Patent Application
20090103074
The present application is directed to methods for performing quality control analyses, and more specifically to performing quality control analyses of a process to plasma treat a lubricant coated surface.
It is often beneficial to apply a coating to medical devices, such as syringes, vials, needles, and the like, to impart or enhance certain properties. For example, syringe barrels may be coated to enhance the lubricous properties of the barrel to allow a plunger to move smoothly within the barrel. In a variety of situations, the coating may require treatment after application in order to obtain the desired property. One example of treating a coating includes exposing the coating to an energy source, such as an ionizing gas plasma.
Syringe manufacturing lines may produce as many as 300 syringes per minute. Because each syringe has the potential to be used in a life threatening situation, quality control of the manufacturing process is critical. Crucial patient treatment time may be lost when a medical device fails in the field. Additionally, failure of the device may lead to inadequate delivery of treatment, which may place a patient's life at risk.
Current quality control methods may involve performing an analysis on a statistical sample of a batch of the medical devices. If the statistical sample passes, then the entire batch passes. However, such methods may overlook intermittent failures in the process and allow defective devices to pass inspection.
The present application is directed to methods for performing quality control analysis of a process to treat a surface of a workpiece. A sensor is placed in proximity to the surface, and a controller analyzes data obtained by analyzing a signal from the sensor. The controller may determine whether the process started properly, the presence of a lubricant on the surface, and the amount of the lubricant.
The present application is directed to methods for performing quality control analyses of a process to treat a lubricant coated surface of a workpiece. The workpiece including the lubricant coated surface is positioned in a treatment apparatus. A sensor is placed in proximity to the workpiece. As the process is started, an analyzing device analyzes a signal from the sensor and outputs data. A controller analyzes the data to first determine whether the process started properly. The controller then further analyzes the data to determine whether lubricant is present on the workpiece, as well as the amount of the lubricant.
One embodiment of the present application may be used with a treatment process utilizing an ionizing gas plasma to treat the lubricant on the surface of the workpiece. An exemplary process is presented in U.S. Patent Publication No. 2004-0231926 A1 filed on Mar. 2, 2004, which is herein incorporated by reference in its entirety. Glow discharge optical emission spectroscopy (GD-OES) may be used to analyze the emission spectrum of the plasma used to treat the lubricant coated surface. As the plasma is initially generated, atoms of the lubricant may be promoted to higher energy levels. As the atoms decay back to a lower energy level, electromagnetic radiation (i.e., light) is emitted. A characteristic emission spectrum is generated for each chemical species present in the plasma, or that is excited by the plasma. The characteristic emission spectrum may include peaks at specific wavelengths. These peaks may be detected by a device such as a spectrometer. The wavelength of the peaks, as well as the intensity of the peaks may be used to perform a quality control analysis of the treatment process.
In one embodiment, a quality control device comprises a sensor 14, an analyzing device 16, a connector 15 between the sensor 14 and the analyzing device 16, a second controller 17, and memory 18. The sensor 14 may be placed in proximity to the workpiece. The sensor 14 is operative to sense the spectrum emitted by the plasma and communicate with the analyzing device 16 by communicating a signal through the connector 15. The second controller 17 is operatively connected to the analyzing device 16 and receives a signal from the analyzing device 16. The second controller 17 may include memory 18 for storing operating parameters and instructions, or for storing data.
The sensor 14 may include a device capable of sensing the emitted spectrum and converting the emitted spectrum to an electronic signal. The electronic signal may then be transmitted by the connector 15 to the analyzing device 16. In one embodiment, the connector 15 is a fiber optic cable and no sensor 14 is used. The fiber optic cable may transmit the emitted spectrum to the analyzing device 16 with or without the sensor 14.
In one embodiment, the analyzing device 16 is a spectrometer. The spectrometer receives the emitted spectrum transmitted by the connector 15. As is well known in the art, the spectrometer measures the intensity of the emitted spectrum across a predetermined wavelength range. The spectrometer outputs data either directly to a user or to the second controller 17. The data may then be used to perform quality control analyses of the treatment process as detailed below.
