Frequently Asked Questions

These questions are some that we are asked from time to time by our pharmaceutical and catalyst customers. To make this information as useful as possible it is updated on a regular basis. If you have any questions about how to use your machine, spheronization or about making pellets in general please ask us so that we can include it here.

Difficult Materials

Are you working with thick, viscous or sticky granulations?

Are you working with thick, viscous or sticky granulations? If so we can help. We are currently working with many of our clients to ease this process. To find out how, contact us now to discuss our new High Viscosity mixing blades.

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What characteristics should my extrudate have?

A formulation required for spheronization needs to go through the following processes and achieve the following properties.  The initial formulation (powder + binder), must reach a suitable consistency for the extrusion process.  This can generally be achieved using a Caleva MTR (Mixer Torque Rheometer), whereby the properties of the formulation can be determined i.e. optimum binder ratio, mixing times and consistency.

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Working with Cosmetics and Personal Care Ingredients

Can you help with my cosmetics formulation?

We recently had a visitor from Asia to Caleva who was trying to solve a problem with formulation development in the cosmetic industry.  The development was a formulation that the investigator wished to have as small (approximately 1 mm diameter) pellets.  The formulation presented was a tough waxy material in irregular broken blocks that were up to about 10 mm in diameter 

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Caleva Product Selection and Evaluation

How do I decide which laboratory extruder and spheronizer I should choose

Caleva offers three different kits for use in the laboratory. These kits are designed to give customers a choice so the equipment chosen will be the most appropriate for their specific needs.

There are three key things to consider.

  • The batch size you want to work with. This is fundamental and is generally the first thing you need to decide.
  • Do you need the ability to work with extrudate or pellets of different density? The effect of density on a formulation can effect product properties. If your formulation is new then the ability to look at the effect of product density is recommended.
  • If your development will lead to production then consider the extruder type you want to use for production now. This can have significant long range practical and financial consequences.
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Can I spheronize directly from a granulation or do I have to extrude the granulated material before spheronization?

If the key objective is making pellets to obtain a batch that has slightly increased density and is approximately round in shape with a smooth surface, then it is possible that the step can be avoided, saving time and cost.  With this two step process the granulation can be pelletized with some rounding and some densification but  the diameter range of the pellets will be very wide.   Read more

Spheronization and Spheronizers

What are the standard processes that I have to consider when trying to develop or manufacture spheroids or pellets?

There are 4 standard processes to consider when creating spheroids.

Wet Granulation - Granules are formed by the addition of a granulation liquid onto a bed of powder under the influence of an impeller. This is typically carried out using a high-shear granulator or a simpler planetary mixer.

Extrusion - The wet granulation is extruded to form cylindrical extrudate (noodles or spaghetti) of a constant diameter (normally 0.5 – 3 mm).

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Where can I find a general guide to spheronization?

Caleva are pleased to provide this brief, very useful introduction to Spheronization.   The industry standard term "Spheronization" was established by Caleva about 50 years ago.   Talk to the experts!  What is Spheronization?   Why consider Spheronization?  What basic equipment do I need for Spheronization? 

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I have a Caleva Spheronizer machine where can I get spare parts?

You can find contact information from our distributor page or send us an email  You may of course call us by telephone +44 (0)1258 471122 or use our chat facility on the website.  

I put the extrudate in the spheronizer but it is not producing spheres after about 10 minutes and I don’t see any changes.

The extruded material is too hard and/or too dry.  The quality of the spheres depends on the quality of the extrudate.  The quality of the extrudate depends on the quality of the formulation.  In general, the reason for having a small spheronizer is to do trial work.  This trial work can be made considerably easier by the use of a Mixer Torque Rheometer.  For more information on formulation development, either contact Caleva or your local distributor.

I put the extrudate in the spheronizer but all the material sticks together.

The extrudate is too wet.  Look again at the formulation.  The quality of the extrudate depends on the quality of the formulation.  In general, the reason to have a small spheronizer is to do trial work.   This trial work can be made considerably easier by the use of a Mixer Torque Rheometer.  For more information on formulation development, either contact Caleva or your local distributor.

A large amount of dust is being produced when I put material in the spheronizer.

The extrudate is too dry.  More binder is needed. The disc speed may be too high.

How can I make smaller (or larger) spheres?

The diameter of the sphere or pellet produced depends principally on the diameter of the extrudate.  In general, smaller diameter spheres are rotated at higher speeds and larger diameter spheres are rotated at slower speeds but this is not the determining factor in the diameter of the spheres.

How long should the extrudate stay in the spheronizer?

This depends on the formulation characteristics.  It could be anything from about 30 seconds to about 10 minutes.  It is dependent on the product and the quality of it.  

Should the spheronizer be running when the extrudate is added or should I add the extrudate and then start the machine?

It makes little difference but aim to be consistent in the method used.

What happens if I add too much or too little product?

The cycle time will be reduced or increased depending on volumes. Too high or low a load can prevent proper spheronization.

Can I pour water in the bowl to wash it?

This is not advisable.  Remove the bowl and clean with a cloth.

How can I remove the disc to clean underneath it?

See the instructions in the operating manual or contact Caleva.

The spheronizer is plugged in and I have pressed the green start button on the front but it will not work. What could it be?

Providing you are sure you have electrical power the first thing you should check is that the emergency stop button is not depressed (you must twist to release it) and that the on/off switch on the rear of the machine is switched on.  Ensure that the drum and chute covers are fitted correctly.  If the problem persists then contact your local distributor or Caleva.

