The K-factor and Y-factor of sheet metal are two measures of its ductility and flexibility, respectively, during bending. When metal sheets are bent, the top surface contracts and the bottom surface stretches. The neutral radius is the internal border between these two phases inside the metal. This border exactly divides the thickness of the metal while the metal is flat, but it moves when the metal is bent.
On standard charts, the K-factor is found by dividing the neutral radius by the thickness of the material, and it ranges from 0.3 to 0.5. The Y-factor is comparable to the K-factor but more accurately accounts for the stresses present in the material being examined.
The developed length of flat sheet metal needed to construct a bend with a certain radius and angle may be calculated with the use of a formula using the component constants Y factor and K factor. The position of the neutral bend line in relation to the thickness of the sheet metal material defines the Y factor and the K factor. The location of the neutral bend line varies in part according on the kind of sheet metal being utilised. Anywhere from zero to one may be used for the numerical references. Both the Y factor and the K factor may take negative values, with lower values indicating a softer material. The developed length is equal to the length of the neutral bending line.
The K factor is defined as the ratio of the inner bend radius to the distance from the neutral bending line, expressed in units of the material's thickness. The K factor formula is K factor = /T. To get the Y factor, multiply the K factor by the inverse square root of /2. The Y-factor is set at 0.50 by default.
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Table of Contents
What Are the Factors in K- And Y-Factors to Consider in Designing Custom Metal Parts?
Due to the fact that not all materials include K-factors or Y-factors on a chart, you may determine these values by experimentation with your prefered metal. If you use the following methods of computation, you won't need to depend on standard parameters to create unique layouts. With this skill, you can go beyond the confines of tabular norms.
You may use either the K-factor or the Y-factor to determine the bend deduction. The OSSB, or outside setback and bend allowance, is where the bend deduction begins. To calculate the bend deduction (BD), multiply the outside setback by two and deduct the bend allowance from the resulting product. Two times the product of the inner radius and the thickness of the material is divided by the tangent of the bend angle to get the OSSB.
B.D. = (2 x OSSB) - B.A.
The OSSB formula is: OSSB = tan(bend angle 2) x (Ir + Mt).
You may recall that BA is the dissimilarity between the fully formed and flat dimensions. The K-factor and the Y-factor may also be used to get this number.
Assuming a K-factor, the BA is calculated as follows: BA = [( 180) x Ir] + [( 180) x K-factor] x Mt
To calculate the BA when the Y-factor is included, we get: Calculating your BA? Plug in [( 2) x Ir + (Y-factor x Mt)].
The bend deduction may be found by applying the appropriate formula to the previously determined K-factor and Y-factor.
What is K-Factor?
The K-factor describes the relationship between the neutral axis and the thickness of a sheet of metal. A metal sheet is bent by compressing the inner area and expanding the outside during the forming process (see Figure 1). The neutral axis shifts from its initial position at 50 percent of the material thickness towards the inner surface of the bend, but no further changes take place in this region where compression and expansion meet. Elongation happens during bending because the neutral axis moves, but its length remains constant. The thickness, inner bend radius, and forming process all have a role in how much the neutral axis moves.
You may calculate the new location of the neutral axis by multiplying the thickness of the material by the standard default K-factor value of 0.446. The length measured (the length of the neutral axis at 50% of the material thickness) is being distorted such that it fits on a smaller radius. We have elongation or surplus material since the same overall length is being measured across a smaller radius.
Think about using a 0.060-inch thick sheet. To achieve 0.0268 inches, we multiply by K = 0.446. Based on measurements taken from the inside of the surface's kink, the axis has moved from a value of 0.030 inches (half the thickness of the material) to a value of 0.0268 inches. In other words, there was an inward shift of 0.0032 inches in the axis. That's where we'll get the data we need to solve for the curve in the road.
It is important to remember that the K-factor varies depending on the kind of material, the forming technique, and the connection between the bend radius and the material thickness. The overall amount of elongation and the necessary bend deductions are subsequently affected by these factors.
What is Y-Factor?
The Y-Factor is a derivative of the more standard K-Factor. Reduce the K-Factor by 0.5, then multiply that result by pi.
As far as I'm aware, PTC's Pro-Engineer (now known as Creo Elements/Pro) is the only product that makes use of the Y-Factor. For sheet metal design, the default value of.5 for and yields a K-Factor of about.318. This is a reasonable place to begin. As the Y and K-Factors determine the degree to which the component expands throughout the transformation from flat pattern to completed product, familiarity with their values is essential. True precision in components and designs, however, nearly always necessitates tweaking the Y-Factor. There are several fundamental approaches that may be used.
