CHAPTER 4: DIRECTIONS AND SOLUTIONS FOR DESIGNING THE MIXING AND
4.2. Directions, solutions and selection of design plans
4.2.2. Analyzing the directions and selecting design plans
Technical requirements:
- Able to mix the filling ingredients, can scrape stuck ingredients around the walls of the hopper.
- Able to eject the filling into the measuring mold.
- Ensure moderate capacity of 10kg.
Option 1: Fixed hopper, rotating shaft including mixer-wing and
auger-filler
Option 2: Rotating hopper, fixed mixing shaft
Action
Putting the filling into the hopper, the mixing wing will rotate to stir the ingredients, then the auger-filler will eject the filling into the measuring mold.
Putting the filling into the rotate hopper, the mixing wing, which installed on the fixed shaft, stir the filling ingredients well, then the auger-filler will eject the filling into the measuring mold.
Advantage
Suitable for small and medium capacity requirements.
Easy to design and manufacture.
Easy to install and repair.
Suitable for large-scale production with large material capacity.
Defect Not suitable for industrial scale production.
Suitable for industrial scale production.
Complex structure.
Difficult to design and manufacture Table 4.4: Choosing the mixing mechanism
Figure 4.10: The mixing mechanisn for option 1 [3]
Figure 4.11: The mixing mechanisn for option 2
Conclusion: Based on the capacity requirements and especially the customer's production scale, we choose option 1 for manufacturing.
Implement the selected plan:
Fabricating a storage hopper suitable to the proposed capacity volume and install it securely with the measuring mold. Install the mixer-wing and auger-filler onto the rotating shaft. Install the rotating shaft with the motor placed above the hopper and connect to the
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rotating shaft through a coupling for easy disassembly and cleaning. The shaft is supported and fixed by thrust ball bearings.
b. Choosing the measuring method Technical requirements:
- Measuring the correct amount of filling mass required by the customer.
- Match the size of the pressed filling to the size of the rice paper to avoid bulging or missing filling during the rolling process.
- The shaped filling has uniform output dimensions.
Option 1: Measuring by screw feeder method
(stated in 3.4.1)
Option 2: Measuring by table feeder method
(stated in 3.4.2)
Option 3: Measuring by the partical quantification method
(stated in 3.4.4)
Action
Using a screw placed horizontally to directly eject the filling into rice paper.
Using the rotating disc, the filling flows down the rotating disc and comes into contact with the plow and then falls onto the rice paper.
Using auger-filler placed vertically to eject and press the filling into the mold to measure and give it the required shape, then it is forced to fall onto the rice paper.
Advantage
Suitable for bulk materials.
Ensuring accurate feeding when
productivity is high.
Suitable for measuring small granular and dry powder materials.
Ensuring accurate feeding when
productivity is high.
Easily measure the filling with high accuracy for small and medium production scales.
Defect
Large in size when manufactured.
Complex structure.
Unable to produce the uniform filling shape and mass.
The method has a
complex structure due to the need to design a measuring mold.
Table 4.5: Choosing the measuring method
Figure 4.12: Screw feeder Figure 4.13: Table feeder Figure 4.14: Partical quantification
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Conclution: For suitable the machine production scale and actual using as well as economics, we choose option 3 for manufacturing.
Implement the selected plan:
Design and manufacture a measuring mold following the customer's requirements for filling volume, combined with ejection using the auger-filler in the mixing mechanism and forced-pushing operation to push the filling fall onto the rice paper at a suitable position that suitable for later rolling stages. The measuring mold is designed to have a cavity with the ability to be pushed out and pulled in by a push cylinder. The dimensions of the cavity mold will be calculated to suit the filling volume required by the customer and the output shaped fillings easy to roll.
c. Choosing material for manufacturing the measuring mold Technical requirements:
- The mold is highly durable and resistant to abrasion.
- Having reasonable manufacturing and processing costs.
- Ensuring food safety and hygiene.
Option 1: Aluminium alloy
Option 2: PTFE
(TEFLON) Option 3: POM
Properties
Aluminum is a metal widely used in industry, is light in weight and highly resistant to corrosion.
Teflon plastic is a high- density engineering thermoplastic with the original English name PTFE, short for Poly TetrafloEtylen
(Polytetrafluorethylene).
