To save time and material, reduce fixture complexity, and improve fixture accuracy, just to name a few benefits.
Tooling jigs and fixtures are indispensable. In a production process, they affect product throughput, quality, and profitability. If time and cost did not constrain you, you could install as many fixtures as a manufacturing process required. Direct digital manufacturing (DDM)
systems, whether your own or accessed through a service provider, can remove those constraints, giving you the freedom to design as few or as many fixtures as you need.
DDM industry analysts say that fewer than 5% of engineers currently use this technology to make jigs and fixtures, although these tools are an excellent application for the technology. Direct digital manufacturing is the process of going directly from an electronic, digital representation of a part to the final product through additive manufacturing, such as fused deposition modeling (FDM). It saves time and material, reduces fixture complexity, improves fixture accuracy, decreases the weight of fixtures, and facilitates the production of multiple variations.
Time constraints eliminated
Traditional methods for producing fixtures are machining or fabrication, both of which take time. When a quality problem or production delay occurs, the cause is often with the fixtures, and engineers must move quickly to devise a fix to keep production rolling.
If you don’t keep replacement fixtures in stock, then you are looking at an average of two to four weeks before a new fixture comes in to replace the defective one. Even a relatively simple
fixture can have a lead-time of several days. In addition to fabrication time, new designs typically require additional time for prototyping.
With digital manufacturing systems or through those that provide DDM services, you can create new fixtures often within a day. The process is fast enough to enable you to prototype and evaluate multiple iterations of a fixture model quickly. All that is required is 3D CAD data, machine capacity, and materials.
To create a new fixture fast with a direct digital manufacturing system or service provider, you need 3D CAD data, machine capacity, and materials.
Complexity friendly
When a fixture is created through traditional methods, its design must conform to design for manufacturability (DFM) and design for assembly (DFA) rules. Machine and fabrication limitations will influence your choices and may even restrict them.
With digital manufacturing though, complexity is not an issue as most of these systems can build anything you can imagine. It is easy to design and build a fixture that contains multiple pieces as a single unit. Plus, you can develop fixtures that can reduce operational time and product rework.
You can also create fixtures that were previously impossible or impractical to produce through traditional machining and fabrication approaches. For example, a handheld fixture can take on a freeform, organic shape that improves the balance.
Lastly, throughput speed can be increased because digital manufacturing systems enable you to
rapidly deploy the best fixture design for an application and eliminate the need for stopgap measures.
Weight reduction
DDM systems typically use some type of thermoplastic material, usually a variation of ABS or polycarbonate. The advantage of the DDM process is that you only use the material you need, so there is no waste that sometimes occurs in machining and fabrication processes.
The plastic materials are inherently lightweight, which reduces ergonomic concerns. A lighter weight tool minimizes the physical stress on a worker. Plus, there are several ways to lighten large parts, which have the added benefit of reducing material usage: hollow out the part, use a honeycomb build, or add numerous cutouts.
Many thermoplastic materials have been developed to meet specific strength, rigidity, and durability needs, among others. You can machine, drill, and tap holes into a fixture built through an FDM process. The same is often true of laser sintering DDM processes as well.
While thermoplastic materials do not replace metals in terms of strength yet, they come very close to matching many of the material properties of metals.
Cost savings
The savings reported by those who use DDM range from 50 to 75% over traditional machining and fabricating processes. For a fixture that costs $600, for example, the savings can range from $300 to $450.
The DDM approach to fixture design gives you the ability to create fixtures that can reduce operational time and product rework.
Direct digital manufacturing for fixtures can also positively affect profit when you consider productivity, efficiency, quality and throughput. For example, instead of designing, documenting, quoting, ordering, scheduling, discussing and monitoring, the fixture creation process is condensed to design and production. Plus, a well-designed fixture yields repeatable, predictable quality, which reduces rejects, scrap, and rework.
Another area of cost savings involves redesign, rework, and repair changes to fixtures. DDM provides a rapid response to each situation.
You can save on stocking spares as well. In many applications, DDM equipment can become a “digital warehouse” from which you “pull” fixtures. Spare or replacement fixtures become available at the push of a button.
Such a digital warehouse concept also facilitates redesign. If engineers revise a product, a modified fixture can be designed and rapidly reproduced. Accessing the digital CAD data, manufacturing engineers can make the design changes, export an STL file and transmit the data for build.
When not to use DDM
While DDM offers many benefits for fixture modeling, there are some limitations. If tight tolerances and high strength are needed, you are better off with a machined fixture. While DDM can produce a dimensionally accurate part, machined metals can offer higher tolerances. And, depending on the digital manufacturing system used, the surface finish of the fixture may not be as smooth and polished as a machined or fabricated fixture.
Direct digital manufacturing is ideal for applications with a low demand for the tolerances on a part, if surface finish is not a requirement, or if the actual overall strength needed is low.
When to use DDM
Choose direct digital manufacturing when your application requires:
– Low production volumes
– High probability for design changes
– Internal features, complex geometries
– Low demand on tolerances, surface finish, and strength
Common benefits of FDM digital manufacturing include:
– No production tools required
– Easy or minimal documentation changes
– In-house production and control
– Multiple design iterations
– Applicable for low-volume “large parts”
– Production parts in days rather than weeks
– Freedom to redesign while in production
– Design without constraints
– Bridge to Tooling
Making fixtures fast
Wair Products manufactures custom valves for a variety of fluids from its Bloomington, Minn. headquarters. The engineers designed a test fixture that clamps to a liquid oxygen economizer valve and automatically sets the valve pressure. Then, the fixture tests complete pressure of the valve assembly. The valve regulates oxygen flow from portable oxygen tanks to humans.
Demand for the valve increased, necessitating additional fixtures for the testing process prior to shipment. The aluminum tooling company that previously machined the fixture needed a three-to-four week lead-time. And the fixture’s complex geometries made it difficult to machine with aluminum. Because the design is complex, aluminum tooling created eight parts that needed assembly before the fixture could actually test the valves.
RedEye was able to alter the design of a valve assembly pressure test fixture, taking it from eight pieces to one for a more accurate piece that lined up. It was digitally manufactured with polycarbonate.
RedEye took on the project to manufacture the fixture. Digitally manufacturing the fixture with polycarbonate took it from eight pieces to one, resulting in a more accurate piece that lined up.
In addition, use of thermoplastic material significantly decreased the weight of the fixture. Wair’s employees were pleased with of the switch to plastic.
When additional fixtures are needed, Wair engineers simply submit a file, which saves engineering time. The time savings enable the engineers to focus on valve design, their core competency, rather than on fixture design. The use of DDM opened their eyes to using this technology for jigs and fixtures in addition to prototypes.
Redeye by Stratasys
www.redeyeondemand.com
MPF
