Print that welding fixture

Figure 1. 3-D-printed fixtures, each designed for a specific application, can be quick to set up and securely hold parts in difficult orientations. (Photos courtesy of Markforged.)

Editor’s Note: This article is adapted from a webinar, “Why 3-D Print Welding Fixtures,” found at https://markforged.com/resources/.

A welder needs two things in addition to knowledge and skill to produce precision welds. First, components going into the assembly need to be positioned accurately. Second, they need to be held securely during the welding process.

Traditionally, welders use either modular, general-use fixturing or custom-designed and machined fixtures for these tasks. However, 3-D-printed fixtures are viable alternatives to the modular or machined supports, particularly for complex applications (see Figure 1).

Alexander Crease, senior content engineer for Markforged, which offers 3-D printers for plastics, metals, and composites, said that the unlimited configurations available through a 3-D design and production process fit well with welding preparations and contribute to productivity in three key areas: enabling precision, speeding setup and teardown, and potentially reducing fixture costs. Each fixture can be designed and printed for a specific application.

Precise Holding

“There are a lot of places where imprecision can occur,” Crease said. “It can be that the tubes are not notched correctly or that the fixture has no precise indicators or measurements so components can be difficult to align. This gets more complex as the structures get larger.”

3-D-printed fixtures can be designed and built to support complex structures with nonstandard geometries. Their solid construction contributes to their ability to secure the components in precise orientations. The solid construction also contributes to reliable repeatability, Crease continued, because it eliminates having a number of fixture components that may shift during welding.

Features built into the 3-D printed fixture can be uniquely positioned to guide part alignment, making it easy and quick to position parts accurately.

Easy Set up and Tear Down

A custom-printed fixture, Crease said, can simplify set up because the fixture can be a single unit that doesn’t require a large time investment to correctly position on the table. Setup time also is reduced because the need to reset and check fixture alignment before welding the next group of parts with the same configuration is eliminated.

Tear-down can be as easy as removing a single fixture from the table when the job is done.

Cost Savings

Machining costs for custom fixtures to support parts in odd orientations can be expensive. Each piece of a complex fixture needs to be designed and have its own computer-aided design (CAD) drawing before being sent to production. Clamps created for unusual orientations also can be pricey, and there can be lead-time considerations.

Figure 2. Some 3-D printing materials have high heat deflection properties and can be used in tack welding applications.

“A huge benefit to 3-D printers is their ability to produce single parts or components that can replace their custom-machined counterparts that are often assemblies of several parts. Cost savings can also be gained because of the materials used to build a fixture. Fiber-reinforced composites being used to build many fixtures provide the strength of metal at a fraction of the cost,” Crease said.

“Some of our customers have seen up to 95 percent reduction on printed versus machined fixtures. And the fixture can be printed and ready to put on the table the next day, which can significantly shorten the overall production cycle.”

Material Choices

The most appropriate material to use for a printed fixture depends largely on the type of welding to be done (see Figure 2). For example, using a fiber-reinforced material for the printed fixture can deliver extra rigidity so the fixture won’t deflect or deform.

“Fixtures printed from fiberglass-reinforced composite materials can be an affordable solution to hold steel for tack welding. One of the reasons this works is that this material gives the fixtures a heat-deflection temperature of about 150 degrees C. Using these fixtures for tack welding, where the heat is heavily concentrated, is feasible as long as the fixture contact points are out of the heat-affected zone. Once the parts are securely positioned, welding can be completed off the fixture,” Crease said.

“Going with stainless steel fixture supports or clamps at the point of contact can isolate the heat around the part. If the heat reaches the fixture area, it won’t permeate into the support and you can continue with the weld operation.”

Before and After

Use of 3-D printed fixtures isn’t limited to before the welding begins. Those same fixtures also can be of use after the weld is complete.

“These fixtures can act as quality assurance tools after the operation is complete to confirm that specifications have been met,” Crease said.

“3-D printing’s customization abilities let you create fixtures that can reduce setup time, minimize job failures, and ensure that the end results are high-quality welds that meet the standards you want. It can add value to your production process both before and after welding.”

Moving to 3-D-printed fixtures, however, doesn’t mean losing the capabilities of existing fixtures. The flexibility of 3-D printing allows the production of jigs, supports, or risers to complement existing welding tools and technologies.