Máy cắt tuốt dây điện tự động 2 đầu dây điện 1 lớp. Đồ án này đã được thông qua và đạt kết quả 910 cuối kì. Báo cáo thể hiện cách tính toán chọn động cơ, thiết kế cơ khí, thiết kế mạch điện và thuật toán sử dụng. Ngoài ra, còn mô phỏng, rồi cho ra kết quả cuối cùng.
OVERVIEW OF METHODS OF CUTTING AND STRIPPING
Popular methods of stripping and cutting electrical wires today
1.1.1 Manual wire cutting and stripping method
The method of using specialized pliers to cut and strip electrical wires is a common method for professional electricians With this method, there are usually the following steps:
Step 1: Place the wire you want to strip into the pliers If you want the strip to be longer, remove the red pin and push in more wire
Step 2: Squeeze the pliers hard, the cutting blade will automatically separate the wire sheath for you with the smaller wires (the gut of the wire above, for example) Doing the same will not cause your wire to break In addition, pliers can also be used to cut electrical wires with very sharp and neat cuts
Cost-effective, flexible and convenient, especially in small and simple jobs
It is time-consuming, labor-intensive, error-prone, and ineffective on a large scale When working with complex wires or in large-scale applications, it is often recommended to use automatic wire cutters and strippers to ensure the best performance and safety
Figure 1.1 Cutting and stripping electrical wires with pliers
1.1.2 Automatic wire cutting and stripping
The method of cutting and stripping electrical wires using a specialized machine is known to be a commonly used method in industrial production Machines are used to remove the outer insulation layer of electrical wires With this type of machine, cutting both ends becomes faster, more accurate, and much easier This method can accommodate many different sizes, helping to save a lot of time and labor
✓ Suitable for all sizes of electrical wires
✓ The working speed of the wire stripper is very fast and highly accurate
✓ The machine's wire stripping speed can be adjusted according to user requirements
✓ The blade of the wire stripper works very effectively thanks to rotating at high speed
✓ The length of the wire stripper layer can also be adjusted depending on requirements
✓ The working principle of the wire stripper is easy, safe, accurate, and extremely durable
✓ To meet user needs, there are 2 types of manual machines on the market: handheld machines and fixed machines
✓ The finished product of the wire stripper is both aesthetically pleasing and clean without affecting the wire core
• During the working process, the machine still makes noise
• The cost of an electric wire stripper is still higher than other types of strippers
Figure 1.2 Kodera Casting C377A and KS-W612 automatic wire stripping machines
Introducing several types of wire stripping machines on the market
1.2.1 KS-09I automatic wire stripping machine [1]
✓ Performs half-threshing, full-threshing and middle-threshing functions
✓ Supports 3-layer stripping, stripping length of each layer can be set differently
✓ The machine is driven by 4 strong rollers, capable of increasing the maximum capacity of 10.0mm2
✓ The sturdy steel blade cuts well and effectively
✓ The wire/cable conductor is designed to push up when stripping the wire end so that the wire end stripping length can reach 70mm
✓ The KS-09I electric wire stripper operates extremely easily, cutting to precise positions, achieving high productivity and operating for a long time
Figure 2: KS-09I automatic wire stripping machine
Threshing length Wire end 0-50mm, wire end 0-70mm
Cutting precision ± (0.002mm × Cutting length)
Display English LCD touch screen
Special functions Can strip 3 layers with different strip length for each layer How to move 4 moving rollers
Blade material hard Vonfram steel
1.2.2 Schleuniger EcoStrip 9380 automatic wire stripping machine [2]
✓ Three-in-one device: Schleuniger EcoStrip 9380 wire stripper with unique 3- position design of the wire feeding system enhances customer customization and can be set for normal mode, mode rolling or short mode - depending on application
✓ Easy to use: The Schleuniger EcoStrip 9380 is easily operated via the 5.7" color touch screen and Schleuniger S.ON software
Figure 1.3 Schleuniger EcoStrip 9380 automatic wire stripping machine
