WO2018217928A1

WO2018217928A1 - Dual channel feedback for ascertaining fiber bundle throughput

Info

Publication number: WO2018217928A1
Application number: PCT/US2018/034193
Authority: WO
Inventors: Scott Caldwell
Original assignee: Branson Ultrasonics Corporation
Priority date: 2017-05-26
Filing date: 2018-05-23
Publication date: 2018-11-29

Abstract

Methods and systems for determining the throughput of a fiber bundle are provided. A first optical sensor and a second optical sensor ascertain a series of baselines before general weld operation, wherein the first optical sensor ascertains only laser energy output directly from a laser source and the second optical sensor ascertains laser energy output directly from the laser source and laser energy reflected back through the fiber bundle. During general weld operation, the first optical sensor and the second optical sensor continue to measure their corresponding laser source outputs and provide these measurements to a control module. The control module compares the outputs against the baselines to determine whether the fiber bundle throughput falls below a threshold.

Description

DUAL CHANNEL FEEDBACK FOR ASCERTAINING FIBER BUNDLE THROUGHPUT

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62/51 1 ,472 filed on May 26, 2017. The entire disclosure of the above application is incorporated herein by reference.

FIELD

[0002] The present disclosure relates to plastics welding and, more particularly, relates to fiber bundle degradation assessment for laser plastics welding. BACKGROUND

[0003] This section provides background information related to the present disclosure which is not necessarily prior art.

[0004] Laser welding is commonly used to join plastic or resinous parts, such as thermoplastic parts, at a welding zone.

[0005] As is well known, lasers provide a semi-focused beam of electromagnetic radiation at a specified wavelength (i.e., coherent monochromatic radiation). There are a number of types of radiant sources available. One example of laser welding is Through Transmission Infrared (TTIr) welding, which is a favored technology for welding plastic or resinous parts. TTIr welding employs infrared laser light passed through a first plastic part and into a second plastic part. In many aspects, the tooling of TTIr assemblies includes fiber optic bundles and wave guides for directing infrared laser light from a light source to the plastic parts to be welded. Fiber optic bundles can degrade over time, resulting in lower-quality welds. Under many TTIr welding methods and other laser welding methods, the use of waveguides is prevalent. As is known, waveguides homogenize the infrared laser light and is positioned abutting the parts being welded; therefore measuring the throughput of the fiber optic bundle downstream of the waveguide is impractical. There is a need to automate measurement of the degradation of fiber optic bundles in laser welding systems so that fiber optic bundles degraded to a particular degree can be replaced while keeping the overall laser tooling relatively simple. SUMMARY

[0006] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0007] According to the principles of the present disclosure, it is desirable to determine the throughput of a fiber bundle to ensure proper welding and to take appropriate action as a result of that determination.

[0008] The present technology provides a method for ascertaining the throughput of a fiber bundle. The method includes establishing a plurality of baseline measurements of the fiber bundle throughput. The method further includes directing a laser source through the fiber bundle to a plurality of work pieces, wherein the work pieces reflect a portion of the laser energy along a path through the fiber bundle. A first optical sensor is positioned upstream of the fiber bundle and is free of the path in which the reflected potion travels. The first optical sensor detects energy directed from the laser source, and it outputs a first measured signal in response to a first measured amount of energy. A second optical sensor is positioned upstream of the fiber bundle and detects energy directed from the laser source and energy reflected from the work pieces. The second optical sensor outputs a second measured signal in response to a second measured amount of energy. A control module calculates the fiber bundle throughput based on a comparison of the baseline measurements to the first measured signal and the second measured signal. In other embodiments, the control module triggers an alarm signal if the fiber bundle throughput falls below a threshold. In yet other embodiments, the control module calculates a true laser output based on at least the calculated fiber bundle throughput. In further embodiments, the fiber bundle throughput is calculated based on the following relationship:

φ * D₃ \ _t=o

Fiber Bundle Throughput = R2 = 0 where

In variations of such further embodiments, a weld joint is rejected if the fiber bundle throughput is determined to fall below a threshold during welding of the weld joint.

