3 Gate Considerations to Improve Mouldability
Examine gate type and location when designing parts for injection moulding
A gate is a necessary element in injection moulding—a deliberate interruption in the otherwise continuous surface of a mould. While its vestiges are typically removed after moulding, either automatically or manually, it leaves its “footprint” on the finished part. Without it there would be no part, so since we cannot do away with gates—and because they can impact both the mouldability and quality of the part—there is good reason to consider their type and location when designing parts.
At Konlida, we use tab gates, hot tip gates, or pin gates depending on the shape and size of the part and the resin being injected.
🔗 ：Injection Moulding services
Tab Gates
The tab gate is the most commonly used of the three types. It consists of a trapezoidal block milled into the parting line on an exterior surface of the part, and is usually placed in a thicker wall section rather than thinner areas. Its position usually makes it easy to trim off, and while it typically leaves the largest vestige of the three gate types, its position at the parting line affects only the edge of the part, where it usually does not interfere with function or cosmetics.
Key advantages:
- Easy to manufacture, maintain, and process
- Considerable flexibility in placement along the parting line
- Confines ejection stress to the tab, which is trimmed off after moulding
- Ideal for use with filled resins (larger gate opening accommodates glass-filled materials)
For all these reasons, the tab gate is the first choice among gates.
Hot Tip Gates
The hot tip gate is positioned near the centre of a part rather than at the edge. This reduces the distance resin must travel to fill the mould and helps centre the clamping force the press applies to the mould. Hot tip gates are always on the A-side (cosmetic side) of the mould.
Key advantages:
- Ideal for round or domed parts requiring radial flow
- Takes up no space at the edge of the mould cavity—suitable for parts approaching maximum footprint size
- Helps centre clamping force
Considerations:
- Leaves a small raised bump (typically 1.52–2.03 mm diameter, 0.25–0.51 mm high) that can be trimmed
- May leave “blush” or flow marks in a circular pattern around the gate site—potentially problematic on cosmetic surfaces
- Can degrade resin in small shot sizes
- Small gate opening can become plugged with high glass‑fill resins
Pin Gates
The pin gate is the least common of the three gates. It is typically used for complex parts that cannot have gate vestiges on the edges (where tab gates would be) or on the cosmetic side (where hot tip gates are located). It is the only gate type located on the B‑side (non‑cosmetic surface) of the mould.
How it works:
Instead of introducing resin directly into the mould cavity, a pin gate injects resin into the ejector pin channel. The ejector pin is shortened, and resin is injected from the cone‑shaped “tunnel” gate through the empty section of the ejector pin channel and into the mould to form the part. Once the resin has hardened, the ejector pin pushes against the cylindrical post in the pin channel to eject the part. The pin gate shears the post from the tunnel gate, leaving a post rising from the surface of the ejected part, which is later removed manually.
Considerations:
- Geometry‑dependent—not suitable for all part designs
- Cone‑shaped tunnel gate precludes many glass‑filled resins
- Shearing during ejection places significant stress on the mould
- Angle and depth of the cone rules out use with many geometries (e.g., housings or cored‑out parts)
Advantage:
- Creates a vestige like an ejector pin mark, but trimmed flush to 0.13 mm proud
Summary Comparison
| Gate Type | Location | Best For | Key Limitation |
|---|---|---|---|
| Tab Gate | Parting line (edge) | Most parts, filled resins | Largest vestige |
| Hot Tip Gate | A‑side (centre) | Round/domed parts, large footprint | Cosmetic marks possible |
| Pin Gate | B‑side (non‑cosmetic) | Complex parts, non‑cosmetic surfaces | Geometry‑dependent, limited resin compatibility |
🔗 内链：Design for Manufacturing Toolkit → /resources/design-for-machining-toolkit/ (green – strong)
How to Specify Gate Location
When you upload a CAD model to Konlida, our quoting platform will automatically suggest gate type and location based on your part geometry and selected resin. You will have the opportunity to review and approve the gate placement on your order confirmation before tooling begins.
If you have questions or concerns about gate selection, our applications engineering team is available to discuss options and help you choose the best approach for your part.
🔗 内链：Upload CAD for a free DFM analysis and quote → /get-instant-quote/ (green – strong)
🔗 ：Contact our applications engineering team
Summary
Gate selection is a critical design consideration that affects both mouldability and part quality. While Konlida will recommend the optimal gate type and position based on your part design and resin choice, understanding the trade‑offs between tab, hot tip, and pin gates will help you make informed decisions during the design phase.
| Key Takeaway | Recommendation |
|---|---|
| Most common gate type | Tab gate – first choice for most applications |
| Best for cosmetic parts | Hot tip gate – but watch for blush marks |
| Best for complex/non‑cosmetic surfaces | Pin gate – geometry‑dependent |
| Filled resins | Avoid hot tip and pin gates; tab gate is preferred |