Methods suitable for manual assembly may not be the best methods for automated assembly. Some assembly operations readily performed by a human worker are quite difficult to automate (e.g., assembly using bolts and nuts). To automate the assembly process, parts fastening methods must be specified during product design that lends themselves to machine insertion and joining techniques and does not require the senses, dexterity, and intelligence of human assembly workers.
Following are the few recommendations and principles that can be applied in product design to facilitate automated assembly:
- Use modularity in product design. Increasing the number of separate individual tasks that are accomplished by an automated assembly system will decrease the reliability of the system. To reduce the reliability problem, Riley suggests that the design of the product be modular in which each module or subassembly has a maximum of 12 or 13 parts to be produced on a single assembly system. Also, the subassembly should be designed around a base part to which other components are added.
- Reduce the need for multiple components to be handled at a time. The best practice for automated assembly is to separate the operations at different stations rather than to simultaneously handle and fasten multiple components at a single workstation.
- Limit the required directions of access. This means that the number of directions in which new components are added to the existing subassembly needs to be minimized. If possible, all components should be added vertically from above for better product design.
- High-quality components. The high performance of an automated assembly system requires that consistently good-quality components are added at each workstation.
Poor quality of components causes jams in feeding and assembly mechanisms that result in downtime.
- Use of snap-fit assembly. The use of snap-fit assembly eliminates the need for threaded fasteners; assembly is by simple insertion, usually from above. It requires that the parts need to be designed with special positive and negative features to facilitate the insertion and fastening.