source of first-article rejection and early production downtime on new three-plate programs.
Pull Rod Sizing and Placement
Pull rods must be sized for the mass of the fully loaded runner plate, including the frozen runner and sprue, and positioned symmetrically to prevent the runner plate from racking or binding during its opening stroke. Undersized or asymmetrically placed pull rods are a leading cause of premature wear and inconsistent runner separation.
Latch Lock (Ball Catch) Tuning
The spring tension in the latch lock mechanism must be calibrated so the runner plate stays fully closed during injection and packing — resisting the injection pressure pushing against it — while still releasing cleanly and consistently at the start of the opening stroke. Tension that is too high risks the runner plate not opening at all on cold-start cycles; tension that is too low risks premature flash at the runner-plate parting line during injection.
Mold Stack Height and Machine Compatibility
Because a three-plate mold adds an entire plate and two opening strokes to the tool, the overall mold height and the required machine daylight (the maximum distance the platens can separate) must be verified against the target injection molding machine specification early in the design phase, not after the tool is built.
Ejector System Coordination with the Second Opening Stroke
Because the ejector system on a three-plate mold only activates after both the runner separation stroke and the main opening stroke are complete, the timing of ejector plate travel must be coordinated so it never begins before the core and cavity plates have fully separated. Molders commonly use a dedicated ejector delay or a mechanically timed knock-out bar to prevent the ejector pins from engaging prematurely, which would otherwise risk part distortion or interference with the still-departing runner system above.
Cold Slug Wells and Sprue Retention
A cold slug well at the base of the sprue bushing captures the initial, partially cooled melt front before it enters the runner system, preventing this cooler material from flowing into the cavity and creating a visible flow defect. In a three-plate mold, the cold slug well also frequently doubles as part of the sprue puller mechanism, using an undercut or reverse-taper geometry to ensure the frozen sprue stays anchored to the runner plate — rather than the stationary sprue bushing — during the first-stage opening.
Guided Ejection and Angle Pin Considerations
On three-plate tools that also incorporate side-action cores or lifters for undercut features, the added opening stroke must be sequenced so that angle pins or hydraulic cylinders do not begin their motion until the runner plate separation is complete. Overlapping these motions without a proper interlock is a frequent cause of tool damage during early production trials, particularly on molds converted from an existing two-plate design rather than designed as three-plate tooling from the outset.
Key Design Parameters for Three-Plate Mold Tooling
| Parameter | Typical Range / Guidance | Design Impact |
|---|---|---|
| Pull rod diameter (small to mid molds) | 16–32 mm | Load capacity for runner plate mass during opening |
| Latch lock (ball catch) release force | Tuned above peak injection pressure at the runner parting line | Prevents premature flash while ensuring reliable release |
| Runner plate stroke distance | Sufficient to clear sprue length plus safety margin | Governs total machine daylight requirement |
| Pin gate land length | 0.5–1.0 mm | Controls shear quality and gate vestige size |
| Sprue puller undercut | Reverse taper or Z-pin retention | Ensures sprue stays with runner plate on first-stage opening |
Tip: During the design review, always request a full open-and-close motion simulation of the three-plate stack before cutting steel. This confirms that the pull rod stroke, latch lock release point, and ejector timing do not interfere with each other under real machine speed conditions — an issue that is far cheaper to correct on a 3D model than on a finished tool during trials.
Common Defects and Troubleshooting in Three-Plate Molds
Because a three-plate mold has more moving elements than a two-plate tool, its defect profile includes issues specific to the runner plate separation mechanism in addition to the standard injection molding defects associated with any tool.
