It is important to first understand that there are a few factors that relate to maximum compression force to take into consideration. The point maybe made easiest when talking about older tablet presses because newer presses can have interchangeable turrets which requires that the tablet press be capable of the higher compression force rated turret. Traditional “B” & “BB” type presses like a Stokes BB2 or a Manesty BB3B type tablet presses have a maximum rating of 4.5 tons (45kn), while a “D” type press like the Stokes D3 and Manesty Unipress 20 have maximum rating of 7-10 tons (70-100kn).
How much compression force do you need? This depends more on the tool tip size than it does on the maximum force rating of the tablet press. As an example I could use a 10 ton press to make a ¼” round diameter tablet. I would simply need to reduce the overload compression force setting to make certain that the press will release to whatever load rating I require. In the case of a ¼” diameter tablet the maximum load a tool can take before bending or breaking would be in the range of 1.0-2.5 tons (10-25kn), so having a press that can exert 10 tons of pressure does little good, unless of course I also need to produce a big ¾” wafer or caplet.
If the formulation is not prepared properly (which happens on a very regular basis) it may take more tonnage to make the tablet than should be safely applied to the tooling (also a very common issue). This is where proper press setup comes into play. The operator should always set the overload pressure release set point (compression force) to the maximum limit of the tooling tip size configuration. Most tablet press manuals contain a chart with the maximum load rating based on tip size. This same information is available in the TSM (Tablet Specification Manual) which is published by the APHA. However, I would suggest that when ordering the tooling from your vendor that you specify that they provide the maximum compression force rating with the tooling order.
If you cannot make a satisfactory tablet within the tooling compression force rating than you must not blame the tooling or the press…you must formulate or process the powders to work within that acceptable force range, period! Many companies make the mistake of going beyond the maximum load rating and damaging the tooling and the press (when a punch breaks nothing good happens).
In summary; most companies do not use the compression force overload adjustment settings correctly which does result in premature wear and damage to the tooling and sometimes the press. Many formulas are not proven and tested properly. Too many companies “validate” a process that turns out to be a mess and does not perform under demands of production.