Custom Plastic Components: 10 Terms To Know

Common Terms Used in Manufacturing Custom Plastic Components

Even if you’re an old hand at plastic injection-moulding and custom plastic components, there are some terms to know that can help facilitate communication between your staff and our design engineers. If you’ve ever spoken with engineers about your product and thought, “What are they talking about?”, this list is for you.

Plastics Industry Terminolgy

1. Cavity. This is the concave space in the mould that is filled with hot plastic to create your part. It’s sometimes referred to as “Side A” and typically makes up the outer surface of the moulded piece.

2. Core. This convex piece is “Side B” of the mould. It usually makes up the inner surface of the moulded piece.

3. Draft or Draft Angle. The draft or draft angle is the degree of tapering found along the sidewall cavity. This tapering helps facilitate ejection from the mould.

4. Flash. This is the excess plastic that goes outside of the moulding. It is located along a seam line and remains attached to the part.

5. Gate. This is the opening through which the liquid plastic enters the mould cavity. Excess plastic is trimmed from the gate area after ejection.

6. Line of Draw. This is the point where the two moulding halves separate. When open or split in half, the line reveals the injection-moulded part. The Line of Draw makes it possible for the piece to be ejected without sustaining damage from obstructions. You can see the Line of Draw on some finished products; it shows where the two halves met when the mould was closed.

7. Runner. The runner is the channel that carries the melted plastic from the injection-moulding machine to the gate and into the cavity.

8. Shrink Rate. All plastic shrinks a bit when it cools. The shrink rate tells you how much it will shrink. Values range from 0.001-0.060 per inch.

9. Sprue. The Sprue connects the runner to the nozzle of the injection-moulding machine.

10. Warp. Warp is exactly what you think it is – a distortion in the completed piece. Distortions are often caused by internal stress or uneven material flow into the cavity but they can also happen during cooling and compression.

Baytech Plastics Is Focused On You

This is just a short list of some of the most common terms used in the creation of custom plastic components. You’ll probably hear more terms used as you meet with our engineers and design staff. Don’t hesitate to ask questions and get clarification about anything during any point in the process of developing your prototype or even after we start production. We want you to feel confident and comfortable at all times during the process and if that means explaining some terms to you, we’ll do it! Our primary focus is your complete and total satisfaction, not just with the end product but also with our entire team from start to finish.

Contact Baytech Plastics at 705-526-7801 for engineering and design services of custom plastic components in Ontario. Email us at for request a quote or arrange a visit in person.