# Determining Flow Groups in Multi-Cavity Molds, Part II

### Determining the Regions of the Mold

In the last tech tip, we discussed determining patterns within the mold in order to analyze “random” filling patterns and how to determine flow groups.  This tech tip will discuss how to determine regions in the mold.

A region is an area of a mold which only contains one cavity from each flow group. Typically, regions often become the quadrants of the mold; however, this is not always the case. But in either case, the number of regions is equal to the number of cavities in flow group 1.

Let’s use example 1 as our demonstration. As shown in the illustration, we have identified four cavities in flow group 1. As a result, we now know that there are four regions in this mold. We will start in the upper left area of the mold and assign letter A to that region. We then continue around the mold clockwise and label each region with a different letter. When identifying regions only one cavity from each flow group can be in a region and they cannot cross one another. Each cavity within each region should now be marked with the corresponding letter as shown in the example below.

Example 1

Example 2 below shows a mold layout where the regions are not quadrants, which can lead to confusion if this is not well understood. When identifying flow group 1, we find that there are eight cavities that belong to flow group 1. Therefore, this mold will have eight regions (A through H).

Example 2

The total number of flow groups in a mold can be found with this simple equation:

Referring back to Example 1, we know it is an eight cavity mold with four cavities that belong to flow group 1. Therefore, this mold will have two total flow groups.

Quiz – How many flow groups are in Example 2?  Tweet with your answer with #Quiz1

Now that we know how many total flow groups are in Example 1, we can begin to label the remaining cavities that belong to each flow group within each region. In example 1, there is only one remaining cavity in region A and therefore that cavity will belong to flow group 2.

Example 3

The final cavity designation (cavity ID) is 2A, indicating it belongs to flow group 2 and is located in region A of the mold. The remaining cavities in the other regions can now be numbered in the same manner, as shown below.

Example 4

This same thought process can be applied to molds with higher cavitation. Below is a 32-cavity mold we looked at in the previous Tech Tip. This mold has four cavities that make up flow group 1, therefore this mold will have four regions as shown below.

Example 5

Now that the regions are labeled, we can assign the remaining flow group numbers. To determine the total number of flow groups, we can refer to the equation above: 32 cavities /4 cavities in Flow Group 1 = 8 flow groups. We can now begin to label the flow groups for the remaining cavities in Region A. The numbering for the remaining flow groups is arbitrary and does not necessarily represent the order in which the cavities will be filled based on a shear trace.

Example 6

The above image shows all eight flow groups in Region A. Note the numbering is arbitrary; these numbers can be switched around to any order except for flow group 1. The final step is to now label the remaining cavities in each of the other regions. Care must be taken to ensure you are identifying the flow groups from region A with the corresponding cavities in the other regions.

Quiz – Identify and label the flow groups in each of the remaining regions in the image above.  Tweet @BeaumontTech with your answer with #Quiz2

Once flow groups are identified, variations in part quality, mold maintenance and fill imbalance can be classified into two categories: steel variations or shear-induced variations (rheological variations). Variations from one flow group to another mostly likely have shear-induced variations as the main root cause. Variations from cavity to cavity within a given flow group are classified as a steel imbalance.

Diagnosing imbalances, part quality and mold maintenance by breaking your data into flow groups will help improve communication among key departments and allow for faster root cause analysis by eliminating much of the guess work.