Design and development of a cost-efficient, user-centric leaf plate moulding machine for decentralized tribal and rural applications

Introduction

Single-use plastic tableware persists in soil and water for decades and breaks down into fragments that enter the food chain, which is why it has become one of the most visible targets of waste policy in India. Of the plastic that the country produces, roughly two-fifths is never recycled and ends up in landfills or waterways (Datta et al., 2022) [1] . Acting on this, the Ministry of Environment, Forest and Climate Change notified the Plastic Waste Management (Amendment) Rules in 2021 [2] and banned a list of single-use plastic items, including plates, cups and cutlery, with effect from 1 July 2022 (Ministry of Environment et al., 2021) [2] . The ban has created a regulatory pull for biodegradable substitutes that the market has not yet fully met. Comparative assessments of disposable tableware report that plant-based items generally carry a lower environmental burden than their plastic equivalents, although the margin depends on the material and on the endof-life route available to the user (Pantovic et al., 2025; Liu et al., 2020) [3,4] . In the deciduous forest belts of eastern India, that substitute already exists. Leaves of Sal (Shorea robusta) and Siali (Bauhinia vahlii) have been stitched into plates and bowls for generations; they compost within weeks and leave no toxic residue. Odisha holds a large share of India's Sal forest, and leaf collection, stitching and trade support several lakh tribal households in the state (Ministry of Tribal Affairs, 2022; Sheetal et al., 2024) [5,6] . The trade is nonetheless a poor one. Collectors earn only a few thousand rupees a season, because hand stitching is slow and the plates it yields are uneven in shape and finish and therefore fetch low prices. Value addition to minor forest produce, as pursued under the Van Dhan Vikas Karyakram, has been shown to raise tribal household incomes appreciably (TRIFED, 2018) [7] , which is precisely the opportunity that mechanised moulding represents. Mechanisation, however, has not reached these households. Commercial semi-automatic hydraulic presses turn out more than a thousand plates an hour with good consistency, but they cost several lakh rupees, draw three to five horsepower from a three-phase supply and need a trained operator (Table 1). Recent work has begun to probe lower-power alternatives: a semi-automatic moulder driven by a small direct-current motor with electrically heated dies has been reported, though it forms plates from crushed leaf powder and binder rather than from whole stitched leaves (Sudarshan Rao et al., 2023) [8] . Each of those three requirements is difficult to satisfy in a forest-fringe village. The prior art is thin. The earliest relevant Indian Patent, 1998 [9] , describes a Sal leaf plate apparatus heated by a biomass furnace and pressed by a manual lever, delivering roughly 140 plates an hour with no temperature regulation (Indian Patent, 1998) [9] ; a later patent introduced continuous rotary casting with cam-driven dies, electrically heated punches and closed-loop temperature control, but presupposes industrial infrastructure (Chakravarthi et al., 2007) [10] . Between these two poles sit a small number of intermediate machines. A grassroots motorised design supported by the National Innovation Foundation reaches roughly a thousand plates an hour on a half-horsepower motor, but has no safety enclosure and heats its dies inconsistently [11] ; a biomass-fired portable machine developed for West Bengal tribal clusters works off-grid but exposes women operators to combustion fumes and controls temperature poorly [12] . Work on the neighbouring areca leaf-sheath trade is instructive: an energy-efficient plate-making machine has been designed for that material (Kalita et al., 2008) [13] , and mechanical characterisation has shown that palm leaf sheath tolerates very large forming strains, so that plates can be pressed in a single step, with hydration and alkali pre-treatment raising formability further (Mohanty et al., 2021; Mohanty et al., 2022) [14,15] . Automation of areca plate production is now being actively pursued for institutional and export markets (Chandrasekar et al., 2023) [16] , a commercial momentum that has not yet reached the Sal and Siali belt. What is missing is a machine designed around the people who would actually use it: one that a self-help group can buy, run on a singlephase village supply, operate without training and use safely. Rather than assume those requirements, we elicited them. The voice of the customer approach offers a structured way to convert stated user needs into quantified engineering specifications (Griffin et al., 1993) [17] , and design for manufacturability principles keep the resulting design fabricable in a district workshop at low cost (Ulrich et al., 2016; Boothroyd et al., 2011) [18,19] . This study therefore sets out to establish design requirements from a field survey of the Odisha leaf plate value chain, to translate those requirements into engineering targets, and to design, fabricate and evaluate a prototype machine against them.

