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annapurna rice huller for the Indian farmer

“Eventually everything connects - people, ideas, objects.� Charles Eames




project proposal








jumping the gun


forces around us








thank you!





There has always been strong ties and a special place for farming and agriculture in the family, for it has been part of our lives for long. Having experienced both the worlds of urban and rural, it was evident that most of the products that are developed are for an urban market, neglecting the needs that arise for a scenario where the people live away from the cities. An app can be a valuable tool for a person to book tickets or stay in touch with their loved ones, but this is valid only if the person owns a device to use such a tool. As designers we create and design for a particular audience but seldom remember the other extreme. The project is an opportunity, a beginning and an avenue to cause change in thinking and in action with a hope to take it as far as possible for the benefit of the neglected majority. Karan Patel Product and Interface Design


project proposal

Just before the proposal were to be submitted, a friend, Stella Paul lead to a meeting with Sahaja Samrudha a NGO supporting farmers cultivating naturally growing varieties of rice. A discussion with Sahaja presented itself with an idea to develop a small scale rice huller that could prove beneficial for the farmers. Farmers marketing brown rice/unpolished rice face different hurdles as majority of the rice mills are designed to cater the market of polished rice. With the demand of brown rice on the rise with the spreading awareness of its higher nutritional value compared to polished rice, an untapped market exists for farmers and in turn an opportunity for design intervention. The brief that was set, aimed at only husking paddy to produce brown/unpolished rice for farmers to add value to their harvest to fetch them a higher market price for good quality and high yield.



The brief made it important to learn and recognize the anatomy of rice to understand how brown rice was different from white. Simultaneously, different ways of husking paddy were studied. The older techniques of hand pounding and husking with the stone mill are used in extremely power deprived regions and are nearly discarded practices. These practices of husking are highly labourious, process very small amount of paddy at a time and as force being used is brutal over the grain, there is more breakage. Modern rice mills use different motorized apparatus to process paddy in a large quantity which includes polishing of rice. Due to this nature of catering to only large quantities, farmers who wish to market brown rice have limited avenues. These rice mills often make use of friction and shear forces to husk paddy,which in turn produce heat that damages the grain. A few tests to husk paddy were carried out. Various mechanisms that were studied were put into action by making simple mock-ups.


Section of a typical paddy grain.

anatomy of rice Rice is a monocotyledon which consists of carbohydrates, proteins, vitamins and minerals. Rice belongs to the millet family like wheat and ragi. In section, the grain’s outermost layer is the husk or the chaff followed by the bran, the endosperm and the germ. Based on the type of rice, the colour of the bran layer might vary from white, brown, red and black. The darker colours usually indicates higher content of antioxidants. The bran layer gives the distinct colour of brown/unpolished rice. This layer consists of the majority of the nutrients in rice that include protein, vitamins, minerals and fibre. With polishing of rice, the bran layer is removed and only the endosperm along with the germ is left behind, which are very high in starch content. Hence for a richer nutritious diet, the unpolished rice is superior to polished rice.


A tourist giving a hand at a Chinese stone mill.

Hand pounding to husk paddy in Orissa.

The traditional ‘Dhenki’ - foot operated pestle.

Images courtesy-; Ken & Nyetta’s flickr photostream ;

husking of paddy - past Paddy is a major crop in most of the Asian countries and many different techniques have been adopted in the past to get rid of its husk. The most commonly seen is hand pounding of paddy with mortar and wooden pestles operated by two people, one to pound and the other to examine the husked paddy. There are different versions of the mortar and pestle, water powered, foot powered and also using a curved bamboo profile as the mortar and small wooden clubs as pestles – commonly seen in the Philippines. A stone mill is also modified to be used for husking paddy. Sometimes the top disc was replaced by wood or the stone mill was used as it is. Animal powered mills have also been in use to reduce labour. Stone mills can be observed in various forms across cultures, from having a crank wheel like mechanism to a peripheral handle to perpendicular handles to be operated by one or more persons. Eventually the rice and husks were separated through winnowing. Many cultivators opt for parboiling of rice to ease the process of husking rice.


A typical steel huller.

Sectional view of a steel huller.