Maximum outer shell diameter 8 mm
Maximum wire cross-section 0.05 – 8 mm2
Option to cut wire short 46 mm (18 mm from cable sheath after stripping)
Connect Standard: Ethernet for PC, USB Optional: SMI
(I/O‘s), Prefeeder, Wire marker (HS), Inkjet printing, Stacker / Coiler
Overview of wire stripping cutting machine
1.3.1 Main structure of electric wire cutting machine:
Most types of automatic wire-stripping machines today have the same general structure As follows:
This motor is often attached to the belt shafts through the rotating shaft to transmit motion to the rollers, conveyor belts, rollers, and pulleys
Depending on the thinking of the designers/manufacturers, the motion mechanism will be equipped with servo motors and stepper motors for control
A roller is an item used to guide, support, or transport products
Rubber roller V groove roller Cylindrical roller
The load of each roller depends on the load of the product passing through it, thereby determining the type of manufacturing material, roller tube thickness, whether to use cast or welded tubes, and roller shaft parameters, use appropriate bearings
These types of rollers often have high durability and simple structures including ball bearings, roller shells, roller shafts, and some accompanying components The roller is installed on the shaft with a ball bearing, the outer ring of the ball bearing is tightly attached to the roller, and the inner ring of the ball bearing is attached to the shaft
The rollers mainly work on the outer surface, so their outer surface is machined with a certain roughness so as not to affect the roller's working process
1.3.1.3 Example of adjusting height and width
The screw is used to adjust the knife or roll opening
Figure 1.7 Example of adjusting height and width
The chassis is the main structure of the device and is responsible for bearing the load and supporting other structures and components It secures the components of the device along with other parts such as motors, batteries, controllers, and systems
The chassis helps protect important components inside the device from impact and damage from the external environment It can be designed to withstand impacts and forces from various road conditions, minimizing the risk of damage and ensuring the safety of users and other critical components
The chassis plays an important role in creating stability and balance for the device It is designed to ensure that gravity is distributed evenly and properly, helping the user maintain stability and control the device with ease
A screw coupling is a mechanical part that connects and transmits torque between two moving component shafts, usually connecting 2 shafts or connecting from a motor to a chain to operate a certain system
1.3.1.6 Wire stripping and cutting pliers
There are many different types of wire cutters such as V blade, C blade, and flat blade to serve different wire cutting purposes
Or we can also use pliers to cut and strip the wire
1.3.2 General operating principles of current wire stripping machines:
The wire taken from the wire supply part is threaded through the wire guide part and inserted wire puller The electric wire will be clamped tightly between two wire pulleys with appropriate clamping force and adjusted by a screw-nut mechanism
From the data the overall length of the wire as well as the length of the part that needs to be stripped
The operator provides information from the keyboard to the control software, which will calculate the number of pulses needed to supply the stepper motor The pulse parameters will be sent to the processor, which will then provide pulses for the stepper motor to operate The stepper motor uses transmissions to make the pulley rotate, pulling the wire to the required length
In manual data entry mode, the user enters the following parameters:
• Length of plucking section at each end
After the data has been validated (wire length to be stripped and line If the wire is within the allowable range of the machine), press the START button to start the machine To ensure safety when using or fixing machine process errors, you can press the STOP buttons to stop all machine processes The cycle can also stop when the number of products has been completed
Wire cutting and stripping blades Wire cutting and stripping pliers
CALCULATION AND DESIGN OF MECHANICAL PARTS
