Insertion Sequencing Rules

Modern PCB assembly needs a new system approach, to automate the entire planning process involving manual operations. That means the capability to call upon an on-line program that produces the optimum component insertion sequence for a new PCB assembly in a way that minimizes the overall manufacturing time. In order to accomplish such objective, the component insertion methodology described in this illustration is based on a series of sequencing decision rules that meet the criteria previously explained.

Rule: Before the Larger Components Insert Smaller Components:

Purpose:

• Ignores component "volleying." The formation of valleys throughout the component insertion process creates difficulties for subsequent component insertion, orientation, and lead guiding throughout the insertion holes as the access space is limited by the earlier inserted components.
• Ignores the blocking of the light guiding system. Since the movable light mechanism shines the PCB from the side or and rear, this is possible for tall components to block the light guiding system from shining on lead holes. Thus a component that is near or and below a tall component should be inserted before the tall components.

Rule 2:  Inset, in One Pass, All the Components of the similar Value and Type

Purpose:

• Decrease the number of wrong value components inserted by the operator.
• By altering the kitting sequence, promotes the separation of identical appearing components.

Rule 3: Kit Components along with Identical Shape and Size but different Identical Value along with other Components of Non-similar Size and Shape

Purpose:

• Decrease the risk of mixing look-alike parts in the bin trays while retrieving parts from the returning extra components to the rotary bin trays.

Rule 4: choose the Insertion Sequence that Results in the Shortest Machine Bed

Movement

Purpose:

• Minimizes the PCB assembly time by eliminating erratic movements.
• Enhances accuracy, since long bed movements tend to reduce the position accuracy of the insertion bed and clinch and cut mechanisms.

The perfect application of the previous rules requires the definition of the component insertion priority shown in given table. This table presents the consensus of several PCB manufacturing and design experts from companies in the public and private sector and also experts working in the academic field. The table is organized based upon the component packaging that is DIP, axial, radial, can, bix, and component prep configuration that is lay down and stand-up. These features are then utilized as the ranking priority criterion. Components along with priority number first must be inserted first followed by the ones along with priority number second and so on.

                                                                         Table of: Component Insertion Priority

Once the component insertion priority has been established, the successful employs of the insertion sequencing rules is facilitated by organizing or partitioning the component data into some primary but independent categories. For illustration, by dividing the sequencing decision rules by component type, this is possible to eliminate a group of components not involved in the methodology or components not being considered at a specific time during an analysis. Such heuristic approach facilitates a search of smaller knowledge space such is most likely to have the answer to question being posted. Hence Heuristic searches incorporate little information about the nature and structures of the problem domains and limit the search space. Following such line of thought, component insertion taxonomy is explained. The goal of this taxonomy is to organize the rules and criteria that will find the relative order of insertion of components of the same type but along with different configuration.