Types of Tooling in Compression Machine

What is Tooling in Tablet Compression?

• Tablet compression machines are made in keeping in view the type of dies and punches that will be used on them. The dies and punches and their setup on the compression machine is called tooling. It determines the shape, size and identification markings of the tablets. 
• The tooling must meet the specific requirements to satisfy the needs of dosage uniformity, production efficiency and esthetic appearance.
• Internationally there are two recognized standards for tablet compression tooling: the TSM standard and the EU standard.
• Based on TSM and EU standards, tablet tooling is mainly classified as B tooling and D tooling. The B tooling punches and dies can be further classified as BB, and D tooling can also be used on B tooling machine which is called as DB. These subcategories of DB, BB type tablet tooling are made depending on the punches and dies requirements of the product.

What is the difference between B & BB tooling and D & B tooling?

1. B Tooling: the same as BB tooling, only difference is the lower punch length is just 3 and 9/16th inch.
2. D Tooling: its punches and dies usually have thicker diameter or greater diameter of their body as well as the tip of punches with greater outer diameter compared to B tooling.

• The productivity will be 20 to 25% more in B tooling compared to D, assuming the same speed and diameter of turret of machine as number of stations.
• Hardness can be achieved might be more in case of tooling due to larger dual time. It can lead slower dissolution if dissolution is hardness dependent.

Tooling for Rotary Tablet Compression:

• The punch consists of head, neck, barrel, and stem. The barrel diameter and the overall length are determined by the machine turret dimensions.
• The working length (i.e., overall length minus any cup depth at the punch tip) determines thickness and mass of the tablets and needs to be controlled regularly. The variation in working length should be within ±10 µm to ensure low variability of tablet properties.
• The die depth should also be accurately cut in order to guarantee a flush fitting with the die table.

Terminology of Tablet Tolling:

Following definitions for direct terminology for tooling (Punches and dies).

1. Head: The end of the punch that guides it through the cam track of tablet machine during rotation.
2. Head flat (Dwell Flat): The flat area of the head that receives the compression force from rollers (in upper punches) and determines the weight and ejection height (in lower punches).
3. Outside head Angle: The area gets in touch with the roller prior to head flat, while compression.
4. Inside Head Angle: This is the area, which pulls down the lower punches after ejection and lifts the upper punches after compression.
5. Neck: The relieved area between the head and barrel, which provides clearance for the cams.
6. Barrel: This area guides the punch (while going up and down) with reference to turret guides.
7. Stem: The area of the punch opposite the head, beginning at the tip and extending to the point where the full diameter of the barrel begins. If the chamfer is present the barrel usually reaches its full diameter just above the chamber.
8. Tip: This determines size, shape & profile of the tablet.
9. Tip face: This area of punch is where the tablet is formed. Good surface finish is required here to bet quality tablets.
10. Working length: This distance between the bottom of the cup and the head flat is called as working length which determines weight and thickness of the tablet.
11. Overall length: Distance between top of the cup and the head flat.
12. Key Angle: The relationship of the punch key to the tablet shape. The keys position is influenced by the tablet shape, take-off angle and turret rotation.
13. Domed Heads: Increases the dwell time and hence help to achieve the better tablet hardness.
14. Dwell time: The time punches spends below the pressure roller while rotating in the machine.

ALSO READ: Working and Principle of Tablet Compression Machine

Die terminology for tablet compression:

1. Die.O.D.: is the outside diameter of the die, which is fitted with the die pocket in the compression press.
2. Die Height: overall height of die from top to bottom.
3. Die Bore: is the part of the die where tablet forms, it determines both the shape and size of tablets.
4. Chamfer: is the entry angle of the die bore.
5. Taper Dies: They are single (one side wider at opening face) and double taper dies (both side wider upper and lower) for easy ejection and prevent capping and delamination problems)
6. Die Groove: The groove outside the periphery of die, witch help in fitted the die in the press.
7. Lined Dies: its also called Insert dies, these dies are fitted with a linear insert made from the materials of tungsten carbide and ceramic.

The life span of the die and punches:

• For all compression machine and tooling approximate all punches and dies life depending on  materials of construction.