A modern huller - disc sheller.

Working of an underrun disc sheller.

Images courtesy- FAO; IRRI

husking of paddy - present To match the output required most modern rice mills use mechanized rice hullers. Amongst the mechanized hullers, there are three different variations based on the part of the machine performing the hulling action: Steel Huller: It combines husking and polishing within a single operation. A fluted revolving cylinder - similar to a feeding/Archimedes screw pushes the paddy towards the outlet, causing it to rub against the peripheral perforated sheet which in turn husks and whitens the rice. It has a very low recovery rate and also causes breakage of kernels. Sheller: It consists of two coaxial horizontal discs coated with an inner abrasive layer, with the upper disc being fixed and the bottom disc rotating to husk the paddy. The feed is from a central hole and as the disc rotates, with the help of centrifugal force the rice and the husk move outwards. The clearance between discs is adjustable to account for various sizes. Larger the disc, higher is the output and also the power consumption. It has a low running lost but there is a disadvantage of damaging the bran layer of the brown rice.


Allen Dong & Roger Edberg modify a grain mill, aimed to help farmers in the third world countries.

Working of a rubber roller.

Images courtesy- Allen Dong & Roger Edberg, IRRI

husking of paddy - present Rubber roller: It consists of two rollers rotating in opposite direction at different speeds. The grains falls in between the rollers and the shearing action causes the paddy husk to free itself from the rice. This reduces damage to the grain. The main disadvantage is the expensive rollers that need replacement once they wear out. Many innovators around the globe have developed their versions of a manual huller. One such is the modified huller for grain that uses rubber discs instead of an abrasive disc. YouTube channel of ‘Rice Harvester’ also shows a hand crank rice huller for domestic use. All these mechanized hullers can be integrated with blowers and vibrating sieves to get rice completely separated from their husks as well as from broken kernels.


One of the manual operated hullers still being used by farmers in West Bengal. This huller is a good example of a transitional model between the modern and old techniques. It is small in nature and has better output and processing speed than hand pounding. This was brought into India as part of green revolution in the 1960s.

Images courtesy- Krishna Prasad, Sahaja Samrudha

comparing the past and the present The various methods of husking adopted over the ages served a certain purpose and were limited by technology of its time. A comparative study of the processes adopted currently and in the past can be summarized in the table below: traditional techniques

modern techniques

Process smaller quantities at a stretch.

Large processing capability.

Labour intensive.

Mechanized for smooth operation.

Lower yields due to breakage of kernels.

Designed for higher quality yield.

Low investment and easy to maintain.

Expensive machinery to procure and maintain.

Small in size, can be customized to needs.

Needs large area for operation.


Hypothetical model of a hand operated huller.

Recreating the ‘beesada kallu’ with rubber.

Husking capability of the rubber discs.

Failed attempt at replicating rubber rollers.

mime testing After learning the different techniques that have been used and currently in use for husking of paddy, small models to imitate the mechanisms were created to experience husking of the grain. Rubber cutouts were taped to cut discs of plastic to replicate the disc sheller. Although the action was very efficient in husking the rice, there were rubber shaving and broken kernels seen in the final result. A scaled model of a hypothetical hand operated was made to understand the mechanics for a manually operated huller. A glitch was spotted in the model. The grain cannot be inserted at the periphery but only axially as the model operates on the basis of centrifugal force. Rubber rollers were also replicated with bottles and plastic frame. There was no sufficient speed or torque that could be provided manually to cause the grain to husk and hence a failed attempt at mimicking an existing mechanism.



With the help of Sahaja, farmers habituated to sell and propagate unpolished rice were met. Rice mills that the farmers frequent to were also visited. The highlights of the visit: • Farmers desire to be self sufficient with increasing labour wages and their shortage. • Agriculture not seen just as a means to earn livelihood but very passionate of paddy and conserving the true nature of the crop to the level of cultivation. • Utilize methods of legume culture and vermi-compost to produce their own organic fertilizer. • Harvesters and tractors are hired as and when required and operate themselves to avoid depending on labour. • Avail supply of single phase power at convenient hours but scarce supply of three phase power. • Do not see a manual huller competent to match their current needs. • Point out the use of stone mill[‘beesad kallu’ in Kannada] as the traditonal method of husking apart from hand pounding. At times modified with wood to go easy on the grains.


