How to blend casting seams

Introduction

In this blog we detail how to blend casting seams. We specifically look at working with aluminium but also a variety of materials.

What is a casting seam?

A casting seam refers to an imperfection or irregularity that occurs during the casting process in manufacturing.

It occurs when two portions of the mould used to shape a molten material (such as metal or plastic) come together, leaving a visible line or mark on the finished product where the two mould sections meet.

These seams can be caused by several factors, including misalignment of the mould sections, wear and tear on the mould, or insufficient pressure during the casting process.

Why are casting seams undesirable?

Casting seams are considered undesirable for several reasons:

Aesthetic appearance: Casting seams can create visible lines or marks on the surface of the finished product, which detracts from its overall appearance. In industries where visual appeal is important, such as automotive, consumer electronics, or luxury goods, casting seams can significantly reduce the perceived quality of the product.
Structural integrity: Casting seams represent weak points in the material where two mold sections meet. These seams can potentially compromise the structural integrity of the product, leading to reduced durability or increased susceptibility to failure, especially under stress or load.
Functionality: In certain applications, such as precision engineering or medical devices, casting seams can interfere with the functionality of the product. They may create irregularities that impede the proper functioning of moving parts or contribute to dimensional inaccuracies, leading to operational issues or functional failures.
Surface finish: Casting seams can result in rough or uneven surface textures, making post-processing treatments, such as polishing or painting, more challenging and time-consuming. Achieving a smooth and uniform surface finish becomes difficult when dealing with prominent casting seams.
Customer perception: Products with visible casting seams may be perceived as lower quality or less refined by consumers. This perception can impact brand reputation and consumer trust, potentially leading to decreased sales or market competitiveness.

How to remove casting seams

Removing casting seams typically involves post-processing techniques aimed at smoothing out or eliminating the imperfections caused by the seam. Here are some common methods used to remove casting seams:

Grinding and sanding: One of the most common methods involves using abrasive tools such as grinding wheels, sandpaper, or abrasive blasting to manually remove the seam. This process gradually smooths out the surface, effectively eliminating the seam. However, it requires skill and precision to avoid over-removal or damaging the surrounding areas.

Machining: For metal castings, machining processes such as milling, turning, or drilling can be employed to remove casting seams. These processes use cutting tools to precisely remove material from the surface, eliminating the seam and achieving the desired dimensions and surface finish.

Chemical treatments: Chemical treatments, such as etching or pickling, can be used to selectively remove material from the surface of the casting, including the casting seam. These methods involve applying chemical solutions that dissolve or loosen the material along the seam, making it easier to remove or smooth out.

Vibratory finishing: Vibratory finishing or tumbling involves placing the castings in a vibratory bowl or tub along with abrasive media. The vibrations and movement of the media against the surface of the castings help to remove the casting seams and achieve a smoother finish. This method is often used for smaller, more intricate castings.

Filling and re-machining: In some cases, particularly if the casting seam is deep or extensive, it may be necessary to fill the seam with a suitable filler material and then re-machine the surface to achieve the desired finish. Common filler materials include epoxy resin or metal alloys that can be machined to match the surrounding surface.

Automated finishing processes: In modern manufacturing facilities, automated finishing processes such as robotic grinding or polishing may be used to remove casting seams efficiently and consistently. These systems are programmed to precisely remove material from the surface of the casting, ensuring uniform results.

The choice of method depends on factors such as the material of the casting, the size and complexity of the part, the desired surface finish, and the available equipment and expertise. In many cases, a combination of different techniques may be employed to achieve the best results.

RODA Point for removing casting seams

In the video below, we have used a RODA Unitized wheel for removing casting seams. Unitized material not only buff and blends but it leaves a bright finish. This is being used on Aluminium and is done in Blue Unitized which is coarse. RODA points come in a range of shapes and sizes – and we can make them here in the UK so can even make bespoke for your application.