Bevel Recognition and Unfolding

Bevel cutting in thick plates can be cut in laser/plasma/waterjet/milling machines with tilt head. FR has developed bevel feature recognition in which four types of bevels such as V-Bevel, Y-Bevel, X-Bevel and K-Bevel can be recognized.  

 

Fig 1. Different Types of Bevels

Bevels are not only recognized on just planar surfaces, but can also be recognized on bent surfaces as shown in Fig 2.

Fig 2. Bevels on Bends

Unfold can also be generated as shown in Fig 3 for components with bevel features. 

Fig 3. Bevel Unfolding

Recognition of Hole types and Compound Cutouts

Sheet metal parts generally contain holes and cutouts. Holes can be simple holes, tapered holes, counter-bore holes, counter-drill holes and counter-sunk holes, as shown in Fig 1 from left to right respectively.

Fig 1. Different Hole Types

Similarly, cutouts can also have such cross sections, which are termed as compound cutouts. Sheet metal feature recognition library can recognize all these compound cutouts and can also classify cutout shapes such as obround, rectangular with/without corner fillets and generic shapes.  

Fig 2. Different Compound Cutouts

All these types of holes and cutouts are recognized by sheet metal feature recognition library as shown in Fig 3. Recognition of such features and associated parameters are very useful in automatic tool selection. For downloading evaluation version click here. 

Fig 3. Feature Recognition of Hole Types and Compound Cutouts

Marking and Half-shear Recognition

FR has recently added capability to recognize marking and half-shear features in sheet metal feature recognition library. Markings are generally inscribed on sheet metal parts, which are depressions that do not penetrate the sheet completely but partially as highlighted in green in Fig 1.

Fig 1. Marking features

Marking features with different cross sections as shown in Fig 2 can be handled efficiently. 

Fig 2. Cross section of various marking features

Half-shears are features that can be of any shape that are sheared partially in a sheet. The cross section of a circular half-shear is shown in Fig 3. Geometrically half-shears create a pocket on one side and island on the other side of the sheet. 

Fig 3. Cross-section of a half-shear

Few half-shears that can be recognized by sheet metal feature recognition library are shown below in Fig 4.

Fig 4a. Pocket side of half-shears

Fig 4b. Island side of half-shears

FR can recognize Fasteners

FR sheet metal library can recognize a variety of fasteners in sheet metal models such as

1. Square weld nuts
2. Hexagonal weld nuts
3. T weld nuts
4. Spacers
5. Stud fasteners

Unfolding Shell Models

For designing design sheet metal models, some designers use solid modeling commands rather than sheet metal commands. Such models are made initially using solid modeling commands and then shell command is used to get uniform wall thickness and finally the model is converted into a sheet metal model. Such models when received by manufacturing vendors are often not suitable for unfolding. There are two reasons for this (i) unripped edges and (ii) sharp bends. To handle such cases, Sheet Metal Feature Recognition library (SMFR) provides options like (i) ripping and (ii) insert bends.

Model with an Unripped Edge and Sharp bends

For example consider the model shown in the figure above. Faces A and B are connected together, whereas to unfold the model, both these faces need to be unconnected. The unripped edge shown in the figure needs to be ripped. Sheet Metal Feature Recognition library provides an option to rip such edges in imported solid models. The edges to be ripped and the rip gap are to be provided for ripping. The imported model after ripping is shown below.

Model after Ripping

The model has two sharp bends with inner radius and outer radius as zero. For accurate unfolding and sheet metal bending, inner radius has to be specified. Sheet Metal Feature Recognition library provides an option to automatically convert such sharp bends into cylindrical bends. The sharp bend and the inner radius are to be specified for automatic conversion. SMFR can also detect sharp bends automatically for such conversion. The imported model after conversion of sharp bends into cylindrical bends and flat pattern obtained using SMFR are shown below.

Model after Conversion of Sharp Bends into Cylindrical BendsFlat Pattern

Unfolding sheet metal models with stamp features

Unfolding sheet metal models with stamp features is handled in different ways by different modelers. Louver, dimple, bridge, lance and features that require forming are referred as stamp features in this context. For example, the model shown below contains few stamp features.

FR unfold has two options for unfolding.
(1) Unfold bend features : This option automatically recognizes all the bend features and unfolds only bends. All other features including stamp features remain as such as shown below.

(2) Unfold with patch stamps : This option automatically recognizes bends and stamps. Unfolding is performed by unfolding bends and patching stamps as shown below.

Click here for an evaluation

Geometric's Feature Recognition

Feature Recognition is a state-of-the-art patented technology from Geometric with more than 100 man-years of research and development. Feature Recognition extracts a wide range of features from solid models and finds applications throughout the product lifecycle like modeling, finite element analysis, machining, inspection, process planning and cost estimation. FR from geometric is the most preferred feature recognition engine, selected by leading CAD/CAM vendors, as FR provides high quality, easy to use API interface and cost-effective to implement.

Feature based design received strong emphasis from the industry, with the aim to utilize feature data in downstream design and manufacturing applications. The time invested in developing parametric feature based designs is expected to have significant pay-offs in such automation. However, feature based design systems employ form/design features rather than manufacturing features, due to which further feature inference is often required for specific applications. Also, in contract manufacturing firms, majority of designs are imported geometry in neutral formats, where valuable feature information is lost. The model is generally received as a dumb solid and editing the model or inferring feature information for downstream applications becomes difficult. Further when a model designed in feature based CAD platforms has to be ported in other tools like analysis softwares or manufacturing softwares, etc., the model is often loaded in neutral formats, which is again a dumb model.