Mini Coater Drier

Mini Coater Drier results - can they be used in the scale up of process development?

Author: Dr Steve Robinson.

We are often asked if parameters used for film coating of materials in the Mini Coater Drier can be used for “scale up” to production. The desire for a process to be scalable is understandable but it is not always feasible or relevant. 

The Caleva Mini Coater Drier has the unique ability to coat very small sample batch sizes (from a single tablet to about 150 tablets or from a few grams to about 60 grams of pellets) and is typically used for teaching principles of tablet and pellet and coating at a very early stage in the development of new products and new formulations. The following is a real example that demonstrates why the question of “scale up” is not always relevant or important when taking advantage of the benefits of the Mini Coater Drier (MCD).

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My tablets are rather large. Will I be able to coat them in the Caleva Mini Coater Drier?

Our general tablet coater literature describes the coating capability of a tablet size of up to 10 mm.  However, this refers to a diameter rather than a capsule style design in length.  It’s important to consider weight/batch size to ensure a good coating motion within the coating apparatus. Please see the image below from a previous trial, where we have coated elongated capsules of 25 mm in length. 

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What is the smallest particle size that I can effectively coat in the Caleva Mini Coater Drier?

If you would like to coat pellets with a diameter of 350 microns, then our recent experience of effectively coating particles as small as 350 microns in diameter may be useful to you.  If such an application (coating particles with 350 microns diameter) would be useful to you then please discuss your requirement with us and let’s see if together we can find a solution for you too.  

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A note about terminology:-

Spheronization, marumerization, pelletization and micropelletization all mean the same thing. The manufacture of products in small spheres (spheroids) for use in pharmaceutical (pharma) and catalyst industries. Within each batch the spheroids are of regular shape and size and are quite dense. The products produced by these processes can be called spheroids, spheres, micro-spheres, pellets, micro-pellets or pharmaceutical or catalyst pellets. All these terms refer to the same thing. The size range is normally from about 0.8 mm to about 1.5 mm in diameter although smaller and larger are possible they are less common. Granulation normally refers to the manufacture of irregularly shaped particles with a large size range included within the batch. Granulated materials are generally less dense.

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Alternative terms and typical spelling variants used for the processes and equipment that Caleva manufacture.

At Caleva we supply our extrusion and spheronization equipment around the world as well as in the UK. We are a British manufacturer. We have customers in Europe, Asia, Middle East, North America, South America and Australasia. We work closely with and support our customers all across the globe.

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General Questions about Extrusion and Extrudates

What type of extruder do I need?

All extrusion processes are based on the generation of pressure within the material. When materials are put under pressure heat is generated. This cannot be avoided but different extrusion types generate different amounts of heat. There are basically three different types of extruder and the one chosen may have far reaching implications on production operations. It is vitally important that the right type of extruder is chosen as this is a critical decision that will have long term implications.

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An Important Note on Pharmaceutical Equipment Product Quality

Do all extruders and spheronizers have the same level of performance - will a model with lower quality cost more in the longer term?

Process yields (the % of the spheroids produced in any batch that are within the size range required) will never be 100%. It is possible to achieve yields of greater than 98% if the formulation, the process parameters and the equipment used are optimised.

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Working with Catalyst Materials

Find out more about the formulation of catalyst materials such as Zeolite and Bentonite?

Caleva is always willing to help our potential users and may offer to help run trials so that we can show that an installation of one of our laboratory machines (and later production machines) would be the right decision for you.  Below is a typical example of a Catalyst trial taken from Dr Steve Robinson's notes.

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Why spheroids or Pellets?

A better therapeutic effect with spheroids?

In many cases the main reason for the use of pellets in the manufacture of products is for its controlled release properties. However there are reasons to believe that pellets or spheroids in any case can offer a superior therapeutic effect even when modified release is not the prime objective. 

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Commonly spheronized pharmaceutical products

What pharmaceutical products or drugs can I make with pellets

View this list of pharmaceutical drugs and medicines that are processed in the form of pellets or spheroids

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Should I use extrusion and spheronization or layering to manufacture pellets?

Should I use extrusion and spheronization or pellet layering to manufacture spheroids for pharmaceutical and nutraceutical active ingredient or drug delivery?

The main reason the process of extrusion and spheronization a much more widely used technique than layering is the ability to produce quantities of products quickly. 
Click to tweetTweet: Extrusion & spheronization is a more widely used technique than layering because it produces quantities of products quickly

In development and testing of formulation, new iterations of small batches (from about 30 g) of product samples for testing can be produced in about 30 minutes or so.  With layering often several hours are required to make a sample batches for trials.  Progress is slow with layering, and development can be prolonged.

This fast v’s slow situation in product development is then carried through to the production operations.   A small commercial manufacturing operation can often produce between 50 and 150 kg per hour of dry pellets ready for packing using Extrusion and Spheronization.  With the layering process a single batch of 20 to 30 kg might require up to 20 hours of the slow layering process to finish this smaller batch.  If significant quantities of pellets are required by layering then a significant amount of capital equipment and space will be needed.

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Do I need to coat omeprazole pellets? Can I just add the right colour to the formulation?

Omeprazole formulations are generally made into small pellets from about 0.7 to about 1.4 mm in diameter These are generally given an enteric coating on the individual pellets (or spheroids).  An enteric coating generally means a coating that will prevent the disintegration or dissolution of the pellets in the acidic environment found in the stomach (pH approximately 3). The active ingredient in the pellets is rapidly degraded in the acidic medium of the stomach.

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