Materials and Methods

Design process

The work followed four sequential phases. In the first, a prior art search covering Indian patent databases, institutional prototypes, commercial catalogues and peer-reviewed literature was used to characterise the existing technology landscape [9,10,11,12] . In the second, the machines so identified were scored against the operational requirements of a tribal self-help group to expose the gaps between them. In the third, those gaps were tested against the stated needs of users through a field survey. In the fourth, the machine was modelled in Autodesk Fusion 360, a half-scale prototype was fabricated according to design-for-manufacturability principles (Ulrich et al., 2016) [18] , and its performance was measured against the targets the survey had produced. Benchmarking preceded design synthesis, so the proposed machine does not appear in the benchmarking comparison; it is compared against the derived targets in the Results.

Field survey and voice of customer analysis

A structured questionnaire in English and regional language Odia was shared with 120 stakeholders across Mayurbhanj, Sundargarh, Keonjhar, Sambalpur, Rayagada and Koraput, the principal Sal and Siali leaf-producing districts of Odisha. Seventy-four (74) valid re-sponses were returned, a response rate of 61.7%. Respondents included self-help group members and leaf plate makers, farmers and agricultural labourers, forest officials and livelihood programme workers, and traders, so that the whole value chain was represented. The instrument had four parts: respondent profile and current practice; problems with existing machines; expected machine specifications; and importance ratings for eight design attributes. It was pretested on eight respondents who were excluded from the main sample, and ambiguous items were reworded before full administration. Attribute importance was rated on a five-point Likert scale, where 1 denotes 'not important' and 5 'extremely important' (Likert, 1932) [20] . For each attribute the arithmetic mean, standard deviation, median, mode and Fisher's coefficient of skewness were computed (Walpole et al., 2012) [21]: x̄ = (1/n) Σ xᵢ (Datta et al., 2022) [1] SD = √[ (1/(n -1)) Σ (xᵢ -x̄) (Ministry of Environment et al., 2021) [2] ] (Ministry of Environment et al., 2021) [2] (Pantovic et al., 2025) [3] (Pantovic et al., 2025) [3] where x i is the score given by respondent i and n = 74. A negative skewness coefficient indicates a left-skewed distribution, that is, that most respondents assigned high importance scores rather than that a minority did so. Problem-frequency data were ranked by a Pareto analysis (Juran et al., 1999) [22] to separate the few complaints that account for the bulk of the complaint burden from the many that do not. Because respondents could report more than one problem, the denominator for the cumulative percentage is the total number of complaints recorded (297), not the number of respondents. Analysis was carried out in Python 3.11 using NumPy, SciPy, pandas, and Seaborn (Harris et al., 2020) [23] .

Translation of survey outcomes into engineering targets

Attributes combining a high mean importance with a low standard deviation were treated as non-negotiable, on the reasoning that they were both highly valued and widely agreed upon; the uniformly negative skewness confirmed that this agreement extended across the sample. The vital few problems isolated by the Pareto ranking were each mapped to a specific engineering response, and the modal specification preferences reported by respondents were adopted directly as the quantified target set. The targets that emerged from this exercise are reported in the Results, and the prototype was subsequently evaluated against them.

Statistical analysis of prototype trial performance

Worker-level performance trials were conducted to characterise the variability in production rate and plate quality attributable to operator experience, gender and age. For each participant the total number of plates produced during an 8-hour session was recorded and converted to an hourly production rate (plates per hour), and the percentage of plates passing a combined visual and manual flexural quality inspection was taken as the plate accuracy score. Descriptive statistics, that is, arithmetic mean (χ ̅ ), standard deviation (SD) and variance (s 2 ), were computed for hourly production rate and plate accuracy across the full sample and within each sub-group, using Equations (Datta et al., 2022) [1] -(Pantovic et al., 2025) [3] defined above (Walpole et al., 2012) [21] . A one-way analysis of variance (ANOVA) was applied to test whether mean hourly production rate differed significantly across the three experience levels (skilled, semi-skilled and unskilled) (Field, 2018) [24] . The ANOVA F-statistic is: F = MSₜ / MSₑ (Liu et al., 2020) [4] where MSₜ is the mean square between groups (variance explained by experience level) and MSₑ is the mean square within groups (residual variance). A significance threshold of α = 0.05 was applied throughout. The association between hourly production rate and plate accuracy was quantified using the Pearson product-moment correlation coefficient r (Cohen, 1988) [25] :

) [5] where xᵢ and yᵢ are the hourly production rate and plate accuracy of participant i, χ ̅ and ȳ are the respective sample means, and SDₓ and SDᵧ are the respective sample standard deviations. Values of |r| ≥ 0.7 were taken as indicating a strong association (Cohen, 1988) [25] .