Prior to initiating the treatment process (i.e., before the plasma is generated), a first reading may be taken by the analyzing device 16 of a background spectrum sensed by the sensor 14. In one embodiment, the analyzing device 16 determines the intensity of the background spectrum across a predetermined range of wavelengths. In another embodiment, the analyzing device 16 determines the intensity of the background spectrum at one or more predetermined wavelengths. The background spectrum intensity may be taken one time, or multiple times. Each background spectrum intensity value may be stored in memory 18.
The treatment process may be initiated by the first controller 20 sending a signal to energize the power supply 25. At this point, the power supply 25 may generate an electric field between the outer electrode 11 and the inner electrode, thereby igniting the plasma in the gas. If the plasma ignites properly, then the emission spectrum may vary from that detected during the background reading. Once the power supply 25 is energized, the second controller 17 obtains a second reading of the emitted spectrum from the analyzing device 16. The intensity of the emitted spectrum is then determined based on the second reading. The intensity is then compared to the background intensity value. If the intensity after energizing the power supply 25 exceeds the background intensity by more than a predetermined amount, then the second controller 17 determines that the plasma has ignited, and the treatment process is allowed to continue.
This step of the quality control method detects whether the plasma has initially ignited. Factors that may influence plasma ignition include electrical connection between the power supply 25 and the outer electrode 11 and the inner electrode, proper grounding of one of the electrodes, and the presence of the gas.
As described previously, lubricants may have more than one characteristic emission peak. In general terms, the lubricant may have an emission peak at a high characteristic wavelength and an emission peak at a low characteristic wavelength. The method of the present application uses a ratio of the intensity at the high characteristic wavelength to the intensity at the low characteristic wavelength to develop a more linear relationship that may be used for quality control purposes to estimate the amount of lubricant present on the workpiece 12. In one embodiment, the high characteristic wavelength may be in the range from about 550 nm to about 900 nm. In one embodiment, the low characteristic wavelength may be in the range from about 250 nm to about 550 nm.
For one embodiment,
The following table summarizes the peak intensities for the three amounts of lubricants at the high characteristic wavelength and the low characteristic wavelength. The ratio of the intensities indicates a more linear relationship. These values may be stored in the memory 18 of the second controller 17. As an emission spectrum is generated for each workpiece 12, the second controller 17 may calculate the ratio of the intensities at the characteristic emission peaks and compare the calculated value to the values stored in the memory 18. Based on the comparison, the workpiece 12 may be accepted if the ratio is at or above a predetermined target value. For example, using the data in the table below, a desired minimum amount of lubricant on the surface 13 of the workpiece 12 may correspond to a ratio of 7.72. A first workpiece 12 is treated and the ratio is calculated to be 3.50. The calculated ratio indicates that only about half (assuming a near linear relationship) of the minimum amount of lubricant was applied to the surface 13 of the workpiece 12, and the workpiece may be rejected. A second workpiece 12 is then treated and the ratio is calculated to be 7.65. The calculated ratio indicates that approximately the minimum amount of lubricant is present on the surface 13 of the workpiece 12, and the workpiece 12 may be accepted.
The analyzing device 16 receives a signal from the sensor 14 prior to beginning the treatment process and determines the intensity of the background emission spectrum sensed by the sensor 14 (506). The intensity background emission spectrum in one embodiment is measured across a range of wavelengths. In one embodiment, the background intensity is measured at one or more predetermined wavelengths. The background intensity value is stored in memory 18 (508).
The first controller 20 energizes the power supply 25 (510). After the power supply 25 is energized, the analyzing device 16 determines a second intensity of the emission spectrum sensed by the sensor 14 (512). The second controller 17 compares the second intensity to the background intensity value stored in memory 18 (514). If the second intensity is greater than the background intensity by at least a predetermined amount, then the second controller 17 determines that the plasma ignited properly (518). If the second intensity is less than or equal to the background intensity value, then the second controller 17 determines that the plasma did not ignite properly and the workpiece 12 may be rejected and/or the process may be stopped (516).
