Improve Product Design by Understanding Accuracy, Precision and Tolerance

Precision Tolerances for Aluminum Extrusions

CAD software is just about every designer’s go to tool for product design. These programs enable simpler and more accurate design iterations, and comprehensive documentation for the manufacturer to make the actual part. They are also capable of drawing dimensions that are far more accurate and exacting than can be actually manufactured. This results in final designs being sent to the manufacturer only to get kicked back with a note that the design is “not manufacturable” or the cost to manufacture is far more than was budgeted due to the requirements.

Understanding the difference between terms like “accuracy,” “precision” and “tolerance” is important if you want to manufacturer your designs more quickly, easily and with better results.

Understanding Accuracy, Precision and Tolerance

Accuracy, precision and tolerance may seem similar and sometimes they are used interchangeably. However, when designing an aluminum extrusion understanding the differences and nuances of these terms can be key to a more efficient and cost-effective design. Sometimes more accuracy, greater precision and higher tolerance are beneficial to your design; sometimes they offer little benefit and some drawbacks. Learning these subtleties will help you make smart design decisions.

What is Accuracy?

The first term, accuracy, can be defined as the degree to which a measurement conforms to a standard. Modern CNC cutting tools are typically very accurate. So, for example, if a machine is programmed to cut the extrusion to 60mm long, it cuts it to 60mm; accuracy is how close to exactly 60mm it gets with no error. The closer to the standard the greater the accuracy. However, more accurate is not necessarily better for many applications. Greater degrees of accuracy may seem like something to strive for, but it can be counter-productive. Achieving ever greater degrees of accuracy costs time and money usually with diminishing returns. Also, getting high accuracy in one area of a design often requires sacrificing accuracy elsewhere.

What is Precision?

Precision ensures the end product turns out the same every time. That is, the creation of perfect, precise products time after time. You may often see or hear the terms “precision manufacturing,” “precision engineering,” and “precision machining.” All refer to the use of automated machinery to deliver precision. The way that precision can be measured is by specifying tolerance.

What is Tolerance?

Tolerance is the deviation away from a known value. For example, if a machine tool has a tolerance of “=/- 1mm” this means the tool can potentially introduce a deviation of 1mm (or some fraction of a mm) longer or shorter than the specifications. When designing parts to be extruded, your measurements need to account for the expansion and contraction of your materials. You don’t want parts to fit together too tightly, without clearance. This would mean they are immovable, or impossible to assemble. Good design means allowing for this natural movement.

Making tolerances tighter may seem like a good idea, but sometimes tighter tolerances may not be necessary and will not benefit the finished product. Tighter tolerances will drive up cost and take the manufacturer longer to produce. Reviewing tolerances with your aluminum extruder early in the design process can help you identify if there are any issues with tolerance settings.

Work with Your Aluminum Extrusion Manufacturer

When designing an aluminum extrusion, it is important to understand accuracy, precision and tolerance and how they can impact your design and the manufacturing process. If you have questions regarding your next design project, Vitex can help. Our aluminum extrusion experts can complete a free design review and point out if they see any issues with accuracy, precision or tolerance settings. Request a free design review today.

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