Hacker's Handbook

AI Laser Metal Cutting - Part 3

Replacing humans by AI optimization as a service

Posted: 2023-06-16

The Optimizer - part 3

Timeline: 2009-2020. Potentially reducing CO2 globally by 1%.

Cutting plan optimization as a service

There are some interesting challenges involved when automatically and non-interactively creating cutting plans for humans to accept. Some are related to how we optimize, others are related to how customers think and feel.

To mention but a few challenges:

• What constitutes a "good" cutting plan. Humans are not logical creatures. Minimal cost may not be good enough, it has to "look good".
• Providing cutting plan optimization as a service puts additional constraints on delivering production safe cutting plans.
• How do you properly sort when you have multidimensional values. Weighted sum is not the way.
• How to break down the optimization problem into smaller parts

If we produce a chaotic looking plan that has 10% lower cost than a organized plan that looks like it makes sense, you can be sure the human operator will reject the chaotic plan. They simply believe the risk of breaking the laser machine's cutting-head is too high (even though we know it is safe). A production stand-still is very costly. Convincing them is not really an option so one has to try to produce a cutting plan that looks good, for some definition of "looks good".

Multidimensional sorting is a concept that is useful in many cases and the basic idea is to group values based on some defined epsilon-function per dimension, recursively. This way you can express things like solution A and B differ in the number of parts placed, but have e.g. a better cutting path, so they should be in the same groups with regards to number of placed parts, but possibly B comes before A since B has better cutting-path cost. This is the way. It is also awesome for debugging.

On the topic of ordering things, we can easily imagine several measures for evaluating different properties of parts and clusters. For example, area-utility, a simple enough idea and one that seems meaningful. How much of the bounding box area is covered by a part's area. Even such simple things have funny properties, for instance, this measure can be interpreted as a circle being 78.54% square. One must take care to use the proper measures at the proper time and place and not draw the wrong conclusions. Indeed, circles and squares are very different when packing.

Our approach to solving the extra everything-2D-packing-problem, was to sort of do what humans do, only better, and in a cold hard computer way. To this end we created many clever algorithms for creating pairs of parts, clusters of parts, expandable patterns, columns and rows, lattices and more. We also created advanced algorithms for splitting large clusters (sometime you must break things), and specialized algorithms to fill empty areas such as holes or other empty areas. But we also optimized in phases to place larger parts over multiple sheets and so forth.

At the core of it all exists a fundamental practical representation of parts and how they interact with other parts allowing us to reason about it logically, a geometry constraint engine, a very reliable and high-precision no-fit-polygon algorithm, and a cutting path optimizer with its own sets of constraints. The result: we could produce cutting plans that far exceed normal nesting in performance, is more production reliable than cutting plans made by humans, and that in practice replaces the human as the nesting controller. This is a huge benefit to the industry.

In the end, due to Tomologic's patents being considered too general, some of Tomologic's ideas of clustering has spread and are now used by some of the more competent nesting softwares, although I imagine no other company has the same rigorous checks to guarantee production safety. Thanks to our ground breaking know-how, algorithms, and our unique way of regarding the 2D Nesting problem, Tomologic has contributed greatly to the reduction of CO2 in the metal cutting industry. I still believe that The Optimizer is the best fully-automatic production-safe AI-service for 2D packing in metal sheet cutting.

To paraphrase Zlatan: Dear World – you're welcome.