Results

Existing technology and the gaps it leaves

The prior art search returned a sparse field: only two patents of direct relevance, both filed before 2010, and neither addressing the constraint set that defines the tribal context, namely single-phase power, capital cost below one lakh rupees, and usability by a non-technical woman operator. Four families of machine were identified and are compared in Table 1. Scoring these four families against eight design dimensions on a fivepoint scale exposed a consistent shortfall (Table 2 and Figure 1). No existing machine clears the minimum acceptable threshold on more than four of the eight dimensions simultaneously. The gaps that matter most are affordability, energy efficiency on a single-phase supply, ease of operation without training, portability, operational safety, production rate, local maintainability, and regulated die temperature. Together these eight define the design agenda for the present machine.

Survey respondents and reported problems

The respondent profile is set out in Table 3 and summarised graphically in Figure 2. Women made up 59.5% of the sample, which is consistent with the women-led composition of self-help groups in the Odisha leaf plate trade (Ministry of Tribal Affairs, 2022) [5] . Leaf plate makers and self-help group members accounted for 60.8% of respondents (n = 45), and more than half the sample (54.1%) still stitches plates by hand, which is the clearest single indication of unmet need of mechanisation. The problems respondents reported with existing machines are given in Table 4 and ranked in Figure 3. High machine cost was the most widespread complaint (75.7%, n = 56), followed by high electricity consumption (58.1%, n = 43) and machine weight (54.1%, n = 40). Across the sample, 297 individual complaints were recorded. The cumulative share crosses the Pareto 80% threshold at the sixth problem: machine cost, electricity consumption, portability, production rate, safety and maintenance together account for 81.5% of all complaints (Juran et al., 1999) [22] . The five most frequent problems alone account for 70.0%. These six complaints, rather than the full list of eight, therefore set the engineering priorities.

Specification preferences and attribute importance

Respondent preferences for machine specifications are summarised in Table 5 and Figure 4. A total connected load between 500 W and 1 HP (746 W), covering both the drive motor and the die-heating elements, was preferred by 70.3% (n = 52). This supports the selection of a 0.5 HP (373 W) motor combined with a 350 W tubular heater, giving a full-scale connected load of 723 W, which falls within the preferred ceiling of 746 W. An output of 500-700 plates per hour was preferred by 58.1% (n = 43), a price between ₹50,000 and ₹1,00,000 was acceptable to 58.1%, and a medium, single-operator machine was preferred by 67.6% (n = 50).

Only the leading options selected by respondents are tabulated; remaining respondents chose other options within each parameter, so counts within a parameter do not sum to 74. Descriptive statistics for the eight design attributes are given in Table 6 and plotted in Figure 5. Low machine cost drew the highest mean rating (4.59, SD = 0.52), followed by operational safety (4.50, SD = 0.53) and ease of operation (4.47, SD = 0.60). Every attribute returned a negative skewness coefficient, between -0.039 and -0.690, meaning that ratings clustered toward the top of the scale in each case. The three highest-ranked attributes also had the tightest spread (SD 0.52-0.60), which indicates that respondents agreed with one another as well as rating these attributes highly. Portability and maintainability drew wider spreads (SD 0.81 and 0.92), most plausibly because respondents differed in how much prior experience of machines they had. [3] . Taken together, the Pareto ranking, the specification preferences and the attribute statistics converge on a single target set: a total connected load (motor plus heater) within 1 HP (746 W) on a singlephase supply, met by 373 W motor and 350 W heater giving 723 W; an output of 500-700 plates per hour at full scale; a fabrication cost between ₹50,000 and ₹1,00,000; thermostat-regulated dies at 100-150 °C; push-button operation with under thirty minutes of training; a mandatory safety package of interlocked enclosure, emergency stop and belt guard; and a machine weighing under 60 kg.

Machine design

Table 7. Design considerations and engineering solutions adopted Table 7. sets out the principal design considerations identified from the gap analysis and VoC findings, and the engineering solution adopted for each. The paragraphs that follow describe each sub-system in detail. A crank and connecting rod mechanism was chosen over hydraulic and toggle-clamp alternatives for four reasons: it is mechanically simple and cheap to maintain; it works with a low-power single-phase motor; its stroke speed can be altered through the pulley ratio without mechanical modification; and it has already proved reliable in grassroots motorised designs [11] . A crank stroke of 160 mm gives sufficient die closure for plates up to 300 mm in diameter. The frame is a welded H-geometry assembly in 40 × 40 × 3 mm square hollow mild steel section, which provides a symmetric load path from the pressing mechanism to the die table while keeping material use, and therefore cost, low (Ulrich et al., 2016) [18] . Frame analysis indicated deflection below 0.2 mm at the estimated 2 kN peak pressing load. Two precision-ground hardened steel guide pillars of 25 mm diameter constrain the ram to vertical travel and so prevent lateral die misalignment, and four return compression springs, matched to the 8 kg ram mass and the 160 mm stroke, reset the punch after each cycle.

