IN THIS ISSUE - Drug Development & Delivery

Drug Development & Delivery July/August 2012 Vol 12 No 6
36
INJECTION
M O L D I N G
Injection Molding in the
Pharmaceutical Industry
By: Andrew Loxley, PhD, and Brett Braker
THE MOLDER
The major components of an
injection molder are shown in Figure 1.
The IM process involves four essential
steps:
1. Melting of material
2. Mass transfer of molten material
from an injector into channels
called “runners” in the mold and
finally into the mold cavity
3. Hardening of the material in the
mold to the shape of the cavity
4. Ejecting the part from the cavity
to produce the final product
The earliest injection molders used a
simple piston to force molten material into
the mold. Modern molders use a combined
heated barrel/screw/ram assembly in which
the solid material is fed to the hopper of
the heated barrel, where it is melted by a
INTRODUCTION
Many of the processes used to manufacture products within the pharmaceutical industry are unique to the particular
product; however, there are also processes that have been borrowed and adapted from other manufacturing industries and
successfully employed in the development of pharmaceutical products. One such example is injection molding (IM); a process
developed in the late 19th century for the manufacture of simple plastic objects, such as combs, and later extended to all
manner of parts made from thermoplastic and thermoset resins. Parts made by IM that are widely used in the pharmaceutical
industry include caps, seals, closures, valves, syringes, inhalers, and the like. As with other plastic processing technologies
that enable pharmaceutical solutions for otherwise difficult problems, IM is now gaining in popularity for manufacturing
more complex device parts, and is even the platform of choice for preparing certain proprietary drug products.
combination of the heat from the heater
bands and the shear forces between the
material, screw, and barrel. The molten
material is conveyed by the screw toward
the nozzle at the end of the barrel, and the
screw then travels forward in the barrel as
a ram to inject the material into the mold
on each cycle. The addition of the screw
also allows for some mixing so that
multiple feedstocks can be added
F I G U R E 1
Diagram of basic injection molding machine.
simultaneously to prepare for example
colored parts, or to reuse scrap from
previous runs. Two examples of pilot-scale
injection molders from Nissei and Arburg
are shown in Figure 2. AB Insturments,
Thermo Haake and Alba are among
makers of lab-scale injection molding
units.
Molders can be hydraulic, electric, or
pneumatic, with electric or pneumatic