The people at Multifix Assembly get a lot of questions about assembly and outsourcing assembly, in the article below we try to answer them. Other questions can of course also be answered, click here if you want to contact our experts.

In the article below, the following topics are discussed:

What is assembly?
Parts of assembly
Types of assembly
Pre-assembly and final assembly
The assembly line
The technique behind assembly
Outsourcing assembly

assemblage

WHAT IS ASSEMBLY?

Assembly has several meanings, but the most common one is industrial: assembling parts into a product (e.g. a computer). This assembly can be done manually or mechanically.

According to the dictionary, assembly is apparently also an art form, a technique from archaeology and a method of producing wine, but in this article these meanings are not discussed further.

Synonyms for assembly are final assembly, putting together, assembling, and merging. The word is derived from the French ‘assembler’, which means ‘to collect or to assemble’. It was not until 1931 that it was used in the Dutch language, albeit still in the context of wine production. According to Wikipedia, the word assemblage can also be used as a noun: an assemblage is a whole consisting of a number of different parts.

THE ASSEMBLY PROCESS

The term assembly is used according to the guideline VDI 2860 to describe the whole of all processes to assemble ‘bodies’ with geometrically defined shapes (lengths, angles). The essential sub-processes (German article) of an assembly process are:

  • Joining (screwing, nailing, welding, gluing, soldering, cutting)
  • Handling (gripping, laying, turning, moving, locking, controlling)
  • Check
  • Adjust (e.g. a setting)
  • Auxiliary operations (e.g. cleaning, heating or cooling for press connections, deburring, unpacking, sealing, oils, …)

In addition to work preparation and parts production, assembly is part of the production system of an industrial company. The reverse of assembly is disassembly, using appropriate disassembly techniques. We will not discuss this further in this article.

TYPES OF ASSEMBLY

The assembly process can be divided into two types: primary assembly and secondary assembly.

Primary assembly: The primary assembly is the assembly of components into a whole: an assembly, an aggregate (technology) or an end product. Primary assembly includes all operations that add value to a product, i.e. that physically change the assembly object. Assembled objects – as opposed to individual parts – can usually be disassembled again. This is very important for maintenance, repair and disposal or recycling.

Secondary assembly: Secondary assembly includes handling, testing, adjustment and special auxiliary operations that support the assembly process, but are not fundamentally required. All secondary assembly operations should be avoided or reduced as much as possible, as they do not alter the assembly object itself and therefore do not directly contribute to the added value. Secondary assembly processes are – depending on the chosen assembly principle – all necessary processes which represent an investment of time, information and energy, without creating any added value for the product.

PRE-ASSEMBLY AND FINAL ASSEMBLY

Due to the increasing complexity of the end products, their assembly is divided into different pre-assemblies and the actual final assembly of the product. This division has advantages because of space and costs, but also because of better production control.

For example, the automotive industry has increasingly evolved towards a highly automated assembly industry, which also includes suppliers. These often deliver pre-assembled modules just-in-time to the vehicle manufacturer’s factory, where they only need to be installed on the final assembly line. The main suppliers can in turn outsource certain pre-assemblies to sub-suppliers, creating a complex supply chain.

THE ASSEMBLY LINE

The conveyor belt (German article) or assembly line is mainly known from the automotive industry, but is now used in many industries.

History of the assembly line
In the automotive industry, the assembly line started with Ransom Eli Olds‘ ‘progressive assembly line’, where the body was attached to a moving carriage that was pushed from workstation to workstation. Henry Ford improved this principle with his engineer Sörensen and his foreman Lewis to create the ‘moving assembly line’. As a result, the production costs and price of his Ford T model could be drastically reduced. This assembly production was then copied by all car manufacturers. In recent years, this form of ‘flow production’ has also established itself in other industrial sectors with complex and varied products, such as aircraft construction, mechanical engineering and electrical engineering.

Building an assembly line
In an assembly line, the different variations of a product are produced by successive assembly activities. For the ongoing assembly, an assembly support is required to which the assembly object is attached. The basic assembly object is usually a static element of the product to be manufactured; this can be a mounting plate, a subframe or – as in automotive construction – a bodywork.

The sequence of the assembly steps is not random, but requires a certain sequence that must be carefully planned in advance. The assembly line is divided into cycles, the assembly object goes through the cycles in a certain cycle time. During this time, the assigned assembly work must be carried out, which is precisely described in a work plan or work instruction in which all the necessary tools and aids – as well as the parts to be assembled, assemblies, etc. – are precisely specified.

Assembly-compatible construction
In order to manufacture a product and its different variants on the same assembly line, the product must be designed for assembly. To this end, the component and assembly variations must be interchangeable as far as possible. The technical connection points and the connection technology between the different units, parts and assemblies and their variations must be standardized as much as possible.

Controlling the assembly line
Controlling the assembly and assembly lines is of great importance for complex and varied products, as these are assembled in more and more variants on one line. Due to the technical complexity, large assemblies such as engines, transmissions, axles or seats are also manufactured in vehicle construction, either on separate assembly lines or even in separate assembly plants.

Extensive assemblies of components such as the cockpit, front end, vehicle doors, sliding roof or power train are often moved to pre-assemblies and/or to a supplier. The pre-assemblies or assemblies are then fully integrated into the final product on the final assembly line.

