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Sometimes manufacturers get confused between precision and accuracy concepts. This confusion in turn can lead to material waste and create additional costs while causing project delays. Therefore in this blogpost we will cover important differences between precision and accuracy along with their advantages.
What is Precision?
In simple terms precision demonstrates repeatability and consistency of measurements across multiple parts during machining. It reflects how similar the dimensions of multiple parts are to each other. For example let say a CNC machine produces 100 holes with measurements between 9.98mm and 10.02mm. This indicates great precision even if the intended measurement was 10mm.
What is Accuracy in Machining?
Machining accuracy describes the degree to which a produced component matches to its predetermined design specifications and true measurements. This process produces parts which fulfill both dimensional and performance standards. For example when CNC machine cuts hole to precisely 10mm as programmed, it shows that machining process has outstanding accuracy.
The Role of Tolerances in Machining
In machining operations, tolerances establish the permissible limits for dimensional variations from the specified measurements. If a shaft has tolerance of ±0.01mm and nominal diameter of 50mm, it must measure between 49.99mm and 50.01mm to be acceptable.
Precision and accuracy are closely related to tolerances. Precision produces repeated measurements that remain within tolerance limits and accuracy assures that dimensions match their intended design specifications. Besides that their combination guarantees manufacturing parts cover both quality and functional standards which in turn leads to improved reliability in production operations.
Precision vs Accuracy in Machining: Top 5 Differences
1. Measurement Errors
In machining, measurement errors are basically divided into two types—random and systematic error.
The accuracy of measurements suffers from systematic errors which create stable deviations due to calibration problems as well as misalignment and tool wear.
Precision is usually influenced by random errors because of unpredictable changes from measurement equipment limitations, machine vibrations and environmental factors.
If CNC machine constantly drills holes at 9.90mm instead of 10mm, it is showing systematic error. And if it is giving different measurements between 9.98mm and 10.02mm, then it is showing random error.
2. Quality Indicators
Quality indicators measure reliability and performance of manufacturing processes during machining. Precision emphasizes on important surface finish characteristics such as peak-to-valley height (Rz) and average roughness (Ra) that are measured by optical scanners and profilometers. Accuracy, on the other side, focuses on dimensional conformity through material integrity verification, concentricity checks and geometric tolerancing.
Further these indicators help in finding deviations which guarantee parts fulfill aesthetic and functional needs.
3. Process Control
Machining operations need different control methods for precision and accuracy. Precision control decreases random variations and keeps constant manufacturing conditions using real time monitoring and statistical process control (SPC). While accuracy control, in contrast, uses tool offset adjustments, systematic error correction and calibration to get target dimensions.
For instance precision control may require monitoring of feed rates and cutting speeds for uniform hole diameters. Accuracy control, on the other hand, demands geometric error corrections & routine tool wear compensation to keep right dimensional specifications.
4. Impact on Manufacturing
Manufacturing proficiency, cost effectiveness and product quality depend greatly on precision and accuracy. Precision machining keeps uniform part dimensions throughout production batches. This improves repeatability, decreases defects as well as variability. Thus it is important for large volume industries such as electronics and automotive.
Accuracy machining, in contrast, assures that parts meet design specifications as this directly impacts their performance and functionality. For example accurate parts are important in aerospace industry for reliability and safety. Poor accuracy usually leads to greater costs, potential failures and rework.
5. Measurement Evaluation
In machining, precision is determined by repeatability studies in which different measurements of same feature are compared under similar conditions.
On the flip side, accuracy is measured by comparing measurements to target or true values. So these assessments are done using tools such as micrometers & coordinate measuring machines.
Examples of Precision vs Accuracy
Precise but not accurate
A CNC machine shows precision but lacks accuracy if it repeatedly produces holes of 9.90 mm instead of the required 10 mm.
Accurate but not precise
Suppose CNC machine produces drilled holes with sizes 9.95mm, 10.05mm and 10.10mm. These measurements average to 10 mm but variation between them shows accuracy without precision.
