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Tablet Hardness Tester: The Complete Guide

Solid tablets are possibly the most often used form of dosage for pharmaceuticals.

Tablet hardness acts as a basis to direct the development of product and as a quality-control stipulation.

Tablets ought not to be too soft or too hard.

Tablet hardness testing is a laboratory method which is applied to measure the breaking point of a tablet.

The procedure is an essential aspect of medicine production.

Tablet hardness testing makes sure that solid tablets are hard enough to sustain mechanical strains during various situations like storage and packaging, delivery and handling by the user, among others.

And in this guide, I am going to show you how to choose the best tablet hardness tester.

 Tablets

Tablets

What is Tablet Hardness Tester Equipment?

Tablet hardness testers, hardness meter, tablet testers, or whatever name you may refer to them, are critical laboratory apparatus for any analytical lab.

You can use the equipment to test regular, delayed-release, and coated tablets.

Tablet hardness testers function on the basis that it requires a specific quantity of force to fracture a tablet.

Tablet hardness tester

Tablet hardness tester

This force is registered in Newton’s and is the hardness value of the tablet.

The figure is what laboratory technicians apply to establish quality control and compliance.

Most tablet hardness testers operate through a simple movement of a jaw or bar which squeezes the tablet between two rigid plates.

Thus, causing it to fracture under the pressure and hence, establishing the force needed.

There exist several varying tablet hardness testers, all operating around the same primary principle.

Hardness testers spun from simple handheld equipment to fully automated appliances.

Why Test Table Hardness?

There are a number of reasons why you need to test hardness of tablets.

Some of these reason include:

Tablet after crushing
Pill (2)

Tablet after crushing

· To determine the tablet disintegration

An exceedingly hard tablet could designate excessive bonding possibilities between excipients and active ingredients, which can hinder proper disintegration of the tablet required for a correct dosage.

Conversely, a softer tablet could indicate weak bonding and may result in premature dissolution when consumed by the patient.

· To determine tablet handling

A soft tablet may not sustain the handling and could crack or chip during the successive processing phases of production,

These many include coating and packaging and during transportation.

· To determine the material ingredients

Knowing the mechanical features of a solid-dose tablet can give important information necessary for optimizing material ingredients.

The nature of active constituent(s), the kind of binder used, and the composition of the constituent(s) in the tablet will impact on the hardness of the tablet.

· To determine the production process

Knowing the right tablet press speed, granulation flow, and air in the powder is important in formulating the appropriate table.

For that matter, you need to control these parameters during production to manufacture a tablet with the correct hardness.

Types of Tablet Hardness Tester Machines

At the moment, there are quite a number of tablet hardness tester machines available in the market.

Even though the end result (testing tablet hardness) the working principle and design may vary slightly.

You will learn more about that shortly.

For now, let’s focus on the following:

Tablet hardness tester

Tablet hardness tester

1. Pfizer Hardness Tester for Tablets

The Pfizer tester squeezes the tablet between a piston and a holding anvil.

The piston is connected to a force-recording meter when you grip its pliers-like handles.

2. Monsanto Tester for Tablets

The Monsanto tester was invented 50 years ago.

The tester’s design comprises a barrel having a compressible spring fixed between two plungers.

You place the tablet on the lower plunger and then release the upper plunger onto it.

3. Strong-Cobb Tester for Tablets

The Strong-Cobb tester pushes an anvil against an unmoving platform.

The tester has a hydraulic meter from which you can see the results, which are the same as that of Monsanto tester.

4. Erweka Tester for Tablets

Erweka tester measures a tablet put on the bottom anvil and a load moving along a rail transfers pressure gradually to the tablet.

5. Dr. Schleuniger Pharmatron Tester for Tablets

The Dr. Schleuniger Pharmatron tester functions in a horizontal posture.

An electric motor propels an anvil to press a tablet at a consistent rate.

The force pushes the tablet against a static anvil until it breaks.

A scale indicator records the reading which is the hardness value of the tablet.

6. Kraemer Elektronik Tablet Testing

The Kraemer Elektronik tablet hardness testing machine was the first automated tablet hardness tester system for self-activation at tablet presses.

The machine was developed by Mr. Norbert Kraemer, a German mechanical engineer in Darmstadt, Germany.