Large production quantities may require multiple assembly lines, in a so-called ‘production plant’. The vehicles must then be assigned to the assembly lines, taking into account existing production constraints. For production planning and control, this results in the task of controlling the sequence and utilization of the assembly lines as part of the planning, so that the deployment of employees and production resources through leveling is as optimal as possible.

The greater the differences in the equipment of the car models, the more difficult and inefficient production on a fixed assembly line becomes. As an alternative to the assembly line, Audi announced in November 2016 that it would pack the bodies on transport carts, which, depending on the workload, would have to autonomously approach the different production islands for the required assembly steps. This involves group assembly.

Group assembly: what is it?
The term group assembly (German article) stands for a kind of production process and describes the spatial arrangement of the machines in a production facility. Often it is not possible to manufacture a product only in power production. Therefore, in practice, combinations of different production processes are increasingly being applied, whereby a group of employees is given responsibility for the production of a product, assembly or family of parts.

All workstations and machines required for production are combined into a production group, in which the employees take on the management and organization of the production. This is called a ‘production island’. The subsequent amalgamation of the individual products of the production groups results in the complete product.

This ‘production island’ fits in with the idea of a humane workplace, because the individual employees follow the entire production process. The motivation of the staff is increased by having them work in different, changing functions. In addition, this way of production strengthens personal responsibility and leads to an increase in quality. In addition to high technical qualifications, it also requires communication and team skills on the part of employees. However, the issue of fair wages within the group and the psychological pressure on individual group members can cause problems.

THE TECHNIQUE BEHIND ASSEMBLY

In assembly, three techniques (German article) come together: internal transport via coupling systems, infeed technology and handling technology.

Internal transport via coupling systems
Coupling systems are used for automatic transport between individual stations within a transfer system. Coupling systems are special transport systems in which the workpieces are transported on workpiece carriers and secured with workpiece holders. Connecting systems thus enable the orderly assembly of the workpieces, the exact positioning and the introduction of forces into the process stations.

A fundamental distinction is made between rigid and loose links. Rigid links are used to transport parts on workpiece carriers from station to station in a fixed cycle. These include rotary indexing tables and linear cycle coupling systems with a rigid cycle.

In the case of transfer systems for workpiece carriers with loose coupling, the connection between the motion of the conveyor line and the workpiece carrier is established by static friction. The workpiece carriers have free circulation and can be stored. Longitudinal transfer systems with fast feed enable a mixed form with a rigid interconnection within the processing stations and with free circulation between the stations. Furthermore, robots of different types can also be used as connecting devices between processing stations.

With rigid couplings, all workpiece carriers are coupled at fixed distances, guided in a closed circuit and centrally driven. Therefore, all workpiece carriers are moved synchronously. Rigid couplings allow high cycle speeds and precise positioning in the machining stations with direct force application, but do not provide flexibility with regard to material flow. Any interference causes the entire coupled line to come to a standstill.

Infeed technology
Feeding systems are used for automated storage and orderly entry of workpieces. A distinction is made between ordered and unordered supply.

Most infeed systems are used to feed unordered parts in bulk. Basically, there are workpiece-specific bulk feeders with sorting by mechanical bulkheads or systems that are flexibly programmable for a certain range of parts and based on image processing systems. Infeed technology includes systems and devices for storing, organizing, transporting, separating and assigning workpieces.

Handling technology
‘Assembly handling modules’, also called ‘pick & place units’ or ‘handling modules’, are universally applicable standardized handling systems for holding grippers and tools. They have been specially developed for integration in automatic assembly systems. These are mainly two-axis systems for handling in the XZ direction. This also includes lifting / rotating units and slewing units, as well as individual horizontal and vertical axes for setting up pick & place systems.

Assembly handling modules are typically designed for shorter routes and for low load handling. The cantilever design is sufficient for short distances on the X-axis; the gantry design is also used for longer distances.

Depending on the type of drive, the handling modules have a fixed sequence of movements or freely programmable mobility. With the mechanical cam control, fixed motion sequences at high speeds can be implemented. For simpler applications, pneumatic actuators can be used, which are usually positioned against fixed stops.

Freely programmed handling modules are usually driven by electric motors via a power transmission with toothed belts or spindles. Direct drives with linear motors are also used.

OUTSOURCING ASSEMBLY

The market is increasingly demanding partnerships and added value, as we can see from the success of Multifix Assembly. This development also fits in well with what we at Multifix have defined as our strategy. Our ideal customers are OEMs with their own products, who are looking for a specialist who is good at combining metal, plastics and electronics. An example is Ventura, click here to read their story.

At Multifix Assembly we take over the supply chain from the customer, we buy the single components for them. Ultimately, we also stock the products, the financial risks are with us. We also do a final check after assembly. The customer only has to buy the article, they don’t have to worry about it.

If a customer is interested in outsourcing the assembly, we first look at how they make the product or have it made. We discuss where we are allowed to buy; sometimes they still have ongoing contracts with other suppliers. Then we apply for the products within our international network, from the Netherlands to China. In this way we check the entire bill of materials, also in the field of electronics. On the basis of a calculation sheet, we calculate what the entire parts list costs us.

There are roughly three processes in assembly by Multifix:

1 The customer delivers first, we do the assembly;

2 We take over the work of existing suppliers, or stocks from the customer;

3 We purchase on the basis of samples from the customer, in our network in China for example. But if a customer has good suppliers, we also make use of them.

The goal is to eventually take care of the complete supply chain.

Interested in assembly at Multifix? Click here.