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Understand Precision, Accuracy And Tolerances To Advance Product Design

Date: Apr 07 2020 | By:LC Rapid
Tag:Product Design, Quality Control, Inspection,

Computer-aided design (CAD) software is nowadays the default tool for drawing excellently rendered objects on a PC screen and then giving them to the manufacturer to make real parts and products. Although, it's dangerous to think about that anything can be designed and can be made just as easily. Software programs can draw more accurate and precise dimensions than the real machine tools and materials in the world. But what do "accuracy" and "precision" two words mean, when we talk about how the parts and products are made by and how they are close to the ideal situations that come out of the PC screen?


To understand any confusion in terms, we would like to know what precision, accuracy and tolerance mean. We can then turn this information into practical advice to help you design faster, easier, and better than before.



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Precision: repeatability of measurements and movements without the random errors range


For the CAD software, it's out of question to say that the design drawings are entirely accurate. They will reliably repeat any design feature with excellent fidelity usually as what you want. This is one of the wonders of saving people in computer design.


In a factory, the precision of a process and machine is the ability to repeat operations in the same case each time, with no introduction and the random errors. Accurate processing or precise process is proof of control process and non-deviation, regardless of process and measurement. This is usual confused with accuracy, and in fact the two terms are used interchangeably. Although, accuracy refers more to repeatability.


Useful information: In this case, precision is in the hands of the manufacturer, which is indeed the performance you are looking for. Its precision ensures that your product is produced in the same way every time, which is one of the basic functions of what we call mass production as "quality". How do we measure the precision? By specifying the tolerance.


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Accuracy: the extent to which an understood value or standard is met


The international length standard is a meter, whose value is general based on the distance the beam travels over a fixed couple of time. Therefore, accuracy is the degree to which spatial measurement or motion conforms to system standards and one of its derivatives, usually in millimeters or microns measured in metric systems.


Therefore, when the CNC machine is touted as greatly accurate, it means that if it's programmed to cut a piece of 40mm-long metal, the machine will actually do it so. The more accurate it is, the closer it gets to exactly 40 mm, with no errors.


Useful information: For many applications, being more accurate is not necessarily better. Achieving a higher level of precision can cost you lots of money and time to reduce returns. In addition, obtaining precision in one area of design usually requires sacrificing precision elsewhere. Although, rest assured that the modern CNC cutting tools are reliable and accurate for most projects.


Tolerance: predictable or allowable standard deviations


All machines have a certain degree of free play or vibration - they must, otherwise they will be frozen, inert blocks. Therefore, the tolerance specifies a deviation from the known value, expressed as a "plus/-" number. Therefore, if we have a machine tool that it claims a tolerance of "plus/-1 mm", this means that the tool may introduce a one-millimeter deviation each time it is cut or passed. It may be an extra millimeter, or it may be too short for a millimeter or some of the fractions.



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Useful information: For your product, the same is true for the machine. You don't want parts and products to be too tightly grouped together without gaps. This will mean that they are immobile or impossible to assemble. Different plastics and metals expand and contract with temperature and moisture, so a good design means allowing this natural movement. When the part and product need to be removed from the injection mold tool, the draft angle must be drafted. We will discuss with you the recommended tolerances on all key dimensions of the project, depending on the geometry, material, and part manufacturing process.


Taken together, this means that the exact work is close to the standard, the precise process is reliable and accurate over and over again, and the tolerances are controlled within the acceptable variability of one part to another.


For more information on this topic, if you want to know more? Contact us for free quotes and design reviews.


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