One option is to alter the so-called "Material" file. Using the Material Definition screen, the PTC INITIAL BEND Y FACTOR option will do the trick. With this, you may give individual materials their own Y-Factors. It seems to be a frequent drawback of design software that you cannot provide unique values to each gauges. Setting a material-specific factor throughout the design process should result in near-perfect components. The K-Factor will stay at the value you specified even if you later decide to remove the assigned content from the role. When making a material swap, keep this in mind.
The 'Set Up' option is the alternative technique of adjusting the Y-Factor. You may set a new default Y-Factor value by doing this. Any additional components you make after the first setup will automatically use your customised Y-Factor. Since various materials have varying Y-Factor requirements, this approach may not be optimal. You may find more information on the K-Factor, including charts and explanations, in our previous article.
The final option is to modify the configuration file such that the Y-Factor is always the same for new components. Like the 'Set Up' command, this is not suggested if you're utilising many materials or attempting to achieve high levels of precision in your finished products.
The Y-Factor may be adjusted independently for each feature, providing a finer degree of control over the final result. At the extremes of the Bend Angles or Radii, when the neutral axis is no longer perpendicular to the appropriate Bend Allowances, this might be helpful.
Pro-Sheet Metal, like the vast majority of design tools, lets you use a bend table in lieu of the Y-Factor if you so want. Tables like these, which are based on the indispensable Machinist's Handbook, are an essential tool for every industrial engineer. Those tables, in turn, were founded on empirical evidence. So far as I'm aware, there is no universal method for determining where a flat pattern begins and ends.
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What Are the Types of Metal Bending?
To determine the overall elongation for a certain kind of bend, or bend deduction, bending and bend formation play crucial roles. The mathematical values utilised in the computation will be impacted by the procedures used.
Folding and bending sheet metal are both forming processes. Where sheets are plastically distorted to alter their form. To achieve a bending stress, the material must be strained beyond its yield strength but under its ultimate tensile strength.
Sheet metal is longer after being bent than it was before. A bend deduction or allowance might be used to express this lengthening or shortening.
Metal Bending Types
For metals, there are four primary types of bends: minimum radius, perfect radius, sharp radius, and sharp bends. The minimum radius bend occurs when the metal is bent to its smallest possible radius without creasing. Find the tightest, most precise turns with this number in hand.
Radii for perfect 90° bends are between 0 and 125% of the material thickness. In order to create a radius bend, the deflection must be greater than 125% of the metal's thickness.
On the other end of the scale, we have right angles, which are 90 degrees. Sharp creases like this form when metal is bent beyond its bending radius.
First, let's take a step back and talk about all the ways we can bend sheet metal. Don't worry, I plan on bringing up the K-factor in the near future. Please wait until then.
There are four main types of bends: minimum-radius, sharp, perfect, and radius. Bends with a minimum radius have an inner radius that is as small as possible without causing wrinkles in the material. An acute bend is the result of attempting to create a radius smaller than the absolute minimum.
When bending, a radius close to the material's thickness is preferable. A bend radius of less than the minimum value and greater than 125% of the material thickness is unacceptable. You can only count a bend as a radius bend if its radius is greater than 125% of the material's thickness.
The minimum bend radius is the smallest radius that can be used in bending calculations and still have the results be correct, even if you are bending the object very sharply. Also, remember that a sharp turn in the air is frequently very erratic. The sharpness and depth of the crease at the centre of the bend amplify any angular fluctuations caused by changes in grain direction, hardness, thickness, or tensile strength of the material.
Also relevant is the punch nose's reach. The punch nose radii of 1/16 in (0.062 in), 1/32 in (0.032 in), and 1/64 in (0.015 in) are all too acute for an inner radius of 0.078 in. As the punch nose radius decreases in relation to the thickness of the material, the resulting angle shift will be more pronounced.
Metal Bending Allowance
By entering the sheet's starting length and thickness into the corresponding cells on the left, we can get the bend allowance, K factor, and derived coefficient Y factor. Insert the inner radius and flanges A and B after bending the sheet. The angle of bend is ninety degrees.
Both bend allowance and bend deduction are equivalent. It is the quantity of material that must be added to the Flange length (A1 and B1) in order to create a flat length.
Sum of Straight Length = Sum of A1 Length + B1 Length + Bending Tolerance
The terms "bend allowance" and "bend deduction" are synonymous with one another. Two times the outside set back is equal to the sum of the bend allowance and the bend deduction.
- BA + BD = 2 x OSSB.