A patented feeder chute separates the tablets moving them on a horizontal star wheel via different testing points.

The Kraemer Elektronik tablet hardness tester machine measures weight, width, length/diameter, thickness, and hardness of capsules and tablets.

Tablet Testing Units of Measurement

Tablet hardness units of measurement majorly follow standards employed in material testing – The International System of Units (SI Units).

Weighing tablets

Weighing tablets – Image source: WELWEB

  • Kilogram (kg) – SI system recognizes kilogram as the main unit of mass.
  • Newton (N) – This is the SI unit of force; the measure for tablet hardness tester machines. 9.807 Newton = 1 kilogram (at earth surface gravity).
  • Pound (lb) – Basically pound is a unit of force though you can as well use it for mass under earth gravity. Even though it is sometimes applied in tablet hardness testing in North America, it is not an SI unit. 2.204 pounds = 1 kilogram.
  • Kilopond (Kp) – A unit of force also referred to as a kilogram of force. But, you should not confuse it with a pound. SI system does not recognize kilopond though it is still employed in some applications. 1 kilopond = 1 kgf.
  • Strong-Cobb (SC) – An extemporary measure of force which a footprint of one of the pioneering tablet hardness tester machines. Though the SC is arbitrary, it was acknowledged as the global standard from the 1950s to 1980s.  1 SC equaled about 7 Newton or 0.7 kilograms of force.

The Strong-Cobb is a unit having a very untypical name for a measurement unit because it derived the name from the company, Strong-Cobb Inc.

Main Parts of Tablet Hardness Tester Machine

Tablet hardness tester is a microprocessor-driven apparatus.

It has a digital display and an exceptionally user-friendly keypad interface guaranteeing quick measurements and precise results.

A hardness tester is a compact device and occupies minimal bench space.

A hardness tester commonly constitutes a tester assembly joined to a frame assembly.

The tester assembly is made up of a tester enclosure that supports a motor that drives to connect with a load unit and an indentor.

The frame assembly consists of a vertically-oriented plate forming a general C-shape characterized by upper and lower arms joined by the main bodywork.

Architective of tablet tester machine

Architecture of tablet tester machine – Image source: PHARMAWIKI

The plate is made from a singular sheet of metal to offer toughness in the vertical direction.

The tester assembly is connected to the frame assembly, and you can isolate and use it as a stand-alone unit.

Tablet hardness tester machine also comes with a distinct ball screw assembly for applying the testing load.

Working Principle of Tablet Hardness Tester

The working of the majority of tablet hardness testing equipment can be broken down to a basic movement of a jaw or bar, which presses the tablet between two plates.

This forces the tablet to fracture under the pressure and hence, establishing the force needed.

When carrying out tablet hardness testing, you place the tablet between the two jaws.

One of which is joined to a load cell and the remaining to a motor which offers the mechanical drive.

The motorized jaw steers forward compressing the tablet against the immobile jaw until the tablet cracks.

Upon breaking, the motorized plate retracts and the device records the force needed to break the tablet.

The common methods of tablet hardness testing include:

· Crush test

The Crush test is normally done on a capsule-like tablet standing parallel to the longest axis, or a round one standing on its rim.

The test is at times referred to as diametrical compression test. You place the test sample on a base table and press it against a flat surface cylindrical probe.

The surface of the cylindrical probe, which is bigger than the sample you are testing, is moved down to break the tablet at a consistent speed.

The force used to break the tablet is recorded, with the registered value relying on the size and construction of the tablet.

· Fracture test

You accomplish fracture testing of tablet hardness by forcing a smaller hemispherical ball probe through the horizontal surface of a tablet.

You must choose an appropriate probe deformation distance to stay clear of the base effect, which is the external impact of the surface on which you place the tablet.

Pressing of a thin tablet sample against the test base of the analyzer device causes the base effect, which inadvertently leads to incorrect readings.

Keeping a deformation distance of not beyond 60% of the sample height is normally sufficient for the ball probe to crack the tablet without effectuating base effect.

The registered force needed to crack the tablet is essential for establishing mechanical features such as tensile strength and Young’s modulus (illustrates the stiffness and toughness of a material).

· Bending test

Another common tablet hardness testing method is the snap or bending test.

