Now that you know what your topic/project is the second Step is to brainstorm about what requirements you have for your design. For example: if you were building a bridge how much weight does it need to suspend? Another way to look at it is: How strong does it have to be? How much amount of weight can it hold before it breaks?  The answers to these questions would be the limits of your design requirements.

Consider the range of your design. Is it a bridge for pedestrians or for cars? If the bridge is for motor vehicles, how many cars/trucks can fit on it? You can use questions like these to further your project requirements and help you determine the proper range of your design limits. 

Relate these design requirements to what kind of materials properties your project needs. We will use these material properties limits for material selection in CES. To begin with, focus on what you think are the key properties needed in your design. Choose two or three of these properties. These key properties will be your project requirements for your design when working with CES. CES will compare these key properties with material attributes that are in its database.

For our example project we are considering a child’s tea-party table…

From pre-established requirements for the table we now can define the requirements for our design. The project requirements for the materials of the table will be simply: Light-weight, low cost, and safe.

Let’s further define these three requirements.

Light-weight

The material chosen must have a low density. The child must be able to pick up and carry the table easily.

Low cost

The material used for the table must be inexpensive.The cost of the process to make the material for the table must be low.

Safety

The material used for the table must not break when the child is playing with the table. The table must be safe for the child to eat on; considering chewing and/or swallowing as well.

Now let us decide on the range of the requirements…

When we think about the range it is mandatory to further define the design of the table. So, we must define the table with the child in mind. Let’s give some educated guesses and assume some reasonable ranges for our key properties.

What range of cost should be acceptable for the parents spend?

            Material cost range of 5 to 20 dollars per table.

What size range should the table be?

The table should be in the range of 2-feet to 3-feet square and the height of the table must be 1.5 feet tall.

What is the age of the children that will play with the table?

            Children from the age of 4 to the age of 8 will play with the table.

So, we could conclude that the table must hold the weight of an average child of 8 years old and an average child of 4 years old must be able to pick up the table. Assuming that the average 8-year old is 50 pounds and the average 3-year old can carry 2 to 4 pounds maximum: the table then must hold max load of 50 lbs and cannot weigh more than 4 lbs.

So in conclusion, the key properties for this child’s tea-party table are as follows:

Selected materials must have:

            Low density (max weight less than 4 lbs)

            Low cost (max material cost of 5 dollars per pound)

            Safety (Non-toxic & Max load 50 lbs)

Now that we have some key properties and ranges for our design let us start the materials selection process using the Cambridge Engineering Selector.