Computer-aided design (CAD) software has become the default tool for drawing fully rendered objects on a computer screen and transferring them to the manufacturer for real parts. However, it is dangerous to think that anything that can be designed is easy to create. Software programs can draw more accurate and accurate dimensions than real machines and materials. But when we talk about how parts are made and how close they are to the ideals generated on a computer, do we mean words like “deviation” or “accuracy”?

To avoid confusion about terms, I would like to clarify the meaning of accuracy and tolerance. It then turns this knowledge into actionable advice, leading designs from computers to manufacturing sites faster, easier, and better.

Accuracy: degree of consistency with known standards or values

The international standard for length is meters, which is a general standard based on the distance the beam travels over a period of time. Therefore, accuracy is such that the measured value or spatial motion complies with the system standard or its derivatives, and is usually measured in millimeters or micrometers.

Therefore, if a CNC machine is touted to be very accurate, this means that the same thing will actually be done even if it is programmed to cut a piece of metal with a length of 40 mm. To do. The more accurate it is, the closer it is to exactly 40 mm, without error.

Useful Information: For many applications, the more accurate ones are not always good. Achieving higher accuracy requires time and money to reduce revenue. Moreover, in order to achieve high accuracy in one aspect of the design, it is usually necessary to sacrifice other aspects of accuracy. But rest assured that the latest CNC tools are reliable and accurate for most projects.

Accuracy: Reproducibility of measurement or operation without random error.

For CAD software, it is safe to assume that the blueprints are absolutely accurate. They will surely repeat any design feature with perfect fidelity as many times as you want. This is one of the great labor-saving wonders in computer design.

In factories, machine and process accuracy is the ability to repeat actions in the same way each time, without the occurrence of introduced or random errors. Precise machining, or precision workmanship, is a testament to controlling and not deviating from any measurement or process. This is often confused with accuracy, and in fact the two terms are casually used interchangeably. However, accuracy means reproducibility.

Useful Information: In this case, the accuracy is in the hands of the manufacturer and this is the performance you are really looking for. Accuracy ensures that your product comes out the same every time, and that is one of the key features we call “quality” for mass production. How do you measure accuracy? By specifying the tolerance.

Tolerance: Tolerance or predictable deviation from the standard

All machine tools have some play and vibration. They must be inert blocks. Therefore, the margin of error specifies the deviation from a known value, represented by the number “+/-“. Therefore, if you are using a machine tool with a tolerance of “+/- 1 mm”, this means that there can be an error of 1 mm per cut or pass. Extra millimeters, or fractions of millimeters or parts thereof, can be too short.

Useful Information: What you can say about machine tools is what you can say about your product. The parts should not fit too tightly together. This means they can’t move or assemble. Good design allows for this natural movement, as various metals and plastics expand and contract in response to temperature and humidity. If the part needs to be removed from the injection mold, a draft is required. We will discuss with you the recommended tolerances for all important dimensions for your project. It will depend heavily on materials, manufacturing processes and part geometry.

In summary, this means that accurate work approaches standards, and accurate workmanship is always accurate, while tolerances are controlled within small tolerances from one part to another. Will be done.

For more information on this topic, there is a manufacturing design page that provides tips and tricks to avoid the most common design mistakes. This chart details the expected tolerances when cnc machining with multiple metal parts. Want to know more? Contact us immediately for free quotes and design reviews.