An Introduction to APQP Documentation - Article 2: Process Flow

The process flow chart is a tabular representation of the current or proposed process flow. It is used to document and analyse the various process steps from the beginning to the end of a manufacturing or assembly process. It is a useful tool for communicating how processes work, and for clearly documenting how a particular job is done. The flow chart also helps to analyse the total process as well as the individual steps and further assists the Product Quality Planning Team to focus on the process when conducting the PFMEA and Control Plan.

APQP Document Tutorial - Cake Diagram

Using the same example we discussed in last week's article on the Design Failure Mode and Effects Analysis (FMEA), let's take a look at a potential example of a process flow chart for the process to create a desert layer cake. This article focusses on the column titles and their contextual meaning. As we are not experts on making cakes ourselves, we ask that you please accept the content of our example process flow chart "with a grain of salt." :)

Step - This field is used to identify the current step in the process. It is often sequential and usually takes an alphanumeric format.

Example: In our example document, we've used numbers 1 through 6 to identify the various process steps.

The next four columns, "Fabricate", "Move", "Store", and "Inspect", use images to identify the type of process step being documented. In our document, these columns are marked using diamonds, circles, triangles, and squares respectively. Let's take a look at the meaning for each column.

Fabricate - This field should be selected if the process step physically alters the product.

Example: In our example, "Spread the Jam onto the bottom layer of cake" is a process step which contributes directly to our product, and is therefore a "fabrication" step in our process flow chart.

Move - If our process step refers to a action which physically moves our product, it should be noted in this column.

Example: "Take both layers of cake out of the oven. Place the bottom layer of cake onto a flat surface" requires us to physically move our product - so we have noted it with the appropriate shape in this column in step number 1.

Store - Actions to "store" or temporarily prevent further actions from taking place to the product should be noted in this column. Examples of this may include placing our product in a particular location while it sets, cools, or dries.

Example: "Store completed cake in a fridge so that it can set correctly before the icing is applied" is an action to store our product so we have marked the appropriate column in our Process Flow Chart.

Inspect - Inspecting the product is a critical in any process. There may be multiple instances when the product (or sample of product) is inspected. These should be noted each time. Reviewing the document for inspection steps after it is complete is a good idea as we may wish to add inspection steps to our process if we see multiple steps between existing inspections.

Example: In our example process flow chart, we've identified two inspection steps - one about half-way through our process and one at the very end to ensure our process was successful.

Operation Description - This field should be used to describe each step in the manufacturing of a system, subsystem, or component process. A brief, but descriptive, summary of the process step should be used. In the event that the process step refers to another process flow chart, that chart's name and description should be entered into this field.

Item # - Here, we should enter a cross reference number from all applicable documents such as, but not limited to, blueprints, FMEAs, and sketches (computer generated or otherwise) which are affected by the process step.

Example: In our example, we reference the various layers of cake and jam which are affected by each process step.

Key Product Characteristic - This field is used to describe the desired result from each process step. Product characteristics are the features of a part or assembled product that are described on drawings or other preliminary engineering information.

Example: From the example process flow chart, we see "The jam should be spread evenly over the bottom layer in order for the top layer to stick properly" is a "key product characteristic" for process step 2.

Item # - Again, we should enter a cross reference number from all applicable documents such as, but not limited to, blueprints, FMEAs, control plans, and sketches (computer generated or otherwise) which are control elements affected by the process step. For example, item numbers representing specific tolerances and control mechanisms may be identified here.

Example: In our example, we reference the various layers of cake and jam which are affected by each process step.

Key Control Characteristic - This column contains a brief description of how the process step will be controlled. Operations may be controlled by, but are not limited to, Statistical Process Control, inspection, attribute data, mistake-proofing, and sampling plans.

Example: For the same process step, we've entered "Jam layer must be within tolerance as specified in dFMEA 'dFMEA_cake' and customer specification" as our control.

QA Assistant Studio™ makes it easy to format the borders, helps ensure the document language is consistent, analyze the document's data, and track the recommended actions. You will save as much as 80% of your current time spent creating and managing this documentation if you use this software! The example document (which you may download by clicking the image to the left) was created in about 5 minutes using QA Assistant Studio™ and was exported to Adobe PDF in just one click!

Now that you know how easy it is to complete a Process Flow and understand the document's content, why not try it yourself?