Dimensional Tolerances in Manufacturing Process

Tolerance is the measurement of the physical characteristics of a part for its optimal functioning and aesthetic accomplishment. Generally, it deals with measuring a part in terms of its X, Y, and Z dimensions. However, it also deals with other characteristics such as colour, texture, shape, or profile.

Dimensional tolerance is an important procedure in precision machining service. Therefore, this article will discuss tolerance, its importance, and what you need to consider.

How To Understand Dimensional Tolerances?

Understanding a part’s dimensional tolerance is an important procedure in any manufacturing process. Tolerance directly affects product functionality. Therefore, the more detail, the better the product quality and the more rewarding the manufacturing process.

Tolerance is important as it gives the creator control over product consistency, accuracy, precision, and product quality. To understand dimensional tolerance, below are some commonly used in the procedure:

●     Basic Size

The basic size of a part is the size to which you can add allowances and tolerances to get the limits. For example, at 5±0.002mm, the 5 is the basic size.

●     Nominal Size

The nominal size is for general identification. It is normally represented in fractions and designated in inches.

●     Design Size

The design size is the size from which you limit the size limit after tolerance application.

●     Actual Size

The actual size is the measured size of a part.

●     Lower Deviation and Upper Deviation

Lower deviation is the difference between the component minimum and basic size. Upper deviation is the difference between the component maximum and basic size.

●     Interchangeable Parts

These are parts manufactured to easily fit another (the mating pair) without further manufacturing process.

●     Allowance

Allowance is the minimum clearance or maximum interference that you can have between the MMC (Maximum Material Condition) of the components that make up a complex product.

●     Unilateral and Bilateral Tolerance

Unilateral tolerance allows variation in a direction, while bilateral tolerance allows both directions from the design size.

●     Tight or Loose

These are two terms used to describe the tolerance of a component. A part can be “loose” or “tight,” depending on its measurement.

On the one hand, a component with tight tolerance allows a little lower and upper deviations. Consequently, they are precise. On the other hand, a part with loose tolerance has lesser precision and usability. Achieving optimal tolerance depends on production cost, the need for precision, and functionality.

Why Dimensional Tolerances Are Important During Manufacturing

Below are a few reasons why the procedure into your manufacturing process.

●     Avoid Problem in Parts Fitting

Dimensional tolerance is necessary for making complex products. This is because a complex product comprises many components that must be compatible with each other. Consequently, you should know and define your tolerance accurately. Having a small inaccuracy in measurements or a variation can lead to product incompatibility.

Decrease Manufacturing Ambiguity and Risk

Ambiguity is something you should avoid in any manufacturing process. If you do not avoid it, there is a high probability that you will end up with an unusable product. You can remove ambiguity and risk by making sure you have done the dimensional tolerance check.

●     Control Manufacturing Cost – Tight Tolerance Means High Cost and Time

Defining your tolerance means upping your precision. Consequently, you save your cost and time since you only need to pay for the materials, tools, and labor you need.

●     They Improve the Look of The End Product

Aesthetics and tolerance go hand in hand. Therefore, if your product requires a high level of aesthetics, you need to make sure you take care of dimensional tolerances. For example, in products that need to sit up against another with no gap, you need to define and control the components’ dimensions and positions carefully.

●     You’ll Get Products to Market Faster

Tolerances allow a certain amount of error. However, when exceeded, the part might no longer be functional. Therefore, when you define what you need in terms of dimensional tolerance, there is a lesser chance of remaking your parts later. While this is an extra yet compulsory step, it saves you time. Consequently, you can get your products to the market faster without measurement errors and inconsistent parts or products.

What You Should Consider as Designers

As a designer who knows the importance of dimensional tolerance, you must consider a few things. Below are a few key considerations that will help you determine tolerances:

●     Materials Consideration

Different types of materials have different chemical and mechanical properties. For example, plastic has a higher tendency to change size due to heat and other factors. Therefore, dimensional tolerances for plastic must account for such variation.

●     Different Machining Methods Cause Different Precision

Also, like the type of materials available, the machining method you use has a huge impact on dimensional tolerance. Some manufacturing methods will require unique measurement errors. For example, the common EDM precision is around 0.01- 0.05 mm. However, injection molding is harder to reach such precision. Also, some machinery can adjust to tighter tolerances

●     Account For Tolerance Slack and Stacking

Tolerance slack is the total tolerance of the components that makes up a product. As a designer, it is important to know your tolerance slack to avoid tolerance stacking. Tolerance stacking is a term that shows the accumulation of small tolerance inaccuracies. Consequently, this leads to bigger miscalculations.

●     Balancing Costs and Benefit

After noting the importance of the considerations above, you must find a balance between cost and benefits. For example, tight tolerance is costly, while an overly loose tolerance renders a part less costly although unusable. Therefore, you should find a balance. You must also find a balance between simplicity, speed, cost-effectiveness while ensuring that every component is of high quality.

Final Thoughts

Understanding dimensional tolerance has many benefits. For example, it removes ambiguity and risk, makes you avoid the problem in parts fitting, decreases manufacturing ambiguity and risk, and improves the product’s look. Consequently, it is an important process in product manufacturing. Finding a company who can help you to monitor every step in the machining process is very important. On-demand machining company RapidDirect understands dimensional tolerance and can help you get the best out of your design, reduce cost and deliver quality parts and products.