Replace five metal, steel and plastic parts in the syringe pump with a single injection molded component

Celanex® 3316: A Good Alternative to Metal Assembled Parts
Celanex® thermoplastic polyester from Ticona enables to replace five metal, steel and plastic parts in the declutch tube of Syringe Pumps with a single injection molded component. The new PBT part lowered cost by a factor of 20 to about $1.10.

The electromechanical pump assembly meters and dispenses drugs from a syringe to provide accurate drip feeding during intravenous therapy and in intensive care monitoring systems. The declutch tube, molded from Celanex® polyester, disengages the 5-to-100-ml syringes from the unit’s transmission so expended ones can be removed and fresh ones loaded.

Pump manufacturers use Celanex® 3316 PBT, a 30 percent glass fiber-reinforced grade, because it resists hospital cleaning chemicals and does not stress crack under long-term contact with O-ring lubricants. It is also rigid enough to withstand the torsional loads involved, has high impact strength and dimensional stability, meets UL94 V-0 flammability standards, offers a smooth surface finish, and can be retrofitted to existing units by ultrasonic welding.

Mold Flow Analysis: A Key Success Factor
The 173-mm-long declutch tube is injection molded around a core pin. Ticona performed mold flow analyses to ensure the cavity would fill without problem. This involved evaluations of the melt front, temperature and pressure across the mold, cooling time to define cycle time, and assessment of weld lines. The PBT enters the mold from a gate at the base of the component and gives an even fill in just over 0.5 second. Mold cooling was adapted to ensure the core pin remained straight as the part hardened. A cap is ultrasonically welded at one end of the part after molding to hold an O-ring.