How Does Dwell Time Affect Tablet Manufacture?

Dwell time does play a huge role in affecting the quality of tablets. In today’s fast trend, manufacturers are continuously pursuing faster, more efficient and economical production process. But sometimes they neglect the problem that fast is more likely to be fault. Actually, too fast or slow manufacturing can both bring unqualified tablets, which is harmful to patients’ health and prejudicial to manufacturer’s goodwill. Then how do you ensure the dwell time in the manufacturing process is optimized to make quality tablets at maximum productivity?


    First, we need to identify what is dwell time?

Dwell time of tablet manufacture is the amount of time each individual punch head flat is in contact with compression roller of a rotary tablet press. Or we can put it in this way, dwell time is also the period when compression force applied in tabletting process is above 90% of its peak value. In such period, granules or powder is compacted into tablets under compression force. Defect tablets are formed due to more or less dwell time involved, or excessive or insufficient pressure exerted.

Excessive force or over pressuring of punch may lead to serious failures of the tooling and damage to the tablet press equipment. Not only more cost is needed, but health and safety risks to the operators and patients are carried. Hence, it is obviously how critical to identify and optimize dwell time during tableting manufacture.

Second, what are the key factors affecting dwell time?

Key factors determining dwell time include but not limited to punch head flat size and shape, pre-compression and RPM(revolution per minute). But sometimes the punch head flat diameter, a major factor, is somehow overlooked or misunderstood. And this is the special field that we Kosbest are engaged in. We are dedicated to producing innovative tablet tooling as well as ameliorating and enhancing condition of machinery.


Third, how does dwell time affect tablet manufacture?

‘Punch displacement velocity (ie. strain rate) and dwell time are two factors that can significantly affect the compression behavior of powders. As a general rule of thumb, slower compression and decompression speeds and longer dwell times will improve the mechanical properties of a tablet. When particles are subjected to a compression force for a longer period of time, further plastic yielding can occur and the degree of elastic recovery is reduced.’

Pharmaceutical Dosage Forms – Tablets, Third Edition – Edited by Larry L. Augsburger, Stephen W. Hoag

Features of the ingredient(particles) can be a factor to be considered to optimize dwell time. In cases of formulations with more time dependent consolidation behavior, a long dwell time is important to create strong bonds between the particles. When particles are subjected to a compression force for a longer period of time, further plastic behavior is demonstrated, resulting in a more stable compacted tablet.

If dwell time is improperly involved, tabletting issues are carried. Defect tablets are formed due to excessive or insufficient dwell time on punches, sticking and picking, capping and chipping, lamination, weight variation, double impression, mottling, etc.

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