[0009] The present technology also provides a feedback detection system for determining the throughput of a fiber bundle. The feedback detection system includes a laser source that outputs laser energy through a fiber bundle to a plurality of work pieces to be welded; the work pieces to be welded reflect a portion of the laser energy through the fiber bundle. A first optical sensor is upstream of the fiber bundle and detects the laser energy outputted from the laser source. The first optical sensor is offset from the direction in which the portion of the laser energy is reflected, and it outputs a first measured signal in response to a first measured amount of the laser energy. A second optical sensor is upstream of the fiber bundle and detects laser energy outputted from the laser source and the portion of the laser energy reflected from the work pieces. The second optical sensor outputs a second measured signal in response to a second measured amount of the laser energy. A control module is configured to receive the first measured signal and the second measured signal and calculate the fiber bundle throughput of the fiber bundle. In other embodiments, the control module is configured to generate an alarm signal if the fiber bundle throughput falls below a threshold. In yet other embodiments, the control module is configured to control the laser source in a closed control loop system. In further embodiments, the fiber bundle throughput is calculated based on the following relationship:

φ * D₃ \ _t=o

Fiber Bundle Throughput =— ^R2~° where

In variations of such further embodiments, the control module is configured to reject a weld if the fiber bundle throughput is determined to have fallen below a threshold during welding.

[0010] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

[0011] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. [0012] FIG. 1 is a schematic view illustrating a prior art Through Transmission Infrared (TTIr) welding system;

[0013] FIG. 2 is a schematic view illustrating a TTIr welding system using a dual channel feedback system according to an aspect of the present disclosure;

[0014] FIG. 3 is a schematic view illustrating an optional first measurement required to establish a throughput bundle output;

[0015] FIG. 4 is a schematic view illustrating a second measurement required to establish a throughput bundle output;

[0016] FIG. 5 is a schematic view illustrating a third measurement required to establish a throughput bundle output;

[0017] FIG. 6 is a flow chart of control logic for a control routine for determining the fiber optic throughput for a laser welder in accordance with an aspect of the present disclosure;

[0018] FIG. 7 is a flow chart of control logic for another control routine for determining the fiber optic throughput for a laser welder in accordance with another aspect of the present disclosure; and

[0019] FIG. 8 is a flow chart of control logic for yet another control routine for determining the fiber optic throughput for a laser welder in accordance with yet another aspect of the present disclosure.

[0020] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

[0021] Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific compositions, components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well- known technologies are not described in detail.

[0022] Although the terms first, second, third, etc. may be used herein to describe various steps, elements, components, regions, layers and/or sections, these steps, elements, components, regions, layers and/or sections should not be limited by these terms, unless otherwise indicated. These terms may be only used to distinguish one step, element, component, region, layer or section from another step, element, component, region, layer or section. Terms such as "first," "second," and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first step, element, component, region, layer or section discussed below could be termed a second step, element, component, region, layer or section without departing from the teachings of the example embodiments.

[0023] Example formula are presented herein demonstrating active steps at time t₀ and ending at t_x relating to a particular sensor, where x is an integer relating to the time number (e.g. , t₇ means time seven at that particular sensor). Further, the example formula presented herein demonstrate measurements (i.e. , readings) at R₀ and end at R_y relating to a particular sensor, where y is an integer relating to the measurement condition (e.g. , R₇ means the seventh measurement condition at that particular sensor).

[0024] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0025] The technology according to the present disclosure provides methods, apparatuses, and work pieces for use in Through Transmission Infrared (TTIr) welding such as the prior art Through Transmission Infrared (TTIr) welding system shown in Fig. 1. It should be understood, however, that the scope of the disclosure extends to any laser welding method or apparatus that may benefit from ascertaining the throughput of a fiber optic bundle. TTIr welding generally involves directing infrared laser light 100 from one or more laser sources 102 through at least an optical device, such as at least a lightguide, at least a waveguide, and/or at least a fiber optic member, to plastic parts to be welded. In many aspects, a first plastic part 110 is transmissive to infrared laser light, thereby permitting the infrared laser light to pass therethrough. A second plastic part 112, on the other hand, is absorptive to infrared laser light and converts the absorbed infrared laser light to heat and in turn melts the first plastic part and the second plastic part at weld joint 114 resulting in the parts being welded together. Alternatively, if both plastic parts are transmissive to infrared laser light, an absorptive medium is positioned at weld joint 114 such that at least a portion of infrared laser light 100 directed from one or more laser sources 102 is absorbed by the medium and converted to heat, which in turn melts the plastic parts causing them to be welded together. According to the technology of the present disclosure, controlling the true output of laser source 102 reaching the plastic parts is desirable to ensure a proper and consistent weld.