1. OHNS Punches and HCHC Dies - 4 Million tablets
2. HCHC Punches and HCHC Dies - 7.5 Million tablets
3. Complete hard chrome plating punches and HCHC dies - 8.5 Million tablets.

Punches and Dies: cleaning, lubrication, wear and tear and storage:

1. Cleaning: 

• Use 0.1% teepol solution with purified water for cleaning after use of punches and dies, also using soft plastic scrubber if required.
• Caution: do not use metal scrubber it will make scratches and mark, roughness on punches and dies.
• Rinse the punches and dies finally two to three times with hot purified water if required do the streaming for cleaning.
• After cleaning intimate QA department to send rinse water or swab sample to QC for testing of a residual trace of detergent and previous product. (Method and cycle of cleaning of punches and dies shall be validated).
• Use oil-free filtered compressed air and suitable dry clean duster for the dry. After cleaning and drying, the disinfection of punches can be done by wiping with 70% isopropyl alcohol.
• Allow to dry the punch and then lubricate the punches before storing. Polishing can also be done by using a polishing kit.

2. Lubrication: 

• Done by using food-grade oil like castor oil or liquid paraffin, but there is a problem of the rancidity of oil. So nowadays various synthetic lubricants and grease are available which have been now used in most of the pharmaceutical companies.
• Now some of the varies of synthetic oil and grease which are 100% synthetic and non-toxic, listed in NSF and USFDA authorized. components are in accordance with FDA regulation 21CFR 178.3570
• Name of some grease and oil are:

1. ET- 2S grease
2. ET- 10S,20S,90S,140S Lubricants
3. HT- 1000G, High temperature, and non-melting grease

• Store the punches and dies in there cabinet (made of a soft material to avoid damage to punches and dies) after proper greasing. 
• Handle punches and dies carefully to increase there life, At the time of use wipe the punches and dies with proper clean and dry lint-free duster with IPA 70%, then allow to dry.

3. Wear and Tear of punches and dies: 

• Checking the punches and dies periodically for any damage and polishing termed as wear and tear.
• For this follow the guidelines and use punch inspection and maintenance kit, inspection, and maintenance of punches and dies shall be done by skilled, experienced and knowledgeable persons with proper records.
• Contents of kit for punches and dies:

1. Motorized chuck: for cleaning, polishing of concave, plane punches also for the cleaning of punch tip, punch barrel, and punch head.
2. Double-ended Polisher: for cleaning, polishing of all types of embossed punch tipe including break lines and shaped punch tips.
3. High-speed Grinder: polishing plain concave punches and die bores.
4. Bench comparator: for measurement and comparison of punch length, checking of punch tip, to barrel concentricity.
5. Emery rolls: polishing of punch head 180 grit for general polishing and 320 grit by lighter polishing.
6. Lapping stone: use for removing bur from punch tip.
7. Nylon brushes: Used for double-ended motor for polishing all embossed punch tipe, flat beveled and shaped punch tip and for cleaning break lines.
8. Micro-polishing paste: for micro-polishing Chalk powder: for drying off polishing compound from punch tip.
9. Lubricants for lubrication Brass wheel
10. turret brushes for remove powder
11. Cotton wool: for cleaning.
12. Magnifying Glass: for inspection punch holder to protect punch from tear and wear.
13. Length gauge: for all length checking (screw gauge and vernier caliper digital)

ALSO READ: What is Maximum Compression Force?

Punches wear and tear:

• Check for overall length it should be within specified limits.
• The inside head angle should not be warned out due to friction on cam, it should be smooth.
• The flathead should be smooth
• Body diameter should be within limits
• Punch tip should be smooth and not warned out due to friction and it should be intact and not damaged.
• The embossing letter and break line-height and uniformity should be sharp and intact, it creat problem during tablet ejection from die, if not proper.
• Dies tear and wear:
• The outer diameter should be within limits.
• inside the cavity, finishing should be mirror finished and smooth,
• Hight of the die should be within limits
• Die grooves should be smooth and not damaged.
• Die chamber should be proper, smooth and appropriate, otherwise, create a problem in tablet ejection.

Which is Better - B Tooling or D Tooling?

