Brake Shoe Seam Welder: Expert Guide to Safe Welding

A brake shoe seam welder, a type of welding machine that is capable of creating strong welds on cylindrical vessels, embodies the concept of seam welding and brake shoe – an essential component in the brake system of a vehicle. As brake shoe is one of the most critically safety-related components of a brake system in a vehicle, you definitely want to make sure that you are following a strict guideline and procedure when welding brake shoes. To help you understand today's topic better, we'll start out by discussing the basics, the brake system of a vehicle as well as the brake shoes.
 

Brake System at a Glance

The purpose of a brake system is to apply certain force on the wheels to forcibly make moving vehicles decelerate on driver's instruction. It also allows drivers to park the moving vehicle at a steady speed under various road conditions, such as on a ramp or steep hill.

A brake system can typically be categorized into a drum brake system or a disc brake system. The drum brake system is a traditional kind of brake system that is usually found in heavy vehicles like trucks and is composed of a piston, brake oil pump, brake pads, and a drum compartment. The brake shoes, to which the piston applies certain force, press tightly against the wall of the drum compartment to realize the brake by preventing the brake drum from turning. 

The disc brake system on the other hand is found in standard vehicles. Since it utilizes brake pads rather than brake shoes for the brake, we are not going to discuss it here in this article.
 

More about Welding Brake Shoe

As we mentioned, brake shoes are found in drum brake systems. When being used, the brake shoe acts as a braking part that pushes outward to press tightly against the inner radius surface of the braking drum with its friction plate. This creates a friction moment owing to the non-rotating brake shoes touching the rotating brake drum, thereby giving a braking force on the brake drum.

Now welding brake shoe typically involves the joining of a friction shoe pad and a shoe rib, the thickness of which normally spans from 6 to 8 mm, and the welding is done by undergoing the hole-plug welding method. There are some technical requirements you need to be aware of when welding brake shoes:

1. The welded shoe pad of brake shoes should be spillage-free, thereby reducing subsequent grinding.

2. You should ensure the penetration depth and strength of each welding spot. And each welding spot should be uniform and consistent without any undercut, crack, incomplete fusion, or other defects.

3. You may need a configuration of multiple welding machines to be able to ensure consistent welding. And with such a setup, it is also important to keep the output welding voltage consistent.

4. It is advised to undergo 24-hour Continuous Welding (we'll discuss this later) for better fatigue resistance and stability.
 

Seam Welding Explained

Seaming welding, or resistance seam welding, is an electrical welding technique that joins two similar or dissimilar materials at the seam by applying electrical current and pressure. The technique is typically used on metals since they have high electrical conductivity and can withstand high pressure. Thanks to the contact resistance created between two metals and the ability to produce very strong welds, seam welding has always been an excellent candidate for welding car parts. A dedicated seam welding machine can manufacture a certain part of a vehicle (e.g., brake shoe) with optimal consistency. 

Now seam welding is only one of the several different types of electrical resistance welding but is the most commonly used welding process among them. What makes a seam welding machine so popular among automobile applications is attributed to the following advantages:
 

Airtight Welds

Thanks to the process of continuous weld, welds produced by resistance seam welding are airtight and watertight. This is especially crucial for many vehicle parts that require the structure of which to be completely protected against water leakage.
 

Fast Weld

Since the entire resistance seam welding process is automatic, the weld is possible at high speeds. It is in fact faster than most other alternatives such as spot welding.
 

No Filler or Flux Needed

It is possible for seam welding to happen without using any filter or flux material.
 

Continuous Motion Seam Weld

In continuous motion seam welding, a continuous weld is possible to offer airtight and watertight seals. The metals are joined together as the electrodes pass through at a constant roller speed. This permits uniform, overlapping welds as the material welded remains under constant pressure. The type of electrodes used in continuous motion seam welding is based on the type of metal that is to be welded. For instance, you'd typically avoid copper electrodes when welding aluminum workpieces because copper alloys with aluminum can lead to much faster deterioration of the electrode.
 

When Buying a Brake Shoe Seam Welder

With the above said, if you are going to tackle brake shoe welding, you can typically find a special-purpose seam welding machine that is specially designed for welding brake shoe assemblies. When choosing a brake shoe welding unit, some of the things that you should make sure the machine is equipped with are a basic welding transformer, microprocessor-based control, a rotary indexing fixture with drives, a vertical welding head, etc. Also, make sure the construction of the machine is made up of a mainframe that is robust, rigidly reinforced with welded metal like steel.