Machine Design Components II

Term Project
Design of an Industrial Spiral Dough Mixer Machine
Spring 2024
Due Date: Would be notified on the class sessions as well as email, for each activity

Introduction:
There are two main types of mixers found in a bakery, planetary and spiral:
Planetary mixers, also know as vertical mixers, offer a variety of options for bakers. While
they are primarily used for mixing cookie, cake and pastry doughs, they can also be used to chop
meat and whip up creams, meringues and icings. Planetary mixers also have a variety of
attachments that work for specific types of recipes. Planetary mixers have one motor with a
non-rotating bowl and come in a variety of sizes from table-top to larger 60-quart bowl mixers.
Spiral mixers are generally larger mixers and placed on a kitchen floor. Space in the
bakery area should be accounted for when looking for a spiral mixer as they take up more room
than a planetary mixer. The types of doughs that require a spiral mixer are artisan breads,
bagels, pizza, and other heavier denser doughs. Unlike the planetary mixer, both the hook (arm)
and bowl are able to rotate. The bowl's ability to rotate in both directions allows for proper
dough consistency and perfectly blended ingredients. The reason one wants to mix the bread
doughs in a spiral mixer as opposed to a planetary mixer is that the spiral hook attachment
mixes and kneads the dough all at once. The movement of the bowl and spiral arm keeps the
dough from overheating and fermenting too quickly.

Fig. 1- Planetary (left) and spiral (right) mixer representation

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A spiral mixer has a fixed dough hook that spins in place in the head of the mixer as the bowl
rotates. Due to the design of the hook and its motion, it is incredibly efficient at quickly
strengthening bread dough. Additionally, it incorporates a relatively large amount of air into the
dough during mixing, which can help result in a more open loaf of bread. In some cases, the
spiral hook could be replaced by other attachments, such as wire whip, and flat beater, via its
connector key, or flange. A spiral hook has been shown below:

Fig. 2- A spiral hook

A breaker bar is a straight piece of metal that extends down into a mixer’s mixing bowl. The bar
is either attached to the mixer’s top and extends down, or sometimes it’s a part of the mixing
bowl itself and extends up. In the case of the mixing, it’s attached to the tilting mixer head,
raising and lowering as the head is unlocked or locked into place, respectively.
When the tilting head is locked, the breaker bar is positioned close to the rotating spiral dough
hook and scrapes dough off the hook as it spins during mixing. Think of it as someone holding a
spatula against the dough hook as it spins: the dough scrapes off the hook with each revolution.
A breaker bar with a spiral dough mixer prevents the dough from climbing up the dough hook,
which will eventually require you to stop the mixer and scrape the dough back into the mixing
bowl. The breaker bar is shown in the subsequent figure.
The mixing bowl rotates around the center of the rotary plate. It fits onto the locking plate by
inserting by some metal nubs into holes cut out into the plate.
For removing the bowl, the mixing head is tilted up. The tilting head locks into place with a set of
screw levers, one on the right and one on the mixer’s left. These levers unlock the tilting mixer
head by screwing it in and out. The on-button will function when the mixer head is down, and
the screw is sufficiently screwed in.

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 Fig. 3- The breaker bar, rotary plate, bowl, and tilting head

The project description:

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 - Weight of the dough: 33 kg (by considering the 1:4 ratio of the total volume of bowl, after
kneading)
- Revolution speed of the hook: 56 rpm
- Revolution speed of the bowl: 7 rpm (the 1:8 ratio between the bowl and the hook
angular velocities)
- Estimated torque at the root of the hook: 500 N.m
- Estimated bending moment at the root of the hook: 60 N.m (due to rotation of the bowl)
- Estimated axial force at the root of the kook: 25 kg (this axial force must be considered in
both directions of rotation of the bowl)
The last three items are related to the weight, density, viscosity, shear rate the dough, which
could be calculated or determined empirically.
A comprehensive and detailed design of this system is the subject of the term project of this
course. This project has a valuable portion of the score of the course. Various items and
activities of the project have to be carried out and submitted during the course sessions, as
listed below:
1- Conceptual design of the machine (20 points)
2- Selection of the electromotor for the power source (using an Iranian electromotor
manufacturer catalog with some technical descriptions) and solid modeling of the
electromotor (5 points)
3- Design of the kinematic chain of the power transmission system of the machine (20
points)
4- Detail Design of the power transmission system of the machine 1: Material selection for
gears and shafts with reasons and descriptions, design of gears using the metric version
of ANSI/AGMA, geometric design of the gearbox shafts, static and fatigue design of the
gearbox shafts, geometric and mechanical design of keys, design and selection of
bearings, solid modeling of the assembly and explosive view. Mechanical design and
calculations must be carried out using KISSsoft (60 points)
5- Detail Design of the power transmission system of the machine 2: Solid modeling of the
remaining parts of the power transmission system of the machine and final assemblage
of the system (15 points)
6- Final design and assembly of the system (25 points)

Some notes:
1- Each one of the project items and activities has the specified points (if done correctly and
submitted by the due date).
2- All of the calculations must be conducted in metric system.
3- There is a desirable concentration on conceptual design, knew of machine elements, and
software skills in the projects.

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4- The report of each item must be submitted in a single PDF file. Other files (such as the
report in the Microsoft Word format, picture files, and drawings) are valueless and will be
ignored. If the drawing files are needed for more accurate investigations, an email will be
sent to the student.
5- Submitting the reference documents (such as datasheets, catalogs, and websites) is
necessary, if it has been emphasis on the description of the project activity.
6- A folder will be made for each student and any of the received files would be saved there.
Hence, please submit the intended report for each activity, and DO NOT SUBMIT THE
PREVIOUS PARTS OF THE PROJECTS.
Disobedience from the above notes would lead to negative effects on the project ratings.

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