In modern medicine, a nearly inestimable variety of tubing is used. Examples for their fields of application include tubing for invasive surgical interventions, dialyse, infusion, catheter, drainage Abrasion, emission of dust, lubricants or vapours, which may settle on the product, must absolutely be avoided. Furthermore, all machine parts, in touch with plastic melt or the ready product, have to be accessible very well to ensure that they can be cleaned easily, etc.

Their diameters vary between diameters which are thinner than the human hair (< 100 µm) and those of about 5 mm. The inner geometry of the hoses reaches from simple mono-lumen hoses to multi-lumen ones, which include up to seven separated channels. It goes without saying, that all geometric parameters are extremely close-toleranced. This geometric variety is multiplied by the application of the most different plastic materials. They include PVC with special plasticizers, polyethylene (PE), cross-linked PE, silicon, rubber, thermo-plastic polyurethane, polyamide, and fluorine plastics.

Certainly, also the method of co-extrusion is applied, to adjust the characteristics of the hose better to the requirements of their application, using a structure with up to five layers. There is the combination of polymer materials with metallic supports of most different geometric forms. More and more, variable diameters in longitudinal direction or different materials of short sections which are stringed together are demanded.

It is obvious that, within such an environment, highest requirements on flexibility and precision have to be satisfied by extrusion machines. Apart from these characteristics, it has to be considered that clean-room production needs the application of special materials.

For more than 35 years Dr. Collin GmbH, certified according to ISO 9001:2000, manufactures highly precise and compact extrusion components and complete lines for R&D application as well as pilot and production purposes. This market segment requires machines and equipments which have to be used very flexible under frequently changing boundary conditions.

Dr. Collin complies with necessary requirements, given for the development of equipment producing parts designated for the medical application and provide services for their successful set up. In addition to a series of special roll mills for the development and production of pharmaceuticals, complete pipe/hoses extrusion lines have been delivered. These lines were designed to produce hoses with diameters between 0.5 mm and 10 mm made of polyolefin, softened PVC, polyamide etc.

Mono-lumen hose with support wire of POM and reinforce with steel wire (left); Triple-lumen hose with 20% bariumsulfat (middle); Mono-lumen hose with support wire of POM (right)

Step by step

The above shown Dr. Collin's extruder is for the production of medical catheter tubes. This extrusion line complies with all directives of the FDA and can be validated accordingly.

The first stage this line was specified for the production of:

• Support wires made of polyacetal with a diameter of 1.37 mm and a tolerance range of +/- 0.05 mm (the inner of the tube in image 4)

• Mono-lumen hoses made of thermoplastic polyurethane or polyether block amide with diameters of 1.98 mm and a wall thickness of 0.3 mm (blue tube in image 4)

• Triple-lumen hoses made of thermoplastic polyurethane with an outer diameter of 2.31 mm and lumen diameters of 1 x 1.0 mm and 2 x 0.8 mm (see image 3)

Thanks to its modular concept such a line can be adjusted to different applications even for production purposes. For example, the conversion of the machine from mono-lumen to a triple-lumen tube is possible within 15 min.

All parts of the machine can be removed quickly and can be cleaned easily. Parts guiding the extruded product, are made of special steel suitable for medical applications. Designed in a way that they are allowed to be used in clean rooms of the ISO class 8:

Extrusion line for the production of medical catheter tubes.

• Complete covering of all heating elements

• Encapsulated motors

• Smooth surfaces without cracks

The line has a central supply unit for air, water and electrical power. Only one external connection for the supply of the machine will be required, which is an important advantage if clean room conditions are specified.

The system consists of the following subassemblies:

Extruder

For a wide range of throughputs from 0.05 kg/h to 15 kg/h, the line is equipped with two extruders, which can be used either individually or within a co-extrusion set-up. For coatings of about 0.06 mm with low throughputs from 0.05kg/h to 1kg/h, an extruder with a screw diameter of 16 mm and L/D of 25 is provided. For the higher outputs an extruder with a screw ratio of 30 mm and L/D of 25 can be added integrated. Both extruders are equipped with AC-servo drives. Using pressure/speed control an absolutely constant melt flow rate over the whole rpm range of the extruders is achieved. The use of melt pumps, usually unacceptable for the FDA approval, can be avoided. Highly precise, digital probes with a bus system do their bit to improve the precision. For both extruders, screw geometries are available for processing of TPU, Pebax, POM or other polymers.

