VSD 4.0 serves the designing of the target condition for the future order-processing process including the associated information flows. In the first step, the approach comprises the traditional VSD, which aims to bring products into flow in order to achieve short throughput times. In the second step, there is a check of which stations can be further stabilized and designed to contain less waste through digitalization in order to improve or expand the product flow.
Finally, in a third step, the product and information flows are integrated and synchronized. The basic rule is that initially it should be striven for a robust flow based on process stability instead of digitalizing complex and inherently instable processes.
Execution of traditional VSD
Through VSD, a value stream vision is developed that preferably satisfies the previously formulated targets regarding throughput time, quality, productivity, etc. The approach was established following Rother , who describes value stream guidelines. The use of these guidelines results in workstations and processes being capable to fulfill a given work content within the scope of customer takt time allowance. Subsequently, adjoining processes can be linked with one another to create the largest flow areas possible. Within those “islands of flow” a product or order can be further processed without waiting times. If processes cannot be directly linked (e.g. due to setup times or different cycle times), they need to be decoupled through pull systems (FIFO systems or supermarkets). The authorization of new orders preferably takes place in one place, the so-called pacemaker process.
Digitally improving product flow
If a value stream vision has been developed in this way, implementation projects are defined that develop the current value stream step-bystep towards this vision. Typically, these projects first address traditional wastes. Fundamental projects are the introduction of standard work and the stabilization of quality. Subsequently, projects follow that bring about the improvement of the material flow, e.g. the line balancing of flow lines, the development of flow layouts, or the organization of a pull-material supply.
Subsequently, digital improvement opportunities through the following questions can be checked systematically:
- Which traditional wastes can be better eliminated through digital measures? Example: The use of flexible pick-by technologies if material trays are too inflexible for zero-defect commissioning.
- Which wastes in information logistics can be eliminated by a better organization? Example: Figures and their recording are unified for all machines in a group and used in the morning meeting for the target/actual comparison.
- Which wastes in information logistics should be eliminated through digital measures? Example: The data for machine availability is recorded directly to the machine control instead of a manual transmission to MES.
Finally, there should be a check of which performance characteristics of the formulated busines model can be supported by the digitalization of the order processing. Example questions could be:
- How can the flow be further improved by automating manual planning steps that are repeated for every order?
- At which point do configurators help in automatically translating customer requests into process parameters?
- How can the product automatically parameterize work stations in order to further decrease setup times and support standard work?
- Where does it make sense to assign process data to the product and make them available to the customer?
Integrating the product and process information flow
In the last step of VSD 4.0 the information defined, which is needed (product, process, and resource information) at the stations of the new value stream to implement the vision of order processing without waiting times. To start processes at a station without delay, all required information must be available at the beginning of the order. With this goal, the information needs of all processes are assessed and recorded as ”activities” in the process boxes. The same applies to the support processes like work preparation, intralogistics and maintenance.
Linking of information sources and storage media
Based on the definition of future informational needs, suitable storage media are defined in cooperation with production-oriented IT and inscribed in the value stream map with the respective horizontal lines. Through vertical lines and the placement of points, a clear and standardized assignment of information sources to storage media takes place. For example, in this step it can be determined that, in the future, all quantity reports are automatically collected in MES. To show this, a vertical line from the data point “quantity” is drawn to the line of the storage medium MES and connected with a point.
In this final step, all activities that use available information are attached by dashed lines. For example, it is determined that the output quantity of every station available in MES is discussed daily in the course of shop floor management in order to recognize deviations and initiate improvements. From data point “quantity”, a dashed line is therefore drawn to the horizontal line of shop floor management and also connected with a point.
Example application of VSD 4.0
For the already exemplarily observed value stream of the special machine manufacturer, the objective of value stream design is to significantly reduce the cycle-time whilst offering simultaneously high flexibility in the configuration for sales and customers. This is essentially achieved through
- consistent digitalization of information sharing from the customer all the way to the machines
- a drastic reduction in manual process steps and the associated processing time (from 6.5 h to 15 min)
- a reduction of storage media (from 12 to 7) and media disruptions
The new process in detail
On the customer side, an online configurator was implemented that depicts the solution spaces possible in production in the dimensions categories, materials, and measurements. In this way, it is possible for the customer to configure and order the product without further communication with sales or development. The product data generated through the configurator is automatically transmitted to a parameterizable CNC code generator. The new CNC program arrives directly at the machine through the Distributed Numerical Control (DNC).
Until now, the order authorization took place through a push principle. The foreman planed the sequence of the orders according to demand and his own judgement (Go-and-see planning). In the course of VSD 4.0, strict FIFO pull processing now takes place (Fig. 20).
In order to stabilize and further improve the new processes, the figures delivery performance and capacity utilization are discussed in future daily shop floor meetings. In the event of deviations the PDCA cycle is started.
Kadıköy, İstanbul – TURKEY
M. Temel AYGÜN, Ph. D. in Aerospace Eng.
Copyright belongs to author.