Geometric’s FR technology automatically extracts a wide range of features from 3D solid models. FR consists of three different libraries; namely, Design View FR, Manufacturing View FR and Sheet Metal FR. FR provides feature tree information and respective feature parameters, parent-child relationship in case of intersecting features and alternate interpretations of features.
MillTurn centers are on the increase, which are turning centers with live milling tool on the tool post with C-axis spindle control. Manufacturing view feature recognition library has added a new functionality to recognize such C-axis features in MillTurn module, apart from recognizing turning and milling features. FR further classifies the feature into C-axis-pockets and C-axis-slots as shown in Fig 1.
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 andK-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.
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
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.
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 imported sheet metal models in CAD modelers always has limitations. Imported models having flanges as that shown in the figure below are not possible to unfold in most of the CAD modelers.
The latest version of Sheet Metal FR now has the capability to unfold imported models with such flanges. By enabling the patch stamps option, the above imported model can be unfolded with ease as shown below.
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.
In sheet metal models, generally various types of cutouts are used. Even holes are special type of cutouts. There are different types of cutouts such as Internal cutouts, External cutouts, Multiface cutouts. Typical examples are shown in the figure below.
Internal cutouts are those which lie completely in a single plane. External cutouts are generally referred as notches and these cutouts lie along the boundary.
Multiface cutouts spread across multiple faces as shown in the figure below.
Sheet Metal FR identifies all these features and even gives flat patterns as shown below.
Why do we need Feature Recognition when we already have Feature Based Modeling Systems (FBMS)?!!
When we design a model in FBMS, we use Extruded Boss, Extruded Cut, Revolved Boss, Revolved Cuts, Loft, Sweep, etc. These are all design features. Even Holes, Countersunks, Counterbores can also be made using revolved cuts. But in order to manufacture the component, we need to infer manufacturing features from design features so that suitable CNC canned cycles can be chosen. This is a manual activity. Geometric’s Manufacturing View FR provides an automated tool for this activity. MfgView FR automatically extracts manufacturing features like Standard Hole types, Pockets and Slots. Even islands in pockets and slots are identified and further parent child relationships are also provided. So by using MfgView FR, a task that would take hours when done manually can be reduced to seconds.
Should costing is the process of determining what a product should cost based upon its component raw material costs, manufacturing costs, production overheads, and reasonable profit margins.
Let me explain history free editing with a simple example. Make a model as shown in Fig A as per the sequence given below. 1. Make a cube (100x100x100). 2. Make a central hole (50 Dia. x 75height) from the bottom of the cube. 3. Make another cube (75x75x75) on top of the first cube.
Fig A. Test model
Now, try to modify the height of the cylinder from 75 to 150. In a history dependent modeler, the height of the cylinder after modification will only be 100 instead of 150 as shown in Fig B.Whereas, in a history free modeler, the height of the cylinder after modification will exactly be 150 as shown in Fig C.
Fig B. Modification in a History Dependent Modeler
Fig C. Modification in a History Free Modeler
The faulty modification caused in history dependent modelers is due to the fact that model re-evaluation is based on the chronological feature creation order i.e. a new boundary model is created by sequentially re-executing the operations in the modified history. Hence, even though the modified height of the cylindrical hole is 150, on subtracting the cylindrical hole with a cube of height 100, the hole becomes a through hole in the first cube. Then the second cube is placed on top of the first cube.
Whereas in history free modelers, the modification is handled in a different manner that only the immediate faces connected to the modified face/dimension are modified. Even though, such modelers are powerful in history free modification, model modification requirements such as converting a through hole/pocket into a blind hole/pocket or vice versa is better accomplished using feature information.
