Production bottlenecks eliminated

Optimized material flow with a high number of variants

The bicycle manufacturer Derby Cycle has been able to escape the price-volume competition in the bicycle market in recent years. The positioning towards customization (adapting bikes to customer requirements) has helped. For production and logistics, this meant making processes more flexible, among other things. In order to meet these requirements with increasing sales in the paint shop and decor area, the management consultancy Abels & Kemmner was commissioned to accompany and coach the optimization process.

Derby Cycle’s brand portfolio includes the main brands Focus, Univega, Kalkhoff, Raleigh and Rixe. The company designs and produces trekking, city, off-road and children’s bikes for everyday and touring use as well as the complete range of sporty mountain bikes and racing bikes for demanding leisure cyclists or competition use. The range is aimed at all age groups and offers numerous variants for every purpose.

To optimize processes in production and logistics, the following work packages were coordinated with the management in the first step:

  • Situation analysis with value stream mapping and bottleneck analysis (constraint analysis),
  • Identification and conception of solution approaches and
  • Economic feasibility study and decision for a solution scenario.

The logistics and production processes were recorded together with the project team, which was made up of production employees from the areas under investigation. This showed that the individual design of the bicycle frames with elaborate paintwork and decorations places considerable demands on the processes. The material flow is synchronized from the straightening process to pre-assembly by using an overhead chain conveyor system. However, it is necessary to interrupt the material flow at certain points; this is the only way to introduce individual design elements, e.g. masking frame parts to retain the natural aluminum color. This creates gaps in the conveyor chain, which are then filled with other frames that have already undergone intermediate processing in order to make optimum use of the paint shop’s capacity. All in all, this involves a great deal of handling, as the example of decor shows.

Decor refers to the design of bicycle frames with the help of decorative films, some of which are customized and applied directly to the frame. Whereas in the past these were applied after the final painting stage, the decor is now applied before the final clearcoat protective layer in order to protect the decor in the long term (undercoat decor). This leads to an interruption in the painting process. The employees remove the frames from the conveyor chain and store them temporarily on special racks. To attach the decor, the frames are then removed from the intermediate storage racks and placed on placement devices. In two shifts, the employees in the decor area manually apply the decors to the areas specified by product management: A work step that can hardly be automated due to the numerous gluing variants. After gluing, the frames are again temporarily stored before they are finally clear-coated. The image provides a simplified schematic overview of the processes.

Figure: Simplified schematic overview of the processes
Figure: Simplified schematic overview of the processes

Identified bottlenecks (constraints)

The capacity of the painting line is not the main bottleneck in the process. The first bottleneck is the decor area, which already operates in two shifts at the height of the season. Due to the increasing proportion of undercoat decors, there are increasing bottlenecks in the decor area in terms of intermediate storage space, handling costs and personnel capacities for gluing. In order to supply the second layer with painted frames for gluing, a storage area is required which, assuming the growth rates, can no longer be provided. Furthermore, the handling effort for removing and repositioning the frames is considerable.

The calculated space requirement for buffers, gluing and DUL (decor-under-varnish) shows the potential space gain when changing the processes.

Using analysis tools to find solutions

A specially adapted analysis tool was used to illustrate the relationships between the daily number of undercoat decorative frames, the storage space requirement and the gluing space and personnel requirements, which made it possible to calculate various quantity and capacity scenarios. The mapping and variation of the layer model in particular led to interesting results. For example, it was found that the space required for intermediate storage to supply the second shift with frames to be glued increased significantly as the number of pieces grew. However, when the shift model was reduced to one shift, the space required for temporary storage decreased, but at the same time the space required by the decorating staff to handle the quantities increased. As a result, the solution of single-shift operation showed considerable advantages over multi-shift operation.

It also became clear that the process could be accelerated and the overall effort reduced if the frames were no longer placed on the intermediate storage racks after painting, but directly on the fixtures for applying the decor. This eliminates the need for handling for relocation. Although these measures increased the space required in the decor area, the storage space freed up in the pre-assembly area could be used for activities after painting, which in turn had advantages for the material flow towards pre-assembly.

Measures and economic efficiency

A number of organizational and structural measures were required to implement the new concept. These included:

  • Modification of the transport routes of the chain conveyor system,
  • Relocation of the small parts attachment and undercoat decorative label application area to the pre-assembly area,
  • Procurement of additional devices for the application of undercoat decorations and
  • Reorganization of the provision of label material.

To approve the concept and the necessary measures, an evaluation of the solution was presented to the management using a return on investment (ROI) calculation. This showed a clear economic advantage of the proposed solution, as the handling effort was significantly reduced. The necessary measures were implemented following a review.

Picture of Prof. Dr. Andreas Kemmner

Prof. Dr. Andreas Kemmner

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