Since the early days of the man-made fiber industry, it has been recognized that the spinneret is one of the most important components in insuring successful production. Fiber uniformity, essential for end-user applications, rests on capillary geometry.
Over the years, much effort has been spent to try to control spinneret quality from the time of its initial manufacture, through the demands of day-today production. In recognition of this, spinneret inspection has played a key role in achieving consistent high quality fiber production.
Many different inspection technologies have been tried over the years. These can broadly be classified into two categories: contact and non-contact inspection.
In the case of contact inspection, a probe is pushed against the spinneret surface and air or oil is then pumped through the capillary. Deviations in the expected flow are recorded.
Although these methods try to approximate the flow of polymer through the capillary, they are often impractical in a production environment due to the difficulty in maintaining a constant viscosity of the oil or air (temperature and/or humidity dependent), leakage of the seal to the spinneret surface, and the slow, sometimes messy, nature of the inspection. In addition, due to the fact that a probe must firmly touch the surface, there exists the possibility that the inspection process itself may damage the spinneret.
In recent years, non-contact systems employing video based microscopes have been introduced with remarkable success. These systems provide rapid and repeatable measurements involving a minimal amount of spinneret handling. In addition a wide variety of measurements impossible with other techniques are easily available.
The SpinTrak™ System
An example of such a system employing state-of the-art vision technology is the SpinTrak™ family of spinneret inspection systems. They are specifically designed to provide synthetic fiber producers with unmatched speed, accuracy and repeatability for spinneret inspection.
The system is a robust, user-friendly spinneret measurement device designed to be used by both engineering and production personnel alike. It features fully automatic inspection of capillaries as small as 0.020mm to as large as 6mm in diameter.
Three SpinTrak™ models are available to accommodate round spinnerets as small as 10mm in diameter to rectangular spinnerets as large as 500mm x 5500mm. An unlimited number of capillaries on each spinneret can be inspected at rates from 0.3 seconds to 1.25 seconds per capillary.
In the following paragraphs we will illustrate some examples of the measurements possible and their impact on fiber quality.
Types of Measurements
Back light Inspection. For each capillary five basic measurements are made:
- Total Open Area
- Maximum Diameter
- Minimum Diameter
- Profile (a curvature indicator)
These measurements are good for finding defects such as dirt and out of round capillaries and surface damage caused by the impact of tools or poor Spinneret handling.
Spinneret manufacturing defects such as capillaries that are not drilled perpendicular to the surface can be detected by pronounced shading around one side of the capillary.
SubCapillary inspection can easily measure features of complex shaped capillaries. Leg length and width or lobe radius can be automatically inspected. Yarn characteristics are directly related to this geometry.
Edge wear, characterized by uneven rounded edges, can also be automatically detected.
Front light Inspection
This type of inspection can find capillary edge wear caused by polymer flow or poor cleaning techniques, as well as edge chips and fractures caused by thermal shock, metal fatigue or other metallurgical problems. In addition, inorganic deposits such as TiO2 can be seen.
Back-Front light Inspection.
By inspecting the capillary first with back light, then with front light, the worn edge (seen in the black ring above) can be measured. This allows an objective determination of wear to be made.
Capillary Depth Inspection.
By inspecting the beginning of the capillary in the counterbore, and then the exit at the spinneret surface, the length of the capillary can be measured. Capillary length uniformity can then be found.
All SpinTrak™ models are fully automatic and come complete with a spinneret platform, a motorized microscope magnification system, and Windows 7 Professional based system controller running SpinTrak™ software.
To start, spinnerets are loaded onto the inspection platform, the serial numbers are entered, and automatic inspection begins. Using its advanced machine vision technology, the SpinTrak™ inspects 100% of the capillaries on each spinneret, magnifying and independently calculating measurements for each capillary.
Based on such criteria such as the tolerance base for each measurement, the number of allowable failed capillaries per spinneret, and the number of allowable plugged capillaries, each spinneret can simply be qualified as either (Passed) or (Failed). In addition, SpinTrak™ provides graphs and pictorials of capillary data, helping to identify cleaning and extrusion problems.
Before each inspection run, the SpinTrak™ automatically calibrates the optical measurement system, assuring high accuracy and repeatability. Also, when new spinneret types are added to the production process, SpinTrak™ automatically learns the capillary locations by scanning the surface at low magnification.
These and other essential features, in a user-friendly software environment, allow fiber producers total control over spinneret inspection.