[0026] Referring now to FIG. 2, in some embodiments, a feedback detection system 12 is employed to provide feedback information in a TTIr laser plastics welding system 10 to monitor the laser intensity downstream from a laser source 14 (which can be similar or identical to laser source 102). Feedback detection system 12 comprises a first optical sensor 15 and a second optical sensor 16, each of which is positioned downstream from laser source 14, yet upstream from fiber optic member 18, which comprises a fiber bundle. In some embodiments, feedback detection system 12 further includes control module 17, which is operably connected in electrical communication with first optical sensor 15 and second optical sensor 16 for receiving real-time laser intensity information from laser source 14. In additional embodiments, control module 17 further includes an alarm.

[0027] Prior to monitoring fiber bundle throughput during general weld operation, several baselines must be assessed, which can be done in any order. These baselines may be undertaken manually (e.g., with a user placing applicable sensors and applicable weld apparatus components in the locations necessary for ascertaining the baselines) or automatically (e.g., with a robot or other automated machine placing applicable sensors and applicable weld apparatus components in the locations necessary for ascertaining the baselines). Further, the measurements may be similarly taken manually or automatically. First, with reference to FIG. 3, the output of laser source 14 is assessed, which is accomplished by measuring the output of laser source 14 at first optical sensor 15 and at fiber optic start location sensor 22 (where fiber optic member 18 would begin; in other words, fiber optic member 18 and waveguide 20 are removed for this particular measurement) (referred to herein as a "first baseline"). The measurements of first optical sensor 15 and fiber optic start location sensor 22 are stored (e.g., in control module 17) as follows:

[0028] D₄ \_t=0 = measurement of laser output at fiber optic start location sensor 22 with no fiber bundle and no waveguide tooling at setup; and

[0029] D₂ \ t=o = measurement of laser output at first optical sensor 15 with no

R1 = 0

fiber bundle and no waveguide tooling at setup.

[0030] Notably, this first baseline is optional if laser plastics welding system 10 will be used exclusively as a closed control loop, as explained more fully below, and if the actual throughput of fiber optic member 18 must be independently determined. [0031] Second, with reference to FIG. 4, a second baseline measures the initial throughput of fiber optic member 18, which is accomplished by measuring the output of laser source 14 at first optical sensor 15, second optical sensor 16, and at fiber optic end location sensor 24 (where fiber optic member 18 ends; in other words, waveguide 20 is removed for this particular measurement) (referred to herein as a "second baseline"). The output of laser source 14 is fired at an intensity identical to that used to determine the first baseline above, such that the first optical sensor 15 measures the same value as the first baseline described above. Second optical sensor 16 measures both the laser energy provided by laser source 14 and the laser energy reflected back through fiber optic member 18 from fiber optic end location sensor 24 as second optical sensor 16 is positioned such that said second optical sensor 16 detects laser energy reflected through fiber optic member 18 from fiber optic end location sensor 24. Notably, first optical sensor 15 is positioned at a location offset from and therefore free from the path in which light is reflected through fiber optic member 18 from fiber optic end location sensor 24. The measurements of first optical sensor 15, second optical sensor 16, and fiber optic end location sensor 24 are stored (e.g., in control module 17) as follows:

[0032] D \ t=o = measurement of laser energy detected at second optical sensor

R2 = 0

16 with fiber bundle attached but no waveguide tooling at setup;

[0033] D₂ \ t=o = D₂ \ t=o = measurement of laser energy detected at first optical

R2 = 0 R1 = 0

sensor 15 with fiber bundle attached but no waveguide tooling at setup; and

[0034] D₃ \ t=o = measurement of laser energy detected at fiber optic end location

R2 = 0

sensor 24 with fiber bundle attached but no waveguide tooling at setup.

