Choosing the Right Coatings and Coating Processes For Tableting Tooling

High efficiency manufacture of solid dosetooling.
pharmaceuticals requires the use of high performanceNitride hardcoatings can also be deposited by a low
tooling, including tablet punches, dies, tamping pins andtemperature ion beam enhanced deposition (IBED)
compacting rolls. Since the tooling is in intimateprocess. Coating temperature does not exceed 200
contact with formulation powders during tableting,degrees Fahrenheit, which is low enough to eliminate
the properties of the tooling surfaces can have athe danger of dimensional distortion or bulk softening
significant impact on both tablet properties andof the punch. Coating adhesion is guaranteed by first
manufacturing efficiency. Wear and corrosion of theforming a layer (termed a case layer) in the surface
working surfaces of the tooling results in picking,of the punch, and then growing the coating out from
sticking and capping which requires the tableting pressthe case layer.
to be stopped and tooling to be removed forMaintenance of the pre-coated surface finish is also
cleaning and polishing. Tablet quality is degraded,an important factor to be considered when choosing
manufacturing productivity is reduced, and revenuesa coating and coating process. Electroplated and PVD
lost.coatings grow with large crystalline grain structures.
Precision coatings, if properly chosen and applied toThis degrades the surface finish originally present on
tableting tooling, can dramatically reduce surface weartooling surfaces, which requires that the surface be
and corrosion, and significantly improve manufacturingre-polished after coating. IBED coatings are
efficiency and tablet quality. There are a variety ofamorphous in nature and replicate the surface finish
wear- and corrosion-resistant coatings available forexactly, thus eliminating the need for post-coating
use on pharmaceutical tableting tooling. Additionally,re-polishing.
there are a variety of coating processes used toFDA Regulation of Precision Metal Coatings -
deposit these coatings. Choice of the correct coating,All equipment, including precision tooling, used in the
and the correct coating process, are the keys tomanufacture of pharmaceutical and nutritional
success in obtaining improved performance forproducts is regulated by the Food and Drug
tableting tooling.Administration. FDA regulations specific to equipment
The various coatings available are deposited by eitherused in the manufacture of solid dosage tablets is
electroplating or by advanced vacuum depositionfound in 21CFR211.65 which states, "equipment shall
processes. Metallic coatings such as nickel andbe constructed so that surfaces that contact
chromium are deposited by electroplating. Materialscomponents, in-process materials, or drug products
such as Boron (B), and Teflon (PTFE), can be addedshall not be reactive, additive, or absorptive so as to
to enhance plated coating hardness, and coatingalter the safety, identity, strength, quality, or purity
lubricity, respectively. Processing temperatures duringof the drug product beyond the official or other
metal plating are below 200 degrees Fahrenheit, butestablished requirements." Thus any coating applied to
the coated tool must be baked post-plating at higherthe working surface of punches and dies cannot
temperatures (375 degrees Fahrenheit) to preventreact with, wear off into, or absorb any ingredient of
hydrogen embrittlement.the formulation being tableted. This is an important
Hard refractory nitride coatings such as Titaniumconsideration when choosing a metal coating and
Nitride and Chromium Nitride are usually deposited byprecision coating process.
physical vapor deposition (PVD) processes. In orderWear and corrosion on tableting tooling can be
to insure sufficient adhesion and optimum coatingsignificantly reduced by choosing the correct coating
properties, the PVD processing temperature must beand precision coating process. Benefits include
done at 900 degrees Fahrenheit or above. At theseimproved tablet quality and manufacturing
temperatures the bulk tool material will soften,productivity, both of which fall right to the bottom
distorting the crucial precision dimensions of theline - better profitability.