- Exterior Delay = tan(A / 2) x (t + r)
Where ;
- Bending Accuracy
- Deduction by Bending
- Overseas Scenario of Failure
- Angular Deflection
- Thickness (T) of the Sheet
- Inside Bend Radius R
Bend Deduction
When sheet metal is bent, it lengthens overall.
There is compression on the inside of the bend and stretching on the outside when the object bends. The overall surface area of the sheet metal components grows as a consequence. That is to say, the Flat Length of the metal sheet is less important than the Total Length (A + B).
Bend Deduction refers to the reduction in overall length from the flat length to the length after bending.
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What Is Metal Bending Forming?
Any number of factors, such as how the metal is bent, could end up changing the final product. You can form your object using one of three primary methods: coining, bottom bending, or air bending. Coin minting is one of the oldest traditions, but it has largely been abandoned in recent decades. Forcing oneself past the neutral radius and into the metal, a punched nose is employed. As a result, the material's strength and durability are compromised after being coined.
Bottom bending, like coining, does not permanently alter the structure of its substrate. The material is pressed around the punch nose rather than into the metal. When punching coins, the radius inside the bend is identical to the punch nose's radius.
Punch nose radius and final bend radius are not always the same when bending air. Instead of using the bend radius, the aperture of the die is used. Popular among engineers is the "20 percent rule," which uses percentages around 20 percent for various metals. By way of illustration, the percentage could range from 20% to 22% for type 304 stainless steel, but it would be closer to 13% and 15% for H-series soft aluminium.
Coining is not the same as bottom bending, either. The punch nose is inserted into the material far enough to pass through the neutral axis during coining. Bottoming occurs at a height roughly 20% higher than the material thickness, measured from the bottom of the die. (It is worth noting that "How the inner bend radius forms," archived at thefabricator.com, has more details on the forming processes in addition to pictures.)
It's possible that your stamping press's die sets are "coining" the material, a sign that they're not being pushed far enough to fully penetrate the sheet. Besides, you're definitely bottom bending, which happens again at about 20% above the material thickness. Both methods limit the material to a set diameter, but the former produces tighter radii. When we calculate the radius for bottoming or coining with a sharp, minimal, perfect, or radius bend, we use the punch nose value to determine the radius.
While air is being formed, however, this is not the case. When using an air form, the finished product's radius is proportional to the size of the die cavity. When a bend is formed in the air, its radius on the inside is dependent on the die's width, but the radius on the outside is unconstrained. Material tensile strength is the determining factor. According to the "20 percent rule," this is exactly the case. But this is just a name, not a description, because different materials have different percentages associated with their tensile strengths.
The radius formed from 304 stainless steel requires a die width of 20-22%, while the radius formed from 5052-H32 aluminium requires a die width of only 13%-15%. Inner radii should be smaller if the material is pliable.
In addition, we opt for 60-KSI mild cold-rolled steel for most uses, including the 20% cap. This material produces a radius that is between 15% and 17% of the total width of the die. We'll adjust up or down from the median estimate of 16%. Assume we are dealing with 120 KSI issues for the sake of argument. Air-forming this 120 KSI sheet will allow you to achieve a radius nearly twice as large as you could achieve with mild cold-rolled steel, or 32 percent of the die opening (16 percent 2). In contrast, our standard material has a tensile strength of only 60 KSI.
How to Calculate K- And Y-Factors?
While the K-factor and Y-factor may be calculated for a wide range of metals, doing so manually is more time-consuming and error-prone than simply utilising a ratio from a reference.
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How to Determine K-Factor?
Measuring multiple different metals will give you the data you need to calculate the K-factor on your own. Knowing the outside dimensions and the pre- and post-bent dimensions isn't enough; you also need to know the interior radius. Gauge pins, radius gauges, or an optical comparator may be used to determine these values. You might begin by calculating the BA, or bend allowance, using this data. (Basic Area = Sum of Formed Interior Dimensions - Flat Interior Dimensions)
Sheet elongation may be determined with the use of a crucial quantity known as the bend allowance. How far the neutral fibre extends from its origin to its destination along the arc formed by the bend.
Then, take readings of the included angle, which is 180 degrees, and the complimentary bend angle, which is Ir minus the included angle. Discovering the material's thickness, Mt, allows one to compute the K-factor for bending sheet metal.
The K-factor may be calculated by dividing 180 by the product of BA and the ratio of Ir to Mt, and by the difference between the product of pi, Mt, and the corresponding bend angle. This formula may be written in mathematics as:
K-factor = 180 x BA ( x Complementary Bend Angle x Mt) - (Ir x Mt)
How to Find Y-Factor for Sheet Metal Bending?