[0035] Third, with reference to FIG. 5, a third baseline measures the throughput of fiber optic member 18 with waveguide 20 attached to fiber optic member 18, which is accomplished by measuring the laser energy detected by firing laser source 14 at an intensity identical to that used to determine the first baseline and second baseline described above, such that the first optical sensor 15 measures the same value as the first baseline measurement described above (referred to herein as a "third baseline"). In other words, the first optical sensor 15 is yet positioned at a location offset from and therefore free from the path in which light is reflected through fiber optic member 18 from waveguide end location sensor 26. Second optical sensor 16, however, measures not only the laser energy provided by laser source 14 but also laser energy reflected back through fiber optic member 18 from waveguide end location sensor 26. The measurements of first optical sensor 15, second optical sensor 16, and waveguide end location sensor 26 are stored (e.g., in control module 17) as follows:

[0036]

measurement of laser energy detected at second optical sensor 16 with fiber bundle and waveguide tooling in place at setup;

[0037] £½ l_t=o = D₂ \ t=o = D₂ \ t=o = measurement of laser energy detected at

R2=0 R1=0

first optical sensor 15 with fiber bundle and waveguide tooling in place at setup; and

[0038] D₃ \_t=0 = measurement of laser energy detected at waveguide end location sensor 26 with fiber bundle and waveguide tooling in place at setup.

[0039] After calculating the first baseline (if necessary and/or desired), the second baseline, and the third baseline, and during general weld operation, laser energy from laser energy source 14 is measured by first optical sensor 15 and second optical sensor 16, and energy reflected back into fiber optic member 18 is measured by second optical sensor 16, such that the fiber bundle throughput can be calculated by the following:

φ * D₃ \ t=o

Fiber Bundle Throughput = R2 = 0

[0040] Where:

[0041] FIG. 6 is a flow chart of control logic for an example control routine implemented in control module 17 for determining the throughput of fiber optic member 18 using the first baseline, second baseline, third baseline (collectively, the "three baselines"), and subsequent active weld measurements disclosed herein. The control routine starts at 600 and proceeds to 602 to ascertain the first baseline. The control routine proceeds to 604 to ascertain the second baseline. The control routine proceeds to 606 to ascertain the third baseline. Notably, in certain embodiments, ascertaining the first baseline is optional. Also notably, establishing the three baselines may be done in any order. The control routine proceeds to 608 where it checks whether the three baselines (unless the first baseline need not be established) have been ascertained. If not, the control routine branches back to 602. If so, the control routine proceeds to 610, where it is ready for active welding. Welding 612 begins. During welding, control module 17 receives measurements from first optical sensor 15 and second optical sensor 16 at 614. Control module 17 calculates the fiber bundle throughput based on the baseline measurements described above and the measurements received from first optical sensor 15 and second optical sensor 16 at 616. The control routine then proceeds to 618, where it determines whether the calculated fiber bundle throughput falls below a threshold. If the fiber bundle throughput falls below the predetermined threshold, control module 17 issues an alarm indicating same at 620. After issuing the alarm or determining no alarm is required, the control routine proceeds to end 622.

[0042] In further embodiments, feedback detection system further includes a closed control loop, as described in US Pat. No. 7,343,218, which is commonly owned by the same assignee and is incorporated herein by reference. More specifically, it is contemplated that control module 17 according to the present disclosure may act as control module 17 for purposes of providing the closed control loop disclosed in the '218 patent, that second optical sensor 16 according to the present disclosure may act as optical sensor 16 for purposes of providing the closed control loop disclosed in the '218 patent, and laser source 14 according to the present disclosure may act as laser source 14 for purposes of providing the closed control loop disclosed in the '218 patent. In such an arrangement, it is further contemplated that control module 17 and laser source 14 would also be in electrical communication with one another.