The analyzing device 16 then receives a signal from the sensor 14 and determines a third intensity of the emitted spectrum at one or more predetermined wavelengths (520). The second controller 17 compares the third intensity at the predetermined wavelength to a predetermined value (522). The predetermined value may be stored in memory 18 and represents the intensity of the emission spectrum when the plasma is ignited but no lubricant is present. If the third intensity is greater than the predetermined value, then the second controller 17 confirms the presence of the lubricant on the workpiece 12 (526). If the third intensity is less than the predetermined amount, then the second controller 17 may reject the workpiece 12 and/or may stop the process (524).
The analyzing device 16 continues to analyze the signal from the sensor 14, and determines the intensity of the emission spectrum at a predetermined high wavelength (528) and a predetermined low wavelength (530). The second controller 17 calculates the ratio of the intensity at the high wavelength to the intensity at the low wavelength (532). If the ratio is greater than or equal to a predetermined value (534), then the second controller 17 determines that the intended amount of lubricant was applied to the workpiece 12, and the workpiece 12 is accepted (538). If the ratio is less than the predetermined value, then the second controller 17 may reject the workpiece 12 and/or may stop the process. The method may then be repeated for one or more additional workpieces 12.
The outer electrode 11 may include a passage (not shown) from an outer surface to the workpiece 12 to an inner chamber in which the workpiece 12 has been placed for treatment. In one embodiment, the sensor 14 may be positioned in proximity to the workpiece 12 by inserting the sensor 14 into the passage. One embodiment may include more than one sensor 14, each positioned within a passage. The sensors 14 may be located at a variety of radial positions around the workpiece 12, as well as a variety of positions along a longitudinal axis of the workpiece 12. For embodiments where more than one sensor 14 is used, the second controller 17 may utilize the emission spectra from all of the sensors 14, a portion of the sensors 14, or one of the sensors 14 in the performance of the methods illustrated in
In addition to quality control, embodiments of the present application may also be used for process control. For example, during a production run, the ratio may be determined for each workpiece 12 processed. Over time, the ratio data may indicate that the amount of lubricant applied has been steadily decreasing. The process may then be adjusted based on this data to maintain the process within acceptable parameters.
The methods of the present application are not limited to determining a ratio between the intensity at a single high wavelength value and the intensity at a single low wavelength value. The second controller 17 may determine the intensity at a plurality of wavelengths and calculate more than one ratio. Quality control decisions of the methods disclosed may be based on more than one ratio and may involve calculations based on multiple ratios. In addition, calculations other than ratios may be performed.
One embodiment of the present application is applicable to a lubricant treatment process utilizing an ionizing gas plasma at about atmospheric pressure. An ionizing gas plasma at about atmospheric pressure is a plasma that is generated without the use of a vacuum pump or vacuum chamber. The treatment apparatus is essentially open to the surrounding atmosphere, and the plasma is generated at conditions essentially the same as the surrounding atmosphere. However, one skilled in the art will readily appreciate that the methods of the present application are equally applicable to plasma processes performed at any pressure.
One embodiment of the present application may be used with a plasma generated in a mixture of argon and helium gases. One skilled in the art will readily appreciate that embodiments of the present application are applicable to plasmas generated in a variety of gases. Example gases suitable for generating plasmas for use with the present application include, either individually or in combination, air, oxygen, nitrogen, helium, neon, argon, krypton, and radon.
The present application is applicable for a variety of lubricants treated with an ionizing plasma. While there are generally no limitations on the lubricant that may be used with the present application, exemplary lubricants include fluorochemical compounds, perfluoropolyether compounds, functionalized perfluoropolyether compounds, and polysiloxane-based compounds.
Spatially relative terms such as “under”, “below”, “lower”, “over”, “upper”, and the like, are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc. and are also not intended to be limiting. Like terms refer to like elements throughout the description.
As used herein, the terms “having”, “containing”, “including”, “comprising”, and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.
The present invention may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.
