The quality of micro injection molded parts weighing 0.065g processed on two machines was investigated. A Cincinnati Milacron T-100 (100 ton, 238 grams) injection molding machine was used to produce parts representative of a traditional macro injection unit and a Nissei AU3E (3 ton, 3 grams) injection molding machine was used to produce parts representative of a micro injection unit. For each injection molding machine at similar processing conditions, the residence time, part weight consistency, rheological properties, and structural properties of the molded parts are evaluated across a typical production run with a 10 second cycle time and an extended production run with a 100 second cycle time. The micro parts were collected at 0, 2, and 4 hour intervals for the 10 second cycle time and the 100 second cycle time on both the injection molding units. Each of the samplings were then tested to determine material degradation. The results indicate that for the tested polycarbonate (GE Plastics Lexan^®, SP1010R), the residence time is a key processing condition in determining the subsequent rheological and structural properties and should be maintained at less than 30 minutes to avoid a decrease or unfavorable change in properties. High performance parts are only achievable when all the key factors are present in the process. Therefore a micro injection unit should be used to produce micro-injected parts of the highest quality.