Common Three-Plate Mold Defects and Root Causes
| Defect / Issue | Likely Root Cause | Corrective Action |
|---|---|---|
| Runner fails to separate from part | Insufficient shear angle or undersized pin gate land | Increase gate taper; verify gate land length |
| Runner plate does not open consistently | Latch lock tension miscalibrated or worn | Re-tune spring tension; inspect ball catch wear |
| Flash at the runner-plate parting line | Latch lock releasing prematurely under injection pressure | Increase latch tension; verify clamp force distribution |
| Sprue does not release from bushing | Inadequate sprue puller undercut | Rework sprue puller geometry; check cold slug well |
| Uneven cavity fill in multi-cavity tools | Unbalanced runner branch lengths or cross-sections | Rebalance runner layout; verify with fill simulation |
| Pull rod binding or premature wear | Asymmetric loading or misalignment during opening | Re-verify pull rod placement and lubrication schedule |
| Gate vestige too large or rough | Oversized pin gate diameter for the resin viscosity | Reduce gate diameter; adjust injection speed profile |
Quality Control and First-Article Inspection for Three-Plate Mold Parts
First-article inspection on a new three-plate mold program needs to verify more than just part dimensions — it must also confirm that the two-stage opening sequence is producing consistent, repeatable gate shear and runner release across the full production shot count, not just during initial sample runs. A part that measures correctly on the first ten shots but shows increasing gate vestige size or occasional runner-retention faults by shot two hundred points to a mechanism that needs further tuning before the tool is released to full production.
First-Article Inspection Checklist for Three-Plate Mold Programs
| Inspection Point | What to Verify |
|---|---|
| Gate vestige consistency | Uniform size and location across all cavities and repeated cycles |
| Runner release reliability | Clean separation over a sustained run, not just initial samples |
| Cavity-to-cavity dimensional variation | Consistent fill and packing across all cavities fed by the runner |
| Weld line location and strength | Matches simulation predictions; no unexpected weld lines from uneven fill |
| Latch lock wear indicators | No drift in release timing after extended cycling |
| Ejector marks and part flatness | No distortion introduced by ejector timing relative to the second opening stroke |
Because the runner separation mechanism is mechanical rather than electronic, its performance can drift gradually as springs relax and wear surfaces polish or roughen over tens of thousands of cycles. Building a scheduled inspection interval for the latch lock and pull rod assembly into the tool’s preventive maintenance plan — rather than waiting for a production defect to surface — helps catch this drift before it affects shipped parts.
Tip: Include a dedicated production validation run of at least 500 to 1,000 continuous cycles before final tool sign-off, specifically to confirm that the runner plate separation mechanism performs consistently under sustained heat cycling rather than only during a handful of sample shots taken from a cold or lightly run tool.
Cost Factors and Lead Time for Three-Plate Mold Tooling
Three-plate mold tooling typically costs 15% to 35% more than an equivalent two-plate tool for the same part, driven primarily by the additional plate, the pull rod and latch lock hardware, and the added machining time required to build a second precision parting line. Lead time is generally extended by one to three weeks compared to a two-plate program of similar complexity, largely due to the additional fitting and motion-testing required to validate the two-stage opening sequence during mold trials.
Three-Plate Mold Cost and Lead Time Drivers
| Cost/Lead Time Driver | Impact |
|---|---|
| Additional runner plate machining | Adds precision machining hours for the second parting line |
| Pull rod and latch lock hardware | Adds component and assembly cost not present in two-plate tools |
| Increased mold base size | Larger mold base stock and higher steel cost |
| Extended trial and fitting time | Two-stage opening motion requires additional bench fitting and trial cycles |
| Cavitation count | Multi-cavity three-plate tools scale cost with runner balancing complexity |
Cavity count, resin selection, and cosmetic surface finish requirements all compound these baseline cost drivers. Programs with tight budgets and moderate production volumes often find that a well-optimized three-plate design still delivers a lower total cost of ownership than a hot runner alternative, particularly when the program includes multiple color variants or is expected to run for a limited number of years before design revision.
Sourcing teams evaluating quotes from different tool shops should request a like-for-like breakdown of steel type, cavitation count, and expected mold life in shots, since two three-plate quotes with a similar headline price can differ substantially in long-term durability and maintenance cost once these variables are accounted for.
Materials Commonly Molded in Three-Plate Tooling
Because three-plate molds use a cold runner rather than a heated manifold, material selection plays a larger role in process stability than it does with hot runner tooling. Every shot’s runner and sprue cool to a solid state and must shear cleanly at the pin gate, so resin flow characteristics, shrinkage behavior, and brittleness all influence how well a given material performs in a three-plate configuration.