• Tablet tooling is one of the quick-wear parts of tablet press machine in the process of making tablets. It is quite confused when it comes to replace the worn tablet tooling with a new one. At this moment, you have to meditate on choosing a station of B tooling or D tooling and compare which one is better. Here, I have to say we couldn’t judge that B tooling is better than D tooling, or that D tooling is better than B tooling. The suitable one must be the best one.
• First, we have to know the fact that the dimensions of B tooling and D tooling of different brand are different, which means that, for an instance, the size of Fette B tooling is different from Stokes B tooling. In addition, the type of tablet tooling must be in accordance with tablet press machine, some of which accepting B tooling could not be equipped with D tooling. Hence, choosing a tablet press machine is also a matter of deciding tablet tooling.
• Second, we should differentiate B tooling and D tooling objectively. Their respective features make them to be used for different purposes. We should take the advantages of different tablet tooling into consideration in the process of purchasing a tablet press machine. Based on their features and merits, we could make a sensible choice of tablet tooling and tablet compression machine.

B Tooling

• B tooling has a long and thin body compared with D tooling, with a smaller punch head and punch tip. Small punch head leaves a restriction on punch pressure, thus the tablets and pills requiring high hardness can not be finished by B tooling, while the small punch tip directly decides the size (diameter) of tablets. Briefly, B tooling is more suitable to make small pills.
• However, due to its small punch body occupying less space, more stations of tablet tooling can be designed on the rotary table. This means that higher yield and quicker production can be achieved at the same working speed. It is worth mentioning that the small pills made by B tooling have smooth surfaces outside.

D Tooling

• On the contrary, D tooling is short and fat in view of its configuration. Fat punch body and big punch head allow high pressure to be engaged, thus the pills can be made hard and strong enough. And big punch tip and tip flat leaves more space for materials, thus big pills with large diameters (20mm) can be made.
• For another, owing to more space the fat punch body occupies, less stations can be set on the premise of the same size of rotary table. With the same working speed, less tablets and pills are processed.

Materials, Manufacture, Finish and Pressure Tolerance:

• Materials and Manufacture Steels are basically classified as carbon and alloy steels which are defined by national and international standards, e.g., ASTM and DIN.
• Carbon steels contain less than 1.65% manganese, 0.6% silicon, 0.6% copper, plus boron and deoxidizers as well as carbon. principal additive increasing hardness. Manganese also increases hardness.
• Silicon acts as a deoxidizer. Alloy steels exceed these limits or contain additional elements, e.g., chromium, vanadium, tungsten, molybdenum, nickel, and cobalt.
• A high-nickel content increases resistance to corrosion caused by HCl released from drug salt. The composition of special steel types for tooling, their provenance, and their thermal treatment is part of the trade secret of tooling manufacturers.
• A high abrasion resistance usually corresponds to the high hardness of a steel type, whereas its ductility and toughness is low and vice versa: very hard tooling may fracture, and ductile material may wear off quickly.

• Hardness and ductility do not only depend on the chemical composition of the steel but also on its heat treatment (tempering). A second tempering procedure for punch tips, which is computer-controlled and carried out at high temperatures in a vacuum furnace, softens the material and prevents fracture.
• Punches usually have a longer lifetime than dies if they are made from the same material; that is why manufacturers often choose different steel qualities.
• The surface of a die bore can become smoother or rougher during its use. The ejection force does not - apart from the composition of the tableting material and the compaction force - necessarily depend on the roughness of the die wall, but to a high degree depends on the metal type of the die.
• For specific tableting tasks, the tooling manufacturer will be able to provide optimum tool properties. 

Finish

• Adhesion, sticking, picking, and filming on punches and dies can in many cases be avoided by a suitable surface finish of the tooling.
• In some cases, the surface is smoothened during continuous use of punches, whereas in other cases, depending on the material compressed, e.g., in the case of crystalline lactose, small scratches may occur on the punch tips after a few thousand compression events. On those small scratches and defects in the surface, corrosion will start.
• Any roughness of the finishing is below 1 mm peak-to-valley height, and particularly punch-tip faces and die bore walls are polished to achieve lower tolerances.

ALSO READ: Use of Binder in Tablet Formulation