Additionally, this absence of data makes it difficult to study the potentially causal relationship between risk factors and injury, to validate the redesign of tasks, or to identify high-risk techniques for performing a specific task.
Therefore, many reasons justify this systematic review, because it detects the technologies used in the instrumented knives and the limitations of the studies; making it possible to create guidelines to build an instrumented knife that can reliably measure the force applied during cutting.
This systematic review aimed to identify the characteristics and measured variables of instrumented knives, and to determine how they should be designed. Additional records were identified in the screening step of this research through an analysis of the articles' references included for eligibility. The principles of PICO were used population, intervention, comparison, and outcomes to group the search terms. The following filters were used for the subject area: ergonomics, medicine, engineering industrial, biomedical, electrical electronic, manufacturing and mechanical , robotics, health professions, material science, multidisciplinary and public environmental occupational health, according to availability in the database.
The exclusion criteria were studies that used apparatus with blade or knife, not a hand tool; those that approached cutting meat using robots; and finally, no studies with cutting manual task using knife. When in doubt of eligibility, the full text was reviewed. In the cases of any disagreement between the two reviewers, a decision was reached by consensus, or a third researcher provided further review and the decision was made by arbitration.
The NIH website NIH, [ 24 ] provides the assessment tools and guidance for determining the quality of each type of study containing explanatory information about each item that should be analyzed in the paper. The quality rating was classified as good, fair, or poor, allowing the general analysis of the evaluators considering all the items NIH, [ 24 ].
According to Wong et al. The quality studies that allowed internal and external validity criteria were used Sanderson et al. Two independent reviewers accomplished the data extraction and review process, in cases of disagreement; consensus was reached through discussion between them or through arbitration with a third reviewer. The following study's characteristics were extracted and described: authors' names, title of the article, publication year; country where the study was conducted; design and objective of the study; characteristics of participants; environment of data acquisition laboratory or company ; what product was cut; type of hand cutting knife same as used by workers in the company, wireless or not, weight ; outcomes measured by the knife; follow up and results.
The search results included potentially eligible studies. Additional studies 36 were included after searching in the eligible article references, totaling 69 full texts for evaluation. After reviewing them, 55 studies were ineligible, ending the process with 14 studies for quality assessment Figure 1 Fig. The collections of the 14 final studies were performed only in a laboratory 6 , in meat packing and meat processing plants 6 and in both environments 2 , involved four types of instrumented knives, additionally, included three countries: United States, New Zealand and Denmark Table 1 Tab.
Only two studies' design types were found in this review, however, the majority were controlled intervention studies 9 as randomized, a randomized trial, a randomized clinical trial, or a Randomized Control Trial - RCT Table 1 Tab.
Four types of knives were identified by the study, which will be detailed later in Table 3. Table 2 Tab. The analysis showed that most of the papers have fair 11 methodological quality and do not have research with good classification.
Thus, in the cross-sectional studies, the population was not specified, the participation rate of eligible persons was less than half; the sample size justification was not provided; the variable measures were not obtained prior to the outcomes; the time frame was insufficient to see an association between exposure and outcome; a single assessment was made; the outcome assessors were not blinded, and finally, potentially confounding variables were not measured and adjusted statistically.
Four instrumented knives were found in the review, where IK-A was the most used in the research 9 and the only ones that had gone through a validation process, are described in Murphy et al. All knives used some type of electrical connection via cable or wire and were not completely the same as the tool used daily by the worker. During data collection, if there was a module attached to the knife user's body, no study cited battery life hours, days or any kind of radio frequency transmission.
The tool characteristics are described in Table 3 Tab. Table 4 Tab. The grip force standard deviation varied among the studies found, the peak was The same occurred with the peak cutting moment, it was For McGorry [ 12 ] , the working range exceeded N for gripping forces, and 28 and 16 Nm for the two applied moment axes, with the upper limits of these variables being larger than the studies presented. The knife forces may vary between-subject differences by site, performing the same meat cutting tasks, within-subject differences by cut, and cut-by-site Waddell et al.
Corroborating results of mean and peak cutting moments were 4. The study by Juul-Kristensen et al. They established that the cutting forces were significantly higher during the cutting task compared to the isolated cutting task. However, there was a small intra-individual coefficient of variation during the 50 cuts in the cutting task. On the other hand, McGorry et al. Different factors interfere in applied force; one of them is the work pace.
McGorry et al. Another factor is the workers' experience level of the task. For McGorry et al. Pontonnier et al. In the study by Juul-Kristensen et al. Task and person-related factors were found to influence the power required to perform the task McGorry et al.
In the development of cutting measurement equipment, according to McGorry et al. The results showed that with a bent blade, the required grip force was significantly higher, Likewise, a significant difference was also found for the effect of cut complexity, with a complex cut as The the workstation configurations and the direction that the cut is made affects the working posture.