The hardness testing technique is popular for an oval capsule-shaped tablet as well as considerably broad round tablet.

You carry out the test with a three-point bend fixture.

Here, you support the tablet at both ends and deform in its center with the aid of a knife-like probe.

This causes the tablet to crack and snap at its weakest point.

To guarantee comparability of outcomes, you must standardize the orientation of the tablet in the fixture.

Preferably in a way that you can easily reproduce, for example, by aligning the tablet’s score line with the blade of the probe.

How to Troubleshoot and Maintain Tablet Hardness Tester Machine

There are several factors that can affect a tablet hardness tester machine result.

In most instances, misleading or incorrect readings are the outcome of poor testing procedures that defy simple yet fundamental testing rules.

 Tablet hardness testing machine

Tablet hardness testing machine

This results in good tablets being scrapped or discarded or, worse of, bad tablets being accepted and used.

· Calibration

You need to calibrate the tablet hardness tester machine after the first installation and regularly thereafter.

This is to ensure that the hardness tester functions with the accuracy it was designed to fulfil.

The calibration intervals depend largely on the workload and the seriousness of the test.

We advise you carry out calibration after every six months.

Ensure to utilize a tablet hardness tester machine that has an up-to-date calibration label from an approved external service provider.

· Cleaning the Jaws

Apart from calibration, your tablet hardness tester equipment needs little regular maintenance.

You need to clean the jaws routinely tablet fragments and powder which could have an impact on accuracy.

  • Unfasten the thumbscrews and the washers that join each jaw. Be cautious not to lose the washers.
  • Uplift both jaws of the equipment.
  • Using an appropriate solution, clean the jaw plate carefully.
  • Using a brush, clean the bottom of the jaws.
  • Make sure the jaw plate is dry. Restore and fasten each jaw with the thumbscrews and washers.

· Replacement of Thickness Gauge Battery

The Tablet Thickness meter is powered by a long-life lithium battery, same as to the type utilized in many common cameras and watches.

You can get these batteries from many pharmacies and most retail photo suppliers.

To replace the battery:

  • Lodge a screwdriver into the groove on the battery holder. Twist the holder one quarter turn anti-clockwise as shown on the device. The battery holder jumps out of the indicator body.
  • Remove the used battery from the housing and substitute with a new one, keeping watch on correct polarity.
  • Return the holder back into the indicator rotate till it locks in place.

You are now set to start operation.

· Fuse Replacement

Tablet hardness tester machine consists of devices, electrical circuits, and parts operating at hazardous voltages.

Contact with these components, circuits, and devices, can result in painful electric shock, serious injury, or death.

To replace the fuse, ensure to follow these steps:

  • Unplug the instrument before examining or trying to replace a fuse.
  • Press the release handle on the fuse casing situated in the power entry component using a small screwdriver or alternative.
  • Upon release, slip the holder from the power entry component.
  • Remove the used fuse and place the new one.
  • Slip the holder back in position in the power entry component till it fastens into place.
  • Replace the power cable.

Never substitute a fuse with another of a higher amperage rating.

Undertaking that may undermine the safety scope and could cause personal injury or damage to the tablet hardness tester machine.

· Printer Configuration

The printer configuration is created by the manufacturer.

You should carry out this procedure only when the printer shows erroneous characters.

Consult your supplier for help if necessary

  • Remove the power cord from the electrical outlet
  • Press and hold the toggle switch of the printer in the Online/Offline position as you plug the power cord into the electrical outlet. Hold the toggle switch of the printer in the Online/Offline position for about six seconds after replacing the power adapter then release the switch
  • The printer needs to print: *** SETUP MENU*** and CONFIGURE… [NEXT/OK]. In case it does not print this message, repeat steps 1 and 2.

You use the printer toggle switch to complete the configuration.

The printer toggle switch is used to complete the configuration.

Pressing down the left side of the toggle switch picks NEXT to move to the succeeding menu item.

Pressing the right side of the toggle switch chooses OK to allow what is highlighted on this section of the menu item.

Each time you press the switch, another segment of the menu prints.

Let the printer complete printing before you press the switch again.

It is easier to read the printout when you remove the printer cover.

Printer Commands

Sample printer commands

Sample printer commands

You have now configured your printer correctly.

