Today’s factories have come a long way from the factories we remember from the old days: temporary, ad hoc line solutions with minimal documentation or oversight, all in the name of more output, faster. However, in today’s typical automotive assembly plant, for example, lean practices, continuous improvement and new process technologies have made significant improvements for the health, safety and productivity of employees, and have kept margins intact in a very competitive industry.
Innovative custom tooling, including assembly and alignment jigs and fixtures, is one example of how new technology and process improvement can help workers achieve better quality and productivity on the factory floor.
“BMW are really experts at this,” said Greg Paulsen, Director of Application Engineering at Xometry. “They're literally world class at making custom jigs and fixtures. And there's almost not a single tool that they make that requires less than two processes. It’s always a CNC component here, a 3D printed part here, urethane casting there—and they're always combining these because they take advantage of the different strengths of each process.”
Xometry, a custom on-demand manufacturing service provider, recently worked with BMW to make a few of these custom tools for BMW production. Engineering.com spoke with Xometry to learn more about the processes and materials that are needed to make the most effective custom tooling.
According to Paulsen, many of BMW’s tools are multi-component assemblies which feature complex conformal shapes. For example, one tool used to align trim to a body panel has a shape which conforms to the curves of the vehicle. The fixture also clamps, plunges and depresses the trim to affix it to the vehicle, precisely aligned.
Advantages of Different Processes and Materials for Different Types of Jigs and Fixtures
Choosing the right manufacturing process technologies, such as CNC machining, injection molding, urethane casting and a variety of additive manufacturing technologies can improve performance and reduce cost of jig and fixture parts.
For example, a jig which requires high stiffness and tight geometric tolerances may be best produced via CNC machining, while a fixture designed to conform to a curved part may be easier to produce via FDM or SLS printing. In addition, some tools are designed to use stock material such as tubing or extrusions, and custom machined or printed brackets or fittings are made to incorporate these.
Material selection also plays an important role. For example, tools that bear directly against finished surfaces, such as a painted body panel, must be non-marring. Color coding is useful as a poka yoke, helping technicians avoid mistakes and eliminate product defects; and to make tools easier to identify, use and organize in the workspace.
Lighter-weight materials, such as carbon, are useful in automotive jigs simply because vehicles are big. Workers need to lift and manipulate tools that span large distances, such as the entire width of the front grill, or even a car length. Not only do lighter, more ergonomic tools improve worker well-being and health and safety, but they also improve quality by ensuring the worker can comfortably take the time to use the tool correctly, rather than struggling with it due to fatigue. BMW engineers used new manufacturing processes such as 3D printing and new materials such as carbon to reduce weight of some tools by 25-50 percent.
“A shift worker's job is to lift, handle and maneuver these objects, and be precise every single time,” said Paulsen. “So, fatigue reduction is huge in the industry, especially on any handheld jigs. So, everything we could do to possibly remove and reduce weight is extremely important for our customers.”
At BMW, the lightweighted tools resulted in higher tool reliability, with the rate of application error decreasing from 10 percent to under 4 percent.
Additive manufacturing has a lot to offer tooling designers based on these objectives, including flexibility, lightweighting, and conformal shapes. In addition, because custom fixtures are typically made as one-offs or in small batches, the relatively slow cycle time of AM is not a major factor.
For lightweighting, 3D printed parts can use infill patterns to massively reduce the mass of a part, while retaining strength. For AM, complexity of the part does not affect the cost or time of the process, so conformal and highly complex shapes are easy to produce. A wide range of materials, including elastomers, flexible polyamides and a range of resins with different Shore hardnesses and other properties are available in a wide array of colors.
On-Demand Manufacturing for Custom Tooling
Despite BMW’s success using highly custom fixtures that require a mix of multiple manufacturing processes, these tools also require a significant investment of engineers’ time to source parts and manage vendors both via internal and external manufacturing facilities. For companies smaller than a global automotive OEM, access to the skills and equipment required for the full range of needed processes may be difficult or impossible.
Because Xometry has a network of manufacturing partner facilities, it offers access to a wide range of manufacturing techniques and processes through one portal. For BMW, this simplified the quoting and ordering process for custom fixture parts.
“Obviously BMW has its own manufacturing capacity,” said Paulsen. “But what Xometry offers is that single supply chain consolidation aspect to it. We’re able to run multiple parts in parallel to add lead times, because time is money—especially on the factory floor.”
In some cases, on-demand manufacturing is the best solution simply because of simplicity. For industrial automation solution provider Melton Machine, which makes automotive welding fixtures and equipment, on-demand manufacturing and additive manufacturing made sense because of the cost and lead time.
For one customer, Melton designed a welding fixture which featured workpiece clamps and a robot arm performing a welding program. The workpiece clamps were designed with sensors to provide an input to the robot to ensure that the part was fixtured correctly, and the program could run the weld properly. However, the customer required a different type of switch than what Melton’s clamp bracket could support.
Weston Miller, mechanical design engineer at Melton Machine, used CAD to design a new switch housing, and had the part made at Xometry from PA-12 material. He selected this polyamide to resist the high heat and welding spatter of the application. “You tell most people that you’re going to put a thermoplastic in a hot welding environment, and they’ll laugh at you,” said Miller. However, Miller is familiar with additive manufacturing and the material’s capabilities, and Melton has since placed a larger order for the SLS-printed PA-12 switch housings.
In addition, Melton Machine has since used on-demand manufacturing, specifically Xometry, to source one-off and small batch parts for odd solutions here and there. Because CNC machining small plastic parts is time consuming, ordering parts online is an obvious choice for Miller and his team.
To try using on-demand manufacturing for custom parts, tooling, jigs and fixtures, get an instant quote from Xometry.
Xometry has sponsored this post. All opinions are mine. --Isaac Maw