Extrusion Die

The die is mounted on a carriage, which enables easy handling for cleaning or change of dimensions. For the various tube geometries and coatings, exchange parts are available which can be mounted and cleaned easily. The die is designed in a way that residential and rinsing times are minimised. Short flow paths, the avoidance of dead zones, as well as a bypass valve for rinsing are necessary preconditions for a production free of degraded polymers and black spots.

Calibration and Cooling Tank

The easily adjustable vacuum calibration and cooling tank is suitable for the production of outer diameters in the range of 0.5 – 5 mm. A central supply unit in the calibration device comprises all required media, e.g. cleaned compressed air, cooling water and electrical power. The calibration itself is designed as disc calibration with close-toleranced discs available for each diameter. The control of the support air is carried out with high precision, by fine adjustable air regulators. They keep the set pressure constant at +/- 0,5% within the range of up to 100 mbar. The temperature of the circulating cooling medium is also regulated.

Haul-off unit with measurement of thickness and ovality

The haul-off unit is driven by two electronically synchronized AC servomotors. The haul-off speed is controlled via the two-axes-laser system for the measurement of diameters and ovality, ensuring close toleranced diameters. However, in case of non-compliance with the set tolerances, the marker and cutting system can distinguish between good and bad parts. Within certain limits, using this regulation, also conical hoses can be produced.

Winder

The winder includes, besides an adjustable changing unit, a tension control for setting the winding tension to the respective product sensitiveness. The adjustment of minimal winding forces avoids the loss of roundness, depending on sensitives of the polymer processed. A manually actuated coil enables the changing of the coil without using tools.

Unwinder with pre-heating oven

The unwinder is also equipped with a tension control. The control speed for unwinding is mastered by the haul-off unit. This ensures the continuous and constant unwinding of the support wire or the basic hose. In case an optimized bond between central wire and coating layer is required, the support wire can be pre-heated up to 250 °C.

Central control via the computer assisted control system

All parts of the extrusion line are linked via a central control system. This system collects and records all quality relevant parameters of the whole line. For each product, the customer can combine individual records, store and print them. A further module allows the creation and management of product-specific formulas which can be re-loaded when the production is restarted. The line automatically ramps up to the process setting.

Source: Dr. Collin GmbH

In modern medicine, a nearly inestimable variety of tubing is used. Examples for their fields of application include tubing for invasive surgical interventions, dialyse, infusion, catheter, drainage Abrasion, emission of dust, lubricants or vapours, which may settle on the product, must absolutely be avoided. Furthermore, all machine parts, in touch with plastic melt or the ready product, have to be accessible very well to ensure that they can be cleaned easily, etc.

Their diameters vary between diameters which are thinner than the human hair (< 100 µm) and those of about 5 mm. The inner geometry of the hoses reaches from simple mono-lumen hoses to multi-lumen ones, which include up to seven separated channels. It goes without saying, that all geometric parameters are extremely close-toleranced. This geometric variety is multiplied by the application of the most different plastic materials. They include PVC with special plasticizers, polyethylene (PE), cross-linked PE, silicon, rubber, thermo-plastic polyurethane, polyamide, and fluorine plastics.

Certainly, also the method of co-extrusion is applied, to adjust the characteristics of the hose better to the requirements of their application, using a structure with up to five layers. There is the combination of polymer materials with metallic supports of most different geometric forms. More and more, variable diameters in longitudinal direction or different materials of short sections which are stringed together are demanded.

It is obvious that, within such an environment, highest requirements on flexibility and precision have to be satisfied by extrusion machines. Apart from these characteristics, it has to be considered that clean-room production needs the application of special materials.

For more than 35 years Dr. Collin GmbH, certified according to ISO 9001:2000, manufactures highly precise and compact extrusion components and complete lines for R&D application as well as pilot and production purposes. This market segment requires machines and equipments which have to be used very flexible under frequently changing boundary conditions.

Dr. Collin complies with necessary requirements, given for the development of equipment producing parts designated for the medical application and provide services for their successful set up. In addition to a series of special roll mills for the development and production of pharmaceuticals, complete pipe/hoses extrusion lines have been delivered. These lines were designed to produce hoses with diameters between 0.5 mm and 10 mm made of polyolefin, softened PVC, polyamide etc.

Mono-lumen hose with support wire of POM and reinforce with steel wire (left); Triple-lumen hose with 20% bariumsulfat (middle); Mono-lumen hose with support wire of POM (right)

Step by step

The above shown Dr. Collin's extruder is for the production of medical catheter tubes. This extrusion line complies with all directives of the FDA and can be validated accordingly.

