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May 15, 2001
6 Min Read
Behind the wheel of the ProAir Nautique are two digital instruments that owe their improvements to Internet technology.
Audiences watching water skiing shows at Sea World aren't aware of it, but the boats used to pull skiers rely, in part, on Internet technology. Improved speedometer and tachometer assemblies in professional Ski Nautique power boats are a result of an online design collaboration project conducted by Aptec and its partner Entec Engineered Resins. Not only did the design team members solve quality problems, reduce assembly steps, and decrease costs by up to 20 percent, they were able to complete the project in less than five weeks.
In March, Entec, a resin distributor and compounder, announced a partnership with Aptec, a product design and development firm, to offer virtual design collaboration services using OneSpace from CoCreate. Aptec uses this CAD-neutral software to link all members of a product design teamâ€”including resin suppliers, molders, toolmakers, and OEMsâ€”in real time to share CAD models and ideas (see "Are You Ready for Online Design? Part 1â€”No Travel Required (Almost)," November 2000 IMM, pp. 44-47).
In this finite-element analysis, the housing is subjected to a stud pulloff test that simulates the force bosses feel when the instrument is assembled into the boat's firewall. With a 30-lb load on each stud, maximum stress is calculated at 1180 psi, well below the ABS material's yield strength of 7000 psi.
One of the first such projects to benefit from this liaison, the instruments are produced by Teleflex, an OEM specializing in marine equipment. The project involved both reverse engineering and redesign for a new series of Ski Nautique water craft. Teleflex engineers asked Entec and Aptec to reduce costs and solve a crazing problem evident on previous instrument lenses.
Five molded parts make up the assembly used for both speedometers and tachometers on the ProAir Nautiqueâ€”a housing, lens, bezel, internal retainer, and keypad. During an initial OneSpace session between Entec, Aptec, Teleflex, and molder/moldmaker Custom Plastics Developments (Kissimmee, FL), Entec's Jack Hand identified material substitutions that could potentially lower costs and improve quality.
"It was apparent that a crazing problem on the polycarbonate lens resulted from using a PC grade with the wrong melt flow," says Hand. "It's a thin-wall part, and at lower melt flow, it retained a fair degree of molded-in stress. On exposure to sun and salt water, that stress resulted in crazing. We recommended switching to a UV-stabilized PC with a higher (25 g/10 min) melt flow."
A secondary concern for the housing was the amount of deflection during installation. Excessive deflection could cause the ABS material to creep. Results show that maximum deflection is within limits.
Another area of the assembly that showed an opportunity for material change was the housing, a structural part required to withstand significant loads as the gauge was mounted to a firewall. Originally designed in PBT/polyester, the housing was proposed in a UV-stabilized ABS to reduce costs and improve weatherability without compromising structural integrity. Last, Hand suggested the former polycarbonate bezel be changed to PC/ABS for cost reduction and durability.
Making material recommendations with all team members present allowed Aptec to run initial benchmark simulations (using the suggested materials) during the session and share the results with everyone via OneSpace. "Using Fusion modeling from Moldflow, we are able to create finite-element models for moldfilling analysis in minutes, rather than days," says Aptec's CIO Tom Morris. While early indications looked good, several followup sessions evaluated more in-depth analyses.
As the largest part, the housing presented several engineering challenges. The back of this part is responsible for maintaining a watertight seal, and after a moldfilling analysis, Morris noticed a potential for weldlines and short shots. "We ran a short-shot study and reviewed results with the team in OneSpace. They were able to clearly see the possible problems and the molder agreed to statistically monitor part weight to avoid failures in the field," he recalls. "We use these tools specifically for this reasonâ€”to prevent errors."
A short-shot study (left) in Moldflow identified possible molding risks that could be prevented by precise SPC of part weight. Weldline formation (right) was also identified as a risk to the watertight seal. Both analyses were communicated to the molder via OneSpace for error prevention before parts were produced.
Bosses on the housing also needed to withstand installation forces. Using 3-D structural analysis, designers simulated the effects of a stud pulloff test, and stresses appeared to be well below the yield strength of the proposed ABS material. Teleflex also wanted to eliminate another installation problem. Studs were originally screwed directly into the plastic housing, often causing alignment issues as they cut into the plastic. The team suggested molding in threaded brass inserts to avoid this issue.
Aside from crazing problems solved by material substitution, the lens component became a pivotal part of a redesigned snapfit. Originally, the instruments were assembled via gluing and ultrasonic welding, but the team came up with a way to incorporate snapfits using the lens and bezel parts. The lens was the only part out of the five that required a new tool. For the bezel, an original three-plate mold was modified to incorporate snapfit features.
A solid model of the entire assembly created in Unigraphics was translated to a VRML file that OneSpace participants could rotate for better viewing.
"One benefit of online collaboration not generally apparent," Morris says, "is that precise communication eliminates rework. For example, when a customer wants me to look at a specific feature on a part, all he or she has to do is move the cursor arrow to that point. I get to see where the customer is pointing immediately. In design, when there is one miscommunication, it propagates. Here, you don't have that initial error."
During the online session, members communicate via phone and Internet. Images, CAD files, analysis results, documents, and presentations can be dropped into OneSpace by any participant for all to see. Together with CoCreate, Aptec has developed a way to translate models into VRML files that can be rotated, panned, and zoomed at will. "Instead of having to send a part," says Morris, "customers can take a digital picture and drop it into the viewer so that we can see it."
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