Design plan for rope pulling parts
2.1.1 Two-axis plan of co-rotation
In order to drive the two axes to rotate together with the requirement that the distance between the two axes can be adjusted, we can have options:
2.1.1.1 Option 1: Use a pair of cylindrical gears
Figure 2.1 The system drives a pair of cylindrical gears
+ The alignment height of the teeth decreases when we increase the axial distance
+ Narrow adjustment range To increase the adjustment interval, we must use gears with large modules
2.1.1.2 Option 2: Use two pairs of cylindrical gears
Figure 2.2 The system drives two pairs of cylindrical gears
+ When the adjustment interval is small, the matching height is not changed much + Avoid having to use gears with large modules
+ Simple structure, easy to arrange
+ Difficult to adjust at low speeds
2.1.2.2 Option 2: Use flat belts and ladder belts
Figure 2.4 Drive system using flat belt and ladder belt
+ Can drive between axes far apart
+ Thanks to the elastic properties of the belt, vibrations generated by loads are avoided
+ Change the effect on the structure
+ Thanks to the slippage of the belt, it is recommended to prevent overload occurring on the engine
+ The size of the belt transmitter is large compared to other transmitters: chains, gears
+ The gear ratio changes due to slippage between the belt and the wheel
+ The load acting on the shaft and drive is large (usually 2-3 times higher than that of the transmission
+ gear) due to the initial belt tension
+ Low belt transmission service life
Design of wire stripping cutting parts
2.2.1 Option 1: One fixed blade and one blade perform cutting movements
In this embodiment, one blade is held in place The other blade is linked into a cluster that can move translationally Translational motion is formed by a mechanism that turns rotation into translational motion, such as nut screw mechanism, tooth-gear rod When the stepper motor rotates, through the tooth belt transmission, the translational movement blade performs cutting, stripping the shell
+ Simple structure, easy to process and assemble
+ The cutting force is uneven, but with soft materials, the effect of this factor negligible
2.2.2 Option 2: Both blades perform the same cutting motion
In this case, similar to option 1, here we use 1 shaft connection and in the tamarind screw transmission, to say that 2 screws are directed in opposite directions to each other The translational and opposite movements of the 2 blades are formed by a mechanism that converts rotation into translational motion, such as a nut screw mechanism, due to opposite teeth
+ Simple structure, easy to process and assemble
Transmission plan for the machine
Large starting torque, easy-to-control speed, and direction, low price
• Must have its power circuit
✓ Powered directly from the AC grid
✓ Diverse and very rich in types, low price
• There must be an isolation circuit between the control part and the actuator to ensure safety and a small starting torque
• Complicated speed control circuit, often using an inverter
✓ Accurate position and speed control, no feedback circuit required
✓ Easy to control speed and direction
• There is no feedback so it may cause errors
✓ Precise speed control thanks to the feedback system
• Do not work in open circuit mode
Distance adjustment structure
Cheap price, easy to manufacture
• High contact stress, high friction, low efficiency
• It is difficult to eliminate the gap between the lead screw and the nut
2.4.2 Ball screw-ball nut transmission
✓ The structure to eliminate gaps and create initial tension is available
High cost, difficult to manufacture
Cheap price, easy to manufacture, simple customization and adjustment
Choose a machine design option with the following technical parameters: 19
From the characteristics and requirements of the project, we have come up with the following options for our cutting machine model:
❖ The design option for the wire drawing unit is to choose a direct-drive rotary shaft type
❖ The design plan for the wire stripping cutting unit selects one fixed blade and one blade to perform the cutting motion
❖ For the design of the transmission part in this project, we choose to use a stepper motor
❖ Design plan for the distance adjustment mechanism with not too high requirements of the model, we choose the adjustment mechanism with adjusting screw.