To calculate the Y-factor, you must first know the K-factor. K-factor is multiplied by pi, and the result is divided in half to get Y-factor.
The Y-factor is calculated as follows: Y-factor = K-factor x 2
Conclusion
Metal sheets' ductility and flexibility when bent are evaluated using two factors: the K-factor and the Y-factor. In the range of 0.3 and 0.5, the K-factor is calculated by dividing the neutral radius by the thickness of the material. When accounting for stresses in a material, the Y-factor is similar to the K-factor but more precise. A formula involving the component constants Y factor and K factor can be used to determine the developed length of flat sheet metal required to construct a bend with a given radius and angle. In materials science, the K factor is defined as the ratio of the inner bend radius to the distance from the neutral bending line, in terms of the material's thickness.
The outside setback and bend allowance (OSSB) is the starting point for the bend deduction. In order to determine the bend deduction (BD), multiply the exterior setback by two and then subtract the bend allowance from the resulting product. OSSB = tan(bend angle 2) x (Ir + Mt) is the formula for determining OSSB. One can also arrive at this figure by utilising the K-factor and the Y-factor. A K-factor can be used to calculate the bend deduction.
Different materials, forming methods, and relationships between the bend radius and material thickness all contribute to the Y-Factor, a derivative of the K-Factor. The Y-Factor is only implemented in PTC's Pro-Engineer (now called Creo Elements/Pro). Multiplying by K = 0.446 gives us a result of 0.0268 inches. Several primary methods can be employed, including tweaking the so-called "Material" file and assigning unique Y-Factors to each material. By establishing a material-specific factor early in the design process, nearly ideal components can be produced.
Don't forget this when you're exchanging materials. Changing the Y-Factor can also be done through the 'Set Up' menu. Each individual feature's settings can be modified independently for greater precision in the final product. Minimum radius, perfect radius, sharp radius, and sharp bends are the four most common varieties of radii. Bending and bend formation play critical roles in deducing the total elongation for a given type of bend.
Sheet metal can be formed in many different ways through bending, folding, and other forming processes that involve plastic deformation of the sheet. The material must be stressed beyond its yield strength but below its ultimate tensile strength in order to bend. This lengthening or shortening could be represented by a bend deduction or allowance. Right angles are 90 degrees, and the arc radius for a 90 degree bend is between zero and twelve and a quarter times the thickness of the material. Minimum-radius, sharp, perfect, and radius bends are the four most common varieties.
To ensure accurate results when calculating bending, the minimum bend radius is the smallest radius that can be used, even when the object is bending sharply. Any angular fluctuations brought on by shifts in grain direction, hardness, thickness, or tensile strength of the material are amplified by the sharpness and depth of the crease at the centre of the bend. In addition to the material's thickness, the punch nose radius matters because a smaller punch nose radius causes a greater angle shift. By adding metal to the Flange length (A1 and B1), a flat length can be formed. When added together, the bend allowance and bend deduction equal two times the outside set back.
Sheet metal lengthens overall when bent, increasing the surface area of the sheet metal parts as a whole. There are three main techniques for bending metal into desired shapes: coining, bottom bending, and air bending. Minting coins is a centuries-old practise that has fallen out of favour in recent times. Although the radius inside the bend of a coin punch is always the same as the radius of the punch nose, this is not always the case when bending air. The "20 percent rule" is widely used in the engineering community; it prescribes a percentage of around 20 percent for most metals.
Coining is distinct from bottom bending because the punch nose is inserted into the material to the point where it crosses the neutral axis. The bottoming height, measured from the bottom of the die, is about 20% greater than the material thickness. They both restrict the material to a fixed diameter, but the former results in more precise radii. Although the final product's radius is proportional to the width of the die cavity when using an air form, the outside radius of a bend formed in air is not limited by this factor. For many metals, the K-factor and Y-factor can be calculated by hand, but doing so requires more effort and introduces more room for error than simply using a ratio found in a reference.
Outside dimensions, pre- and post-bent dimensions, interior radius, and bend allowance are just some of the measurements that can be used to determine the K-factor. To determine the K-factor, multiply the bend angle by the K-factor, which can be found by dividing the sum of pi, Mt, and the K-factor by 180. Following is the formula for determining the Y-factor: The Y-factor is calculated by multiplying the K-factor by 2.
Content Summary
- The K-factor and Y-factor of sheet metal are two measures of its ductility and flexibility, respectively, during bending.
- On standard charts, the K-factor is found by dividing the neutral radius by the thickness of the material, and it ranges from 0.3 to 0.5.
