Circuits Assembly Online Magazine - Improving Placement Modularity through Shared Resources

Novel functionality accommodates changing production requirements without reconfiguring the line.

Setup and changeover requirements go hand-in-hand with high-mix production and short runs. The less flexibility assembly equipment has in accommodating changeovers, the more time such changeovers take, and these cumulative operational losses directly affect throughput. The goal, therefore, is to maximize equipment flexibility and capability to minimize changeover time and the required operator intervention that accompanies it.

Increased production volume is a good sign, but the manufacturer may not have the resources – including manufacturing floor space – to buy additional capital equipment to accommodate it. How, then, can the manufacturer increase capability when needed without having to make a major investment in a new line or machine? By maximizing the flexibility of existing equipment, and sharing equipment resources so as to not require duplication whenever possible.

Hitachi’s patented Overdrive functionality adds flexibility to the assembly process through the use of shared system resources with different line configurations (e.g., single lane, dual lane). In the simplest terms, the patented functionality enables both heads (high speed or multifunction) to pick from the other’s component supply – on either side of the machine – and place on the same board simultaneously and without restriction, and without sacrificing accuracy or quality.

With a placement machine equipped with both front and rear component supplies, both heads can pick from either supply as needed. Feeder changes are not necessary, nor do heads need to be exchanged, because each head has unlimited access to both the front and rear component supply. Additionally, both heads can share options, such as a high-resolution camera, as the assembly task requires. It isn’t necessary to have a high-resolution camera for each head, or for one head to be restricted to high-resolution applications.

Shared options are a key feature. Coplanarity is one example. In the event that, due to feeder restrictions, a component was placed on the side of a machine without coplanarity, a conventional machine would require a second coplanarity unit. When both heads have total access to both sides of the machine, however, a component from the feeder side of the machine can easily be picked by either the HS or MF head and scanned by the coplanarity module.

Consider another scenario. The fluxing module is usually included with the tray supply-side of the machine and, due to the consequent loss of feeder positions, if a larger component feeder will not fit next to the flux module, the customer then has two options: First, remove the high-speed head on the opposite feeder bank with an MF head, and add a second fluxing module, a switch that would have a significant detrimental effect on the machine’s cycle rate. The second option would be to add an additional machine to the end of the line to increase machine throughput, thus adding cost and consuming additional floor space. If the single MF head can pick from the opposite feeder bank with minimal effect on machine cycle rate, it eliminates the need to duplicate options or add a machine, saving on equipment investment and line reconfiguration.

Sharing resources can also make room for a reject conveyor, which provides the means of removing rejected components and saving them for refurbishing and reuse. In the instance of having multiple large feeders (due to component size), or the inclusion of the flux module on the tray unit bank of the machine, there would be no space for a reject conveyor. Without the reject conveyor, the users would have to move the faulty part to a reject bin, possibly damaging it further. But with the novel technology, the reject conveyor could be relocated to the opposite feeder bank and rejected components saved and repaired for use later.

Fewer heads and head changes. This added functionality eliminates the need for additional heads or equipment. Consider the complexity of the production line. Challenges include many large components, and a lack of feeder slots beside the tray. With the novel functionality, component pickup from opposite sides for each head is possible with no restrictions. There is no need for head changes or additional equipment due to a lack of feeder positions on a specific side of a machine.
This eases adapting to varying production requirements without reconfiguring the line. The following capability study was done to illustrate this point.
As in almost all cases, board complexity determines line configuration. Board “A” was a complex assembly, a device used for automobile navigation.

PCB size:

150 x 120mm.
110 unique components.
844 component placements.

The manufacturer required a 38-sec. cycle rate. The presence of multiple connectors and large devices required the use of an MF head to place special reeled and tray components. The line consisted of three Sigma G5 series systems, with five HS heads, one MF head, plus the tray. With Overdrive enabled, the cycle time was realized (Figure 1); without it, and using a necessarily different line configuration (four HS heads, two MF heads and the tray), cycle times exceed the requirement (Figure 2).

Indeed, in almost all situations, without the use of Overdrive, cycle times will be slower without head replacement. To achieve the required cycle rate on Board “A,” a conventional SMT line would require an additional mounter unit due to feeder space restrictions. In this example, the novel technology provides the necessary flexibility such that it is not necessary to add more machines to the line in order to meet cycle time and throughput requirements.

The novel functionality expands placement flexibility, capability and speed. By optimizing the use of available features and machine resources, and sharing them between the two operating HS and MF heads, ownership costs are minimized through resource sharing; changeover times are minimized through greater flexibility; throughput and yields are boosted via streamlined optimization; and productivity increases are realized without the need for configuration changes.