Anjeneya uses the wet waste from his home and cattle to vermi compost it and use it as a fertilizer for his paddy cultivation. The other farmer, Nandish Shikaripura for long has adopted legume farming and does not require any other form of pest control or chemical fertilizer. Navadarshanam recently dug an underground water tank on their own to avoid entry of excavators onto their premises. Farmers strive to carry out every task on their own, of course with the help of their family.

A mix of polished, unpolished rice along with paddy at the latest rice mill opened at Davangere. Context of use of the rice mill is different from what it is designed for. Paddy is processed in small batches and also with different varieties. Hence high chances of mixing of rice varieties from different batches of processing.

• Rice has to pass through the polisher with no thorough control to keep bran intact. • Believe hand pounding fetches better quality of grains as no heat is produced during husking unlike with modern rice mills. • See unpolished rice as means of higher pay off as yield of unpolished rice is higher compared to polished rice. Premium of crop being organic is an extra bonus. • Hire conveyance and labour to transport paddy to the rice mills, an overhead to the expense of husking the given paddy. • Queue up at the mill to get paddy processed and irrespective of the quantity, spend the whole day at the mill. • Rice mills have no provision for extracting rice right after hulling, forcing the grain to go through polishing and hence causing loss of the bran layer. • Clearance between rollers is not adjusted by the operators to suit the variety of rice being processed. • Farmers pay extra to clean out rice from previous batches.


Nandish Shikaripura talkiing about ‘One Straw Revolution’.

Nagaraj talking about ‘market driven cultivation’

Anjeneya and his collection of awards and seeds below.

new Indian farmer There are a new breed of cultivators on the rise. People with highly educated backgrounds have dropped their routines to turn farmers. This farmer is highly passionate of agriculture and well versed with sowing, germination, harvesting and post harvesting methods and processes along with different theories and methods to organically cultivate crops. Mr. Nandish Shikaripura claims to be a lazy farmer. He is highly inspired by Masanobu Fukuoka and his theory penned in the book called ‘One Straw Revolution’ which propagates methods of agriculture that do not involve any artificial input. Mr.Anjeneya is devoted to conserve naturally growing rice varieties through his seed bank. He is also famous for his Japanese paddy art, sowing paddy to form a desired pattern when looked from above the fields. Also a winner of the ‘Krushi Ratna’. Mr.Nagaraj is part of the trust of Navadarshanam which was a brain child of many IIT graduates. Believes every farmer has their own set of values and usually tested by the market to change their ways.


Latest rice mill near Kumblur, a village in Davangere district.

A rubber roller housing.

Conveyor bucket lift paddy from the reservoir.

Anjeneya explaining the working of separating tray.

rice mills The paddy that is brought in by the farmers goes through various stages of processing at a rice mill. The paddy travels a long path to reach its next destination. Paddy is first fed into an underground reservoir. A conveyor lift paddy to feed into the husker. The rice and husks are dumped into another underground reservoir. Hence forth the kernels and husks pass through a cyclone separator and polisher in a similar manner. The use of the underground reservoir causes mixing of grains from different batches of processing unless cleaned. The yield is also less as not all grains go through different passes of the mill. Many rice mills have also shut down as they were unable to pay their electricity bills. Amongst the rice mills visited, most catered to farmers as individuals. Certain large mills also exist which buy out the produce completely from the farmers and market them under their own brand. Such mills have even larger capacities and usually run only on select days to increase their efficiency.


Movement of the commodity - rice.

the consumer The consumer is the ultimate benefactor of the valuable nutrition of the unpolished rice. Many consumers cannot differentiate the different qualities of rice and hence depend on certification agency and their markings over brands for assurance. Farmers currently grade the rice visually. Although the grain has to pass through the polisher, the amount of abrasion can be controlled, therefore the grains are not truly unpolished. They pick out burnt and broken kernels before packaging for retail sale. India has not set standards for the quality of rice. USDA has set quality standards for packaged brown rice and hence keep a check over the grade of the rice a consumer buys.