- The developed length of flat sheet metal needed to construct a bend with a certain radius and angle may be calculated with the use of a formula using the component constants Y factor and K factor.
- The position of the neutral bend line in relation to the thickness of the sheet metal material defines the Y factor and the K factor.
- The developed length is equal to the length of the neutral bending line.
- The K factor is defined as the ratio of the inner bend radius to the distance from the neutral bending line, expressed in units of the material's thickness.
- Due to the fact that not all materials include K-factors or Y-factors on a chart, you may determine these values by experimentation with your prefered metal.
- You may use either the K-factor or the Y-factor to determine the bend deduction.
- The OSSB, or outside setback and bend allowance, is where the bend deduction begins.
- Two times the product of the inner radius and the thickness of the material is divided by the tangent of the bend angle to get the OSSB.B.D. = (2 x OSSB) - B.A.The OSSB formula is: OSSB = tan(bend angle 2) x (Ir + Mt).You may recall that BA is the dissimilarity between the fully formed and flat dimensions.
- The K-factor describes the relationship between the neutral axis and the thickness of a sheet of metal.
- It is important to remember that the K-factor varies depending on the kind of material, the forming technique, and the connection between the bend radius and the material thickness.
- The Y-Factor is a derivative of the more standard K-Factor.
- Reduce the K-Factor by 0.5, then multiply that result by pi.
- As the Y and K-Factors determine the degree to which the component expands throughout the transformation from flat pattern to completed product, familiarity with their values is essential.
- Setting a material-specific factor throughout the design process should result in near-perfect components.
- The K-Factor will stay at the value you specified even if you later decide to remove the assigned content from the role.
- The 'Set Up' option is the alternative technique of adjusting the Y-Factor.
- The final option is to modify the configuration file such that the Y-Factor is always the same for new components.
- Like the 'Set Up' command, this is not suggested if you're utilising many materials or attempting to achieve high levels of precision in your finished products.
- Pro-Sheet Metal, like the vast majority of design tools, lets you use a bend table in lieu of the Y-Factor if you so want.
- Folding and bending sheet metal are both forming processes.
- Radii for perfect 90° bends are between 0 and 125% of the material thickness.
- There are four main types of bends: minimum-radius, sharp, perfect, and radius.
- As the punch nose radius decreases in relation to the thickness of the material, the resulting angle shift will be more pronounced.
- Two times the outside set back is equal to the sum of the bend allowance and the bend deduction.
- There is compression on the inside of the bend and stretching on the outside when the object bends.
- You can form your object using one of three primary methods: coining, bottom bending, or air bending.
- Bottoming occurs at a height roughly 20% higher than the material thickness, measured from the bottom of the die.
- When we calculate the radius for bottoming or coining with a sharp, minimal, perfect, or radius bend, we use the punch nose value to determine the radius.
- When using an air form, the finished product's radius is proportional to the size of the die cavity.
- When a bend is formed in the air, its radius on the inside is dependent on the die's width, but the radius on the outside is unconstrained.
- Material tensile strength is the determining factor.
- This material produces a radius that is between 15% and 17% of the total width of the die.
- Measuring multiple different metals will give you the data you need to calculate the K-factor on your own.
- Knowing the outside dimensions and the pre- and post-bent dimensions isn't enough; you also need to know the interior radius.
- Discovering the material's thickness, Mt, allows one to compute the K-factor for bending sheet metal.
- The K-factor may be calculated by dividing 180 by the product of BA and the ratio of Ir to Mt, and by the difference between the product of pi, Mt, and the corresponding bend angle.
- K-factor = 180 x BA (x Complementary Bend Angle x Mt) - (Ir x Mt)How to Find Y-Factor for Sheet Metal Bending?To calculate the Y-factor, you must first know the K-factor.
FAQs About Metal
Y factor and K factor represent part constants used in formulas to calculate the developed length of flat sheet metal required to make a bend of a specific radius and angle in a design. Y factor and K factor are defined by the location of the sheet metal material's neutral bend line with respect to the thickness.
K- and Y-factors make metal bending more precise without damaging the material. Once you know the K-factor you can identify the location of the neutral axis after bending in addition to how much the material elongates during bending.
The K-Factor is used to calculate flat patterns because it is directly related to how much material is stretched during the bend. It's used to determine Bend Allowances and Bend Deductions ahead of the first piece.
How to calculate the k-factor? The most common formula is k-factor = i*c, where i is an average number of invitations sent by one user, c is an average conversion from received invitation into registration.
K-Factors are calibration values (pulses per unit of volume) used to convert flow sensor output frequencies to flow rates. This calculation tool helps you to determine the correct K-Factor for your flow sensor.