The first stage this line was specified for the production of:

• Support wires made of polyacetal with a diameter of 1.37 mm and a tolerance range of +/- 0.05 mm (the inner of the tube in image 4)

• Mono-lumen hoses made of thermoplastic polyurethane or polyether block amide with diameters of 1.98 mm and a wall thickness of 0.3 mm (blue tube in image 4)

• Triple-lumen hoses made of thermoplastic polyurethane with an outer diameter of 2.31 mm and lumen diameters of 1 x 1.0 mm and 2 x 0.8 mm (see image 3)

Thanks to its modular concept such a line can be adjusted to different applications even for production purposes. For example, the conversion of the machine from mono-lumen to a triple-lumen tube is possible within 15 min.

All parts of the machine can be removed quickly and can be cleaned easily. Parts guiding the extruded product, are made of special steel suitable for medical applications. Designed in a way that they are allowed to be used in clean rooms of the ISO class 8:

Extrusion line for the production of medical catheter tubes.

• Complete covering of all heating elements

• Encapsulated motors

• Smooth surfaces without cracks

The line has a central supply unit for air, water and electrical power. Only one external connection for the supply of the machine will be required, which is an important advantage if clean room conditions are specified.

The system consists of the following subassemblies:

Extruder

For a wide range of throughputs from 0.05 kg/h to 15 kg/h, the line is equipped with two extruders, which can be used either individually or within a co-extrusion set-up. For coatings of about 0.06 mm with low throughputs from 0.05kg/h to 1kg/h, an extruder with a screw diameter of 16 mm and L/D of 25 is provided. For the higher outputs an extruder with a screw ratio of 30 mm and L/D of 25 can be added integrated. Both extruders are equipped with AC-servo drives. Using pressure/speed control an absolutely constant melt flow rate over the whole rpm range of the extruders is achieved. The use of melt pumps, usually unacceptable for the FDA approval, can be avoided. Highly precise, digital probes with a bus system do their bit to improve the precision. For both extruders, screw geometries are available for processing of TPU, Pebax, POM or other polymers.

Extrusion Die

The die is mounted on a carriage, which enables easy handling for cleaning or change of dimensions. For the various tube geometries and coatings, exchange parts are available which can be mounted and cleaned easily. The die is designed in a way that residential and rinsing times are minimised. Short flow paths, the avoidance of dead zones, as well as a bypass valve for rinsing are necessary preconditions for a production free of degraded polymers and black spots.

Calibration and Cooling Tank

The easily adjustable vacuum calibration and cooling tank is suitable for the production of outer diameters in the range of 0.5 – 5 mm. A central supply unit in the calibration device comprises all required media, e.g. cleaned compressed air, cooling water and electrical power. The calibration itself is designed as disc calibration with close-toleranced discs available for each diameter. The control of the support air is carried out with high precision, by fine adjustable air regulators. They keep the set pressure constant at +/- 0,5% within the range of up to 100 mbar. The temperature of the circulating cooling medium is also regulated.

Haul-off unit with measurement of thickness and ovality

The haul-off unit is driven by two electronically synchronized AC servomotors. The haul-off speed is controlled via the two-axes-laser system for the measurement of diameters and ovality, ensuring close toleranced diameters. However, in case of non-compliance with the set tolerances, the marker and cutting system can distinguish between good and bad parts. Within certain limits, using this regulation, also conical hoses can be produced.

Winder

The winder includes, besides an adjustable changing unit, a tension control for setting the winding tension to the respective product sensitiveness. The adjustment of minimal winding forces avoids the loss of roundness, depending on sensitives of the polymer processed. A manually actuated coil enables the changing of the coil without using tools.

Unwinder with pre-heating oven

The unwinder is also equipped with a tension control. The control speed for unwinding is mastered by the haul-off unit. This ensures the continuous and constant unwinding of the support wire or the basic hose. In case an optimized bond between central wire and coating layer is required, the support wire can be pre-heated up to 250 °C.

Central control via the computer assisted control system

All parts of the extrusion line are linked via a central control system. This system collects and records all quality relevant parameters of the whole line. For each product, the customer can combine individual records, store and print them. A further module allows the creation and management of product-specific formulas which can be re-loaded when the production is restarted. The line automatically ramps up to the process setting.

Source: Dr. Collin GmbH