Insights from the research were pulled out and an outline was drawn for the product in mind to sketch out its various characteristics and features to prove worthy of the farmer’s needs. From the primary research it was evident that: • The farmer aspires to be self sufficient due to which he is on the run most of the times. • Also has utmost care and concern for each grain. • Scarcity of three phase power is a hurdle to operate high-tech machinery. • Fixed overheads in addition to the cost of milling rice sum the total cost of processing paddy. • Rice processed at mills is not the genuine unpolished rice, irrespective of preserved bran layer. • Willing to consider an alternative device/processor as long as it matches the current costs of paddy milling. • Still reckon the traditional techniques produce quality yield compared to the rice mills.


From the insights a detailed character list of an ideal machine was created: • Is a reflection of the farmer- efficient, hardworking and just as gentle with the grains. • Accommodates different varieties of rice. • Works on single phase power. • Output of 200Kgs of brown rice in 1hour. [3.5kgs per minute] • Low maintenance with ease to service and repair/replace. • Minimum efficiency of 95%. • Output free of husks and unhusked paddy with bran intact. • Maximum weight of 200kgs. Although the list was ambitious to begin with, the panel of advisors was very supportive of it even if the ultimate concept and design did not meet all the requirements of being an ideal huller.


jumping the gun

Considering hand pounding produced quality output, the idea of mechanizing the process was worked upon. Initial inspiration was from engines which use reciprocating motion for generation of power. The idea was dropped keeping in mind the yield rate as hand pounding causes kernels to break easily. Further research was carried out to learn the latest developments in the grain processing industry. Big wigs like Schule Foods and B端hler create end to end solutions for rice mills that start from cleaners, hullers, separators, polishers and even optical grading not only for paddy but also soy beans, sunflower seeds and pulses. Many Korean and Italian manufacturers like Huan Tai Machinery and RePietro have developed small scale rice mills. All the mills designed for paddy utilize rubber rollers to husk paddy. A document released by AgriCoop, part of the Department of Agriculture of India showcases various agricultural implements and processing machines which includes a small scale sheller. It also mentions that the rubber rollers produce significant higher output and therefore all mill in India are required to utilize rubber shellers only as per the norms set by the Government. Having a strong influence of rubber rollers in the research and visit to the rice mills, a decision was made in haste to develop concepts utilising the certain mechanism without substantially ideating over the essential action of husking which could have either been through friction or shear or a magical solution that dissolved husks.


Still from an animation of the working of a radial engine.

Manoharan’s rotary huller with 6 cylinders.W

Images courtesy- ; NIF.

mechanizing hand pounding The motion of pounding grains using a mortar and pestle can be compared to the reciprocating motion of an engine. One such mechanical fixture is the ‘Withworth Quick Return Mechanism’ that replicates the pounding action perfectly. Even the intensity of the stroke can be adjusted by changing the position of a pin that holds the plunger to the crank. For an increased output, multiple strokes are required and they could be combined in a single rotation like in a radial engine. AN Manoharan developed a rotatry huller for spices as part of the National Innovation Foundation. Solid metal rods are inserted along with spices into cylinder along the periphery of a rotating disc. As the disc turns the metal rod pounds the spices into finer powder. Paddy was pounded with wood along with cushioned foam to see its husking capabilities. Paddy was no doubt easily husked but a lot of broken grains could be spotted.


Schule’s conical huller used for harder grains like lentils.

Rubber rollers at work.

Images courtesy- Schule Product Catalogue; HTM.

HTM’s entry level rice huller for small operations.

commercial grain processors German companies have been leaders in the grain processing industry. Catalogues of such firms show the wide range of products just for husking grains. Rubber rollers are used specifically for paddy. A conical stone is also used in hulling machines meant for cereals and pulses that are very hard in nature. Impact hullers that throw out grain centrifugally to husk them on impact are used for sunflower seeds, oat, spelt and buckwheat. Such hullers are usually designed for processing at a large scale but small scale versions are also available and are usually manufactured by Chinese and Koreans firms to suit the needs of the Asian market. Optical sorting techniques are adopted are very large scales where a the grains are scanned by a camera and the discoloured, disfigured, unhusked and unpolished grains are removed to be fed back into the process.