Troubleshooting

You can trace many problems to simple sources and you can easily solve them.

The following troubleshooting guide may assist you when you encounter the highlighted problems.

ProblemPossible CauseSuggested Solution
The LED on the fore panel displayscreen is not illuminating and the jaws are not moving when you press TESTThere is no power supply at the outletMake sure the outlet is getting a power supply
You have not plugged in the unit.Make sure to securely connect the unit to an electrical outlet.
The fuse is blown.Change the fuse.
Hardness figures are lower or higher than expected.The system is out of calibration.Carry out calibration
The product you are testing is out of specificationCheck the process of producing the tablet.
Hardness readings incline to be inconsistent or jaws do not size tablet appropriately.There is an accumulation of debris below the jawsClean the jaws.
The strain beam is defective or destroyedContact the supplier of your tablet hardness tester machine.
The jaw plates are not optimal for the shape of the tablet.Contact the supplier of your hardness testing equipment for optional jaw plates.
The optional Report Center Printer is not functioningYou have disabled the printer.Enable the printer.
There is no power supply at the outlet.Make sure the outlet is having a power supply.
The printer is unpluggedMake sure to securely connect the printer to an electrical outlet.
The printer is offline.Turn online the toggle switch of the printer.
The unit does not record thickness readings.The thickness meter battery is low or deadChange the battery.
The thickness meter is switched off.Examine the LCD display on the fore of the meter. If invisible, press ON/OFF
You are removing tablets from the thickness meter too fast.Wait until the thickness value shows on the hardness tester machine LED and the thickness meter LCD before you remove the tablets.

 

Quality Standards for Tablet Hardness Testing

Generally, all tablet hardness tester machines must conform to some set quality standards.

That’s exactly what you’re going to learn in this section.

a) Tablet Tester USP Quality Standards

The new USP chapter <1217> in USP 31 NF6 titled “Tablet Breaking Force” highlights a number of essential factors that you must consider when using a tablet hardness tester machine.

Let’s look at some of the USP quality standards for tablet hardness testing devices.

· Platens

Ensure that the platens are parallel and the polishing of their faces is done smoothly.

Also, the platens faces should be precision-ground at a right angle to the direction of motion.

Perpendicularity needs to be maintained during the movement of the platen, and the mechanism must be free of any torsion displacements or bending as you apply the load.

The contact face should be broader than the surface of contact with the solid tablet.

Section of tablet hardness tester machine

Section of tablet hardness tester machine

· Rate and Uniformity of Loading

Either the rate at which you apply the compressive force (i.e., load rate) or the rate of platen movement must be consistent.

Maintaining a consistent loading rate helps avoid the quick accumulation of compressive loads.

This may result in shear failure or uncontrolled crushing, and greater variability in the recorded breaking force.

Nonetheless, constant loading rate recordings may be too sluggish for real-time tracking of tablet manufacturing.

· Units, Resolution, and Calibration

Your tablet hardness tester equipment should express the test results in standard units of force which enable communication.

The calibration of a majority of modern tablet hardness testing devices is in Newton or kiloponds.

As we had seen, the correlation between these units of force is 1 kilogram-force (kgf) = 1 kilopond (kp) = 9.80 N.

Some hardness tester machines as well will offer a scale in Strong-Cobb units (SCU), a unit used back then when there was a common use of Strong-Cobb hardness testers.

However, you should be keen with the conversion between SCU and kp or N, since the SCU is gotten from a hydraulic instrument and is a pressure.

Breaking force must be readable to within 1 N according to USP quality standards on tablet hardness testing machines.

Typically, modern hardness testers use contemporary electronic designs with digital displays.

Some testers can also be interfaced with a printer or have an integral printer.

The USP standards require that you calibrate your tablet hardness tester regularly.

You should factor in the mechanics and the force sensor of the device.

In the case of the force sensor, the total measuring range or, at a minimum, the range you use to measure the test sample must have a calibration with a precision of 1 N, using either dynamic or static technique.

The functional calibration of a tablet hardness tester needs also to affirm that the constancy of velocity, and the velocity for load displacement or application, are within stipulated tolerance all through the range of platen movement.

b) cGMP Compliant Tablet Hardness Tester Machine

The quality systems for items controlled by the US Food and Drug Administration (FDA), constituting biologics, devices, food, and drugs, are referred to as current good manufacturing practices (cGMPs).

cGMPs guarantees for systems that ensure correct design, monitoring, and management of manufacturing operations and facilities.

