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Compression Force to Weight Relationship on a tablet press

Compression Force to Weight Relationship on a tablet press

Tablet weight changes can be detected and controlled by monitoring compression force.

A tablet press can be instrumented with a strain gauge that senses and reacts to compression force changes. Compression force fluctuation is the result of slight changes in tablet weights. It is normal and expected that powder blends are not perfectly uniform, this fluctuation is detected by checking tablet weights during compression. When tablet weights change they typically trend, either increasing or decreasing in average tablet weight. As the tablet weights increases the compression force increases and as tablet weights decrease the compression force decreases.

As blended powders are being compressed there is a consistent and measurable force rhythm that is detected using a strain gauge. The strain gauge sends a signal to control the volumetric powder fill level (weight adjustment cam), which controls tablet weights. Thus we have created a loop; the amount of force to compress is really reporting tablet weight. The controls can be setup to react to the compression force changes and adjust the weights within a range or stop the press. If the amount of force is too much or not enough this is directly attributable to tablet weight, provided that the press is being operated correctly and all parts and components are in good operating condition.

When using an automatic weight control device it is important to note that changes to press settings like thickness, speed, force feeders, and pre-compression can be misinterpreted by the force monitor. Proper steps must be followed to prevent improper operation. Then acceptable tablet weight ranges are established so that off weight tablets are rejected.

The objective is cost effective manufacturing

The objective is cost effective manufacturing

There are key elements to becoming a cost effective manufacturing team. Managers should be armed with the right tools to guide the productivity and optimization. Their teams should be prepared to react to common problems in the manufacturing environment. Employee performance is the key to holding it all together or seeing the process fail. Effective learning techniques pinpoint key avenues to solving defects and increasing productivity. A simple, yet effective key to managing people is to help them learn. The challenge is that the learning curve is a variable that changes from employee to employee. Repetitive and consistent reinforcement is the key to enhancing the knowledge base rapidly and effectively. Not everyone is willing to admit that they do not comprehend subjects or learn as quickly as their peers, and guessing and assuming leads to trouble. Training the trainers has its limitations and trainer burn out is a real and significant issue. The demand on the manufacturing floor is to understand and follow SOP’s (standard operating procedures) while employing a GMP (Good Manufacturing Practices) mentality. These requirements must be balanced with equipment function and reliability to ensure everything is in good operating condition and ready to perform. The single most effective key is having a learning system that combines SOP’s, batch records, theory, and actual employee function with a swat team approach. The learning system must be a single source and not be effected on the trainer having an off day, poor attendance, lack of trainee comprehension, or interruptions. The ideal scenario would be a learning station that can be used in a training room or on the production floor. This system could be used to review a procedure, provide self evaluations, and document employee comprehension and performance. This is the most effective way to achieve Cost Effective Manufacturing.

Magnesium Stearate in Tablets

Magnesium Stearate in Tablets

Many “health experts” are forcing tablet and capsule manufacturers to eliminate the use of Magnesium Stearate. I have never seen anything work as well and without it tablet quality will suffer. I’m hearing from more and more companies that they must make their tablets without magnesium stearate because of some false claim that it is harmful to cardiovascular health.

Now Foods has a nice write-up and does about as good a job as anything I have read… http://nowfoods.com/Quality/QualityNotes/M093528.htm

Magnesium stearate is used two ways for tablet making.

The first and most common use is as a lubricant. Without it the tablet would bind in the die during compression and ejection forces will break the tablet apart. Without it tooling life would be greatly reduced and the cost of the final product would rise significantly. Too much mag. stearate will reduce tablet hardness and prevent dissolution because it is non-soluble in water. So if it coats a particle completely than the chances that it will dissolve properly are limited. However, most formulas require less 1% magnesium stearate and only a few require as much as 2%.

The second use is to use Mag. Stearate in a pre-blend to reduce positive charges. It can help combine products that want to push each other away. A very small quantity can make a big difference.

The bottom line is that alternative products are not as effective and until something else comes along its use will continue.

Blending Basics for Tablet Making

Blending Basics for Tablet Making

Blending in solid dose manufacturing has two objectives; 1) To achieve blend uniformity and 2) to distribute the lubricant. In (objective 1) the blend step(s) are designed to achieve homogeneity of all components prior to the final blend of the lubricant (objective 2). The challenge is that there is no such thing as a perfect blend. Blending is like shuffling a deck of playing cards; there is just no such thing as a perfect shuffle. As with shuffling playing cards, blending powders is even more of a challenge due to particle size, moisture content, structure, bulk density and flow characteristics. The bottom line is that blending techniques for tablet making must produce predictable and repeatable results to achieve content uniformity and proper function. The first step in achieving predictable results in a blend is to introduce the proper particle profile within a range; between 40 – 180 mesh for most oral solid dosages. We do not want any particles larger than 20 mesh and try hard to limit the percentage of fines to less than 20% smaller than 200 mesh. The next step is to complete pre-blending steps in a carefully planned order of addition. In other words we need to blend powders with a strategy. Many formulators blend actives and then excipients, others add based on percentages. Over the years I have found that the best success is to know your objective. Simply realize the goal to deliver an active ingredient that holds together, produces predictable results, disintegrates correctly and dissolves when you want it to, only after having sustained the correct shelf life…so what could be the problem? The best thing is an example of an existing formula; say I have a dry granular formula and a number of overly fine waxy actives, along with a flow agent, bulk agent, and a binder. My first question is how does it flow, then how does it compress and the how does it eject, then how does it disintegrate, dissolve and stability and shelf life. I would use the waxy fine particles to coat the larger dry particles to aid compressibility. Then I would add the binder and bulk agents and test between steps for proper parameters of the deleveloping tablet. Too many formulas are old recipes without rhyme or reason. Many formulas are excellent but are not blended correctly; the key to a successful formula is the order of addition. Since each formula is different there are many factors to be considered for each and every formula. When all ingredients are dumped into the blender, optimization is rarely achieved and many times flow, compression and ejection are put into jeopardy. The key is proper addition including the lubricant. Add the lubricant last, by itself; never blend it with anything else, and only blend for a short duration. Under blending a lubricant is better than over blending it.

I hope this helps….any questions or comments please let us know.