A gear driven concept with an idler to change direction of the rollers.

Hypothetical concept involving belt drive with differential speed for the rollers.

Single layer of was chiselled from cardboard cutouts.

Gears stuck with mutiple layers of cardboard.

realizing driving mechanism for rubber shellers To develop the prototype of using roller shellers, basic knowledge of the drive mechanism needed to be worked out. Belt drive, gear drive, AC motors and DC motors were studied to understand the merits of each over the other. Digital mock-ups were created to visualize how the rollers could be powered such that the spin in opposite in direction as well as with difference in their speed. To understand how the clearance could be adjusted between the rollers, small gears were made out of paper board and played with to learn that the clearance could not be manipulated when powered with a gear drive. PVC pipes were bought and a motor of an exhaust fan salvaged to start with the construction. The feedback from the advisors was that there was a rush to start with making the prototype and the ultimate goal of husking could also be achieved through other means which had not been completely looked into. The feeling of lack in preparedness and efforts to achieve an appropriate concept was mutual and the idea of making the said concept was put on hold.


forces around us

A fresh start was made by ideating through sketches with inspiration from mundane objects and activities one would observe in an average surrounding. A starting point suggested by the panel was rollers used to make corrugated sheets. It was interpreted as pair corrugates rollers that could husk paddy while they rotate - similar on principle with rubber shellers. This was further stretched to air bellows that can could contract and expand based and create a force to husk paddy. Idea of combining feed and husking in the same action was another path explored with pumps forming the core of most ideas. A step back also helped to understand the science of breakage of a grain and introduced the phenomenon of ‘optimum friction’. Average grain size and parboiling of paddy were also paid attention. A clear direction could still not be found until a thorough brainstorm of trivial forces around us led to the concept of using wood as a material gentle to handle husking efficiently with optimum force required.


Exploration involving corrugated rollers and air bellows.

corrugations and bellows A beginning of hard core ideation was made by looking into corrugated rollers. Idea was to use a pair of interlocking rollers between which paddy could be introduced. When the rollers would turn in opposite direction, there would be frictional force for the paddy to be husked. Due to the curvature of the roller, there is always a high probability for the grain to break. The profile of the corrugated roller is similar to that of an air bellow. Air bellows easily contract and expand, creating a change in the clearance of the bellow surface from almost being nil to being circular. This change in clearance could be adopted to husk paddy but due to the flexible and elastic nature of an air bellow, it cannot offer sufficient amounts of force for hulling. Air bellows also require precise pneumatics to function as per requirement which would draw the costs upward.


Understanding the working of various pumps.

Two right handed screws.

Parts of the first mechanized huller - Engelberg’s.

pumps - integrating flow and husking The other set of concepts were driven by the idea of extracting the husking action from the flow of grains. An obvious choice was to look at the functioning of pumps as they handle pressure and flow all at once. Various pumps like the lobe, scroll, gear etc were studied to gauge the feasibility of grains being husked. Scroll pump seemed most promising in providing the right amount of force but again due to the curvature, there is a high probability of grains breaking. Grain pumps are used by huge granaries to move the grains from truck to storage and vice versa. Simply put, this is a helical screw and works on the principle of an Archimedes pump/screw or a drill bit. An auger or a helical screw was made out of paper to understand the movement of matter through the screw’s length. Combination of screws were also pondered over. A logical fact was overlooked. A screw of certain direction can mate only with a screw of an opposite direction. A right hand screw can mate only with a left hand screw and vice versa. Later it was found that the Engelberg huller works on a similar principle of a helical screw to husk paddy an even polish the grain. The force created by the turning of a screw against the cylindrical surface is very high and therefore causes the husking as well as polishing with high broken kernels. This huller is the steel huller mentioned earlier and is widely used in many Asian and African countries.


The fracture pattern of a grain that is dry. All mills calibrate their capacities based on the moisture content of the grain. Paddy grains are required to have 14% or less moisture content to be husked easily.

Fracture pattern of a grain with higher moisture content.

