China SubContract Manufacturing and Sourcing Solutions

Metal Fabrication

ChinaSavvy’s five part article takes an in-depth look at the history of fabrication, the processes and latest developments of the process within China, as well the types of products made and the pros and cons associated with it.

In this Article:

Page 1: An Historical Overview
Page 2: Developments and Processes in China
Page 3: Pros and Cons of Metal Fabrication
Page 4: Products Made using Fabrication
Page 5: ChinaSavvy’s Fabrication Videos

An Historical Overview

Fabrication is a term defined as “the action or process of manufacturing something.” Today, the term relates to production, which may involve several processes to, at the end of the day, yield a finished article.

These processes often relates to the shaping of materials as well as the joining of materials. Typically, processes involved in fabrication includes folding, welding, riveting, powder coating, punching and painting.

Many of the above named features are used in cabinet productions such as the type of housings made for electronic products, ‘white’ goods and, at another extreme of the spectrum, oil and gas platforms.

The family of processes applied in fabrication can also include the precision machining of parts.

Looking at the history of fabrication, you will see that it is more the individual histories of each process and how , at a later stage, these various skills and processes were brought together by fabrication companies in order to offer a ‘one-stop’ shop for customers.

The Key Processes:

  1. Metal Punching
  2. Metal Cutting
  3. Machining
  4. Metal Joining & Welding
  5. Metal Coating

Metal Punching

This process is an evolution of the use of shears. Notable developments occurred in this sector in the mid 1920s when Trumpf (a key equipment supplier) started evolving automated punching systems.

Today, punching machines are computer controlled with many manufacturers offering services similar to that of Trumpf.

Metal Cutting

Depending on the nature of the finished metal product, it can be cut in various different ways using a variety of processes. The most widely used processes when it comes to metal cutting include flame cutting, guillotining and laser cutting.

  1. Flame Cutting
    This process is used for cutting or profiling sheet material that is relatively thick. In use since the 1900s, the latest developments introduced a computer controlled cutting path. This entails either moving the work piece below a fixed head or moving the cutting head over the work piece.
  2. Guillotining
    This process is commonly used where sheet material has to be reduced to simple shapes with straight edges. This is also often the first operation that takes place in a manufacturing sequence.
  3. Laser Cutting
    The first laser cutting machine was used to drill holes in diamond dies in 1965. By 1967, the British had pioneered laser-assisted oxygen jet cutting metals and, in the early 1970s, this technology was incorporated into the production process to cut titanium used in aerospace applications. The process has enjoyed further refinement through the offering of different types of laser and systems, so much so that it has become a mainstream process used for cutting most metals. Development in this arena focusses on capacity, throughput and the quality of the cut edges.

Machined components are generally shaped in metals and plastics through the use of equipment such as drills, milling machines, lathes and grinders. These techniques all have roots in ancient times.

Grinding’s roots are deep into the use of stones to abrade soft metals, while turning, milling and drilling has roots in the ‘bodging’ operations of ancient foresters, for which there are references dating all the way back to Egypt in 1 300 B.C.

These processes has developed extremely, giving us a wide range of tools which today, are often computer controlled and capable of high precision processes. One can also say that the development of the equipment has been paralleled by the development of the drilling, cutting and grinding tools.

Some notable landmark developments in this process includes:

  • Verbruggens gun boring lathe of 1772
  • Computer control of lathes from the 1950s onwards

Metal Joining & Welding

Dating back several millennia, the history of joining metals (called forge welding) has early examples in the Bronze and Iron Age in Europe and the Middle East.

The Middle Ages brought great advances in forge welding. Blacksmiths pounded heated metal repeatedly until bonding of the metals occurred.

Russian scientist, Vasily Petrov, discovered the electric arc in 1802 and, subsequently, proposed its possible practical applications, which included welding.

In the final decades of the 19th Century, resistance welding also developed, the first patent going to Elihu Thomson n 1885. He also produced further advances in the next 15 years and, today, this process in known as spot welding.

Edmund Davy discovered Acetylene in 1836, but it was not very practical in welding until about 1900 when a suitable blow torch was developed. Falling out of favour for industrial applications, it was largely replaced with arc welding as metal coverings (known as flux) for the electrode enjoyed continued development.

With World War II came a surge in the use of welding processes – each military power attempted to determine which welding process would be best for the use in ship and aircraft production.

Welding development has, since the mid 1900s, centred around the improvement of the quality of the welds, the increase in the range of materials that can be welded, as well as increasing the throughput of the welding processes.

These centralised concentration has resulted in TIG and MIG welding processes and their automation.

Metal Coating

Metal coating is the protective and cosmetic coatings on products and falls into three, main categories:

  1. Metallic Plating and Coating
  2. Powder Coating
  3. Air Gun Spraying

Metallic Plating and Coating:

With age old processes such as nickel and chrome plating and zinc galvanising, this process dates back to the Quin dynasty in China. More recent developments in the process being more from an environmental aspect of the chemical used.

Powder Coating:

Within this process, the coating is applied to the material as a free-flowing, dry powder. The main difference that this process shows when compared to conventional liquid paint is that it does not require a solvent to keep the binder and filler parts in a liquid suspension form.

Typically applied electrostatically, it is cured under heat in order to allow it to flow and form a ‘skin’, where the powder used can be either thermoset polymer or thermoplastic. Usually used to create a hard finish that’s tougher than conventional paint, it is process mainly used for coating metals such as automobile and bicycle parts, household appliances, and aluminium extrusions.

Since its introduction as a protective coating in the 1960s, powder coating formulations have gone through vast developments and improvements. Today, this type of coating is available as part of multi-layer coatings or as a standalone coating.

Air Gun Spraying:

Paint is, in this process, applied to the object using a pressurised (air) spray gun. This air gun has a paint basin, nozzle and air compressor. Once the trigger is pressed, the paint mixes with the compressed air stream and is released in a fine spray.

Working under extremely tight deadlines to complete the World’s Columbian Exposition in 1892, Francis Davis Millet was appointed to replace William Pretyman. Millet experimented and settled on a mix of oil and white lead that could be applied using a hose and special nozzle. This meant that the job could be done in less time (when compared to brush painting) and so, spray painting was born.

Edward Seymour developed a spar paint that could be delivered from an aerosol can in 1949 and today still remains in use for touch-up operations such as car repairs.

Today however, three main spraying processes are widely used in the industry:

  1. The manual operated method is the simplest method used and entails the spray gun being held by a skilled operator (6 to 10 inches or 15 – 25 cm from the object) and moved back and forth over the surface of the object. Each coat overlaps the previous one to ensure a continues coat.
  2. The automation of this process is also used. This entails the gun being attached to a fixed mounting block and deliver the paint from that position. The object is usually placed on a turntable or rollers to ensure an overall equal application of the paint on all sides.
  3. the third process is the most complex variant entailing a robot ‘hand’ holding the pray gun head and following a pre-launched path. This ensures that the object is completely and equally painted. It is usually applied for spraying large objects that are produced in medium to high volumes.

A generic term, fabrication brings together a number of processes to, in the end, realise a final product. Many of these processes used in fabrication today, has developed over centuries and millennia.

Next Page: Developments and Processes in China

No Comments Yet

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>