For some manufacturing applications, ensuring that parts handling is kept to a minimum is a major concern. To this end, using a custom wire basket that can carry parts throughout multiple finishing processes can be highly useful.
Some reasons manufacturers may want to use a single basket for multiple processes include:
- Minimizing Risk of Scratching Parts. Every time you have to unload a basket and load the parts into a different one, there’s a risk of parts getting damaged from mishandling, in addition to the labor cost.
- Reducing Production Complexity. Adding more steps to the production process, with different baskets, can reduce productivity and increase the risk of a mishap. Being able to use a single basket to carry parts simplifies things considerably—which can save time and increase productivity.
- Minimizing Floor Space Impact. When you have to use different types of baskets, you also need to set aside extra space on the factory floor for those baskets for when they’re not in use. Also, each type of basket needs to be stored separately so as to prevent a mix-up. Universal basket designs eliminate this particular problem.
- Needing to Maintain Traceability. A numbered wire basket makes it easier to trace a load from start to finish—if the parts don’t have to be moved from one basket to the next between each process.
However, it isn’t always easy to design a basket that will work with every parts finishing process you have to perform. Recently, Marlin was contacted about making a basket to hold small fuel injector components through two wash processes and a heat treat process.
Additionally, every part had to be held securely in place at a specific orientation to ensure proper tempering of the part—and the tolerance for each part was ±400 microns (0.0157”). Because the final process was a heat treat process, metal expansion was a concern.
Picking a Material
One of the most important decisions for this wire basket design was the choice of material. Not only did this material need to be able to withstand repeated exposure to the chemicals and stresses of two separate wash processes, it had to be able to take exposure to extreme temperatures without scaling or losing shape.
For this application, the grade 304 stainless steel Marlin normally uses might have worked—if not for the problem of metal expansion and scaling in the heat treat process. Instead, a high-nickel metal alloy such as Inconel® would be a better choice because of the heat treat process.
Inconel® has excellent corrosive resistance properties similar to stainless steel, but with a much higher tolerance to temperature extremes. This alloy wouldn’t expand as much or get covered in a thick layer of scale because of the heat treat process—allowing the basket to stay within the production of the process.
Ensuring Consistent Tolerances
With a metal alloy designed to take extreme temperatures, you can keep the basket from deforming or expanding out of tolerance during the heat treat process. However, that still requires the basket to be made so as to meet tolerances of 0.015” in the first place.
Here, manual labor just isn’t good enough. When bending metal by hand, variance between baskets can be measured in inches.
Instead, Marlin would use advanced wire bending robots to cut and shape the metal so that bends would be as close to identical as possible. For heavier bends, CNC press brakes can apply multiple tons of force with exacting precision to achieve a consistent angle.
To further increase consistency, automated welding machines can be used to make sure that the same welds are applied to the same joints on every wire basket.
Even with precise automation tools, meeting such tight tolerances can be an enormous challenge, and the design of the basket needs to account for requirements such as the minimum internal radius of a bend that the alloy can take.
Can it Be Done?
Creating a custom wire basket that can meet such tight tolerances while accounting for thermal expansion of metal and optimizing it for two other wash processes is possible—depending on the specific stress factors of the wash processes.
It would be a difficult task for most manufacturers. But, with the right tools and experience, it can be done. Marlin specializes in this.
Do you have a particular challenge that your current parts baskets can’t handle? Get some advice from an experienced Marlin mechanical engineer about how to overcome these challenges with a better basket design!