CALCULATION AND DESIGN OF CONTROL PARTS
Calculations for choosing an engine
We choose a wire with a length of 50m, and a cut wire with a defined width of 10mm2 Look up standard TCVN 6610-3- type of conductor that cannot be pressed tightly (NC) We have a mass of wire of 116.3 Kg/km
50m of electric wire has a mass of:
• The total mass of the coil (including the wire and the drum) 6 (Kg)
• The total weight of the coil (including wire and drum): 6 (Kg) => P = 60(N)
Calculate the energy in the drive
• The friction coefficient in transmission f = 0.15
3.1.1 Calculate the zipper and required clamping force:
• Force Required to pull the rope:
In there: k1 is the experimental coefficient of the wire-pulling part Get k1 = 1,2 k2 is the actual coefficient under load Get k2 = 1,2
• To make the rope pulley workable, the compression load Fn is:
K: is the contact safety factor
For power transmitters, K = 1.2÷1.5 For transmitters in measuring instruments,
K = 3÷5 f: is the friction coefficient between the pulley surfaces
• Substituting into the formula we have: ×
• To ensure a design productivity of 360 (m/min), equivalent to 100 (mm/s) Rotation speed of pulley: n = V day = 100 = 0,59 (round/s)
• We choose (rpm/s) = 36 (rpm/minutes)n2 = 0,6
• Capacity on the pulley shaft:
• To choose a motor, it is necessary to calculate the required capacity Call be the required power:𝑁 𝑐𝑡
In there, is the general performance: = = 0,98 × 1
We choose a stepper motor with the symbol: NEMA 17 40418 The basic parameters of this motor are as follows:
• We have the mass of the pulley pulling the rope: m puly = V × d
• With V being the volume of the pulley:
• With plastic pulley, d = 1,5(g/cm^3): 2 m puly = 117,81 × 1,5 ≈ 177(g)
• Weight of rubber coating: ≈ 23(g) ol
• Total mass of the pulley pulling the rope: m t = 177 + 23 = 200(g)
3.1.2.3 Torque acting on the shaft
• Considering in the OXY plane, we have:
• Considering in the OYZ plane we have:
Figure 3.1 Force distribution on the active axis
3.1.2.4 Calculate bending moments at dangerous points
• Calculate the diameter at 2 sections n-n and m-m according to formula (7-3)
• Shaft diameter at cross section n-n:
[σ] = 50( N (Table 7-2 [1]) mm d n−n ≥ 3 √ 2286 = 7,7mm Choose d n−n = 8(mm)
• Shaft diameter at cross section m-m:
• Diameter of shaft fitted with bearing: d = 8 mm a σ m a σ m a f σ
3.1.2.5 Test shaft according to safety factor
• We choose n-n cross section for testing
• The safety factor is calculated according to the following formula: n σ × n τ n = √n 2 × √n 2 ≥ [n] σ τ
• With the coefficient , the safety factor only considers normal stress:n σ σ −1 n σ K σ × δ ×𝖴 × σ σ × β
• With the safety factor only considers tangential stresses:n τ τ −1 n τ K τ × δ ×𝖴 × τ σ × β
• We have a two-dimensional rotation axis, so the stress changes in a symmetrical cycle: σ a = σ max = −σ min With M u = 2269 (N mm)
• The shear stress (torsion) changes according to the dynamic cycle τ max M X τ a = τ m = 2 2 × W o
• Flexural and torsional fatigue limits correspond to symmetrical cycles σ −1 ≈ (0,4 ÷ 0.5) × σ b I take (N/)σ −1 = 0.45 × σ b = 0,45 × 600 = 270 mm 2 τ −1 ≈ (0,2 ÷ 0.3) × σ b I take (N/)τ −1 = 0.25 × σ b = 0,25 × 600 = 150 mm 2
Coefficient that considers the influence of the average stress value on fatigue strength
• Choose by material For medium carbon steel: 0,1 và ≈ ≈0.05
• Based on table 7.4 (page 128), choose 0,88 = và 0,95, = 0.95 σ τ
• Looking at table 7.10 (page 128), choose Kσ = 1,95
− 1) = 1 + 1,6 × (1,95 − 1) = 1,57 When we change the parameters into the formulas we have
• With the safety factor only considers normal stress :n σ n σ = 270
• With the safety factor only considers tangential stresses :n t n τ = 150
• The safety factor is calculated according to the formula
Where n is the allowable safety factor In normal working conditions ≈ 1,5 n ÷ 2,5
The shaft satisfies fatigue strength
We plan to choose ball bearings
• Workability coefficient according to formula 8-1 page 158
In there : n: number of shaft rotations: n=0.6 (rpm/s) = 36 (rpm/min) h: service time: h00 hours
• Because we use a single row bearing, the equivalent density is calculated by the formula:
R: is the radial load (total reaction force at the support)
Kv: Coefficient considering which ring of the bearing is the rotating ring Looking up table 8-5, we have Kv = 1 m: is the axial load system in terms of radial load Looking up table 8-2, we have m=1.5
Kn: Temperature coefficient Looking at table 8-4 we have Kn = 1.1