POM
(Polyoxymethylene) is an engineering
thermoplastic widely used in many industries.
Advantage
Light-weight High corrosion resistance No rust
Easy to process and cutting
Easy to clean
Not transformed into toxic substances Good weather resistance
Ensuring the best
hygiene and food safety Able to control
Good heat resistance Fire protection Great hardness Resistant to most chemicals
No adhesion No change in state between -190°C and 300°C
Friction coefficient is very low
High hardness
High abrasion resistance Wide operating
temperature range (-40°C
~ 120°C)
Good impact resistance Low friction coefficient Resistant to water and chemicals
Most reasonable price (6,500,000 VND/plate)
44 tolerances when
machining
Defect
High price (8,500,000 VND/A6061 aluminum plate)
Easily deformed when impacted to external forces.
The price is very high compared to POM and aluminum alloy
(27,000,000 VND/plate).
Surface gets dirty easily Easily deformed when machining or cutting High expansion rate when weather condition changes.
Table 4.6: Choosing materials for manufacturing the measuring mold
Figure 4.15: Materials options for manufacturing the measuring mold
*Plate dimentions: 1000mm x 1000mm x 30mm.
*Material costs are referenced andsynthesized on the market.
Conclution: The cost requirements have been set by the customer, we choose option 3 for manufacturing.
Implement the selected plan:
Machining measuring mold made of POM plastic according to each part using a CNC machine and completely assembling, the filling mass parameters will be calculated and the most suitable mold cavity dimensions will be calculated to ensure low weight error and the most uniform output shaped-filling to ensure the smooth operation of the next working structures on the entire automatic spring roll rolling machine line.
d. Choosing the mold cavity pushing mechanism Technical requirements:
- The mold cavity ejection mechanism must operate stably and smoothly.
- Easy to design, manufacture, assemble and control.
- The structure is highly durable, does not require too strict maintenance.
45 Option 1: The mold cavity is pushed and pulled by a pneumatic
cylinder
Option 2: The mold cavity is pushed and pulled by a rack and
pinion mechanism Action
Using a pneumatic cylinder to pull and push the mold cavity into and out of the measuring mold.
Using a rack and pinion
mechanism to pull and push the mold cavity.
Advantage
Simple structure
Easy to design and manufacture Easy to install
High traction
Stable push-pull movement
Defect Not suitable for heavy molds Complex structure
High manufacturing costs Table 4.7: Choosing the mold cavity pushing mechanism
Figure 4.16: The mold cavity pushing
mechanism for option 1 Figure 4.17: The mold cavity pushing mechanism for option 2
Conclution: The structure does not require high tensile force, it must have a low price and be easy to manufacture. assembly and maintenance, so we choose option 1 to manufacture.
Implement the selected plan:
Installing the pneumatic cylinder with the mold cavity to perform push-pull motion. The cylinder is connected to the mold cavity through a threaded fastener for easy disassembly and cleaning of the mold after use.
e. Choosing material for manufacturing the push-head of forced-pushing structure Technical requirements:
- Good impact resistance.
- High adhesion resistance.
- Ensuring food safety and hygiene.
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Option 1: POM Option 2: PTFE (TEFLON)
Action
The forced-pushing mechanism is activated, the cylinder pushes the POM plastic block down, forcing the filling to fall onto the rice paper on the conveyor.
The forced-pushing mechanism is activated, the cylinder pushes the Teflon plastic block down, forcing the filling to fall onto the rice paper on the conveyor belt.
Advantage Low price to buy material Anti-adhesion ability
Defect
The filling easily sticks to the surface of push-head.
Easily deformed when machining or cutting.
High price to buy material
Table 4.8: Choosing material for manufacturing the push-head of forced-pushing structure Conclution: Due to the small dimensions of the push-head, we can choose to make it with Teflon material to both ensure material costs, have good anti-adhesion ability according to the requirements and ensure food hygiene and safety. Choosing option 2 to manufacture.
Implement the selected plan:
The push-head is machined from Teflon plastic material with the appropriate dimensions so that the forced-pushing mechanism can operate effectively and the filling does not stick to the push-head suface, avoiding delay the time of the filling falling, causing deviations in position of the filling on the rice paper.