A Novel Approach to Robotic Pizza Preparation

University of Florida | Herbert Wertheim College of Engineering | Honors Thesis | Spring 2020 1

Abstract— This study aims to design, build, and test a robotic

system to produce four 10-inch pizzas in under 5 minutes. To

support subsystems that apply tomato sauce and shred cheese, a

rotating cantilever beam robotic system was designed. Motor

specifications were calculated before implementation. Subsystems

and their actuators showed desirable performance during

actuation. As well, stiffness and improved tolerances would benefit

the entire system for future system-level integration.

Index Terms— Design, Pizza, Robot, Tolerances, Torque

I. INTRODUCTION

HE topic of this study includes creating the proof of

concept of a robotic system that prepares food. The purpose

of this technology is to alleviate the fast-casual restaurant

industry’s 150 percent turnover rate [1]. With over 300,000

quick service and fast casual restaurants in the US, this

volatility becomes a problem at scale [2]. Implementation of

robotic systems may exclude workers from tedious tasks,

kitchen hazards, and proactively reduce food-borne illness

transmissions. Used as a tool, this technology can reduce the

demanding nature of the job, easing turnover.

Some examples of technology currently in-use, includes

McDonalds’ ordering kiosks and Caliburger’s installment of

Flippy, a robotic arm that flips burgers and works a fryer [3-4].

An area that this technology may automate includes pizza. Not

only a very popular food, pizza has layers and offers simple

preparation processes.

This study aims to explore the mechanical and electrical

engineering design of a robot that prepares four 10-inch pizzas

in under 5 minutes. Tested features of the system will be cheese

shredding, sauce pumping, and pepperoni slicing. Once the

designed machine has ingredients manually loaded and set to

run, the processing should be entirely hands-off to exhibit

autonomy and practicality over pre-existing appliances.

II. METHODOLOGY

Designs and approaches were selected based on simplicity,

economy, and food safety. The system design was pipelined

into different categories to develop the product. Subsystems

were programmed and tested individually before final system

integration. Design reviews were held as needed to ensure

milestones were reached with punctuality and efficacy.

Hardware Design

The subsystems automated the following processes: sauce

extrusion and cheese grating. Unique designs were hand

sketched, illustrating potential designs (Fig. 1). The rotating

cantilever beam (crane) design was selected for its minimal

footprint and lenient tolerances. The structure consisted of

mostly t-slotted structural framing and additively manufactured

with ABS plastic. The framing easily assembles, offering high

modularity. ABS plastic offered higher flexural strength than

PLA and was the most available material in terms of resources.

Fig. 1 Hand sketches of different structures to support the subsystems. Some

designs resemble a translating gantry system and others draw from 3D printer

frames. The rotating cantilever beam was the selected design.

As well, the cheese grater design selection prioritized the

least amount of actuators and the easiest setup. This led to a

design of a grating drum mounted at an incline of 45 degrees

with cheese fed from above by dead weight. The grating drum

belonged to a manually cranked cheese grater before

incorporation into the system. As well, a load cell on the

carriage monitors the weight of the cheese subsystem (Fig. 2).

Fig. 2 The carriage subsystem. The carriage’s load cell connects the cheese

grater subsystem to the rest of the carriage. The carriage has hosing nipples for

sauce dispensing.

A Novel Approach to Robotic Pizza Preparation Aaron Sager

Herbert Wertheim College of Engineering

T


Using the density of mozzarella cheese and the

recommended serving by weight on a given pizza diameter, the

volume of the cheese container was calculated to accommodate

at least four pizzas [5-6]. Dividing the volume V by the length l

of the container, the cross-sectional area for a box tube was

found and searched on McMaster-Carr for part sourcing (1).

𝐶𝑟𝑜𝑠𝑠 − 𝑆𝑒𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝐴𝑟𝑒𝑎 = 𝑉/𝑙 (1)

For the sauce extrusion method, a peristaltic pump offered

high flowrate processing and allowed high flexibility for the

sauce reservoir location (Fig. 3).

Fig. 3 The peristaltic pump (dark blue part) and transparent sauce jar are located

at the end opposite of the carriage. That location utilizes their weight as

counterbalances to the carriage. As well, bringing a mass closer to the point of

rotation reduced the system actuator’s torque requirements.