Material Suitability for Three-Plate Mold Gating
| Material | Suitability for Pin Gating | Design Note |
|---|---|---|
| ABS | Excellent | Shears cleanly at small gate diameters; low gate vestige |
| Polypropylene (PP) | Good | High shrinkage requires careful cavity dimensioning |
| Polycarbonate (PC) | Fair to good | Higher melt viscosity may require a slightly larger gate |
| Nylon (PA6, PA66) | Good | Fast crystallization aids clean gate shear |
| POM (Acetal) | Excellent | Low viscosity flows well through small pin gates |
| Glass-filled resins | Fair | Abrasive fillers accelerate gate land wear; harden gate inserts |
| TPE/TPU | Poor to fair | Flexible materials resist clean shear; often better suited to a different gate type |
For brittle or highly abrasive materials, gate inserts are frequently specified as replaceable, hardened components rather than machined directly into the cavity plate steel. This allows the gate land to be refreshed or resized after wear without requiring a full cavity insert replacement, extending the useful production life of the tool.
Tip: When a program is expected to run a glass-filled or mineral-filled resin through a three-plate mold, specify a hardened, replaceable gate bushing at the design stage rather than cutting the gate directly into the main cavity steel. The incremental tooling cost is small compared to the cost of reworking a worn gate on a production tool later.
Frequently Asked Questions
Q1. What makes a mold a “three-plate” mold instead of a two-plate mold?
A mold is classified as three-plate when it has two independent parting lines and opens in two sequential stages, controlled by pull rods and a latch lock mechanism. A two-plate mold has only one parting line and one opening stroke. The extra plate — the runner (stripper) plate — is what allows the runner system to separate automatically from the part.
Q2. Why would an engineer choose center gating over edge gating?
Center gating fills radially symmetric parts evenly from the middle outward, minimizing weld lines and balancing shrinkage around the part’s circumference. Edge gating on the same part geometry typically produces uneven fill, visible flow lines, and a gate scar on a potentially cosmetic surface — problems that a three-plate mold’s pin gate is specifically designed to avoid.
Q3. Does a three-plate mold cost significantly more than a two-plate mold?
Yes, typically 15% to 35% more for a comparable part, due to the additional runner plate, pull rod, latch lock hardware, and extended fitting and trial time needed to validate the two-stage opening sequence. The exact premium depends on part size, cavitation count, and runner complexity.
Q4. How does the runner separate from the part automatically?
During the first stage of mold opening, pull rods hold the runner plate stationary while the cavity plate begins to move away, shearing the pin gates at their narrowest point. A latch lock releases at a calibrated tension to permit this motion, after which the runner and sprue drop free of the tool before the main opening stroke proceeds.
Q5. Is a three-plate mold suitable for high-volume production?
Three-plate molds work well for low to mid production volumes. For very high annual volumes, the recurring cost of runner scrap and the added dry cycle time from the extra opening stroke generally make a hot runner system more economical over the tool’s production life, despite its higher upfront cost.
Q6. What causes a three-plate mold’s runner plate to open inconsistently?
Inconsistent runner plate opening is most often caused by miscalibrated or worn latch lock tension, asymmetric or undersized pull rods, or insufficient gate taper preventing clean shear at the pin gate. A design review with a full motion simulation before tool build significantly reduces this risk.
Q7. Can a three-plate mold run multiple cavities from one sprue?
Yes, and this is one of the architecture’s most common applications. A single sprue feeds a balanced runner network in the runner plate, which distributes melt to multiple center-gated cavities. Runner balance — equal flow length and cross-section to every cavity — is critical to prevent short shots and flash between cavities.
Q8. How much taller is a three-plate mold compared to a two-plate mold, and does it matter?
The added runner plate typically increases overall mold stack height, which in turn increases the machine daylight (maximum platen separation) required to complete both opening strokes. This must be checked against the target injection molding machine’s specifications during the design phase, since an undersized machine cannot fully open a three-plate tool.