Turner BioSystems Inc. opted to thermoform and pressure form major components of a new light gauge.
The Sunnyvale, Calif., firm initially looked at technologies such as reaction injection molding and structural foam molding, said Michael Taylor, senior mechanical engineer, but ultimately chose to work in forming technologies with Specialty Manufacturing Inc. of San Diego for the lid and part of the light-tight housing.
``The twin-sheet [thermoforming] process proved to be the most logical approach'' for the lid, said Haydn Forward, Specialty vice president of sales. ``Single-sheet pressure forming could not achieve the 2.3-inch undercut on a 1-inch-deep side wall. Twin-sheet forming allows control of the entire second surface.''
Bonding the sections would have increased costs substantially, he said. Specialty pressure formed the housing using an insulated plug assist and snap-back forming technique.
In December, Turner introduced the new Veritas microplate luminometer to a target market that includes chemists, biologists and DNA researchers. The tabletop unit measures 19.4 inches by 18.8 inches by 9.3 inches and has a base price of $12,000.
The firm said the unit is 10 times more sensitive than the leading competitor's instrument and comparable in sensitivity to a single-tube luminometer.
Developers decided to acid-etch a texture into tools for the lid and housing and use extruded sheets of Kydex acrylic/PVC alloy in a custom black. The result: no painting of the final unit.
During lid forming, Specialty blows air between the two sheets to pick up the texture from the tool. ``This is where twin-sheet differs from blow molding and rotomolding,'' Forward said.
For the lid, Specialty uses formed-in, threaded inserts for mounting, avoiding the need for secondary bonding or insert placement. Air pressure forces hot resin around and into the gnarled surface of the insert.
With twin-sheet forming, ``designers can develop hollow components using differing color material on top or bottom surfaces and choose from materials ranging from styrene to Ultem'' polyetherimide, Forward said.
Specialty Manufacturing employs 45 in 24,000 square feet of space and had estimated sales of $6.5 million for the fiscal year ended June 30.