We often encounter the Great Wall board in our work, and the main method I want to show you is the method of bending with a large angle and back bending. When bending the Great Wall board with a large angle and back bending, it is important to note that the lower die needs to be reversed. This method is also required for products like this that require a large angle and back bending.
The most important thing here is to learn how to calculate the bending unfold. Because we need to bend from the inside to the outside, in the case of a micro groove of 6 times, it is generally deducted by the thickness of the plate multiplied by 1.65 compensation factor and multiplied by 0.35.
We start bending from the middle. What is the unfolding coefficient for the first and second bends? There are two calculation methods, and I will list them separately.
- The first method is to add up all the bending dimensions and subtract the number of bending tools multiplied by the plate thickness multiplied by 1.65.
- The second method is to subtract the sum of all the bending dimensions from the number of bending tools multiplied by the plate thickness multiplied by 2. This is because each bend will have a thickness of two plates, plus the coefficient of the number of bending tools multiplied by the plate thickness. The plate thickness coefficient is equal to the plate thickness multiplied by 0.35. Therefore, the calculated bending dimension for the first bend is 200.425.
Then we need to learn how to use the bending pressure line position to calculate the large angle for the first bend. The pressure line position should be equal to 200.4. Subtracting one plate thickness plus half of the coefficient, we get 199.18, which corresponds to a large angle of 135 degrees.
In any bending process, we need to learn the pressure line position because it allows us to calculate the size after bending to 90 degrees. After calculating the pressure line position, we complete the first bend to approximately 135 degrees.
The lower die V-groove is reversed to prevent it from hitting the lower die during the second bend. Then, we calculate the bending dimension for the second bend, which unfolds to 90 degrees. The calculation method is the same as for the first bend.
Method 1: 33.8 + 15 + 93 + 41 - 2 × 1.5 × 4 + 4 × (1.5 × 0.35) = 187.9
Method 2: 197.8 - 12 + 2.08 = 187.9
After the second bend reaches 90 degrees, we check if the height is equal to 15. Then we calculate the unfolding for the fourth and fifth bends. The bending unfolding we calculate refers to the number of bending tools.
The previous bending dimensions refer to the unfolding dimensions reserved after bending to 90 degrees. For example, if the fourth bend is bent to 90 degrees, we need to calculate how much space should be reserved to ensure that the dimensions for subsequent bending processes are sufficient. When back bending with a large angle, beginners often encounter the problem of a small back bending angle.
For beginners in bending, it is important to develop a habit of aligning the bending closely with the upper film to ensure that the bending lines match. Additionally, the compensation factor should be considered. Some factories use a factor of 1.65, while others use factors of 1.7 or even 1.8. For ease of understanding, I use a 6x V-groove and a compensation factor of 1.65.
The vast majority of precision sheet metal factories use a uniform factor of 1.65 for compensation. Even if our factory uses 1.8 and you use 1.65, the difference is not significant because only precision sheet metal requires a tolerance of ±0.2. For rough sheet metal, a compensation factor of 1.65 can also be adjusted later if the size differs by a small amount.
The most important thing here is to learn how to calculate the bending unfold. Because we need to bend from the inside to the outside, in the case of a micro groove of 6 times, it is generally deducted by the thickness of the plate multiplied by 1.65 compensation factor and multiplied by 0.35.
We start bending from the middle. What is the unfolding coefficient for the first and second bends? There are two calculation methods, and I will list them separately.
- The first method is to add up all the bending dimensions and subtract the number of bending tools multiplied by the plate thickness multiplied by 1.65.
- The second method is to subtract the sum of all the bending dimensions from the number of bending tools multiplied by the plate thickness multiplied by 2. This is because each bend will have a thickness of two plates, plus the coefficient of the number of bending tools multiplied by the plate thickness. The plate thickness coefficient is equal to the plate thickness multiplied by 0.35. Therefore, the calculated bending dimension for the first bend is 200.425.
Then we need to learn how to use the bending pressure line position to calculate the large angle for the first bend. The pressure line position should be equal to 200.4. Subtracting one plate thickness plus half of the coefficient, we get 199.18, which corresponds to a large angle of 135 degrees.
In any bending process, we need to learn the pressure line position because it allows us to calculate the size after bending to 90 degrees. After calculating the pressure line position, we complete the first bend to approximately 135 degrees.
The lower die V-groove is reversed to prevent it from hitting the lower die during the second bend. Then, we calculate the bending dimension for the second bend, which unfolds to 90 degrees. The calculation method is the same as for the first bend.
Method 1: 33.8 + 15 + 93 + 41 - 2 × 1.5 × 4 + 4 × (1.5 × 0.35) = 187.9
Method 2: 197.8 - 12 + 2.08 = 187.9
After the second bend reaches 90 degrees, we check if the height is equal to 15. Then we calculate the unfolding for the fourth and fifth bends. The bending unfolding we calculate refers to the number of bending tools.
The previous bending dimensions refer to the unfolding dimensions reserved after bending to 90 degrees. For example, if the fourth bend is bent to 90 degrees, we need to calculate how much space should be reserved to ensure that the dimensions for subsequent bending processes are sufficient. When back bending with a large angle, beginners often encounter the problem of a small back bending angle.
For beginners in bending, it is important to develop a habit of aligning the bending closely with the upper film to ensure that the bending lines match. Additionally, the compensation factor should be considered. Some factories use a factor of 1.65, while others use factors of 1.7 or even 1.8. For ease of understanding, I use a 6x V-groove and a compensation factor of 1.65.
The vast majority of precision sheet metal factories use a uniform factor of 1.65 for compensation. Even if our factory uses 1.8 and you use 1.65, the difference is not significant because only precision sheet metal requires a tolerance of ±0.2. For rough sheet metal, a compensation factor of 1.65 can also be adjusted later if the size differs by a small amount.
