Weigh optimization methods against your company's benchmarks to find the solution for your plant.
Optimization is a phrase we hear quite often these days, and it seems everyone has a strong opinion on the topic. The key to optimization is one size does not fit all. Much like each truss plant is run a bit differently than the next, optimization reflects the capabilities, limitations and goals of a specific plant.
Our design department optimized trusses to reduce lumber usage, which caused some unintended issues and inefficiencies on the shop floor. What parts of the plant should optimization take into account?
When optimization is brought up, the first thing that comes to mind is usually reducing lumber usage. While lumber usage generates the largest percentage of cost in truss fabrication, other variables (see pie chart) also need to be considered to achieve optimization of the overall operation.
Understanding the cost percentages in your operation is critical to how you optimize your components. Just because a solution uses less lumber, or saves time at one step of the truss design and manufacturing process, does not guarantee it will optimize overall operations. While it goes without saying that every part of the business has costs attached to it, the following are some possibilities to consider when reviewing each operational area for changes that could help improve overall economics.
Remove extra members
- Use maximum panel lengths to eliminate webs.
- Remove diagonals on short span trusses where possible.
- Run verticals through the bottom chord if it reduces the bottom chord to a common stock length.
- Set standard slider lengths to less than 2'.
Lumber costs can be reduced not only by splicing and optimizing webs, but also by reusing lumber drops. For example, if lumber is 45 percent of a plant’s total cost, with a waste factor of seven percent, lumber waste is two percent of total cost. By reducing material waste to 3.5 percent of lumber cost, one percent is added to the bottom line.
When reclaiming drops for use in floor trusses or as wall blocking, this is essentially free material because it has already been charged to a job. Finally, wood waste that is kept clean and free of other trash can be resold for a small profit to vendors looking for wood to grind up for press board products.
Optimize Chords and Web Lengths to Stock Lengths
Most pricing programs price material to the stock length, meaning a 16' board costs the same as a 14'-1" board. While a good first step is to optimize the lumber used in components to 1-2" less than the stock length to allow sawyers to make accurate cuts, it is not always the best option for the shop if it adds extra members or joints.
Make sure the design department is up to date on price differences between stock lengths of lumber, which change based on the market supply demand changes. If 14' material is $10/1,000 board foot less expensive than 12' material, it makes more sense to splice a 36' bottom chord with two 14' members and one 8' instead of using three 12' members. Given all the lumber market changes due to design value adjustments, this conversation has taken on new importance.
Removing a member from a truss usually will result in both a labor and lumber savings. However, in some cases, this can have the opposite effect. Removing a member may require extra set-up stops to hold panel points or cause shipping issues, which can lead to damaged trusses.
Saving labor in the plant is a matter of seconds. Saving five seconds per truss on the line nets 10 to 15 extra trusses per day. This can work out to $200,000 dollars of increased production per year for that production line or a cost savings to your customer. That five seconds of labor can come from how a plant handles material, stocks plates, sets up the fixtures, or designs the trusses.
Saw setup time, which used to take two to three minutes, now takes less than a minute with computerized saws and setup devices. This eliminates one of the main bottlenecks at the plant. From a design standpoint, it has become less important to match members between truss types to limit the number of setup changes. Additionally, while manual saws had a high learning curve and can take months to learn, computerized saws can be learned in a week.
Nevertheless, improvements can still be made to sawing operations. Matching and aligning webs, matching grades, using standard hip jack spans, and using common splice lengths, help reduce the total amount of setups on the saw and control the number of parts on the production line. Batching components efficiently helps the person staging the saw pick larger quantities to saw at one time.
Material flow from the saw to the production lines is another area where improvements may be made. Looking at overall benchmarks is important; it may make sense to run one or two workers on a saw at five to six percent less efficient than they could be in order to speed up material flow and make 10-12 production workers two to three percent more efficient.
The responsibility of implementing many of the aforementioned ideas rests on the design department. Although optimizing jobs may mean adding labor to the design department, there are ways to reduce design time per project.
Design software now includes many optimization tools; however, it can still be a daunting task. It pays to have someone experienced with the software who understands how the default settings impact the unmodified truss design. Significant design time can be saved in the long run by taking the time up front to set default panel lengths, web patterns, splices, plating, web cuts, end conditions and default grades so the initial truss will be as close to optimized as possible.
While default settings and software have given the designer many helpful tools, the human eye is still crucial. Placing trusses systematically and looking for like members through common runs is difficult for current software, but will increase savings.
The final product and customer satisfaction are critical when optimizing. A customer building a custom home is likely to focus on a high-quality truss that has minimum deflection, dimensional accuracy, truss design variations to meet architectural design needs, engineering defined load paths and, potentially, larger members. On the other hand, a customer building a tract or multifamily project will probably be more interested in price, lead times, dimensional accuracy and speed of installation.
In addition to making optimization work in the plant, the concept also needs to be sold to end users in a way that meets their specific installation needs. Ease of handling and installation need to remain a priority, along with producing a more efficient truss using less material and plant labor. This is ultimately the true definition of providing a quality product.