The actuators in the system had hand calculations performed

to achieve desired performance. To calculate the torque T of the

actuator on the carriage, the carriage mass m and acceleration a

were selected as nominal values and the distance r set to the

radius of the pulley (2). To find the value for acceleration a, a

desired velocity v was divided by the desired amount of startup

time t to achieve it (3).

𝑇 = 𝑚 ∗ 𝑎 ∗ 𝑟 (2)

𝑎 = 𝑣/𝑡 (3)

To calculate the torque T of the actuator rotating the beam,

the carriage mass m and distance to the point of rotation d

squared were used to find the rotational inertia (4). That

approximated the carriage mass as a point mass in space,

assuming the beam weight as negligible. With rotational inertia

I multiplied by rotational acceleration α, torque T was found (5).

𝐼 = 𝑚 ∗ 𝑑2 (4)

𝑇 = 𝐼 ∗ 𝛼 (5)

The peristaltic pump flowrate was sized to pump twice as

much what the system would require to produce one pizza in

under one minute (Fig. 4).

Fig. 4 The INZOK 12 V DC peristaltic pump used for saucing the pizza. It has

food safe functionality as sauce never makes connect with anything other than

the hosing. Maximum flowrate is 400 ml/min [7].

As well, the brushed DC motor for the cheese shredder was

sized to have comparable power P as commercial OTS electric

handheld cheese graters (6).

𝑃 = 𝑟𝑝𝑚 ∗ 𝑇 (6)

SolidWorks CAD software was utilized to realize the

design’s assembly for sizing and fabrications processes (Fig. 5).

The final design had the cheese grater subsystem mounted to

the translating carriage. A jar full of sauce adjacent to the pump,

incrementally forces out sauce through hosing and a nipple

mounted to the carriage.

Fig. 5 Isometric view of system assembly produced in SolidWorks. The

system’s base stays in the center of the work area and prepares ingredients atop

the dough of four pizzas surrounding it.

Limit switches keep the carriage within the acceptable

operating range and to help home the system’s starting location.

Encoders attached to the stepper motors actuating the carriage

and beam rotations also ensure accuracy within the system.


Electrical Design

For control of the DC motor and peristaltic pump, an H-

bridge actuated each motor independently at different speeds

based on separate enable and pulse-width modulation (PWM)

signals. The H-bridge and stepper motor drivers operated with

a 12 volt (V) and a 24 V power supply, respectively.

To control the entire system, an Arduino MEGA 2560 R3

offered an ample 54 digital input/output (IO) pins with 15

capable of providing PWM. Additional electronics include an

OLED display to indicate to the user the current function or

process of the robotic system.

Programming and Software Design

At a high level, the process flow of the robot system begins

with homing the carriage’s theta and rho position. From there

each stepper motor moves a prescribed amount to reach a

dispensing location. The robot repeats that sequence twice,

once for saucing and once for cheese shredding. Once

completed, the robot would rotate 90 degrees and repeat the two

sequences twice, reoccurring twice more after to get 360 degree

coverage (Fig. 6).

Fig. 6 Top view of system assembly. The system operates in polar coordinates

to access dispensing locations. Once one pizza has toppings, the system offsets

90 degrees and restarts all sequences.

If the robot’s carriage or beam’s rotation angle exceeded the

acceptable operating range, interrupts tied to limit switches

ensured the actuators back-tracked to the safe operating zone.

The programming of the robot occurred in MATLAB and the

Arduino Integrated Development Environment (IDE). In

MATLAB, an array of steps for each stepper motor was created.

To create this, cartesian coordinates of concentric rings

decreasing in size were added to an array. The coordinates were

transformed into steps per inch SPI through knowing the

number of steps per revolution SPR, the microstepping factor

MF, the pulley pitch and the number of teeth on the pulley (7).

𝑆𝑃𝐼 =(𝑆𝑃𝑅 ∗ 𝑀𝐹)

𝑃𝑢𝑙𝑙𝑒𝑦 𝑃𝑖𝑡𝑐ℎ ∗ # 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ

(7)

After that the coordinates were transformed to polar

coordinates (Fig. 7). Indexing through the array, the rounded

difference between each adjacent values were inserted into the

final array. This array serves as an instruction list for the

machine to occupy the dispensing locations.

