By Christopher Lyon
President at Tournesol Siteworks
About 25-30% of what we manufacture at Tournesol Siteworks is purpose-built to the site, custom built to the client's specification. We frequently get asked "why does it cost more to make something custom, or "how much will it cost?" The question is a valid one and is easiest to understand when the estimating and engineering processes are properly explained. I’ll break it down into three parts.
- The design concept estimate - When we're asked to work on a project like this, our Customworks estimating team reviews the concepts or drawings, and applies a series of cost rates to the material and labor required for the project. As you might imagine, these rates are higher than those we use for standard products - typically between 15-35% more. These rates are based on the complexity of the product as well as the project, and which material is used.
- Next, when we receive an order our engineering team gets involved. Initially they create a model in our CAD program that represents how we will make the product. From that they create a set of submittal drawings that will tell the customer just what we're proposing. Usually this step takes 2+ weeks (depending upon the size and complexity of the project). The back-and-forth determining the exact product details frequently takes extra time, and may add cost to the project.
- Finally, once the submittals have been approved, a set of production drawings needs to be generated. These have a high level of detail, telling the fabricator exactly what dimensions go where, creating cutting patterns for metal products, and assembly drawings for more complicated fabrications. At this point they will also create installation instructions for the customer, if required. While the customer doesn't see this happening, it can easily take 2-4 weeks (or more).
As you might imagine, there is a significant amount of work that goes into engineering custom products. We attempt to reflect this cost in a line-item on our estimates (called, logically enough, custom engineering). A rule-of-thumb that you can use for budgets is that engineering cost is approx. 10% of the overall product cost. It will be more for metal, less for FRP and GFRC.
Here's why - it's typically pretty easy to engineer a FRP fiberglass or GFRC concrete part - one simple model shows the patternmaker or foam cutting robot what to make. Then, however, a tool must be made to fabricate the parts (that's the cost we put in the custom tooling line-item). In contrast, there isn't a tool required for metal fabrications - but the engineering is much more complicated. It usually results in small unit quantities looking less expensive in metal, and large quantities less expensive in FRP and GFRC.
We go through the same process (mostly) when we make a standard product. However, the engineering costs are spread over the much larger quantities that we manufacture. The total manufactured cost is comparably much lower than when we have to include all the costs on a small number of custom products. It's also why it makes more sense for us to make custom products for much larger projects - the engineering expense can be spread out over the larger quantities. Typically, smaller projects don’t pencil out. Don’t worry, we have a solution – see Part II, Making Custom from Standard!