Draft angles are small but essential. In Electronic Injection Molding, they help the part release smoothly from the mold. A proper draft angle prevents surface scratches, ejection issues, and damage to the mold or the housing. Every expert Mold Maker knows that the right draft angle is not optional—it is necessary.
In this article, we explain what draft angles are, why they matter, and how to apply them to your plastic housing mold design. These tips will improve your molding results and extend mold life.
What Is a Draft Angle?
A draft angle is a slight taper added to the vertical walls of a plastic part. It allows the molded housing to eject from the mold without scraping the sides.
Without a draft angle, the plastic sticks. This can damage the surface or cause the mold to open improperly. In Electronic Injection Molding, where tight tolerances are essential, such damage is unacceptable.
A typical draft angle is between 1° and 3°, but it varies depending on part shape, plastic type, and mold texture.
Why Draft Angles Matter in Housing Molds
Plastic shrinks slightly when it cools. This shrinkage causes the part to press against the core of the mold. If the wall is vertical with no draft, the part grabs the mold tightly. This makes it hard to eject.
A good draft angle solves this problem. It reduces friction. It allows air to get between the part and the mold. It also ensures the housing looks clean and professional when it comes out.
In Electronic Injection Molding, clean release is critical. Devices must look perfect, fit together, and perform well. A skilled Mold Maker always adds proper draft to avoid sticking, warping, or surface marks.
Tip 1: Add Draft to All Vertical Surfaces
Many beginner designers forget to add draft to vertical walls. This mistake causes expensive mold corrections later.
In any plastic housing project, vertical walls—especially deep ones—must have a draft angle. This includes internal walls, external walls, screw towers, ribs, and clips.
A good Mold Maker reviews all vertical surfaces before cutting the mold. They may even use software to highlight undrafted areas.
Tip 2: Increase Draft for Textured Surfaces
In Electronic Injection Molding, surface textures are often used for visual appeal or to hide defects. These textures increase friction between the part and the mold.
For textured surfaces, more draft is required. A minimum of 3° is standard, but deeper textures may need 5° or more.
The Mold Maker can advise on draft angles based on your chosen texture. They may suggest sample molding tests to avoid issues later.
Tip 3: Use Greater Draft for Deep Parts
If your housing design is deep or tall, the draft angle should be larger. This helps the plastic part release without dragging along the length of the mold wall.
A good rule is: the deeper the cavity, the more draft you need. For deep housings, 2°–4° is often used.
Professional Mold Makers apply draft early in the design. If they wait too long, changing the part shape later can delay the project.
Tip 4: Match Draft with Ejection Methods
Draft angles work with ejector pins or plates. These systems push the plastic part out of the mold.
If the draft angle is too small, the ejectors must work harder. This can deform or crack the housing. Worse, it can break small features like snap fits.
A smart Mold Maker plans the ejection system around the draft. They choose angles that let parts slide out with gentle force.
Tip 5: Don’t Forget Internal Features
It’s easy to forget the inside. But in Electronic Injection Molding, many housings have interior ribs, walls, or bosses. These must also have draft.
Without draft on internal features, parts can lock inside the mold. This leads to damage or failure during ejection.
A detailed mold design includes draft on everything. The Mold Maker uses CAD tools to apply draft to even the smallest ribs or clips.
Tip 6: Consider Assembly Needs
Some parts snap together. Others are fastened or glued. In each case, the draft angle affects how well the parts fit.
Too much draft may cause gaps. Too little may stop the parts from seating. You need just enough draft for release—but not so much that it harms assembly.
A good Mold Maker balances draft and fit. They understand both mold function and product design. They may even build a trial mold to test how parts join together.
Tip 7: Align Draft with Mold Parting Line
The parting line is where the mold opens. Draft angles must flow in the direction of mold opening.
If draft goes the wrong way, it causes undercuts. These are shapes that trap the part inside the mold. Undercuts require slides or lifters, which increase cost.
A professional Mold Maker positions the parting line carefully. They adjust draft angles to match the mold’s opening direction and avoid complex mechanics.
Tip 8: Review Draft in the CAD Stage
Never wait until tooling to check draft. Always review it early using 3D CAD software.
Most CAD systems include draft analysis tools. These tools show angles in color maps. They make it easy to see where draft is missing or too small.
Good communication between engineers and the Mold Maker during CAD review helps prevent costly changes later.
Tip 9: Follow Material Guidelines
Different plastics behave differently. Some shrink more. Some have higher friction. Each one needs different draft angles.
For example:
- ABS: needs 1°–2°
- Polycarbonate: needs 1° minimum
- Nylon: needs 1.5° or more
- Textured materials: need 3° or higher
Your Mold Maker knows these details. They will help you choose angles that match the plastic used in your electronic housing.
Tip 10: Think Long-Term Mold Life
Good draft not only helps the first part—it helps thousands that follow.
Molds wear over time. Surfaces get scratched. Ejection gets harder. If draft angles are too small, the mold wears faster. Parts start to stick or come out damaged.
A Mold Maker thinks long-term. They build draft angles that protect both the mold and the product through the entire production run.
Draft angles may seem small, but they have a big impact. In Electronic Injection Molding, they ensure smooth part release, better appearance, and longer mold life.
Every successful plastic housing includes proper draft. Whether it’s a flat wall, rib, boss, or snap, each feature must release easily from the mold. That’s where a skilled Mold Maker comes in.
By applying the tips above and working closely with your Mold Maker, you’ll avoid costly mold changes. Your electronic housings will look better, fit better, and perform better.
Start your housing project with draft in mind—and you’ll end it with a stronger, more reliable product.