[0043] It is further contemplated that in embodiments where closed loop control is utilized, the true laser output of the laser source, taking into account any degradation of fiber optic member 18, may be assessed as follows:

Output = φ * £>₃

\ t=o

[0044] The true laser output value can be used to adjust the power of laser source 14 in accord with the teachings of the '218 patent. FIG. 7 is a flow chart of control logic for an example control routine implemented in control module 17 for determining the throughput of fiber optic member 18 using the three baselines and subsequent active weld measurements disclosed herein and subsequently determining to alter the power of laser source 14. The control routine starts at 700 and proceeds to 702 to ascertain the first baseline. The control routine proceeds to 704 to ascertain the second baseline. The control routine proceeds to 706 to ascertain the third baseline. Notably, in certain embodiments, ascertaining the first baseline is optional. Also notably, establishing the three baselines may be done in any order. The control routine proceeds to 708 where it checks whether the three baselines (unless the first baseline need not be established) have been ascertained. If not, the control routine branches back to 702. If so, the control routine proceeds to 710, where it is ready for active welding. Welding 712 begins. During welding, control module 17 receives measurements from first optical sensor 15 and second optical sensor 16 at 714. Control module 17 calculates the fiber bundle throughput based on the baseline measurements described above and the measurements received from first optical sensor 15 and second optical sensor 16 at 716. The control routine then proceeds to 718, where it calculates the true laser output from laser source 14. The control routine then proceeds to 720, where the power level of laser source 14 is adjusted if necessary (e.g., if the true laser output is determined to be below a predetermined threshold). After adjusting the power level if necessary, the control routine proceeds to end 722.

[0045] According to certain embodiments, when the fiber bundle throughput drops below a certain desired threshold, an alarm is provided to indicate fiber optic member 18 should be replaced.

[0046] In yet other embodiments, control module 17 adjusts the output of laser source 14 in response to changing efficiencies of fiber optic member 18. By way of nonlimiting example, if fiber optic member 18 is operating at 90% efficiency, the power level of laser source 14 is adjusted to about 1 1 1 %. Further, it is contemplated that control module 17 further directs the power level of laser source 14 to accommodate fluctuations detected as a result of running a closed control loop system. Returning to FIG. 7, the control routine starts at 700 and proceeds to 702 to ascertain the first baseline. The control routine proceeds to 704 to ascertain the second baseline. The control routine proceeds to 706 to ascertain the third baseline. Notably, in certain embodiments, ascertaining the first baseline is optional. Also notably, establishing the three baselines may be done in any order. The control routine proceeds to 708 where it checks whether the three baselines (unless the first baseline need not be established) have been ascertained. If not, the control routine branches back to 702. If so, the control routine proceeds to 710, where it is ready for active welding. Welding 712 begins. During welding, control module 17 receives measurements from first optical sensor 15 and second optical sensor 16 at 714. Control module 17 calculates the fiber bundle throughput based on the baseline measurements described above and the measurements received from first optical sensor 15 and second optical sensor 16 at 716. The control routine then proceeds to 718, where it calculates the true laser output from laser source 14. The control routine then proceeds to 720, where the power level of laser source 14 is adjusted if necessary (e.g. , if fiber optic member 18 is operating at 90% efficiency as described above). After adjusting the power level if necessary, the control routine proceeds to end 722.

[0047] In certain other embodiments, a method of determining whether a weld joint is acceptable is disclosed. More specifically, control module 17 monitors the fiber bundle throughput during weld processes of work pieces, such as first plastic part 110 and second plastic part 112. When control module 17 detects that fiber optic member 18 is operating below a desired threshold efficiency, control module 17 generates a rejection signal indicating that weld joint 114 is unsatisfactory and the work pieces should be discarded. In other embodiments, control module 17 first attempts to salvage the weld by adjusting the output of laser source 14. If deemed unsalvageable based on applicable criteria, control module 17 then generates a rejection signal.