The height decrease of the workbench tended to lower the muscle activation levels, except for the deltoideus medialis Pontonnier et al. Analyzing the posture during the cutting task at four workbench heights, Pontonnier et al.
Waddell et al. The optimal bench height for the meat-cutting task requiring force of approx. The surface height had a significant effect on the grip force requirements, but the magnitude of the difference was around 2 N McGorry et al. As reported by McGorry et al. Blade sharpness was found to effect grip forces, cutting moments, and cutting time, with sharper blades requiring statistically and significantly lower peak and mean cutting moments, and grip forces than dull knives McGorry et al.
Therefore, efforts to provide and maintain sharp blades can have a significant impact on force exposure McGorry et al. In one of the two analyzed tasks, McGorry et al. This corroborates the findings of Waddell et al. Dempsey and McGorry [ 6 ] verified considerable variations among workers in the sharpness differences between the initial reading and 2- and 5-hour readings, which could lead to different levels of exposure.
Based on the results of this study, the specific research questions are answered as follows:. All knives used some type of electrical connection via cable or wires, even the most recent study Pontonnier et al. Of the 14 studies, 6 were exclusively in the laboratory and 6 exclusively on the factory floor, with 2 studies in both locations. Cutting force; cutting torque; cutting time; grip force and number of cutting cycles per time. By analyzing related articles it is possible to understand which instrumentalization action of instrumenting characteristics can interfere during data acquisition in the real environment of developing the workers' tasks.
In this sense, the instrumentalization of manual cutting tools should consider some basic points: the visual non-mischaracterization of the tool, that is, maintaining the original features of the knife.
When boarding an electronic system in a tool, there should be no increase in weight or change in the center of mass. Essential questions for this approach are the use of wireless data transmission and battery charging via magnetic induction. In this research field, there would be instrumentation entirely associated with the work tool and imperceptible by the worker.
In this regard, deeper studies without adjacent variables should be performed. Reliable data acquisition of the task would be one example since the worker does not experience physical and psychological interference due to the tool's instrumentalization.
Physical, in terms of obstructing the natural movement. By altering the shape of the cable and adding an electric cable or electrical connection wires would change the weight and center of mass. Psychological, in the sense of removing the spontaneity of the movement by knowing that it is being observed and measured. The cutting force between the tool and the workpiece causes small motions of the top plate relative to the bottom plate proportional to the stiffness of the load cells.
That small motion deforms the load cell, and the deformation produces the measurement signal. As useful as the table-type dynamometer is, it has limitations. It consumes some of the workspace. The piezoelectric components are sensitive to the presence of fluids, so the gap between the plates must be sealed. The piezoelectric crystals are all slightly different, and the differences combined with the slight misalignments of the load cells change the resulting sensitivity of the dynamometer in the coordinate directions of the table.
Therefore, the dynamometer must be calibrated. However, the most vexing problem—bandwidth—derives directly from the principle of operation.
Because the piezoelectric elements must deform to produce a signal, they are flexible but stiff springs. The top plate has mass, so the dynamometer is a mass sitting on springs.
It has a natural frequency at which it would like to vibrate. It has a frequency response function, which means that the dynamometer amplifies or attenuates the signal, depending on the frequency of the cutting force Figure 2. If the frequency of the cutting force is low, then the cutting force signal is faithfully transmitted by the dynamometer. If the frequency of the cutting force is close to the natural frequency of the dynamometer system, the cutting force signal is amplified—sometimes greatly.
If the cutting force is far above the natural frequency of the dynamometer system, the cutting force signal is attenuated—sometimes greatly. Therefore, dynamometer builders try to place the natural frequency as high as possible. They choose very stiff load cells and install them with a high preload. They try to make the mass of the top plate as low as possible. Typical dynamometer manufacturers quote bandwidths the range of the useful leftmost oval in Figure 2 from 2, to 3, Hz.
Dynamometer users should be aware, however, that the quoted band width is with no load on the top plate. The workpiece and mounting hardware add mass to the top plate and lower the natural frequency, moving the peak in the figure to the left and reducing the useful bandwidth. For practical aplications, the natural frequency with the workpiece mounted is often well below 1, Hz.
For a spindle rotating at 24, rpm, and holding a tool with two teeth, the tooth passing frequency is Hz, so the peak in the figure needs to be substantially higher than that. The dynamometer bandwidth limitation is one of the major reasons that cutting force measurements are not typically available in production machine tools.
About the Author: Dr. This optional attachment greatly expands the range of materials the Force is capable of cutting and engraving. For example, they have difficulty recognizing registration marks in low-contrast situations. This grants us the ability to do both automatic and manual print and cuts as well as easily calibrate any combination of accessories in the dual cutting heads.
Plus, you can seamlessly switch from one device to another. Send the file from your PC or Mac, then switch to your smartphone or tablet, while standing right next to the cutter! We wanted the KNK Force to be a true network device. The built-in storage and drop down table allows you to store all of your tools, blades, blade holders and other goodies, to help keep your work space clutter free!
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