By Steve Adkins, Director of Engineering at Optimas Solutions
The fastener plays a critical role in holding together machines ranging from construction equipment to wind turbines.
There are times when fasteners don’t meet performance standards and require redesigning. However, redesigning fasteners is a complex process that requires a thorough understanding of the current design’s performance expectations, operating conditions and potential design flaws.
Deciding to redesign fasteners can be daunting when one considers how critical fasteners are to a product and the financial, logistical and operational impact it may have on future products.
So, equipment manufacturers should carefully explore why a redesign is a good idea before proceeding.
There are several reasons why a manufacturer decides to redesign fasteners, including:
- Changes in the application or environment
- The need to improve performance
- An update design on a current model
- Reduce cost
- Improve efficiency
Regardless of why a manufacturer wants to redesign fasteners, a good supplier can help make the decision easier, so it is always important to get them involved early in the process.
Problems and goals
Redesigning fasteners requires a thorough understanding of the problem and goals for the redesign.
First, a manufacturer needs to determine the requirements of the fasteners, brainstorming potential design changes, and evaluating the manufacturability, aesthetic value and price of each design. The best solution is then selected and tested before being implemented in production. Monitoring the performance of the new fastener during testing and making further refinements, if needed, is essential.
Common performance requirements
In 1998, the National Institute of Standards and Technology (NIST) discovered one of the Titanic’s smallest components — the 3 million wrought iron rivets used to hold the hull sections together — were the reason the ship sank. The metallurgical properties of the rivets made them brittle when exposed to very cold temperatures, strongly suggesting that Titanic’s collision with the iceberg caused the rivet fasteners’ heads to break off.
Understanding the performance requirements for fasteners being designed into a product is critical as in the case of the Titanic. Some of the simplest specifications or manufacturing practices of a fastener can cause catastrophic performance problems.
In regard to nuts and bolts, the most common performance requirements they fail to meet include inadequate strength grade and poor plating that results in corrosion that causes the fasteners to break under stress. Additionally, thread issues and poor production quality can lead to the fasteners failing to meet their intended purpose.
In terms of washers, common problems include inadequate plating, hydrogen embrittlement, incorrect material selection and manufacturing issues. Fittings also often fail to meet material and manufacturing requirements.
Just like the Titanic, understanding how environmental factors such as temperature, humidity, exposure to corrosive chemicals and UV exposure along with potential design flaws can affect the performance of fasteners is a critical step in the redesign process. It is essential to consider these factors when redesigning fasteners, particularly in industries where electrification is becoming popular, such as construction equipment.
Given the distinctive nature of the operation of EVs and fastener performance needs, designers must consider corrosion issues, weight displacement needs and fastener strength requirements.
These environmental factors need to be fully explored and understood in each application.
Streamlined fastener redesign
As manufacturers work to reduce costs and improving operational efficiencies, a redesign can be instrumental in helping address these aspects of production. For example, moving to lightweight materials, such as going from steel to plastic, can reduce weight in areas such as in non-structural rivet applications.
In larger bolted applications, working with the manufacturer to understand the application, and even requiring durability testing are a few ways to verify weight reduction projects.
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Also, depending on the critical nature of the fastener, the diameter and grade can be reduced to save weight. Rationalization or consolidation programs can be completed to reduce the number of fasteners in a product as well.
Assembly and installation requirements can impact the efficiency and cost of installation and manufacturing processes. There are one-sided drive systems which can reduce labour on the assembly line and other non-torque drive products. These fasteners are usually more expensive but reduce quality issues, usually install faster, and deliver repeatable clamp loads.
Trends in analyses, tools and tech
There are various tools and analyses available to help identify and redesign fasteners, including computer-aided design (CAD) software like SolidWorks, BOLTCALC for fastener analysis and assembly tools to install fasteners.
BOLTCALC allows fastener makers to theoretically calculate clamp load and torque by adding variables such as plating, material and other inputs while identifying potential issues prior to production and can ensure the new fastener meets the products’ necessary performance requirements.
Automation, new thread and drive designs, nut shapes and sizes, non-ferrous material for EV applications, non-torque related assembly processes (Huck) and assembling tooling for small fasteners are a few of the areas where fastener innovation is taking place every day.
Testing and validation
Various testing and validation methods, such as tensile testing, torque testing, vibration testing and environmental testing should be used to ensure the redesigned fastener perform optimally. These tests evaluate performance and durability under different conditions and ensure they meet industry standards. In addition to these testing processes, user feedback and data are also crucial in the fastener redesign process.
Working with a fastener maker that has comprehensive and effective testing and QA capabilities is important to addressing this issue. This integrated approach enables engineers to test anything from tensile strength, plating thickness and even small screw drives easily and effectively.
Regardless of the reason for a redesign, cost reduction is always a goal of the process. As with the actual design of a product, it is important to understand early in the process the potential cost implications with changes in design.
Cost implications vary and will depend on the equipment manufacturer’s requirements. These can include reducing quality issues, speed of manufacturing, and material that expands the fastener and product’s useful life. Also, cost-saving can be achieved by changing the fastener design and characteristics to better meet use-case requirements.
To ensure safety and performance can achieve production cost reductions, a fastener redesign may be the right move for construction equipment manufacturers. With the right tools, materials and experts, and the right partner, this process can lead to significant improvements and cost savings.