[0048] FIG. 8 is a flow chart of control logic for an example control routine implemented in control module 17 for determining the throughput of fiber optic member 18 using the first baseline, second baseline, third baseline (collectively, the "three baselines"), and subsequent active weld measurements disclosed herein. The control routine starts at 800 and proceeds to 802 to ascertain the first baseline. The control routine proceeds to 804 to ascertain the second baseline. The control routine proceeds to 806 to ascertain the third baseline. Notably, in certain embodiments, ascertaining the first baseline is optional. Also notably, establishing the three baselines may be done in any order. The control routine proceeds to 808 where it checks whether the three baselines (unless the first baseline need not be established) have been ascertained. If not, the control routine branches back to 802. If so, the control routine proceeds to 810, where it is ready for active welding. Welding 812 begins. During welding, control module 17 receives measurements from first optical sensor 15 and second optical sensor 16 at 814. Control module 17 calculates the fiber bundle throughput based on the baseline measurements described above and the measurements received from first optical sensor 15 and second optical sensor 16 at 816. The control routine then proceeds to 818, where it determines whether the calculated fiber bundle throughput falls below a threshold. If the fiber bundle throughput falls below the predetermined threshold, control module 17 instructs rejection of the weld. After determining whether rejecting the weld is required, the control routine proceeds to end 822. [0049] Control module 17 can be or includes any of a digital processor (DSP), microprocessor, microcontroller, or other programmable device which are programmed with software implementing the above described logic. It should be understood that alternatively it is or includes other logic devices, such as a Field Programmable Gate Array (FPGA), a complex programmable logic device (CPLD), or application specific integrated circuit (ASIC). When it is stated that control module 17 performs a function or is configured to perform a function, it should be understood that control module 17 is configured to do so with appropriate logic (such as in software, logic devices, or a combination thereof), such as control logic shown in the flow charts of FIGS. 6 - 8. When it is stated that control module 17 has logic for a function, it should be understood that such logic can include hardware, software, or a combination thereof.

[0050] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

CLAIMS What is claimed is:

1 . A method for ascertaining the throughput of a fiber bundle, the method comprising:

establishing a plurality of baseline measurements of the fiber bundle throughput; directing a laser source through said fiber bundle to a plurality of work pieces, wherein said work pieces reflect a portion of the laser energy along a path through said fiber bundle;

positioning a first optical sensor upstream of said fiber bundle and free from the path in which the reflected portion travels, wherein the first optical sensor detects energy directed from said laser source, wherein said first optical sensor outputs a first measured signal in response to a first measured amount of said energy;

positioning a second optical sensor upstream of said fiber bundle, wherein the second optical sensor detects energy directed from said laser source and said energy reflected from said work pieces, wherein said second optical sensor outputs a second measured signal in response to a second measured amount of said energy; and

calculating the fiber bundle throughput with a control module based on comparing said baseline measurement to the first measured signal and the second measured signal.

2. The method of claim 1 , wherein the control module triggers an alarm signal if the fiber bundle throughput falls below a threshold.

3. The method of claim 1 , wherein the control module calculates the true laser output based at least on the calculated fiber bundle throughput.

4. The method of claim 1 , wherein the fiber bundle throughput is calculated based on the following relationship:

φ * D₃ \ _t=o

Fiber Bundle Throughput =— ^R2~° where

5. The method of claim 4, wherein a weld joint is rejected if the fiber bundle throughput is determined to fall below a threshold during welding of the weld joint.

6. A feedback detection system for determining the throughput of a fiber bundle, the feedback detection system comprising:

a laser source outputting laser energy through a fiber bundle to a plurality of work pieces to be welded, said work pieces to be welded reflecting a portion of the laser energy through said fiber bundle;

a first optical sensor upstream of the fiber bundle and detecting said laser energy outputted from said laser source and offset from the direction in which the portion of the laser energy is reflected, said first optical sensor outputting a first measured signal in response to a first measured amount of said laser energy;

a second optical sensor upstream of the fiber bundle and detecting said laser energy outputted from said laser source and said portion of the laser energy reflected from the work pieces, said second optical sensor outputting a second measured signal in response to a second measured amount of said laser energy; and

a control module configured to receive said first measured signal and second measured signal and calculate the fiber bundle throughput of said fiber bundle.

7. The feedback detection system of claim 6, wherein the control module is configured to generate an alarm signal if the fiber bundle throughput falls below a threshold.

8. The feedback detection system of claim 6, wherein the control module is configured to control the laser source in a closed control loop system.

9. The feedback detection system of claim 6, wherein the fiber bundle throughput is calculated based on the following relationship:

φ * D₃ \ _t=o

Fiber Bundle Throughput =— ^{R2 ~}° where

10. The feedback detection system of claim 9, wherein the control module is configured to reject a weld if the fiber bundle throughput is determined to have fallen below a threshold during welding.