Fabrication: Reduce Workload with Specifications/Pressure Classes (Pt.1)

17 June 2019All, autodesk, Fabrication



There are a lot of benefits to be gained using Autodesk Fabrication software if you take the time to set up your specifications (otherwise known as pressure classes) for all ductwork. These benefits can be realized through greater cohesion among departments, confidence on fittings input, and overall consistency in what is pushed out onto the shop floor. Too often we see that those in the CAM department feel that the jobs being sent from the CAD side are incorrect or off in small ways that always need to be fixed. Often these issues can be rectified using specifications.

Typically, all a user must do is take the set of rules or standards that their company maintains for their ductwork (typically SMACNA) and manually input this information into their software. While you may not be able to account for every foreseeable combination as set out by your standards, at the very least you’ll be able to maintain a solid foundation to reduce the workload for all users from drafting to manufacturing.

To begin the setup of specifications, make your way to the main database. This is the book icon located in the Utility Bar of ESTmep/CAMduct or on the toolbar for CADmep:

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Once you are in the database, click on the Fittings tab option, and then select the option for Specifications.

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When you are in the specifications screen, you are greeted with a few different drop-down selections, as well as different buttons/tools to edit and create specifications. The drop-downs include specification name, selected material for the specification, the library fitting type used for the specification, and the type of fittings the current table of the specification is valid for. To the side, four main buttons (shown above) serve specific purposes:

  1. Specification Properties – Edit specification information regarding naming, breakpoints or alternate seams and connectors.
  2. Owner Info – Manually track changes to specifications and implement versioning.
  3. Create New specification. Note that if a current specification is selected, it will initially prompt you to make a copy.
  4. Delete the currently selected specification.

Select the green rectangle button to create a new specification. If you currently have a specification selected when you press that button, it will prompt you to make a copy. Click “No” in this instance, and start it from scratch. You should see the following window (without any information set up).

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Name: The name of your specification typically follows the name of the pressure class being used.

Group: For sorting purposes, often your specifications can be grouped together by common Groups. These are often materials, maybe pressure classes based off specific connections.

Abrv: An abbreviation can be used if your specification name is long, and you need a shorter name to pull and report on in labels or other printouts.

Breakpoint type: Determines the size of breakpoint style in your specification tables and appears as follows:                 

  1. LS/SS Dimensions – Breaks out the specification table to allow pressure classification based on both long side and short side.
  2. LS/SS Dimensions + Length – Breaks out the specification table to allow pressure classification based on long side, short side and length.
  3. Single Dimension – Breaks out the specification table to allow pressure classification based on long side only.
  4. Single Dimension + Length – Breaks out specification table to allow pressure classification based on long side and length.

The breakpoint type you use is dependent on how specific your pressure class is. Some pressure classes focus primarily on the longest side of the part and little else; others will have different levels of connection or reinforcement dependent on the long and short side of the piece or the length of the fitting.

Stiffen By: Allows you to determine how you want to set your stiffener or tie rod reinforcement when applicable. The options are either by a spacing set in the specification, or by quantity where that value is set in the specification. Typically, the spacing option is set to allow for automatic increase in stiffener quantities based on size and length.

Default Material: This is the material the specification defaults to when initially being applied to an item. You can input information for multiple materials in a single specification, but the default material is the one the software will implement on first input.

Alt Connectors: Used when fittings require a specific connection that is not the connection the specification explicitly calls out. This can be due to the need for a specific notch on an item (like a square to round) or any other ease of manufacturing purpose.

Alt Seams: Similar in nature to the Alt Connectors, but for seams in the event a fitting requires a different seam than the specification calls for.

Once you input the initial data, you can click OK. For purposes of this example, the settings used in the previous graphic will continue to be used. At this point the specification appears as follows:

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You can see it carries the Specification name of +2WG as well as the default material in Galvanized set before. What about the other fields?

Library: Sets the fitting type for the selected table of the specification. The options are Rectangular, Round, Flat Oval, Standard, Pipework, and Electrical. Rectangular will be the selected library for the example.

Valid for: Determines what type of item the table applies to. The options are Straights Only, Fittings Only, or All Types. Note that the values you put in for Straights Only will only apply to your standard straights, the Fittings Only will apply to non-standard straights and other fittings, and All Types applies to standard straights, non-standard straights, and other fittings. You must use either Straights Only AND Fittings Only, or use All Types.  If you put information in for All Types as well as one of the other categories for that material, the software will not know which one takes precedence. For the example, go ahead and select All Types.

Below the Valid For section is the table for the specification itself. You can see it starts by looking for a size with a <=Dim (less than or equal to dimension). This is where the size breakpoints of your pressure class come into play, so go ahead and take a look at the pressure classes your company uses for reference. In this case, we will build this one off a SMACNA 2wg.

When determining what sizes to use as your breakpoints, take a look at the pressure classes you have on hand. The mark of a good, clean specification is one that simplifies the data you see in your pressure class. Remember, we’re dealing with breakpoints that encompass sizes less than what is specifically called out. If you look in your pressure class and see that an 18-inch long side duct and a 16-inch long side duct have the exact same gauge, connections, and reinforcement, then when you are building the specification you don’t need to call out the 16-inch long side, because the 18-inch will already encompass that information.

When the Applied Software professional services group works with customers to build specifications, time is spent up front to streamline the process. Prior to inputting the various data within the specification, customers are encouraged to make a copy of their pressure classes and highlight the exact moments when the specification breaks up. This also ensures that everyone is on the same page about the exact standards that are utilized. Sometimes drafters may keep specifications around to make generating automatic drawings easier, but those specifications may be out of date or outside shop standards.

In Part 2, we’ll go through the steps to input a new entry, set options and apply specifications.

If you’d like to learn more about how Autodesk Fabrication products can improve your processes, contact the industry-trained experts at Applied Software. They’ll show you how to achieve greater unity among departments, confidence in your project data and consistency in what goes to your shop floor.



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