Basics of Tablet Tooling
Tablet Tooling: Tablet compression machines are made keeping in view the type of dies and punches that will be used on them. The dies and punches and their setup on compression machine are called tooling, it is classified as B and D mainly.
The B tooling dies and punch can further have specifications as BB and D tooling can also be dies and punches can be utilized on the B tooling machine which is called DB.
Mainly there are two standards, D and B, in the US specification provided by Tableting Specification Manual (TSM) is followed whereas in Europe European standard is known as the EU or the “Euronorm” standard. There is not much difference in both the specifications but both are very different.
Punch
1. Head: The end of the punch that guides it through the cam track of the 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 before 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 relived area between the head and barrel, which provides clearance for the cams.
6. Barrel: This area guides the punch (while going up and down) concerning 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 chamfer.
8. Tip: This determines size, shape & profile
9. Tip face: This area of punch is where the tablet is formed. A good surface finish is required here to get quality tablets.
10. Working length: This distance between the bottom of the cup and the head flat is called working length which determines the 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 helps to achieve better tablet hardness.
14. Dwell time: The time punches spend below the pressure roller while rotating in the machine.
15. Clearance: Die bore dia – punch tip dia = Clearance.
16. Hardness: Usually measured in HRC (Rockwell ‘C’ scale) and optimum readings are as follows:
Die
It is a hardened steel (HCHC) mold to make the shape of a tablet.
Die Terminology:
1. Die O.D.: The outside diameter of the die, which is compatible with the die pockets in the press.
2. Die Height: The overall height of the die.
3. Die Bore: The cavity where the tablet is made. The Cavity’s shape and size determine the same form of a tablet.
4. Chamfer: Entry angle of the die bore.
5. Taper dies: dies with a tapered bore on one or both sides. They are used for easy ejection of tablets (mainly for double-layered tablets.
6. Die Groove: The groove around the periphery of the die, which allows the die to be fixed in the press.
7. Lined (Insert) Dies: Dies fitted with a linear insert made from a much harder, more wear-resistant material such as tungsten carbide and ceramic.
There are the following types of tooling available:
- ‘B’ -Tooling
- ‘D’ – Tooling
- ‘BB’ -Tooling
- ‘DB’ – Tooling
Tip diameter of punches: Check the tip diameter with the help of a Vernier caliper. Check and set the zero reading of the Vernier caliper. Place the punch tip in a vertical position. Check the fine setting of the Vernier caliper and record the reading. The readings should be within ± 0.1 mm of the standard dimension.
The difference in height of the punches: Set the dial gauge of the inspection kit at zero position with the help of the standard punch height of 133.60 mm. Keep the punches one by one inside the punch holder over the metal pad of the inspection kit and check the difference in deflection from the zero position. The difference should not be more than ±0.08 mm of the standard dimension.
Body diameter of punches: Check the body diameter with the help of a Vernier caliper. Check and set the zero reading of the Vernier caliper. Check the fine setting of the Vernier caliper and record the reading. The standard dimensions and limit areas are in the table.
Embossing of punches: Visually check the embossing and record the observation.
The difference in concentricity of punches: Keep the punch over a ‘V’ block pad horizontally by keeping the magnet on and set the dial gauge at zero position over the punch body. Rotate the punch in the clockwise direction, take two readings each from the punch (one from the top and one from the bottom of the punch body) and record the observations. The deflection should be within ± 0.05 mm of the standard dimension. Keep the punch over a ‘V’ block pad horizontally by keeping the magnet ON and set the dial gauge at zero position over the highest point on tip diameter. Rotate the punch in the clockwise direction and record the observations. The deflection should be within ± 0.025 mm of the standard dimension.
Go and No-Go of punch head: Take “B” or “D” type tooling “Go-No Go” punch head tester for checking punch head. Move the punch head through the “go” side of the punch head tester it should pass easily. Move the punch head through the “no go” side of the punch head tester & it should not pass through it. Record the observations.
The outer diameter of dies: Set the dial gauge of the inspection kit at zero position with the help of the standard die masterpiece. Keep the dies horizontal position one by one over the metal pad (V BLOCK) of the inspection kit and check the outer dimension deflection from the zero position. Record the reading.
Height of the die: Set the dial gauge of the inspection kit at zero position with the help of the standard die masterpiece. Place the dies in a vertical position one by one over the metal pad of the inspection kit and check the height deflection from the zero position. Record the reading.
The difference in concentricity of dies: Keep the die over a ‘V’ block in horizontal position and set the dial gauge at zero position over the dead body. Rotate the die in the clockwise direction, take two readings each from the die (both sides) and record the observations. The deflection should be within ± 0.05 mm.
Frequency: Inspection of punches and dies to be done after receiving a new punch set and after compression of two million tablets per subset.
Make sure you also check our other amazing Article on : Problems and Remedies for Tablet Coating