Geometric’s Feature Recognition technology helps to develop a smart, parametric feature based models from imported B-Rep solids. Feature Recognition breathes life into 3D CAD (solid) models and catalyses data re-use and interoperability.

Feature Recognition (FR) Technology

Geometric’s FR technology automatically identifies features from 3D models. It provides feature tree information and respective feature parameters, parent-child relationship in case of intersecting features and alternate interpretations of features. Features that are not recognized automatically are recognized using an optional interactive feature recognition mode. FR also supports local feature recognition where features from a particular region are identified. Further, it supports user-defined features. FR consists of three different libraries; namely, Design View FR, Manufacturing View FR and Sheet Metal FR.

Design view FR extracts design features from dumb models to facilitate model editing and to create variant designs. It can automatically identify various design features such as holes (simple, taper, counter-bore, counter-sunk, counter-drill, split holes, hole-chains), fillets, chamfers, extrudes (drafted, cut, boss), revolves (cut, boss) ribs, drafts, lofts and sweeps. FR facilitates recognition and suppression of features. During analysis, suppression of certain features like, fillets, chamfers and small holes can easily be done with feature data from FR. This helps to improve the mesh quality and to reduce analysis time. With feature data from FR, dimensioning can be automated and further it facilitates Geometric Dimensioning and Tolerancing.

Manufacturing view FR extracts manufacturing features and provides information suitable for downstream applications like CNC code generation, machining sequence generation, process planning, inspection planning, etc. It extracts a variety of features that can be processed by Milling, Turning, Mill-Turn and WireEDM. List of manufacturing features identified include holes (simple, taper, counter-bore, counter-sunk, counter-drill, split holes and hole-chains), hole patterns (linear, rectangular and circular), fillets, chamfers, pockets (blind, through, drafted, filleted and chamfered), slots (simple, drafted, filleted and chamfered), islands, machinable volumes, machinable slabs, intersecting features, external turned profiles, internal turned profiles, turned grooves (filleted, chamfered, vee, radius and dovetail), slots and pocket in turned profiles (mill-turn). Feature data from FR helps to use standard machining cycles in CNC code generation for drilling, counter-sinking, counter-boring, pocket machining, etc. It is also helpful to identify and cluster the features to be machined in a particular setup. The parent child relationship of features from FR further helps to determine the machining sequence to be adopted. It also helps to minimize the number of setups required. FR can be used to identify inspection features, which can be helpful in probe movement programming and inspection planning. With feature data from FR, design checks such as use of standard hole sizes, minimum distance between various features, etc., can be ensured. Such checks help to avoid costly design errors which are difficult to tackle during manufacturing. Features that are costly to manufacture can also be easily identified using FR, which can be helpful in cost optimization. FR data can be further used for manufacturing cost estimation.

Sheet Metal FR extracts features from a sheet metal perspective along with unfolding. It can also handle Tramoggia flattening. Various features identified include walls, bends, holes, counter-sunk, counter-bore, flanged holes, cutouts, flanged cutouts, notches, flanges (open hem, closed hem, teardrop hem, roll hem, jog flange, edge flange, contour flange), stamps (louver, lance, bridge, dimple, bead)and ribs. For sheet metal models, FR helps to edit models for creating variant designs and to create flat patterns. Feature data is useful in selecting tools required for specific features, tool availability checking, design for manufacturing, determining the punching sequence to be adopted, determining an optimal bending sequence and cost estimation.

Features

• Recognizes features automatically and generates feature tree
• Provides parent-child relationship for intersecting features
• Provides alternate interpretation of features
• Provides control to recognize features interactively or on a local region
• Supports standard and user-defined features
• Supports kernels including Parasolid (V18, V19, V20), ACIS (R16, R17, R18)
• Supports CAD APIs like SolidWorks (2008, 2009), CATIA V5
• Is available as 32 bit and 64 bit Static Library and DLL

Benefits

• Facilitates integration of CAD and CAM
• Enhances interoperability, recreates design intent, and improves process automation thereby reducing time-to-market
• Improves productivity with minimal manual intervention
• Enables automatic recognition of machinable features
• Reduces errors in G-code generation through feature based machining
• Provides scalability for varied component manufacturing
• Allows 3D data reusability throughout product development

Applications

Design (Computer Aided Design) – Model editing, feature suppression, creating variant designs, auto dimensioning, geometric dimensioning and tolerancing, and flat pattern development from dumb solids for sheet metal (SM)

Manufacturability Analysis (Design for Manufacturing) – Design check, and manufacturing feasibility check

Analysis (Computer Aided Engineering) – Feature suppression (suppression of fillets, chamfers and holes) to improve mesh quality and to reduce analysis time

Process Planning (Computer Aided Process Planning) – Machining sequence generation, tool selection, setup planning, punch sequencing (SM), bend sequencing (SM)

Machining (Computer Aided Manufacturing) – CNC code generation (Milling, Turning, Mill Turn, WireEDM, PunchPress, PressBrake, etc.)

Inspection (Computer Aided Inspection) – Coordinate Measuring Machine (CMM) probe movement programming, and inspection planning

Costing – Design analysis for cost optimization, and cost estimation