Compliance with the cGMP regulations guarantees the quality, identity, strength, and purity of products.

For that matter, a tablet hardness testing machine must meet all the cGMPs requirements for it to be distributed in the U.S.

For instance, a cGMP complaint tablet harness tester should have its body made of stainless steel or painted mild steel.

c) FDA Approved Tablet Hardness Tester Machine

As I have already mentioned, all medical equipment sold in the United States are controlled by the US FDA.

More particularly, any medical equipment produced, relabeled, repackaged, and/or shipped by any firm or company to sell in the U.S. has to comply with the FDA regulations.

FDA has put in place several rules in the form of “Code of Federal Regulations 21” (CFR21).

Pharmaceutical, drug, biotechnology, and medical devices manufacturers regulated by the FDA should be familiar with the CFR21 regulations.

That is, encompassing the acceptance stipulations for electronic signatures and documents, and management of electronic documents.

Specifically, 21 CFR 11 necessitates that closed computer systems should offer a collection of technological and procedural controls to safeguard data inside the system.

Open computer systems should also have controls to make sure that all records are valid, incorruptible, and confidential.

A tablet hardness tester machines stores and processes some information to arrive at some quality tests decisions.

Therefore, it must conform to the FDA must meet the 21 CFR 11 regulations.

In laboratory scenarios, this consists of any lab results applied to determine, quality, efficacy, safety, purity, or strength.

Manual Tablet Hardness Tester vs. Automatic Tablet Hardness Tester (An Ultimate Comparison)

Generally, you can classify the existing tablet hardness tester machines as:

1. Manual Tablet Hardness Tester

Manual tablet tester devices are very easy to operate.

You simply put the table sample on the testing surface and rotate the handle manually.

This will make the jaw to move, applying force to the tablet.

The hardness tester monitors the force electronically and displays the readings immediately the sample breaks.

Manual tablet hardness tester machine

Manual tablet hardness tester machine

The tablet breaking force value is displayed on an LED display in either Kilopond (Kp), Pounds (Lb), Newton (N), or Strong Cobb (Sc).

On some hardness testing devices, you can change the unit by pressing a button on the equipment’s control panel.

2. Automatic Tablet Hardness Tester

The physical testing of tablets, their width, length, weight, thickness, disintegration time, and hardness, is time-consuming and labor-intensive.

Automatic tablet hardness testing systems are more precise and productive, saving time and money, and freeing you from a very tiring task.

 Automatic tablet hardness tester machine

 Automatic tablet hardness tester machine

Automatic ­tablet hardness testing equipment blends the measurement of the physical parameters thickness, weight, ­ diameter and hardness.

You can use an automatic hardness tester on tablet samples of various shapes and sizes without the necessity of changing settings between products.

You can set up all the information that the hardness tester needs to know in a stored product profile.

Starting the tablet hardness testing process involves a number of simple mouse clicks and then the hardness tester machine performs the tests automatically.

· Improved efficiency

The easiest answer to improve efficiency is to consolidate several measurements in a single report.

Advanced automatic tablet hardness testers permit programming of up to 100 products.

The testers measure 5 parameters comprising nominal values and limits for thickness, width, weight, thickness, length/diameter and hardness.

This eliminates specification input errors and gives evaluated data in the form of a report.

The manual registering of measurements as is the case with manual tablet hardness testers is no longer needed, making the whole procedure much faster.

You can either print the reports directly on an Ethernet LAN printer or store them electronically on a central computer for further analysis if necessary.

· System Integration

To reduce the time-span between carrying out a test and undertaking corrective action if necessary.

It is possible to integrate modern automatic hardness testers with high-performance tablet presses from separate manufacturers.

The integrated system diverts samples automatically to the hardness tester at a constant time interval, and the recorded results are immediately transmitted to the tablet press.

Applying advanced algorithms, the tablet press software can automatically adjust manufacturing parameters relying on the measured results.

Commonly known as ‘lightly attended operation’, you need not have an operator permanently stationed at the compression room..

That is, neither for regulating the tablet press nor for carrying out hardness tests.

