Abstract
In this research, a device for peeling green almond skins with the ability to use single-phase electricity. This study aims to design and evaluate an almond peeling machine. The mechanical design of the machine components was carried out based on design principles Three variables including the rotational speed of the drum, its distance from the concave, and the thickness of the rubbers were selected as the test factors. Statistical analysis showed that the rotary speed of the crusher and its distance from the concave significantly affected the peeling efficiency (with a confidence level of 1%). Taguchi analysis indicated that the ranks of 1 to 3 were obtained for the factors of impactor speed, distance between impactor and concave, and rubber thickness on the capacity of the device respectively. In relation to comparing the effect of the factors of the speed of the threshing machine, the distance between the threshing machine and the concave and the thickness of the rubbers on the percentage of almond breakage by the device, shows the ranks 1 to 3 for these three factors, respectively. The device was successfully designed and built and its performance was evaluated based on practical needs and application expectations. The results showed that the designed device was able to achieve the intended goals well.

Introduction
Post-harvest processing of almonds involves removing the outer green skin (hull) from the almonds, which is an important step in product preparation. The moisture content of the green skin has a significant impact on the ease and quality of peeling. Almond kernel breakage is considered as one of the key indicators in the process of evaluating product quality. Cracking or breaking of the hard shell of almonds can cause mechanical damage such as breakage or scratches on the kernel, which ultimately leads to a decrease in the marketable quality of the product. The design and development of an almond peeling machine is considered an important technical need, given the increasing need for mechanization in agricultural processes. This machine reduces production costs by improving the speed and accuracy of the peeling process. Green almond shellers are mainly designed based on the principles of controlled abrasion and impact. The most common design of these machines consists of a shelling cylinder in which the almonds are guided into a horizontal lattice or cage cylinder. This study aims to design and evaluate an almond peeling machine. This device is designed to be able to operate with single-phase and three-phase electricity, combustion engines, and tractor power, making it easy for farmers and gardeners to use. It has the ability to separate the green skin of almonds from their hard skin, and to clean all types of stone and paper almonds.
Material and Methods
In this research, a device for peeling green almond skins with the ability to use single-phase electricity, a combustion engine, or a tractor's power axle was designed, manufactured, and evaluated. The main components of the machine include the chassis, feed hopper, thresher, concave, carrying handles, tractor attachment arms, bearings, and carrier wheels. Three variables including the rotational speed of the drum, its distance from the concave, and the thickness of the rubbers were selected as the test factors. In evaluating the performance of the device, the effect of the parameters of the agitator rotational speed at three levels (150, 300, and 540 rpm), the distance of the agitator from the grooved cylinder at three levels (20, 30, and 50 mm), and the thickness of the rubber at three levels. ‌Surface (60, 80, and 100 mm) was evaluated in a factorial design based on randomized complete blocks on peeling efficiency and fracture percentage of almond kernels.
Results and Discussion
The mechanical design of the machine components was carried out based on design principles and was manufactured and assembled taking into account a sufficient safety factor in each part of the machine. Based on the results of variance analysis, the factors of the rotary speed of the crusher, the distance between the crusher and the concave, and the thickness of the rubbers had a direct effect on the peeling efficiency and the percentage of broken hard skin of almonds. Statistical analysis showed that the rotary speed of the crusher and its distance from the concave significantly affected the peeling efficiency (with a confidence level of 1%). The percentage of broken skin was also affected by the distance between the crusher and the counter-crusher, the rotary speed, and the thickness of the rubbers. In terms of comparing the effects of the three factors considered in the present study, Taguchi analysis indicated that the ranks of 1 to 3 were obtained for the factors of impactor speed, distance between impactor and concave, and rubber thickness on the capacity of the device, and the delta values for these three factors were 277.8, 188.8, and 37.5, respectively. In terms of optimal levels for increasing efficiency, based on the results obtained, the highest speed level, the lowest distance level, and the middle level of rubber thickness were seen to be better. Also derived from the same analysis, the increasing trend of the capacity of the device has occurred with increasing the speed of the threshing and conversely with decreasing the distance. A similar study has been conducted in relation to comparing the effect of the factors of the speed of the threshing machine, the distance between the threshing machine and the concave and the thickness of the rubbers on the percentage of almond breakage by the device, which shows the ranks 1 to 3 for these three factors, respectively, with delta values of 0.389, 0.232 and 0.106. Also, the lowest level of threshing speed, the highest level of distance and the middle level of the thickness of the rubbers, have included a better signal-to-noise ratio.
Conclusions
The device studied in this research was successfully designed and built. Considering the existing research needs, its performance was evaluated based on practical needs and application expectations. The results showed that the designed device was able to achieve the intended goals well.The findings show that in the design and construction of almond shellers, the quality of the threshing surfaces, the speed, and the blade spacing are key factors in determining efficiency. The decrease in efficiency with increasing distance between the thresher and the counter-thresher indicates the need for a balance between efficiency and durability, which can be considered in future designs. Some of the advantages of the manufactured device include: the ability to operate the device with different power sources, the ability to effectively separate green almond skins completely and uniformly, the ability to clean hard and papery almonds with minimal, significant economic savings such that the total price of this device, compact design and easy transportation (which makes it easy to move and use in different conditions), the ability to adapt to peeling other nut products, and the availability of after-sales service and technical support in the country due to the localization of the production process.

Acknowledgements
The authors would like to acknowledge the Urmia University for finantcial support.

Author Contributions
Ghafari Azad: Methodology
Mardani Aref:Supervisor
Sharifian Faroogh: Supervisor
Data Availability Statement
Not applicable.
Ethical Considerations
Authors proclaim that ethical considerations have been observed in conducting this study and confirm adherence to ethical standards, including avoidance of data fabrication, falsification, plagiarism, and misconduct.
Conflict of Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Conflict of Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper
Funding Statement
The authors received no specific funding for this research.