Many BIM software users know that with the BIM model they can easily prepare shop drawings (plans, elevations, sections, element legends and schedules). BIM model allows you to save a lot of time in the preparation of project documentation: BIM software automatically or semi-automatically forms lists of project elements, performs their numbering, grouping, prepares shop drawings. Wide potentials of various BIM technologies reduce the need for project data export to other software, which sort and optimize the quantity of elements or form the project estimates.
However, many designers stop at the BIM model creation, and preparation of project shop drawings, although BIM software provides much more possibilities. Most of them equate concepts of BIM workflow and BIM model therefore they don't seize all BIM possibilities to the utmost. BIM model is just a 3D model with all its data, and the BIM process does not end with BIM model creation. So, what's next? How to extend the BIM model usage to manufacturing and building, in order to increase the benefits of BIM technology? The answer - you need as far as possible to extend usage of the opportunities that the BIM model possibilities provide.
In this article, I will give you an example of how to fully use the BIM model. It is just one of the ways, but knowing the principles you will be able to plan your BIM workflow. The example discussed below is about a BIM model of a log house: how to submit project data for the production (to CNC machines) and the construction under a right procedure, which is reflected in the working with BIM model diagram:
I want to attract attention to usage possibilities of the log house BIM model created with BIM software Autodesk® Revit® and its extensions developed by AGA CAD, which all are described in this article. All tasks can be done using the plain Revit software as well, but when working without the productivity increasing applications, Revit users need to create all log house elements, cut, number and group them manually. All of these actions would take lots of time. In addition, it would be difficult to provide BIM model data for manufacture and construction. Wood Framing Wall+ is an application for Revit that includes features for the log building frame creation. This BIM solution helps Revit users quicker performance of all the modeling and documentation preparation tasks.
Using the same tools and working principles described in this article below it is easy to organize light-framed house production. But at this time let's come back to the example of the log house BIM model:
To get the right data for the construction of this project, first thing that should be done: all logs of the BIM model need to be numbered. This can be done in several ways:
Numbering logs by wall mark
Numbering logs by crown number
The numbering is required for recognition of each element and assigning them into specific groups (each wall or crown packs). Grouping (packing) logs by walls or by crown number depends on dimensions of a building.
The next important stage - all logs should be grouped according to additional features such as given priority to standard and non-standard cutting procedures. There are at least two types of logs: those which are sufficient for standard cutting operations, and those who need additional cutting work. Grouping of logs by additional attributes (priorities) depends on the necessary to perform cutting operations and on the CNC machine type: some machines can perform all cutting operations, while others have only a certain special actions (horizontal cuts, scraps of angles and so on). Thus depending on time saving, the logs are grouped according to the following criteria:
- The first priority - standard cutting with additional cutting operations on different woodworking machines. Logs with first priority go to manufacturing first, because their production requires more time for additional cutting operations;
- The second priority - standard cutting.
Every group (pack) has at least two lists of logs required for standard and additional cutting operations.
When elements' numbering and grouping in the BIM model are completed, it is time to prepare CNC files that will be sent to the manufacturing machines. All process of CNC file creation can be shortly described in such a scheme:
CNC file number depends on the expected number of packages, which provides the designer / manufacturer concerned with capacity of transportation vehicles, the number of shipments, planning of fitting works and so on. Every cutting list goes through linear optimization procedure that helps to reduce waste of cutting work. Using Wood Framing Wall+ the designer / manufacturer can specify the thickness of a saw: that let's to know exactly how much material will be consumed during cutting.
Optimization depends on the number of CNC files. The more information is in the single CNC file, the better optimization procedure works: the manufacturer can save more material, because several different wall elements can be cut from one log. However, if one CNC file is formed, material costs reduce, but more time is spent for packing elements. If the information for manufacturing is expanded into separate CNC files, optimization will be carried out only for specific crown or wall pack. A lot of CNC files save labor time, but increase material consumption. Anyway, when creating files for production the manufacturer chooses his priorities, and then creates single or multiple CNC files.
Making the lists optimization procedure, Revit application Wood Framing Wall+ puts shorter logs (that are around openings) into one row and draw their data (eg. Wall 1, Crown 10, Log 1, 2, 3, 4 ...), also submits material balances to schedules. Below is an example of shop drawing of a specific type of logs:
Using AGACAD BIM solutions for Revit, designers and manufacturers can easily create CNC files. Simultaneously these applications automatically create and prepare for printing label files that are generated in true way. Labels (barcodes) mark all the elements of a log building that are packed after cutting in accordance with the number of walls or log crowns:
It is important to keep in mind that all logs must be marked according to the number of crowns, and should go to the cutting machine in the reverse order of assembly, i.e. from the top to down. Reordering of cutting list allows to get on top of packing logs with lowest crown number (ground logs). This procedure helps to ensure smooth assembly of all structure.
Using AGA CAD application for Revit Wood Framing Wall+ and other BIM solutions for framing, building assembly drawings are generated automatically and numbering of logs in shop drawing tags is fully compatible with data in labels which are attached to logs.
By the way, AGACAD extensions' usage can accelerate many steps of shop drawings preparation: Wood Framing Wall+ automatically identifies priorities of logs; numbering of elements can be accelerated with Revit add-on Sort Mark, and packages can be easily formed with BIM Tree Manager or Smart Assemblies (depending on the predictable volume of the package).
So BIM model can help to reduce time wasting of manual numbering, grouping, data export to different external software which can optimize and produce CNC and labeling files. Furthermore, the information contained in the BIM model allows designers to avoid errors. However, to get maximum benefits of BIM, we need to use BIM model in the right way according to all (designers, manufacturers, builders) needs.
Dr. Gintaris Aksomitas
AGA CAD Ltd