The Conflict Between Crate Pro and Yield Optimization
A brief overview of the challenges with yield optimization and why Crate Pro doesn’t do it
Many new Crate Pro users are challenged to understand why, for example, a design shows it requires 3.5 sheets of plywood but making the crate requires the purchase and cutting of 5 sheets. Before thinking why Crate Pro is ‘wrong’ in the above example, you should know not to use the Design > Materials > Unit Quantity value as a shopping list.
It’s assumed that you apply standard methods and use standard materials, and that you keep some material stock on hand. Even if it’s only an extra 4 or 5 sheets of plywood and 5 to 10 pieces of lumber.
Crate Pro applies a rolling waste factor. The default waste for most plywood is 20% meaning that over time, you will throw out 20% of that plywood item. That doesn’t mean that on that one Design you’ll throw away 20% of the plywood. In fact, you may have no waste on that Design, or 50% plywood waste, but over time, your waste for that material will be about 20%. (That’s the default value set in Crate Pro 6. 20% is close for a lot of companies but if yours is different change it.) Also note that many companies will reuse most of the waste, and because any waste is already written off, when a company reuses a waste piece, they often won’t factor it into the cost. This constant reuse of waste of different materials and quantities is a major factor, and across customers supports the benefit of a rolling waste factor.
Yield Optimization is the cutting of specified size pieces from larger standard sized materials while minimizing waste. There are many factors to consider which are typically termed the “Cutting Stock Problem”.
If you want to search for ‘Cutting Stock Problem’ you can dip your toe into the simplest part of the problem. The Cutting Stock Problem occurs when attempting to apply the same yield optimization rules for every instance in certain industries or industry segments when:
- More than one [Crate] is in the [Design] and the cutting process could use two or more pieces of material.
- More than one [Design] is cut during the same process.
- The cutting process is ongoing, and any pieces queued may be cut in advance or retarded in the que to merge with the subject design, project, or customer.
- The size of a piece(s) exceeds the size of the material.
- The size of a piece can vary within a range based on the cut size of a different variable sized piece.
- Multiple sizes of materials must be considered.
- Multiple saws with different characteristics are available for the same material type (2D or 3D)
- The saw is limited to guillotine cuts and cannot make a partial cut on either axis.
- The quantity of materials that can be cut at one time exceeds one.
- The estimated value of changing optimization methods exceeds the actual savings of the change.
- The cost of setup labor and yield improvements are both considered.
- The cutting saw operating time is considered.
- The material may include defects which are not acceptable in certain locations of a finished piece.
This probably isn’t a full list of the issues that create the Cutting Stock Problem, but they are ones that affect Crate Pro. Trying to solve some of the problems listed can result in the creation of that same problem being created in a different way. For the most part though, they exist because of the breadth of the crating industry from companies that have a retail location and need to cut wood in their back parking lot to large government contractors in the US and elsewhere. A small company may only need to overcome one problem every year or so (which wouldn’t likely actually be a problem.) In that case, the process could easily seem opaque and can become expensive as a percentage of the job. Things could be worst for a large company because many of the problems would intersect at one-time or another.
As you can see, yield optimization has been on our minds, and we’ll make available different levels of optimization as they’re integrated. There’s a lot of yield optimization software on the internet including some pretty good free ones. We recommend reviewing your companies processes, policies and equipment to find a good fit. We are working on a Project report which will allow you to export an amalgamated report of all pieces on that Project.
Unit Quantity for Plywood - How to determine costs by FULL SHEETS