Thickness of a ‘doddabairanallu’ grain.

science of breakage Before moving any further with ideation, another FAO research paper was stumbled upon. This document discussed in detailed about the various causes of grain breakage. Even moisture content plays a huge role in adding to the strength of the grain and the force required to husk paddy. Dry grains are hard and brittle and require lower amount of force to be husked or polished and therefore can easily break. With an increase in moisture content, the elastic strength of the grain increases and therefore require higher forces to be husked or polished and also higher amount of force to break. The kernels can either break due to compressive or shear forces. An optimum range of force is required to ensure appropriate husking and avoid breakage of the grains.


Forces at action.

trifling forces With no obvious direction ahead, a very basic exercise of observing actions and objects involving opposing forces were listed. The list was made as exhaustive as possible. An interesting action of ‘shuffling of cards’ was explored. Few quick experiments were carried out using materials easily available like wood[softwood, hardwood and plywood], emery paper and sharpening stone - materials with a wide range of abrasive quality. The motion of linear reciprocation with shuffling of cards was replicated with these materials along with paddy being sandwiched between them. Although paddy was husked very efficiently with the help of all the materials, the highly abrasive emery paper and the sharpening stone proved to be very harsh over the grains. Wood - soft and hard proved to be very gentle with the grain while plywood’s surface was not appropriate for efficient husking. The softwood in a way provides a cushion for the grains and helps it to experience optimum friction for easy husking.


Soft cushioned seating for grains.

Timber v/s plywood - breakage of kernels but efficient husking.

Carborundum stone v/s wood - low husking capability.

Emery paper v/s wood - bad capability & emery traces.

Efficient husking capability of wood v/s wood with different varieties of rice with varying bran layers.


Exploration of interlocking patterns.

trifling forces Various iterations of interlocking profiles were sketched out. In a linear reciprocation, grains in different orientation do not experience uniform force and hence linear motion would not be the appropriate to apply the required force. The forces have to be radial in nature for all the grain to undergo uniform friction



The direction of using radial wooden discs to husk paddy was taken to expand and develop into a working concept. The concept of wooden discs to husk paddy is very similar to the stone mills that have been used in the past as hullers and sometimes modified with replacing the top disc with wood. In the state of Karnataka, they are referred to as ‘beesada kallu’ to be translated as ‘grinding stone’ in English. Various patents, designs from the past and present related to the stone mill were studied to grasp its essence and understand its working completely. A simple working test model was constructed which proved to be a very efficient huller. Hence the idea of using wooden discs to husk paddy was taken forward and developed to become a complete finished and working prototype.


Probable patterns and textures to aid husking.

Radial patterns that could help enahce husking action were sketched. Even the section of the discs were pondered over to visualise the flow of the grain. Patterns and textures over wood do not endure wear well and simple plain surface of wood that proved its worth earlier was persisted with. Being very similar in nature to the ‘beesada kallu’, various versions of the stone mill were studied. Water powered mills that have been in existence for long but were typically used as flour mills. Modern day grain mills have become so compact that manufacturers have produced a very compact stone mill that can sit on top of one’s dining table. Hand operated as well as powered mills of this compact natures are available commercially. Once such are the Slazburger mills from Germany. Mills mentioned above either place the stones horizontally or vertically. The advantage of the horizontally inclined stones are that the grains move out only depending on the speed of the bottom disc whereas in the vertical arrangement the centrifugal force opposes gravity. Vertical stones work best for manually operated mills as placement of the mechanics becomes much easier.


Mounting the motor on to the plywood frame.

Drilling calculated holes over the top wooden disc.

Motor was placed over rubber to level its axis as well as avoid vibrations while running.

A hand drill was used to drill until the desired depth while the power drill was used only for an initial bore.

A working test model was fabricated at home to put the theory to test. The motor salvaged earlier was utilized in powering a wooden disc. Brackets from the exhaust fan itself were used to mount the motor over a piece of strong plywood. Vertical member was created by sticking multiple pieces of cut plywood. Once the motor was mounted on to the frame, the wooden discs needed to be machined to seat itself over the motor as well as suspend itself. The bottom disc was bored for a blind hole and seated directly over the motor’s shaft. The top disc was attached to a long strip of wood that in turn was suspended by screw fastened from the brackets. Initially the discs were not perfectly horizontal. The motor’s shaft was taped to give a cushioning for the disc to sit on. This proved to give a higher stability to the disc while turning at a high speed. The top disc had a tendency to be wobbly and so did the whole structure until the model was placed over a rubber mat which reduced the vibrations for the structure only.