Kt: Is the dynamic load coefficient Looking up table 8-3, we have Kt = 1.1
C = 6,47 × (36 × 8000) 0,3 = 281,44 Looking at table 14P, we get a single row ball bearing with symbol 608 with the following basic parameters:
3.1.3 Choose the controller and motor for the machine:
From the characteristics and requirements of the project, we choose the motor and controller for the machine as follows:
Components contained in the machine
Arduino Uno is a microcontroller board based on the Atmega328P chip
Digital I/O pin 16 (with 6 PWM output pin)
NEMA 17 stepper motor divides a circle into 200 steps Therefore, each angular step is 1.8 degrees
Flat beveled shaft end helps keep the pulley/coupling from loosening during operation
Rotation angle per step 1.8° (200 steps/revolution)
Step angle accuracy ±5% (full step, no load)
❖ This is an upgrade from the MG995 servo in terms of speed, traction and precision
❖ Servo MG996R has large torque
Pulling force 9.4 kg/cm (at 4.8V); 11 kg/cm (at 6V)
✓ Default address: 0X27 (connected to pins A0/A1/A2)
✓ Integrated rotary resistor to adjust contrast for LCD
Figure 3.6 16x2 LCD display and I2C circuit
3.2.5 TB6560 DRIVER CIRCUIT CONTROLS STEPPER MOTOR
The stepper motor control circuit TB6560 is the most commonly used type today, the circuit can control a 2-phase stepper motor (10 - 35VDC) with a maximum capacity of 3A TB6560 stepper motor control circuit is used to control stepper motors, applied in CNC machines or precision mechanical systems
Figure 3.7 TB6560 Driver Circuit Controls Stepper Motor
✓ Integrated high-speed 6N137 isolation Opto helps control the signal with the control panel, safe and anti-interference
✓ Integrated aluminum heatsink helps dissipate heat for TB6560
✓ Suitable for stepper motors 43, 57, 86 | 2 or 4 phase | 4 wires or 6 wires.
AutoCad Design
Solidwords Design
Figure 3.12 Exploded – view drawing 3.5.5 3D model design
Figure 3.13 Top side of the machine
Figure 3.14 Left side of the machine
Figure 3.15 Front side of the machine
CONCLUSION
Results achieved
✓ Increase productivity: The Automatic wire cutting and stripping machine can operate continuously without pauses, helping to increase production productivity
It can cut wire at high speed and consistency, surpassing the speed and ability of manual labor
✓ Accuracy and uniformity: The Automatic wire cutting and stripping machine is set up to cut wire with high precision and uniformity This ensures that wire cuts are consistent and error-free, enhancing the quality of the final product
✓ Save time and labor: The Automatic wire cutting and stripping machine can perform cutting more quickly and effectively than manual methods This saves employees' time and labor, allowing them to focus on other more important tasks
✓ Reduce errors and handling: The Automatic wire cutting and stripping machine eliminates the human factor and minimizes the risk of cutting metal wires that are dangerous to people This helps reduce energy and save production costs
✓ Versatility and Customization: The Automatic wire cutting and stripping machine can be customized to fit a company's wire-cutting requirements Parameters such as cutting length, speed, and type can be adjusted to meet special production requirements.
Restrictions
❖ Cost: Automatic wire cutting and stripping machines often cost more than manual methods This can be a barrier for small businesses that do not have large investment resources
❖ Limited customization: Automatic wire cutters and strippers are often customized to fit a specific wire type or a small number of different wire types This means that if you need to process many different types of wire, you may need different machines or re-adjust the machine
❖ Ability to handle complex situations: Automatic wire cutters and strippers are typically designed to handle simple cutting and stripping tasks When encountering complex or irregular situations, the machine may not be able to respond or require manual intervention and adjustment
❖ Size and volume limitations: Automatic wire cutting and stripping machines are often large in size and volume, requiring appropriate space and infrastructure to operate
❖ Dependence on power supply: Automatic wire cutters and strippers need a stable power supply to operate Power outages or electrical problems can affect the machine's performance and reliability
[1] https://www.kingsing.com/product/86.html
[2] https://www.schleuniger.com/en-us/products/cut-strip/ecostrip-9380/
[3] Nguyễn Trọng Hiệp, Nguyễn Văn Lẫm, “Thiết kế chi tiết máy”, NXB Giáo dục,