TABLETING 81
The stearate spray system mounted on a tablet press.
the tablet and the die wall during ejection.
Another ‘should-have’ option is a punch pressure- or dosage relief system, to allow the press to start up easily without stopping right away due to too high compression force, caused by dies becoming overfilled during a machine stoppage. With a dosage relief function, the dosing (powder fill) is reduced until the machine has reached operating speed, when the dosing increases back to the original values/ settings.
Punches and dies Punches should have EU1”-441 punch heads, offering a larger contact area on the punch head in order to provide increased compression time (dwell time). Meanwhile, dies should have an increased taper to reduce ejection forces.
lubricating oil, e.g. vegetable oil or almond oil, which is sprayed onto the lower punches with a spray gun. Tis oil lubrication helps to reduce the ejection forces in the dies, preventing cams, punches and tablets from being damaged. Te disadvantages are that excess oil drops down to the bottom, and the machine needs to be placed onto a drip tray. Operating this way can be quite messy due to the oil in the drip tray. Also the felt/material will get worn and need replacing.
Gerd Hüffmann is with Killian Tableting in Germany.
www.romaco.com
Te alternative method involves an external stearate spraying system being used, to spray/ coat the die walls (in addition to the punch tip) with magnesium stearate. Te layer/ coating of magnesium stearate prevents the powder/tablet from sticking to the die walls, thus reducing the ejection force.
Again, the only disadvantage with this approach is the investment cost for the stearate system.
Te advantages are: no special lower punches (e.g. with felt inserts) required; no drip tray required; and no contamination due to dripping oil.
Tere are a number of other general measures to be considered relating to the machine configuration. Firstly, pre-compression force measurement is a ‘must-have’ function to prevent tablets from capping. Ejection force monitoring meanwhile, is a ‘should-have’ option. Effervescent tablets are usually rather large (20mm to 25mm in diameter) and difficult to eject. Te measured ejection force is a very good indication if there is sufficient lubrication between
When it comes to measures in respect to the tablet handling after the tablet press, there are also a number of considerations. As effervescent tablets are rather soft and brittle they cannot be de-burred/de-dusted in a mechanical de-duster. In some cases however, a vibrating de-duster can be used, after a thorough evaluation of the mechanical durability of the tablets.
After the tablets exit from the tablet press, they cannot be allowed to just drop down from the exit chute into a receiving drum or bin. Te tablets will need to be supported right into a receptacle. Ideally a conveyor belt is placed under the tablet exit chute to transport the tablets directly to the packaging machine (in-line packaging).
Finally, the tablets need to remain in a humidity-controlled environment until they are packed into a tube or a strip pack.
For more information ✔ at
www.scientistlive.com/eurolab www.scientistlive.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92