About Shrinkage Compensation or Accuracy Control

Whenever a stiffener/beam welds to a plate, the plate undergoes deformation because the heating-cooling effect encountered by this.

1. Material shrinkage: This depicts how the material (shrinkage) compensates industrially.

   
   
   

   There is an additional material provided on both sides of plate edges, and also an offset on the reference line feature to compensate the shrinkage. When the plate shrinks after welding the plate with additional material, it reaches its design specification indicated with a black rectangle. The reference line reaches its correct position, example, from red to black as in the above figure.

   To summarize, shrinkage is compensated by providing additional material at the ends, and a cumulative offset to all marking features at the beginning itself. Although the shrinkage compensation applies to manufacturing features, the philosophy integrates into this app from process planning onwards by having a different process model for shrinkage. So, addressing shrinkage compensation requirements involves three steps:

   1. A new process data model for shrinkage.
   2. A new IPM/MA data model for shrinkage.
   3. The geometrical modifications requires at the manufacturing feature layer.
2. Material distortion: addressed in subsequent releases.

Shrinkage uses dimensional compensation on manufacturing features be an added margin on both ends of the plate or an offset applied to the marking line manufacturing feature. However, we also need the real representation of manufacturing features, example, to be able visualize under MAs. Then this situation demands two different IPMs:

• One with shrinkage compensated manufacturing features, namely IPM_SC, where in each most of the manufacturing features (especially the marking line) are geometrically modified to account for shrinkage.
• Other that consists of manufacturing features with correct representations so that they visualize at MA level. This is nothing but the IPMs that we have now in this app.

The picture above depicts both these IPMs with one overlapping on the other to indicate the dimensional compensations. So, it is evident that we need two IPMs for one design piece part to address the shrinkage compensation.

To seamlessly integrate this two IPMs for one design approach into the process model, it is essential that there is altogether a different process data model. This model captures the shrinkage at the assemble process level. To address shrinkage for flat panel and curved panels independently, ensure that there are no loose ends in the model.

This section explains the Item structure for a flat panel with a shrinkage.

Item Structure for a flat panel with shrinkage part.

Functional Item Data Model - Basic planning for flat panel with shrinkage.

We observe:

• A Shrinkage (An item, which is of type Transform) is created for each plate under the manufacturing assembly as a sibling to the plate’s manufactured part.
• Shrinkage (Item) creates as child to manufacturing assembly because the shrinkage happens only during welding that captures under manufacturing assembly.
• DR link creates between Shrinkage (Item) and Manufactured part.
• Shrinkage has DM link to real IPM that gets instantiated under MA, whereas manufactured part has DM link to SC_IPM, a new IPM that contains manufacturing features with shrinkage compensation.
• SC_IPM is instantiated under IPM.
• All such IPMs are prefixed by SC_.
• Shrinkage occurs at the time assemble, example, welding the profiles to plates. However, the compensation accounts even before we mark and cut the plate. So, it is obvious that SC_IPM is in the in-process models until proceeding with assemble, and IPM is in the in-process model from there on. Hence,
  • Manufactured part has DM link to SC_IPM and shrinkage (Item) has DM link to IPM.
  • SC_IPM instantiates under IPMs.
• SC_IPM have a Mfg REP that consists of all the manufacturing tools and features like IPM, but there is no design instance under this.
  
  

This section contains information for a curved panel with shrinkage.

It is complicating for curved panels, as they already have two IPMs, curved and flattened.

This section explains how to achieve these dimensional/geometrical modifications to the feature, the Affinity functionality is used. Affinity is basically a transformation function/operation that enables to apply directional scaling to the features with respect to a reference axis system.

The required inputs:

1. Feature itself
2. Reference Axis system
3. Ratios along
   1. X - Dir
   2. Y - Dir
   3. Z - Dir (Fixed to 1)

Reference axis system for shrinkage compensation of any manufacturing feature is the corresponding BSU, example, the BSU of the corresponding IPM. Although affinity provides an ability to scale a feature three dimensionally by providing three scaling ratios as shown above, we need two-dimensional scalings. Example, along the plane in which the feature is lying. Another example, the opening (in red) and is translated and elongated along X - Dir and is decreased in the Y-Direction. No scaling is required along the Z-direction of a manufacturing feature. This cannot be a three-dimensional feature (All structure manufacturing features are either curve (1D) or surface (2D) features). Hence the ratio along Z-direction, example, Z-Ratio fixes to 1, and you can modify X-Ratio and Y-Ratio through the Shrinkage edit panel.

Figure below depicts the few manufacturing features in an IPM and how they appear in IPM_SC after shrinkage compensation.

As soon as the item structure creates this generates IPMs using the two respective commands, shrinkage item and shrinkage IPM creates for each plate. At this juncture, both IPM and SC_IPM look similar, with whatever manufacturing features (attachment lines, openings) that you chose to generate automatically. Whenever you edit the manufactured item to create more features on the IPM, these features are created also on the SC_IPM. In the case of margin and bevel features, which are impacting the size of the panel, these include as input for shrinkage compensation. As consequence, the same ratio values apply to the expanded part by margin and bevel features. You can then add shrinkage compensation to the features. Excluding margins and bevels since these captures by editing shrinkage (Item).

There are intermediate manufacturing features created which represent the shrinkage compensated result for plates. And these intermediate features are not mandatory to generate the results of this app, but optional. Part Planning, Simplified Mode provides the capability not to create dedicated transformed items and intermediate manufacturing features. This is only for shrinkage compensation, which consumes resources and time but to apply shrinkage compensation to end manufacturing features directly.

It only takes the objects, which are part planned as Simplified Mode. During Shrinkage Planning execution, it behaves as;

For Flat and Curved plate design objects.

• Shrinkage part in the manufactured item structure it does not create a dedicated item.
• Feature Planning
  • Does not create Manufacturing features that represent only shrinkage compensation.
  • Shrinkage compensation applies to the manufacturing features directly without intermediate feature creation. Single manufacturing features exist for individual information for fabrication, which includes shrinkage compensation and flattened.

Shrinkage Data model change: Shrinkage part and its resulting products do not create in Simplified Mode.

Shrinkage Data model in Simplified Mode.

As the above model changes, using shrinkage planning, there are no feature containers for the shrinkage. Unlike normal mode, the shrinkage compensation values apply to manufacturing features directly.

Differences

• Normal mode (Current behavior without this function):

  Manufacturing features exist in both In-Process Model and Shrinkage In-Process Model representing a single feature. For example, OuterContour: There are two different manufacturing features under In-Process Model and Shrinkage In-Process Model. Each of them represents an original outer shape of design data and shrinkage compensated outer shape by applying affinity ratio.

• Simplified mode:

  One manufacturing feature exists only under In-Process Model (Flat design part case) or Flattened In-Process Model(Curved design part case) represents fabrication information including shrinkage compensation.

  For example, OuterContour: There is only one OuterContour feature under In-Process Model (Flat design part case) or Flattened In-Process Model (Curved design part case) which represents outer shape including shrinkage compensated values.

Potential difference in curved design part. Shrinkage compensation values then apply on the curved manufacturing features. And these shrinkage applied features transfer onto the flattened result. With this function (in simplified mode), shrinkage compensation values apply on flattened manufacturing features directly. And uses flattened attachment lines to compute the direction and ration values.