Fig. 7 Polar coordinates of topping dispensing locations. The red dot indicates

the start location for the first pizza. The unit of rho is inches.

Testing Procedures

The goal of testing was incremental validation and parameter

tuning. The plan for testing stepper motors involved

independent operation, then together, then with limit switches

interrupting normal operation, and then finally on the system.

The brushed DC motor and peristaltic pump plan was similar

except they were tested with nothing and water, respectively,

before processing cheese and sauce, respectively.

Troubleshooting tools utilized during testing include a

multimeter, an oscilloscope, and the built-in LED of the

Arduino MEGA. The multimeter identified weak connection

points and verified when desired voltages were not present. The

oscilloscope verified switch bouncing (Fig. 8). Lastly, the

LED’s flashing offered rapid testing of new code.

Fig. 8 Voltage signal (V) vs time (s) during limit switch pressing. The sudden

bouncing of the signal indicates switch bouncing characteristics.


As well, during functionality definition of the system,

shearing cured meats like pepperoni was explored. Other

research papers recorded the shear force required to slice beef

salami as 178.4 ± 18.8 N [8]. A pepperoni stick shear strength

test was conducted with a universal testing machine, indicating

a 125.6 ± 0.628 N shear force was required to slice (Fig. 9-10).

As well, 11.3 ± 5.65 E-2 Nm of torque would be needed for

blades 2.25 inches long.

Fig. 9 Load (N) vs Extension (mm) for pepperoni stick specimen. A maximum

shear force of 125.6 ± 0.628 N was found in test 1.

Fig. 10 The pepperoni stick shear testing setup used an in-house sheet metal

blade design. The universal testing machine used an Instron 2580 Series load

cell.

III. RESULTS

The project demonstrated subsystem efficacy as the

peristaltic pump effectively delivered tomato sauce and the

cheese shredder shredded cheese (Figs. 11-12). The stepper

motor actuators indicate they can hit all dispensing locations

within the desired time limit.

Fig. 11 Cheese Shredder subsystem created a pile of cheese that it shredded.

The subsystem performed better when cheese was more recently chilled than

compared to a block exposed to room temperature.

Fig. 12 The sauce pump moved sauce from one jar to another. The peristaltic

pump delivered the sauce in incremental slugs as the rollers of the pump were

actuated.

The final structure assembles together with a need for support

at the end of the cantilever beam (Fig. 13). Results are to be

determined for the entire integrated system.

Fig. 13 A portion of the robot’s frame structure was finished. The base could

utilize added weight to the bottom of the base for tipping protection.

0

20

40

60

80

100

120

140

0 10 20 30 40

Lo

ad (

N)

Extension (mm)

Test 1

Test 2


IV. DISCUSSION

The project showed the efficacy of the subsystem designs. As

well, the programming of the machine showed desired

performance in testing. The study had value outside of

anticipated results as they were a good exercise in robotics, too.

Room for Improvement

Tolerances, clearances, and stiffness within the system could

be improved further. The tolerance stack at the connection at

the column of the static mount on the beam was not tight enough

(Fig. 14). The oversized clearance within the hole that a flanged

bearing sits in resulted in a drive shaft that wobbles, causing the

driven gears to not mesh consistently and the horizontal beam

to rest at a decline. To fix this, test articles should have been

printed to quantify the tolerances on inner and outer diameters.

With those printer specific tolerances, parts could be revised for

more accurate clearances.

Fig. 14 This vertical column that supports the horizontal beam required tighter

tolerances for the hole where the flanged bearing and D-shaft fit. Printing test

articles to get a better idea of the specific printer tolerances would be valuable

in the future.

As well, the tolerances for the heat insert holes on the 3D

printed gears were too small and required multiple placements

and removals until a fastener could thread through the heat

insert without plastic clogging the insert’s threads. After

successful installation, a fastener torqued too much could

uproot the heat insert (Fig. 15). Purchasing gears with set

screws would have been the optimal choice. Alternatively, the

hole tolerances could have been adjusted with more accurate

tolerances from test articles.

