Part Inspection

3 Key excerpts on "Part Inspection"

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  eBook - ePub

  Total Quality Management

  Key Concepts and Case Studies

  • D.R. Kiran(Author)
  • 2016(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  Operations in the process that are generally skipped for inspection : While literally process inspection has to be carried out after every operation, sometimes only certain operations in the process are selected for inspection. For example, if a reaming operation is to be followed after drilling on a separate machine, the inspection is done after reaming only.

  Last piece inspection is carried out in the final pieces of a batch of components being manufactured. This allows any modifications necessary to be made in the set-up to rectify the faults in the equipment before commencing the next batch.

  Final inspection is done after the final operation on the component. The purpose is to prevent faulty components being sent to assembly or getting shipped to the customer. Visual and functional testing are performed during the final inspection.

  Endurance inspection : This is done mostly on assembled components to test how long an assembly will withstand its use and to determine its weaknesses for correction.

  Pre-shipping inspection : Several companies give wide publicity to the systems they adapt in final product testing and the buyers receive the QC report to create confidence among the buyers. The objectives of final inspection can be summarized as:

  ●  Ensure product safety prior to shipping

  ●  Minimize the quantum of defective merchandise

  ●  Reduce customer complaints due to inferior purchased components

  ●  Detect merchandise having non-standard or non-compliant components

  ●  Eliminate late shipments

  19.9 Tools of Inspection

  The following are some tools and instruments and methods that are commonly used in inspection.

  Measuring instruments , where the exact dimensions are determined by measuring with micrometer, Vernier calipers, torque indicating wrenches, etc.

  Limit gauges , which can be used even by the unskilled operator to know whether the dimensions are within tolerance limits.

  Multiple gauges , like electrical current operated instruments which can simultaneously measure more than one parameter.

  Air gauges , useful in the inspection of mass production work.

  Optical sensors for on-line testing of the dimensional accuracy, as illustrated Fig. 19.2

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  eBook - ePub

  Additive Manufacturing and 3D Printing Technology

  Principles and Applications

  • G. K. Awari, C. S. Thorat, Vishwjeet Ambade, D. P. Kothari(Authors)
  • 2021(Publication Date)
  • CRC Press

    (Publisher)

  Figure 10.9 identifies nondestructive test methods being applied to AM parts. Visual inspection is often employed to identify gross defects such as distortions, surface conditions, and gross anomalies. Camera and image inspection can accurately and rapidly capture and classify part features and compare them with a standard definition or part model. Cameras may also utilize magnified views of regions to verify conditions against a standard or population of parts. Bore scope inspection may be incorporated to verify clearances or deposit conditions within enclosed volumes or passageways. Multiple image cameras combined with software are capable of measuring distances and other characteristics of AM parts.

  FIGURE 10.9 Nondestructive testing techniques for AM.

  In another example of visual inspection, titanium surface discoloration can indicate contamination of the powder before or during processing and may be cause for part rejection. Supporting this example, the AWS, Specification for Welding Procedure and Performance Qualification, specifies color acceptance criteria for class A, B, C critical welds. Challenges to visual inspection presented by AM can include complex shapes and internal feature beyond the line of sight of inspectors or cameras. Unless the part was specified to be built in the same orientation, using the same support structures and build parameters, the occurrence of surface defects, such as stair stepping, may occur in different locations on parts built to the same 3D model.

  Dimensional inspection relies on measurement tools for dimensional verification, while gauges may offer a faster way to verify a part dimension or extent by using a GO-NO-GO gauge. Various nondestructive methods may be used to assure the clearance of internal passageways and volumes such as by using displaced liquid, pressure–volume–temperature, flow rate. Coordinate measurement machines (CMM) are precision measurement devices employing a touch probe, manipulated using CNC or robotic motion, to measure the location of part features.

  Software may take these measurements and compare them to locations on the part definition model. On-machine gauging can incorporate an inspection gauge directly into a CNC milling or turning environment. With the advent of hybrid AM/SM machines, the logical next step is combining CNC with AM and in-process measurements. Methods such as this are currently under development potentially enabling a single machine to produce a fully certified part without the need for subsequent inspection steps.

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  Reliability Engineering

  • Kailash C. Kapur, Michael G. Pecht, Michael Pecht(Authors)
  • 2014(Publication Date)
  • Wiley

    (Publisher)

  Many product design teams maintain a list of preferred parts of proven performance and reliability. A “preferred part” is typically mature, and has a history of successful manufacturing, assembly, and field operation, so it is usually the conservative approach to parts selection. Thus, in some cases, new technologies, processes, markets, materials, and price pressures make a mature part undesirable or obsolete. When a new product is being developed or a mature product improved, a new part may be required.

  Because a company might make parts for many different customers, who have different target applications, it is not always possible for a customer of parts to dictate requirements. An “eyes-on, hands-off” approach may be needed to select parts with the required attributes. In some cases, the selection of a proper part might require an evaluation of the part, beyond that conducted by the part manufacturer.

  Key elements of part assessment (see Figure 9.1 ) include performance quality, reliability, and ease of assembly. Performance is evaluated by functional assessment against the datasheet specifications. Quality is evaluated by process capability and outgoing quality metrics. Reliability is evaluated through part qualification and reliability test results. A part is acceptable from an assembly viewpoint if it is compatible with the downstream assembly equipment and processes.

  Figure 9.1     Part assessment process.

  Part assessment results may not remain valid if ingredients and process changes are made to the part. Even parts that are deemed acceptable may need to be reassessed periodically to ensure their continued acceptability.

  If the part is not acceptable, then the assessment team must determine if an acceptable alternative is available. When no alternative is available, the team may have to pursue intervention techniques (e.g., work with the part manufacturer and conduct special screens) to mitigate the possible risks.

  9.1.1    Performance Assessment

  The goal of performance assessment is to evaluate the part's ability to meet the functional requirements (e.g., structural, mechanical, electrical, thermal, and biological) of the product. In general, there is often a minimum and a maximum limit beyond which the part may not function properly according to the datasheet specifications. These limits, or ratings, are often called the recommended operating conditions.

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