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Bison Floors Limited

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Bison Steps Up With Parametrics

User Profile : November 1995

PUBLISHED IN CAD USER Magazine U.K. Dec 1995

Written by Michelle Greening - The SYNTHESIS Company

Bison Floors Limited has been the largest producer of precast concrete structural components in the U.K. for the last 75 years. The company operates from four factories located in England and Scotland and offers the construction industry a full package for the design, manufacture, delivery and erection of many types of precast concrete floors.

Bison has been using AutoCAD since 1987 to create their designs. They found, however, that AutoCAD was not contributing to the detailing of their precast stairs. An inquiry into "parametric" software led Bison to a company specializing in this area, The SYNTHESIS Company of Bellingham, Washington, in the U.S.

They found that parametric software is an automatic drafting and design tool, whereas, we would categorize AutoCAD as a general manual drafting tool. The difference is that the parametric software will automatically recreate and change variables within a design to produce countless variations, and doing so with minimal amount of time spent. Creating variations in an AutoCAD design, without the use of parametrics, could take literally hours, rather than minutes, to accomplish.

The SYNTHESIS R-13 uses two tools to implement parametric design: the master drawing and the SpecSheet. The master drawing is created in AutoCAD and is then saved as a DXF format drawing. The parameters, indicated in the master drawing, will serve as a basic template for the design. Once the master drawing has been created, these parameters can be manipulated and changed within the SYNTHESIS environment to create customized drawings.

To create a variation of the master drawing, the design parameters must be redefined. This is possible through a programmable spreadsheet, or "SpecSheet", within the SYNTHESIS program. Working with AutoCAD, the SpecSheet references the master drawing, and through a series of on-screen prompts the user can alter the design by eliminating, adding, or rectifying the original parameters.

"Rectification", a key concept in the SYNTHESIS R-13 program, can be compared to AutoCAD's associative dimensions, although it works in the opposite way. With associative dimensioning, you alter the drawing geometry and the associated dimension tracks the change. When designing parametrically, you input the dimensions into the drawing database, using the SpecSheet, and the drawing geometry is then modified. The benefit of rectification is that the input of the parameters to the drawings is unattended. In other words, AutoCAD reads the SpecSheet and drives the dimension and geometry changes automatically.

The SpecSheet drives drawing rectifications. Created in the SpecSheet Editor, the SpecSheet comprises three main areas: the variables region, the master region and the formula region. The variables region contains three columns and up to 500 rows which operate much like a conventional spreadsheet. The cells can contain values or the underlying formulas used to derive those values. The master region controls the use of the SpecSheet. The formula region indicates the constant or formula cell currently highlighted in the variable or master region. It is in this area that you actually enter or modify the cell.

The SpecSheet Editor does not require AutoCAD and can be operated on any available PC. This feature is important in that it allows the user to free up valuable CAD workstations for actual drawing work.

Once rectification of the master drawing has been made, and the desired drawings have been created, the R-13 program will produce to-scale numerical control drawings, as well as sales presentation drawings, and a bill of materials automatically. Literally, within minutes, the SYNTHESIS R-13 parametric program has accomplished what would take an AutoCAD draftsman hours to complete.

Bill Freeman has been with Bison for 45 years, joining the company in the summer of 1950. Mr. Freeman currently provides Technical Services within the company; providing and issuing technical data and standards. This work involves the development and use of CAD software. Mr. Freeman remembers the reaction to the SYNTHESIS Parametric Program from those using the software as, "simple disbelief that SYNTHESIS could be so easy to use and do the job claimed so quickly". Bison decided to take on the SYNTHESIS software because it "demonstrated the ability to quickly produce a proportionately accurate drawing whilst calculating all required dimensions and quantities", states Freeman.

Prior to using SYNTHESIS, staircase detailing consisted of non-scale standard drawing forms with dimensions filled in by hand. These dimensions were calculated manually, or in some cases drawn to full size and measured. A typical manually drawn detail would take approximately two hours per drawing. The same detail produced using SYNTHESIS R-13 would take only five minutes. This calculates to an increase in productivity by ninety-five percent!

Bison continues to successfully use the SYNTHESIS Parametric Program to prepare staircase layouts, produce structural designs, as well as staircase detailing. An understanding of the importance of utilizing parametric technology within their designs has, "...certainly helped us remain competitive", states Mr. Freeman. "In addition to a great improvement in the time required to produce details, it imposes a discipline and standards on the output from the design office".