Reverse Engineering for Complex Parts: Water Pump Impeller

Introduction to Reverse Engineering

Reverse engineering is a sophisticated process that involves measuring a physical object or model using advanced techniques to reconstruct its CAD model. This method proves invaluable when design drawings are incomplete or unavailable, enabling precise and rapid capture of a sample's surface data or contours through three-dimensional scanning instruments. The workflow encompasses point data processing, surface creation, and three-dimensional solid model reconstruction, culminating in manufacturing via CAM systems, CNC machining, or rapid prototyping.

In industrial applications, reverse engineering serves multiple purposes:

• Designing new parts, particularly for product modification or imitation.
• Measuring and replicating existing parts to recreate the original design intent and reconstruct three-dimensional digital models.
• Restoring damaged or worn parts for repair or remanufacturing.
• Inspecting products, such as analyzing deformations, assessing welding quality, and comparing processed items with their digital models for error analysis.

Reverse engineering integrates two core technologies: digitization, which employs three-dimensional scanners to collect surface data, and surface reconstruction, which builds curves and surfaces from measured points to form a complete three-dimensional model. This technology accelerates product development, supports rapid prototyping, and facilitates mold processing by outputting versatile data formats.

Three-dimensional Data Measurement of Water Pump Impeller

Data Collection Conditions

Advancements in sensing, control, image processing, and computer vision technologies have led to diverse methods for acquiring an object's surface geometry. Equipment such as three-dimensional scanners and coordinate measuring machines (CMMs), manufactured in countries like Germany, the UK, Italy, and the USA, provides the necessary hardware. These devices fall into two categories: contact-based, using hard or soft probes (e.g., CMMs), and non-contact, encompassing optical methods, industrial CT, ultrasound, and MRI. In reverse engineering, optical measurement stands out as the most widely adopted approach, leveraging principles of optics and lasers.

Advantages of Optical Scanners in Surface Scanning

The speed and quality of three-dimensional sampling significantly influence reverse engineering's effectiveness. CMMs, a mature contact measurement technology, offer low noise, high precision (±0.5μm), and excellent repeatability. However, their limitations include slow measurement speeds, low efficiency, challenges in measuring soft objects, and the need for probe damage and radius compensation, resulting in high-precision but low-density data.

In contrast, optical scanners, such as the ATOS mobile optical three-dimensional scanner from Germany’s GOM company, excel in performance. With a measurement speed exceeding 43,000 points per second, a single photo capturing up to 400,000 points, a single photo accuracy of ±0.03mm, and an overall accuracy below 0.1mm/m, optical scanners outperform CMMs in scanning complex surfaces. While CMMs measure limited points on intricate shapes, reducing overall accuracy, optical scanners capture comprehensive surface data. Additional benefits include a large scanning range (up to 8m×8m with high-resolution camera systems) and portability, making them ideal for applications like automotive and motorcycle part modeling.

Preparation for Water Pump Impeller Scanning

Accurate scanning of a water pump impeller requires meticulous preparation. This includes attaching reference points to the impeller’s surface, spraying it with a developer to enhance visibility, and calibrating the scanning instrument and software to ensure precision.

Scanning Process of Water Pump Impeller

Given the impeller’s complex geometry, a single scan cannot capture its entire shape. The component, measuring approximately φ370×85mm, is divided into upper and lower sections for separate scanning. Using the ATOS optical scanner (model ATOS I 600 EU), multiple angles and orientations are scanned. The software automatically aligns each scan using common reference points, merging the data into a complete three-dimensional representation of the impeller.

Below is a table summarizing the ATOS scanner’s specifications:

Point Cloud Processing and Three-dimensional Reconstruction Using Imageware and UG NX

Processing Point Cloud Data with Imageware

The scanned point cloud data is imported into Imageware software, where auxiliary datums are created based on the data’s characteristics to align the impeller’s point cloud for section line extraction. The raw data often contains stray points, necessitating filtering and optimization to remove redundant points and reduce density, thereby enhancing processing efficiency.

Feature line extraction is critical for surface reconstruction. The impeller’s shape is segmented into quadric surfaces (e.g., planes, cylindrical surfaces, spherical surfaces), which are fitted accordingly. Planes are defined by three points or two intersecting lines, while cylindrical surfaces rely on section lines and vectors. For freeform surfaces, section lines are extracted, stray points are removed, and the data is smoothed before fitting curves. In challenging areas, such as the impeller’s internal helical groove, a helix is constructed in UG NX by projecting a circle onto the point cloud, fitting a helical section line, and calculating a pitch of 29.86mm, averaged from multiple measurements for accuracy.

Building Surface Model with UG NX

The processed feature curves from Imageware are exported in *.IMW format and imported into UG NX, ensuring coordinate system consistency. These curves are analyzed, smoothed, or edited as needed. UG NX’s feature and surface modeling capabilities are then utilized to complete the impeller’s three-dimensional model. Post-reconstruction, the model is re-imported into Imageware to assess deviations from the original point cloud using a color map, verifying accuracy within specified tolerance bands.

Product Inspection Using Reverse Engineering

Inspection Method

Reverse engineering enhances product inspection, particularly for complex parts where traditional methods falter. The processed part is scanned, and its point cloud is compared with the original three-dimensional digital model in Imageware. Deviations are visualized via a color map, enabling precise evaluation of machining accuracy.

Advantages in Batch Production

This technology proves advantageous in both single-piece and batch production. For instance, in mass-produced items like injection-molded phone cases, reverse engineering facilitates rapid sampling inspections, ensuring quality control across production runs.

Conclusion

Reverse engineering combines optical scanning and advanced software like Imageware and UG NX to transform physical objects into precise digital models. The process hinges on accurate curve construction, with surface quality dependent on smooth feature lines. By enabling replication, modification, and innovation, reverse engineering streamlines product development, shortens cycles, and boosts innovation success rates, making it an indispensable tool in modern manufacturing.

KeSu Impeller Machining Service

KeSu CNC manufacturing team, composed of professional engineers and machinists, applies optimized programming and efficient toolpaths for impeller company.

5-axis impeller continuous CNC machining provides greater accuracy and flexibility for producing complex impeller designs.

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