Manual assembly

Feeding presentation of a component to the handling equipment in the correct orientation by a variety of methods. Parts manually taken from storage bins and then orientated by operator. Orientation can be achieved by vibratory/centrifugal bowl feeders, parts already orientated in pallet/magazine/strip form or use of part-feeding escapement mechanisms. 

Handling bringing components and/or sub-assemblies together such that later composition can occur. Use of hands, simple lifting aids and jigs and fixtures. 

Checking detection of missing, incorrect, misshapen or wrongly orientated components by high-level sensing and checking capabilities of operators and mechanical/electrical aids. Also detection of foreign bodies, part-failure and machine in-operation. 

Transfer typically, the various assembly operations required are carried out at separate stations, usually built up on a work carrier, pallet or holder. Therefore, a system for transferring the partly 

Manual assembly is not suitable for harsh environments. Also, size and weight of parts to be assembled must be considered for safety handling. 

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The intent in this chapter is not to present in great detail the mathematics behind the statistical methods discussed. An excellent reference manual assembled by the Automotive Industry Action Group (AIAG), Fundamental Statistical Process Control, details process control systems, variation, action on special or common causes, process control and capability, process improvement, control charting, and benefits derived from using each of these tools. Reprinted with permission from the Fundamental Statistacal Process Control Reference Manual (Chrysler, Ford, General Motors Supplier uality Requirements Task Force , Measurement Systems Analysis, MSA Second Edition, 1995, ASQC Press. 

Exposure Registries. New York State has instituted a Heavy Metals Registry that monitors occupational exposure to heavy metals, including mercury. Cases are reported when mercury exposure is equal to or exceeds 50 g/L (ppb) in blood or 20 g/L (ppb) in urine. Between 1982 and 1986, 1,000 cases of mercury exposure were reported and linked to 47 companies. Most exposures (494 cases) occurred in workers in the alkali and chlorine industry, where mercury is used as a cathode because exposure occurs when the cells are opened the median blood mercury concentration was 76 g/L (ppb) (maximum concentration 916 g/L [ppb]). The second most frequent exposure category (213 cases) was the manufacture of industrial instruments, such as the manual assembly and fabrication of thermometers median blood mercury concentration was 145 g/L (ppb) and the maximum concentration was 889 g/L (ppb) (Baser and Marion 1990). 

The manual assembly can be divided into four basic steps ... 

Flex-link systems also allow a different level of automation at each of the assembly stations. Depending on the respective assembly tasks, the automation level can be stipulated according to technical and economic factors. In addition, step-by-step automation of the assembly system is possible because individual manual assembly equipment can still be replaced by automatic assembly station later on. 

The manual assembly systems are divided into two main categories, manual single-station assemblies and assembly lines. 

Manual assembly hues consist of multi-workstations in which the assembly work is executed as the product (or subassembly) is passed from station to station along the line (see Figure 3). 

Manual assembly fines are used in high-production situations where the sequences to be performed cem be divided into small tasks and the tasks assigned to the workstations on the fine. One of the key adveuitages of using assembly fines is the resulting specialization of labor. Because each worker is given a limited set of tasks to perform repeatedly, the worker becomes a specialist in those tasks and is able to perform them more quickly and consistently. 

Figure 33 Software-Based Optimization of a Manual Assembly Station.

Fiberoptic cables are currently assembled almost completely manually. Semiautomatic devices are available on the market for the premanufacturing process. After this process is completed, the ceramic ferrule of the connector is filled with glue, then the glass fiber is introduced into the ferrule hole. This assembly sequence is executed only manually at present. However, because no measuring systems are available for this purpose, manual assembly cannot ensure that the critical joining force will not be exceeded. If this happens, the fiber wftl break off. The fiber will be damaged and the connector win become waste. 

Description of Manual Assembly Systems and Their Components... 

The components for the basic parts and the assembly parts are the substantial constituents of manual assembly systems. The assembly parts are often supplied in grab containers. The distances to be covered by the workers arms should be short and in the same direction. The intention is to shorten the cycle time and reduce the physical strain on the workers. This can be realized by arranging the grab containers in paternoster or on rotation plates. Further important criteria are glare-free lighting and adapted devices such as footrests or work chairs (Lotter and SchiUing 1994). 

When assembly at a workstation is impossible for technological or economical reasons, the assembly can be carried out with several chained manual assembly stations (Lotter 1992). Manual assembly systems consist of a multiplicity of components, as shown in Figure 20. The stations are chained by double-belt conveyors or transport rollers. The modules rest on carriers with adapted devices for fixing the modules. The carriers form a defined interface between the module and the... 

Figure 20 Components of Manual Assembly Systems. (Source Teamtechnik)...

The following criteria have to be considered in designing manual assembly systems. 

Correlation between feedback and execution speed during the learning phase of a manual assembly task (mean values of 10 subjects and 8 hand and arm muscles). 

Decomposition of long-term trend, periodic, and stochastic components using the example of cycle duration of a manual assembly task. 

Automation is the cmiversion of a procedure, a process, or equipment to an automatic operation without intervention by a human operator (CIRP 2004). In the field of assembly, assembly automation describes the cmiversion of a manual assembly process to an assembly without a human operator, fii general, the term describes the process of increasing the number of assembly steps carried out by automatic assembly machines in a plant. 

While the market needs were met with a high batch size of standardized products a few years ago, the current assembly and production lines have to be flexible and agile in order to satisfy the requirements of customers. Due to these requirements, optimized manual assembly systems have become an alternative to automated production systems (Feldmann and Junker 2003). Nowadays, around half of companies use some kind of automation of assembly (Butala et al. 2002). 

Due to the low investment risk with a high level of adaptability and productivity, manual assembly is the best form of assembly in... 

Manual Assembly Line Assembly systems in which all operations are carried out manually or that consist entirely of manual workstations (CIRP 2004). 

When the product has not been designed automated based, manual assembly is probably the only possibility. Similarly, the automation will not be practical unless the anticipated production... 

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