Designing for Assembly and Automation
Machining process is the last step in manufacturing. It is the most flexible and most accurate step in a manufacturing process. This means that engineers should make considerations about the system down to the component level during the design phase to produce goods at a reasonable cost, that are easy to build, maintain, and manufacture.
Designing for assembly is important because it factors into 5% of the time to produce a product but influences 70% of the product's cost.
Taking a deeper look at the current typical design process as three levels:
1.Preliminary/conceptual
Brainstorming, functional analysis, design layouts, engineering sketches.
2.Detailed/engineered design
Tolerance studies, performance analysis, engineering analysis, feasibility study.
3.Production
Manufacturability, inspectability, testability, maintainability, supportability, cost analysis, rapid prototyping, lab testing, hardware development, field testing, competitive procurement, inspection policy, service policy.
How to implement DFA and Automation
Design for assembly requires that a certain set of rules are followed to meet a compliance that allows for automation. Assembly is the process to integrate various components to be a sub-assembly or final product. These considerations must be taken into account during the early state of product design.
This can be achieved by making considerations to compliance, the self-alignment of parts, hidden features, symmetry, compatibility with equipment. More specifically we can look into parts feeding consideration such as parts tangling prevention and parts jamming prevention.
Fasteners should be avoided. Instead considerations should be made for parts that have a snap fit. If fasteners must be used they should be the same fastener throughout the equipment, placed vertically, and to use fasteners that are easily fed with flat sides and tops.
Parts that are to be assembled should be rigid and stiff. Parts like covers and frames should be strengthened. Wires and cables should be plugged directly together or integrated.
Labels should be minimized. If labels are required they should be designed into the part.
Packaging should be designed for parts presentation. Trays, compartment, magazines, or partitions can be utilized for locating parts in known positions within the box. Most easily 'pickable' side should be facing the approach angle of the robot. Boxes should be dimensionally stable and have lids instead of flaps. The final product should be shipped in the same container as one of the parts that came in.
Other considerations to product packaging can include changing the product design to simplify packaging. That requires avoiding the need for the support of internal parts in the product with packaging material. Avoiding the openings in the product in which the packaging material may enter. Finally, have the carton designed so that the unit may be placed straight down in the shipping container, with the packaging material already inside the container.
Additional considerations should be made for the automation of testing electrical devices. This includes the use of only standard connector types that have lead-in or chamfered surfaces to help guide the test probe. If adjustments must be made at final test time, use knobs and screws that are readily accessible and easily manipulated. The connector routing surface on the product must be able to withstand the force required to plug and unplug all connectors simultaneously. To ensure the accuracy of the position of the test points when the unit is in the test station, locate their positions in reference to the base of a side of the product accurately as possible. Locating pins or holes should be on the test point or connector surface to help guide and align the test probe or fixture. There should be no internal test points in the product that must be probed at a final test time. Internal points that must be tested should have parallel external test points. All test points, connectors, and switches should be readily accessible and preferable on the same surface of the product. Do not have any wires or flexible parts that must be probed and tested. Avoid designing machines requiring warm-up and burn-in chambers since these chambers will complicate the test process. Design machines that can be tested independently without being connected to other machines. Provide common test connector points within a product family.
These rules should serve as guidelines when economically feasible and allowing for a continuous improvement effort in product design to be made.