Andrey Armyagov | Dreamstime
Complex milling/turning on a CNC machine.

Strategies for Complex Machining Challenges

Dec. 29, 2022
Subject-matter expertise, machining experience, and the right equipment are all increasingly important resources for machine shops, so solving emerging problems is feasible for operations that adopt flexible and open-minded approaches.

The manufacturing sector needs as many skilled machinists as possible. In turn, skilled machinists must be well-versed in various particulars of the trade and the practical solutions for overcoming them. Solving complex machining challenges requires ongoing learning, strategic investments and, sometimes, the right outside partner.

Following here is a look at some of those challenges and a few valuable troubleshooting steps to consider.

1. Machining thin-walled components. Even a machine shop known for its standards and tight tolerances may struggle when machining thin-walled components — particularly larger ones. Housings for engines, transmissions and compressors cover large surface areas but need to be thin and light. Helicopter blades, for example, are produced by creating hollows in large workpieces.

Use standard formulas beforehand to determine whether these thin walls and hollows will compromise a part's strength. There are two primary formulas for the pre-machining phase of product design:
 External Removed Material Ratio (ERMR): Divide the part bounding box volume by the stock volume.
 Internal Removed Material Ratio
(IRMR): Divide the part volume by the part bounding box volume.

For IRMR, aim for 85% or greater, meaning you’ve removed 15% or less of the interior material. For ERMR, the calculated ratio should translate to 30% or more.

If your numbers check out, it’s safe to proceed with prototyping.

2. Machining complex geometries. There are several points worth consideration when creating complex or convoluted geometries out of a solid material.

Particular niches — such as automotive, aerospace and medical device manufacturing — require more intricate part geometries than others. Solving complex machining challenges like this sometimes requires strategic investments. In this case, a new machine with more axes could let you surmount your current design challenges and unlock new competitive opportunities. In many other cases, it’s advisable to iterate on the design until you eliminate any design flourishes that don’t provide function or value.

Another option is to incorporate 3D printing into your workflows. 3D printers are excellent for prototyping before machining, but they also allow fabrication of complex geometries that conventional CNC machines may struggle to reproduce.

Machining environments present the additional challenge of offering limited customization opportunities — at least on a wide scale. Adding 3D printing to machine shops could allow contract manufacturers and others to expand their design palette and the range of services they offer.

3. Fabricating large components. Due to its complexity, one of the more frustrating machining challenges is fabricating large components. With or without complex geometries or hollows, it may take experience — and sometimes the right partners — to determine how to proceed.

Just as with achieving intricate shapes, it’s best to start simply. Can the design be modified for multi-part fabrication? If you don’t have an appropriate CNC machine for the size of the part you’re trying to create, you may achieve a similar result with multiple parts instead of one – provided you’re aware of the tradeoffs:
 Multi-part fabrication increases the weight of the finished component compared to single-piece machining.
 The finished component may not have the dimensional strength or other qualities required if it’s not an uninterrupted piece.

This is a conversation where form and function frequently have to compromise. Is there another way?

You could find a business partner with the capabilities you require. Large-scale CNC machines are a value-adding part of the manufacturing as a service industry, which gives smaller-scale, niche or smaller-run manufacturers access to tools they couldn’t justify buying outright.

4. Achieving specific material properties. Achieving certain metallurgical properties — like durability, strength, and hardness — often requires heat treatment. The primary challenges with heat treating are the investment in the necessary apparatus, and the fact that heat treating alters the workpiece’s dimensions.

Regarding the first point, there are cases in which it is a machine shops’ best interest to invest in heat treatment equipment, just as how “future proofing” a machine shop means leaning into 3D printers, which require more post-fabrication finishing than casting and machining typically do. Heat treatment is becoming a common finishing technique among 3D printing operations, so investing in in-house heat-treatment capabilities could address your machining challenges, and lead to future success.

The alternative is to match the needs of the workpiece and the limits of your manufacturing environment with the proper heat treatment process and to perform it at the right time. You can treat the material before machining, limiting late-in-the-process dimensional changes.

You might also consider heat treating a machined component, but that will necessitate additional finishing.

There are yet more options to consider when adapting heat treatment to a shop’s capabilities or minimizing its impact on the workpiece. Consider press quenching versus oil quenching. The former cools the piece more slowly, reducing some of the dimensional changes you’ll need to address with additional processing.

5. Labor shortages and talent-pool limitations. The global pandemic resulted in a widespread, voluntary retirement of older skilled workers, and manufacturing employers continue to face many talent-related challenges, including recruiting workers and retaining an aging workforce.

According to the U.S. Chamber of Commerce, even if every unemployed but otherwise skilled American worker found a job in durable goods manufacturing today, the nation still would find half its needed manufacturing roles unfilled. This is one of the more urgent challenges in manufacturing today.

Cross-training is one of the strongest actions manufacturers and supply-chain and logistics service providers can take to answer this challenge. It will help workplaces weather periods of talent unavailability that will hobble their competitors.

These recommendations should give you a place to start next time you face one of these obstacles. Solving complex machining challenges requires subject-matter expertise, experience, and the right equipment, but it’s also deeply rewarding. The demand for manufactured durable consumer goods will only increase, so taking the lean approach and finding economical solutions will set you up for lasting success.

Emily Newton is the Editor-in-Chief of  Revolutionized, an online magazine exploring the latest industrial innovations.

Latest from Shop Operations

Stephan Pietzko | Dreamstime
Sirinarth Mekvorawuth | Dreamstime
Sergey Gavrilichev | Dreamstime
BiancoBlue | Dreamstime
Divinesky27 | Dreamstime