Standard Work and the Role of Work Instructions in Preventing Defects
The Make-to-Order Challenge
Standard work is a means of preventing errors, and plays a very important role in controlling product quality in make-to-order environments. Unfortunately, most organizations fail to recognize the importance of standard work, and operate inconsistent manufacturing processes, resulting in a high number of product defects and occasionally in serious safety issues.
Often organizations are intimidated by the volume of documentation required for the large number of possible end-product configurations in a make-to-order environment. As an example, there are hundreds of possible end-item configurations for each type of machine in semiconductor manufacturing. Creating and maintaining work instructions is seen as an onerous task with no tangible returns.
However, in my experience, creating and maintaining work instructions can be quick and easy, and can help significantly improve product quality.
Standard work is the documented best method of performing a task or series of tasks. It includes the following information: the raw material needed, the tools, machinery & fixtures to be used, work instructions, sequence of tasks, product flow or travel path including transport and storage steps, operator's movements, quality checks, safety checks, capacity at each stage, and desired takt-time.
In high volume manufacturing, standard work sheets need not be used by technicians on an hourly or daily basis. Instead, standard work sheets can be used as training tools, and as a basis for Kaizen (improving the process).
In contrast, in a make-to-order environment, the large variety and infrequency of manufacturing process steps make it critical for a technician to refer to work instructions and standard work sheets either before beginning a task or after completing a task to ensure that they haven't missed a step.
To successfully deploy standard work in your factory, you need to answer three questions:
- What is the current state of work instructions?
- Who will create and own the work instructions?
- What role will information technology play in the development and deployment of work instructions?
1. Are Your Work Instructions Static, Fragmented and Distributed?
Early in my tenure as manufacturing plant manager, I discovered that our assembly instructions were fragmented across assembly drawings and written procedures (very long write-ups that were difficult to read), and distributed across multiple electronic databases. In addition, these instructions were static in that they were specific to only one configuration of the product. As a result, an assembler would end up spending time searching for information in multiple places, and would either find incomplete information or not find the information required to complete his task. Actual steps therefore varied significantly from the documented.
Our test instructions suffered from similar deficiencies. Each test task required a sign-off from the assembler verifying that the task had been performed. However, most tasks were marked N/A (not applicable) as the actual product being tested differed significantly in configuration from what was described in the procedure. Most testing was performed by experienced technicians that relied on tribal knowledge to get the task done.
Given the static, fragmented and distributed nature of work instructions, it was clear that the risk of defect from an incorrect or omitted task was high.
We therefore needed to solve two problems for assembly documentation: first we needed to create assembly instructions that were complete and were available in one location, and second we needed to ensure that assembly instructions changed with product configuration.
2. Employee Ownership - Creating Work Instructions The Quick & Easy Way
I started by asking the technicians to write down every task they performed during the day. They recorded everything they did from searching for tools, instructions, and fasteners to installing or reworking o-rings, valves, brackets and pumps. This exercise was revelatory: 80% of what they captured was not to be found in any procedure. In addition, each employee had followed their own preferred work sequence. No wonder we were unable to tell how far along we were in the assembly process or provide a definitive ship date!
Next, with the help of two of the most experienced technicians, we agreed on the best work sequence for assembling the product and documented the flow in a table. We then added more information to this table including the tools to be used, the safety precautions to be followed, the quality checks required, and how long each step would take. Finally, we added a series of pictures showing how all of this information was used to perform each task. Upkeep of the documentation was the responsibility of the technicians.
We carried out a similar exercise to improve our product test instructions. One of the most experienced technicians documented the actual test procedure for each product. Next he reviewed the outline with his colleagues for sequence, completeness, and accuracy. Finally, he added in pass / fail values for each test and had them reviewed by a design engineer. The revised test procedures were considerably shorter, had fewer "not applicable" sections and were actually being referred to regularly by the technicians.
3. Moving from Static to Dynamic Instructions - The Role of Information Technology
Our first visual work instructions (operation method sheets) were built in excel which worked well but had one major limitation: the instructions did not change with configuration or with engineering changes. So, we designed and implemented an IT solution that allowed us to configure work instructions based on the configuration of the product. Every part on the bill of material (BoM) was required to be associated with one or more tasks. Engineering changes or new configurations without work instructions were automatically highlighted. As a result, the system detected and flagged missing instructions well before the product arrived on the floor allowing us to address the deficiencies in a timely manner. It also allowed us to drive corrective actions for quality issues down to the specific task level.
Making our work instructions easy to find, freed up between 5% to 10% of assembly capacity. More importantly, improving the quality of work instructions, ended our reliance on tribal knowledge, made cross-training easier, and made it possible for a new worker to perform a task with the same level of quality as an experienced worker.
A few years later, the availability of these detailed work instructions, allowed the company to transfer without interruption, a large portion of its manufacturing from one plant to another during one of its busiest quarters ever.