A single operator can for a fact control manufacturing in several compression rooms.

In case of a limit breach, the system triggers alarms to notify the operator.

In some setups, the tablet press can even discontinue automatically to inhibit waste production.

· Multiple Testing

If a single tablet hardness tester is to be used by a whole team, a fully automatic tablet hardness testing system gives the ultimate solution at near zero labor costs.

You simply load an undefined quantity of tablets onto the tester, and testing starts automatically till you reach the set sample size.

You can also load different batches or products simultaneously.

In addition, you can set up new tests, so that your operators do not have to wait until the completion of the current running test.

Whether the goal is to minimize costs or increase quantities (or both), efficient tablet hardness tester machines save time and money.

It offers companies or firms with an increasingly crucial competitive edge in the present-day challenging environment.

Most automatic tablet hardness tester equipment enables you to customize processes to satisfy your manufacturing requirements in order to increase return on investment.

Technical Specification of Tablet Hardness Tester Machine

Technical Specification
AccuracyMax.*( ±0.05%) of full scale 
Probe Testing Range20mm – 40mm
Dimension320 * 180 * 110mm3, 500 * 300 * 160 mm3, 400 * 240 * 145 mm3 
Working PrincipleThere are 2 major methods for tablet hardness testing: 3 point bend testing and compression testing.
Test Range(2 – 199.9)N
Test Period>20S/P 
Material
Body made of stainless steel or painted mild steel to comply with cGMP regulations
TechnologyManual or automatic

 

SaintyCo Tablet Hardness Tester Machines

saintyCo’s latest model of tablet hardness testers are the YD-1YD-2, and YD-3 series.

The design and technical specifications of these hardness testers comply with necessary USP regulations and codes.

· YD-1 Manual Tablet Hardness Tester

The hardness tester model YD-1 is a high-performance device, which can precisely measure the tensile strength of tablets.

It uses MPU to run all processes and has an accuracy press sensor.

The device also has an LED display which shows the tensile strength results in kilograms.

YD-1 tablet hardness tester tests the sample with loop, and its data display and lock automatically.

There is no need for reset as this model of hardness tester auto-resets.

· YD-2 Automatic Tablet Hardness Tester

The hardness tester model YD-2 ensures precise measuring of the tensile strength of tablet, giving the minimum value, the maximum value, the average value, and the number of tablets. The instrument has an MPU which runs all operations, high accuracy press sensor and an LED display which shows tablet breaking force results in kilograms.

The tablet loading is manual and with the press of a button, the instrument automatically tests the samples.

The hardness tester resets automatically, tests the tablet samples with loop and can hold up to 100 samples printing results as a group.

Model YD-2 fulfils USP <1217> on tablet orientation and 3-point calibration to ensure accuracy in tablet hardness testing. It comes with the calibration procedure as well.

· YD-3 Automatic Tablet Hardness Tester

The hardness tester YD-3 has similar features as YD-3 though it does not come with a printer.

· YD-1/2/3 Tablet Hardness Tester

Tablet Hardness TesterYD-1YD-2 Hardness Tester w/PrinterYD-3 Hardness Tester
Test Range0.20 ~ 20Kgf0 ~ 20 kgf  (Optional Up to 50 kgf)
 Test Accuracy+/-5%  +/-0.05Kgf+/-0.05Kgf
Probe Testing Range20 mm40 mm
 Test PeriodManual(per Operator Skill)First Tablet 25sec.next 10 S/P
 Max. Number in each Group100 P
 Continuous Working Time> 24 hours> 24 hours
 Power110V   60Hz   10W or as required110V   60Hz   40W or as required
 Dimension320 * 180 * 110 mm3500 * 300 *160 mm3400*240*145 mm3
 Weight5KG (11lbs)12 kg (26lbs)9 kg (26lbs)

Conclusion

Pharmaceutical production is increasingly competitive.

The capability to ensure consistent quality, minimize the direct cost of manufacturing and immediately analyze test results can be fundamental in retaining a competitive edge.

Increasing the efficiency of your physical testing operations by investing in a high-quality tablet hardness tester machine will help you save on cost and maintain a competitive edge.

Here at SaintyCo, we offer a perfect solution in tablet hardness testing equipment.

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