Assembled model right before testing.

The clearance between the discs was adjusted by two screws. An approximate clearance was set initially and then a single paddy grain was dropped on to the rotating disc through the central hole. When it came out unhusked, the clearance was reduced until the paddy was completely husked. Due to the sheer speed of the bottom disc just a little pressure was required from the top disc. The grain shot out as soon as it was dropped on to the disc leaving behind the husk. The test was a success with the paddy not only being husked completely but also retaining its bran layer. With the initial few tests, the grains of rice would fly all over the table and hence a casing was made to collect the grains and husks. The casing around the discs was intended to collect just the grains but proved to have another function as well. It proved to be similar to an impact huller where the grain would hit the surface to be hulled. A few grains would go out unhusked as the top disc could not maintain its horizontal axis, a lesson that was put into effect for the final model. The estimated processing capacity from the test model was around 40-60 kgs of paddy per hour.


A normal scene right after testing.

A small hole in the casing was enough to spill all the grains out due to the vibrations



A comprehensive solution was aimed where the farmers not just got to husk his paddy but also could separate the husks from the rice. Concept building started with sketches of individual elements like backing/pressure plates, belt drives and hopper. A jump was made into 3D modelling to develop the concept holistically. The initial concept was taken to the fabricator to check for the feasibility of manufacturing/fabrication. Various elements like motor capacity, bearing, shaft dimensions and elements of the power drive were finalised with the help of Mr.Balamurugan who is experienced in designing rice mills. Even the motor selected has been typically used for ‘ghar ghanti’ which is a simple stone flour mills for domestic use. The concept was refined time and over until it was satisfactory to begin with fabrication.


Various explorations to decide on the different elements that will be required to create the machine. From power drives to pressure plates to casing, all were kept in mind before virtual modelling begun. Required volume of the hopper was calculated to accommodate 40-50kgs of an average sized paddy to help decide the scale of the model. Top powered disc had complicated construction and hence was avoided to simplify the machine. The wooden discs were to be screwed onto metal plated which in turn would be fastened on to the frame to adjust clearance and keyed to the shaft for the rotating disc.


Assembled model right before testing.

The primary concept that was taken to the fabricator, Gupta Electical Industries to initiate talks an explain the idea of working, along with videos of a test model. The hopper was perceived to be cylindrical to facilitate only one operation of rolling and then to be riveted. This raised concerns over transporting the huller if ever it was to go into production. A single large piece of hopper would not only take a large volume but also increase the weight of the machine. Due to dependability on a rolling machine outside of the fabricator’s premises, circular framework was avoided in the further concepts. A major element that was overlooked was the separator. In this concept, only a blower was to hit the husks and grains at high intensity throwing the husks far away and also littering the surroundings. The other feasibility issue was that the blower could not be powered through the motor as a special blower had to be manufactured. Hence the concept was reworked at various levels with the inputs of the fabricator.


Modular panel hopper.

Standard bulk bag unloaders.

Images courtesy-

The hopper was the most voluminous part of the machine. A panel rectangular hopper was suggested by the fabricator to make it modular in nature but this would still increase the weight of the machine. A fabric hopper seemed an appropriate alternative. Bulk bag unloaders of the pharmaceutical industries were understood and various scale models were made to comprehend the working with the overall concept in mind


Various ways that a casing could fit around the discs were iterated. It was inevitable but to have to be split into two parts. A rhomboid form was chosen over the others as it could feed into the separator more easily.

The feed plate was made part of the top backing plate along with the provision for the hopper bag to slide over it and be clamped. The concept on the right was taken forward to be detailed.


Husks + Rice




Working of the separator box - influenced by DIY bird seed cleaner. Section on the left and orthographic view on right

Rice free from husks.