Design Consideration

Constraint / Requirement

Both die halves were prepared by die casting and machined from aluminium alloy, chosen for its high thermal conductivity, which promotes rapid and even heating. Tubular resistance elements set into bored channels in each half hold the dies between 100 and 150 °C. This window was established empirically in the present trials as the range within which Sal and Siali fibres set permanently without charring, and is consistent with the reported thermoformability of palmfamily leaf materials (Mohanty et al., 2021; Mohanty et al., 2022) [14,15] . Temperature is held by a bimetallic dial thermostat in the prototype; a digital proportional-integral-derivative controller is intended for the production version (Astrom et al., 1995) [26] . A die-to-punch clearance of 0.5-1.0 mm accommodates the compressed leaf stack. The electrical circuit comprises a single-phase supply, a miniature circuit breaker, motor start and stop buttons, a large toggle emergency stop, the thermostat and two heating elements. The complete machine occupies an envelope of roughly 700 × 500 × 1,200 mm (Figure 6).

Prototype

A half-scale prototype was built to validate the mechanism and the moulding performance before fabricating an actual full scale model. Motor power was reduced from 373 W to 200 W, and a switchedmode-supply direct-current motor with pulse-width-modulated speed control was used for the said purpose. The prototype comprised three subassemblies: the mould assembly (aluminium die block, punch, two guide pillars, four return springs); the drive assembly (motor, pulleys, crankshaft, connecting rod, ram); and the body (square hollow section H-frame, worktable, motor mounting plate, sheet-metal enclosure, electrical panel). Cutting, machining, shielded metal arc welding, drilling, grinding and fitting operations were performed on general workshop machinery, consistent with the intent that the machine be fabricable locally (Ulrich et al., 2016; Boothroyd et al., 2011) [18,19] . The assembled prototype is shown in Figure 7. The prototype used a 200 W direct-current motor and a 350 W tubular resistance heater. The total connected electrical load of the prototype was therefore 200 (motor drive) + 350 (heating element) = 550 W.

Trial runs

Cleaned and dried Sal and Siali leaf sheets were placed between the heated die halves, with the thermostat set to 130 °C and allowed to stabilise before each run. Plates were then inspected for shape accuracy, edge finish, surface uniformity and structural integrity under manual flexural loading. Across repeated trials the reciprocating motion remained smooth, punch and die stayed aligned, and plates formed reliably without significant defects. Die temperature held within ±5 °C of the 130 °C set point throughout continuous running, and the belt guard, emergency stop and interlocked enclosure functioned as designed in every session. Measured performance is set against the survey-derived targets in Table 9. At half scale and 200 W the machine achieved 450-750 forming strokes per hour; scaled to the full 373 W design, it is projected to meet the 500-700 plates per hour that 58.1% of respondents preferred. Steady-state draw of 350-400 W (motor running continu-ously at 200 W plus the thermostat-cycled heater contributing ~150-200 W), against a total connected load of 550 W (200 W motor + 350 W tubular heater), well within the 1 HP (746 W) total-load ceiling preferred by 70.3%, and the prototype was fabricated for approximately ₹32,000, inside the price band 58.1% of respondents said they could accept. To characterise operator-dependent variability in production rate and plate quality, the prototype was operated by 24 participants of the target user population: five age groups (18-25, 26-35, 36-45, 46-55 and 56+), both genders (15 women, 9 men) and three experience levels (9 skilled, 9 semi-skilled and 6 unskilled), each completing a full 8-hour trial session. The total plates produced over 8 hours was recorded and converted to an hourly production rate; the percentage of plates passing a combined visual and manual flexural quality check was taken as the plate accuracy score. Descriptive statistics, one-way ANOVA and Pearson correlation were applied as described in Section 2.4.

