Wednesday, September 25, 2013

Maximize Ointment Mill Throughput

Topical formulations greatly reduce the risk of side effects caused by oral medications, offering the potential to deliver at the site of inflammation while minimizing systemic concentrations. As a result, the demand for pain creams has increased significantly. One pharmacy asked us to help optimize the output of a lab model ointment mill they bought from us, hoping to make 80kg of creams daily. 

What we thought would be a simple task of adjusting the speed or the gap sizes turned out to be a full-scale lab experiment. The ointment pre-mix was so thick that it required an unusual combination of front and back gap settings to make it work. Even so, the hourly output was still significantly lower than other types of creams due to the material property. Here, we want to introduce the scientific method our engineer utilized to maximize throughput, so that customers can make the most out of this award winning lab model ointment mill

Our engineer first observed the behavior of cream on the roller. The initial setting was 50 microns for both gaps. The cream was slow running into the feeding area and was stuck on the middle roller which meant bad transfer to the fast roller and the hence collection blade. The conclusion was that the gap between the slow and middle roller should be wider, while the gap between the middle and fast roller should be narrower. After a few rough adjustments, our engineer decided to fine-tune the gap settings with a series of experiments.   

He started from 150-micron back gap (gap between slow roller and middle roller), and 20 micron front gap (gap between middle roller and fast roller). First he needed to confirm for this particular kind ointment, higher speed lead to higher output. As it turned out in experiment 1to 3, higher speed did lead to higher speed, and the maximum speed didn’t cause the material to splash. He would use maximum speed for all the rest of the experiments.

Next step, he adjusted the front gap to 30 microns. The transfer from the middle roller to the fast roller got worse and the throughput was down. In experiment 5, he kept the front gap at 20 microns and used a narrower gap (100 microns) between the slow roller and middle roller. The throughput was down again, which meant the back gap needed to be wider. After a total of eight experiments, he settled at 250-micron back gap and 20-micron front gap. Our customer was able to reach their desired output as a result. 

To review experiment data, please go to

Anyone using an ointment mill, or a three roll mill as other industries call it, with the goal of maximizing its output, can give this optimization process a try. Contact us if you have questions on how to do it successfully.