Separation of husks was not thoroughly studied in the earlier part of the project. Initial concepts made use of a centrifugal blower to remove the husks. As the weight difference between the husks and the grain is high, blowers could be substituted with axial fans. The rice being heavier falls down by gravity and the air from the fan gives the husk higher velocity to sway into the other chamber. A capacitor controlled fan was opted whose speed could be regulated as per requirement. The adaptation of the bird seed cleaner worked very well to clear out the husks from rice and paddy as well. Testing jig.


Exploded view of concept before being corrected for dimensions and strength by the fabricator.

CAD of the side view of the machine that utilized for cutting and punching of various parts.


Thus ‘annapurna’ was finally born. The name being derived from the fact that the output of the machine were grains in their purest form. The salient features of the machine would be: • A fabric hopper to reduce weight and volume. • MS powder coated frame and body to reduce cost and increase longevity . • Ease of service and repair as simplest mechanisms and parts are used. • Ergonomic height to fill hopper. • 0.5HP single phase motor to optimise power consumption. • Frame can be dismantled for easy transportation.



Once the final model was developed for cutting and fabrication with the help of Jubin, there were many hurdles on the way to the finish. There was an initial delay with cutting of profiles that were meant to be bent later on. Planned to be laser cut, the profiles had to be punched. The punched parts were then bent and welded to give the desired form. Another delay was met on the way due to the festivities being celebrated. To match the levels of the pulley, the motor was overturned as the clearance for the belt was too less with the motor being upright. This was the only deviation from the final design. The final hurdle to cross was the finishing. Powder coating was delayed due to unforeseen circumstances. Finally the prototype completed its journey from being just a render to being a physical model. A successful trial run was carried out.


Jubin sending the G-codes and M-codes to the punching machine.

MS sheet being loaded for the punching operation.

Change of tools to suit the operation.

Punched profiles of various parts.


Rajesbhai measuring the distance at which the part is to be bent.

Frame coming to life.


Checking the position of various parts.

Boring the pulley.

Finishing the welded joints.


Just before bringing the machine to life.

Motor being overturned to level with the shaft pulley.

Right before being sent in for powder coating.





The husker is not complete in many of the aspects and hence needs to be refine further to create a commercially feasible and successful product. The existing efficiency of the machine stands at around 50-60% measured with respect to the ratios of the weights of rice to unhusked paddy. The torque at the rotating disc needs to be increased in order to achieve a higher efficiency. The overall output does not seem appealing to a farmer and this can be improved by providing larger area for husking through larger discs. Many other aspects of the design have not been looked into during the project due to the time constraint and hence there is scope for further development to mould the existing concept into a viable commercial solution for the paddy farmer.


thank you!

Many people have contributed to the success of this project, knowing or unknowingly. The following have had a major impact on the project without whom ‘annapurna’ would not have seen the light of the day. Sudipto Dasgupta & Sharath Chandra for being very supportive & keeping me grounded with constructive feedback. Stella Paul for introducing the avenue to pursue a project of interest. Sahaja Samrudha’s Krishna Prasad & Praveen for their help and support. Nandish, Anjeneya, Malnad Rice Grower’s Association and Navadarshanam for providing valuable insights. FAO, IRRI, TNAU and Agricoop for publishing various research and handbooks for free access. Kandaraji & Bala Murugan for guiding towards a direction of manufacturing feasibility. Gupta Electrical Industries - Girijesh Gupta, Gadadhar Gupta, Jubin and Narasimhanna for undertaking the engineering and fabrication of my design My big, supportive family & friends Devraj Bhadra and Arango along with my faculty at MSRIT and Srishti School of Art, Design and Technology.



Various resources were utilised to gain appropriate knowledge to conceive certain theories and to put them to test. Multi faceted farmers who provided with valuable inputs and feedback for numerous queries of mine. Research papers and knowledge bank of FAO, IRRI and Agrinoop were of most relevance to the field of husking paddy. Many innovators and manufacturers around the globe proved to be of prominent inspiration to pursue the idea of creating a small scale huller for the farmers.


Diploma Project 2013


Karan Patel


Product and Interface Design

annapurna - rice huller for the Indian farmer  
annapurna - rice huller for the Indian farmer