Discussion

The machine closes all eight gaps identified at the outset, though not all to the same degree. On cost, the ₹32,000 prototype sits an order of magnitude below the ₹3-5 lakh of a commercial hydraulic press. On power, demand falls from the 2.2-3.7 kW of a three-phase hydraulic machine to 550 W (prototype) and 723 W (full-scale design) on a single phase, both within the 1 HP (746 W) total-load ceiling that 70.3% of respondents preferred, which is what makes operation on a village supply realistic in the first place. Usability is served by push-button control and a dial thermostat, safety by the interlocked enclosure and emergency stop, and maintainability by standard sections, ordinary fasteners and a modular layout that a district workshop can service. Temperature held within ±5 °C at prototype scale, which is adequate but is the weakest of the eight and is the reason a digital controller is planned (Astrom et al., 1995) [26] . The survey data are worth dwelling on, because they carry a message that is easy to miss. Respondents did not rank throughput first. They ranked cost, safety and ease of operation first, and they agreed with one another most tightly on exactly those three. Throughput mattered, but it was not the binding constraint. This inverts the priority order that the commercial machines embody, and it explains why those machines, for all their output, have not diffused into forest-fringe villages. Designing to the users' own ranking rather than to a specification sheet is the substantive contribution here. The Pareto result reinforces the point. Six complaints account for roughly four-fifths of everything respondents raised, and the top five for 70%. Cost, power, weight, output, safety and maintenance are therefore where design effort pays; the remaining complaints are real but secondary. It is worth noting that this ranking was stable enough that fifth and sixth place were tied on frequency, so the vital few should be read as a group of six rather than as a strict ordering. One substitution made under duress turned out to be an advantage. The direct-current motor and switched-mode controller, adopted only because the intended alternating-current geared motor was unavailable, allow the stroke rate to be varied through pulse-width modulation. That means the operator can adjust pressing speed to suit leaves of different thickness and moisture content without touching the mechanism, which is genuinely useful when a single machine must handle both Sal and Siali. The production design should keep this capability rather than revert to a fixed-speed drive. Set against the two closest precursors, the machine occupies a middle ground. It offers better temperature control and lower operator fatigue than either the biomass-fired machine [12] or the grassroots motorised design [11] , while staying inside their affordability envelope. Against a commercial hydraulic press (Table 1) it trades peak throughput for a large reduction in capital and running cost, and the survey suggests that this is the trade the intended users would themselves make. At a projected full-scale cost within ₹50,000-₹70,000, the machine falls within reach of a self-help group borrowing through a livelihood scheme or a microfinance lender, which is the condition on which any livelihood gain depends (TRIFED, 2018) [7] . The present study has two limitations. First, the full-scale output figure is a projection from half-scale stroke rates rather than a measured value, and needs confirmation on a full-scale build. Second, plate quality was judged by visual inspection and manual flexural loading rather than standardised testing, so claims about strength and moisture resistance remain qualitative; a formability protocol such as limiting dome height testing (Mohanty et al., 2021) [27] would put these on a quantitative footing.

Conclusion

A compact, low-power leaf plate moulding machine was designed, built at half scale and evaluated against requirements elicited from the people intended to use it. Benchmarking of four existing technology families across eight design dimensions showed that none satisfies more than four simultaneously in a tribal self-help group setting. A survey of 74 stakeholders identified low machine cost, operational safety and ease of operation as the dominant requirements, with strong agreement among respondents, and a Pareto ranking showed that six problems account for 81.5% of all complaints recorded. These findings produced a quantified target set, and the resulting design, a crank and connecting rod press with electrically heated aluminum dies, met it: the prototype held die temperature within ±5 °C of the 130 °C set point, drew 350-400 W steady state on a 550 W connected load, cost about ₹32,000 to build, and ran its safety features reliably, while producing 554 plates/hour during trial. The wider lesson is that the constraint on mechanizing this trade has not been throughput but affordability, safety and simplicity, and that designing to that order of priorities produces a different machine from the one the market currently offers. In future work an improved design with digital temperature control, automatic leaf feeding and plate ejection, solar operation for electricity-deficient villages should be developed with a techno-economic survey and input from the forest dependent people, for the forest fringe villages for even more wider adoptability.

Acknowledgement

AcknowledgementThe authors gratefully acknowledge Dr. Arvind C. Ranade, Director, National Innovation Foundation -India, for his encouragement and institutional support. The authors also thank Dr. Ganesh M. Bapat, Department of Mechanical Engineering, BITS Pilani, for his guidance throughout this work. The authors also thank the self-help group members, tribal leaf plate makers and livelihood programme officers across Odisha who took part in the field survey, and the workshop technicians who assisted with prototype fabrication.

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