Both accurate & precise
A CNC machine cutting holes that precisely measure 10 mm each time shows precision and accuracy.
Neither accurate nor precise
When the target is 10mm and the CNC machine produces holes that are between 9.95mm, 10.15mm and 9.85mm in diameter. So it shows poor calibration and process control.
Advantages of Accuracy and Precision in Part Production
Better Product Quality
In machining, accuracy and precision provide strict dimensional control (±0.005 mm) & outstanding product quality. Besides that, in important operations they guarantee longer lifespan and better component performance.
Improved Interchangeability & Assembly
Precise and accurate measurements permit interchangeability of parts that perform an important part in assembly. Components which maintain precision and accuracy throughout manufacturing create perfect assemblies without needing additional rework or adjustments. This not only decreases assembly time and effort but also leads to smoother production processes.
Cost Efficiency
High precision and accuracy reduce rework, decrease waste and also lower labor, downtime and material costs. Apart from that, this proficiency makes production easy and consistently produces outstanding quality parts in order to improve profitability.
Compliance with Tolerances
Precision and accurate machining assure parts meet specified tolerances—from general-purpose ±0.1mm to high-precision ±0.001mm. This reliability in different manufacturing industries guarantees compliance with regulatory requirements and rigorous industry standards.
Enhanced Reputation & Market Competitiveness
A company that produces products with high accuracy and precision establishes a reputation for quality. This reliability creates customer satisfaction and trust that distinguishes company from market competition.
How to Achieve High Precision and Accuracy in Machining
Improve Environmental Control
You can achieve machining precision using vibration dampening setups and precise temperature control.
You need to keep correct humidity levels and uniform ambient conditions in order to obtain measurement accuracy. A climate controlled facility can also help you avoid equipment calibration shifts and material expansion.
Proper Machine Selection & Maintenance
You should pick machines that have advanced motion control setups if you want to improve precision. Also monitor spindle runout tolerances and keep regular calibration schedules.
You should use CNC equipment with proper geometric specifications and resolution so you can improve accuracy. In addition you should apply tool wear compensation setups and perform routine maintenance on ball screws as well.
Quality Control Measures
You can improve precision by conducting regular repeatability studies and monitoring variations using statistical process control. You can use modern inspection tools & coordinate measuring machines (CMMs) to check dimensional consistency.
You need to perform in-process inspection and post-machining checks using calibration tools to obtain operational accuracy. Additionally you can keep dimensions within tolerance limits by modifying cutting settings and tracking tool wear.
Operator Skill Development & Training
In CNC machining, operators need proficiency in techniques such as tool path optimization and parameter adjustment methods to improve precision. Similarly operators should be proficient in error correction and calibration methods to achieve outstanding accuracy during machining.
Conclusion
In short precision and accuracy are both important in machining. Each performs an important part in making quality parts. Precision focuses on consistency across parts whereas accuracy assures parts meet design specifications.
If you require any kind of CNC machining services–with outstanding precision and accuracy, then RICHCONN is best option. You can contact us anytime.
Related Questions
Why are both precision and accuracy important in CNC machining？
In CNC machining precision produces uniform parts while accuracy verifies adherence to intended specifications. This combination provides both smooth assembly and functional reliability of components for medical device and aerospace applications．
Can high precision compensate for low accuracy in machining？
No high precision itself cannot compensate for low accuracy. The continuous output of incorrect dimensions produces parts that do not meet functional requirements.
How does operator skill level affect machining precision and accuracy？
Operators who possess technical proficiency know how to improve operational parameters and pick appropriate tools. Besides that the depth of operator knowledge in troubleshooting and programming determines both part quality and consistency．
What are common challenges in maintaining high precision during large scale production？
Manufacturers face several major challenges when producing high precision items including thermal variations along with material inconsistencies and tool wear management．
How do modern CNC machines enhance precision and accuracy？
Modern CNC machines achieve greater precision and accuracy by combined use of thermal compensation technologies and automated calibration as well as high-resolution feedback setups. Moreover their combination reduces all kinds of measurement errors including random and systematic ones.