Fig. 15 After installation, the fastener had uprooted the threaded heat insert. The

hole diameter where the heat insert goes should have been increased or an OTS

gear with a set screw should have been purchased.

Lastly, the 3D printed part that connects the carriage to the

cheese shredder subsystem deflected a non-significant amount

(Fig. 16). To address this, the deflection could be decreased by

increasing the print in-fill density, increasing the moment area

of inertia of the 3D printed cross-section, and/or bringing the

center of gravity of the cheese shredder subsystem closer to the

point fastened to the carriage.

Fig. 16 The load cell connecting the cheese shredder subassembly to the rest of

the carriage displays deflected a nonsignificant amount. The load cell would

ideally be parallel to the table if deflection was not present.

Study Limitations

Due to the COVID-19 pandemic, there was limited access to

3D printing parts with new tolerances and added stiffness. Parts

can be revised and reprinted at a future date when resources

become more available.

V. CONCLUSION

In conclusion, a rotating cantilever beam robotic system was

designed to produce four 10-inch pizzas in under five minutes.

It utilized two stepper motors, one brushed DC motor, and one

peristaltic pump to dispense tomato sauce and shred mozzarella

cheese. The subsystems and programming of the actuators

showed desirable performance. Pepperoni slicing functionality

feasibility struggled after a shear test indicated a need for over

11.3 Nm of torque.


At the system level, verifying tolerances before all parts are

printed could ensure better coupling. As well, stiffness could be

added to the carriage through increasing print infill density

and/or increasing the moment area of inertia of cross-sections.

REFERENCES

[1] E. Rosenbaum, Panera is losing nearly 100% of its workers every year as fast-food turnover crisis worsens, CNBC, Aug. 29, 2019. Accessed

on: April 17, 2020. [Online]. Available:

https://www.cnbc.com/2019/08/29/fast-food-restaurants-in-america-are-losing-100percent-of-workers-every-year.html

[2] QRS Magazine Report: Total U.S. Restaurant Count Down 2 Percent in

2017, QRS Magazine, Feb. 15, 2018. Accessed on: April 17, 2020. [Online]. Available: https://www.qsrmagazine.com/news/report-total-us-

restaurant-count-down-2-percent-2017

[3] S. Whitten: McDonald’s to add self-order kiosks to 1,000 stores each

quarter, June 4, 2018. Accessed on: April 17, 2020. [Online]. Available:

https://www.cnbc.com/2018/06/04/mcdonalds-to-add-self-order-kiosks-

to-1000-stores-each-quarter.html [4] C. Albrecht: CaliBurger Adds a Second Flippy Robot to Make French

Fries, Oct. 2, 2019. Accessed on: April 17, 2020. [Online]. Available:

https://thespoon.tech/caliburger-adds-a-second-flippy-robot-to-make-french-fries/

[5] Burke Corporation: Pizza Topping Portion guide, Burke Corporation.

Accessed on: April 17, 2020. [Online]. Available: https://www.burkecorp.com/wp- content/uploads/2017/01/

BurkeCorporation_PizzaToppingsPortionGuide.pdf [6] Aqua-Calc: Cheese, mozzarella, low moisture, part-skim, Aqua-Calc.

Accessed on: April 17, 2020. [Online]. Available: https://www.aqua-

calc.com/page/density-table/substance/cheese-coma-and-blank-mozzarella-coma-and-blank-low-blank-moisture-coma-and-blank-part-

skim-blank--op-cubic-blank-inch-cp-

[7] Amazon INZOK 12v DC Large Flow Dosing Pump Peristaltic Pump Upgrade 304 Stainless Steel Roller for Vacuum Aquarium Lab

Analytical, Amazon. Accessed on: April 17, 2020. [Online]. Available:

https://smile.amazon.com/Peristaltic-Dosing-Vacuum-Aquarium-Analytical/dp/B07HDQJT8P/ref=sr_1_10?keywords=peristaltic%2Bpu

mp&qid=1566494797&s=gateway&sr=8-10&th=1

[8] Dincer, Tolga & Erdem, Ömer & Şen Yılmaz, Evren. (2017). Comparison of the mechanical properties of meat and fish salamis. Ege

Journal of Fisheries and Aquatic Sciences. 34. 443-449.

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A Novel Approach to Robotic Pizza Preparation