How To Get The Best Value With Pound-Volume Cost
It’s important when sourcing and selecting materials that you understand the real cost of what you are purchasing. It’s common for many people to do a price per pound comparison. However, this doesn’t give you the full picture. If you buy 100 pounds of feathers and 100 pounds of bricks for the same price, which will give you more product in the end? With Pound-Volume Cost, we can analyze this and determine that in the end you will get significantly more feathers than you would bricks for the same price. In this case “price per pound” only gives you half the picture.
Understanding Pound-Volume Cost
Pound-Volume Cost is a calculation for price comparison that factors in specific gravity. Simply it’s the amount of space a pound of material occupies. The higher the specific gravity the less space per pound that is occupied. To find the true price we use the pound-volume cost equation:
Specific Gravity X Price per Pound = Pound-Volume Cost
For TPEs, this is one of the best ways to compare the price of a material because it factors in a given volume which can be related to mold cavities and finished parts. TPEs come in a large range of specific gravities and other properties. You may find that there are multiple TPEs for your application with various specific gravities and comparing the pound-volume cost will help you determine which will produce the best value when molded.
In TPEs, the specific gravity is a result of the fillers and additives that have been compounded into the polymer during the production process. If a material is unfilled it will likely have a lower specific gravity than a material with filler in it. We will take a look at a few materials with various specific gravities and work through a few calculations to demonstrate how the concept works.
Example of Pound-Volume Cost Calculations
In our examples to follow let’s assume the part we are comparing measures 1 x 1 x 1. This will give us a standard volume that is easy to calculate across all 3 materials. Below is a chart that explains details of each material.
Just like in our example of feathers and bricks, if all of the 3 materials are priced the same and, of course, are a match for your application, then most would select Material C because per pound of material you can manufacture more parts.
However, not at all materials you will test will be the same price and comparing the pound-volume cost of each material will give you a complete look at it.
When comparing, you can see Material A has a higher price per pound than the other two materials. It represents the Best Value because when considering the specific gravity, you can manufacture more parts per pound of material purchased. It gives you the best value for your dollar spent.
Want to see more examples of Pound-Volume Cost? Download the guide at the right. Understanding pound-volume cost when evaluating your material options will help make sure you maximize your budget.