The k factor is a physical value defining the ratio of distance from the inner side of the bend to the neutral layer and sheet metal. K factor a constant determined by dividing the thickness of the sheet by the location of the neutral axis, which is the part of sheet metal that does not change length. Kfactors, yfactors, and press brake bending precision. For a vdie, this equation can often be approximated as. Press brake bend allowance chart free technical charts. These parameters can also be set using the bend allowance area of the sheetmetal preferences dialog box. This publication shares a part of that expertise with the engineers, designers. With this free online tool you can calculate the k factor, a fundamental parameter used to calculate sheet metal elongation according to your bending setting.
For all metals, however, there is a minimum bend radius at which the outer edge of the bend will crack. The k factordepends on the material, the type of bending operation coining, airbending. Bending in a vdie is a widely used process where the part is initially air bend until. Bend allowances are calculated using a kfactor as follows. Then input the bend angle to get the arc length, bend allowance and bend deduction. K factor is actually the ratio of the offset t of the neutral axis from the inside bend and the thickness of the sheet t when a piece of sheet metal is bent. Then input leg length a and b to get the flat size of the sheet. And if you know the bend allowance, you can extract the k factor from it. Generally, k factor is used to calculate the flat pattern or flat length of sheet metal.
The k factor is defined as the ratio between the material thickness t and the neutral fibre axis t, i. Since the inside compression can not exceed the outside tension, the k factor can never exceed. The solidworks application also comes with a kfactor bend table in microsoft excel format. The k factor is the most important and elusive variable of bending, because it varies both as a function of the material and according to parameters such as angle and tooling. In this article we will discuss sheetmetal bend deduction, bend allowance, k factor, y factor and sheet metal flat pattern calculations. Kfactor calculator for sheet metal bending smlease design. In over 50 years of serving the mechanical system marketplace, mcgill airflow has gained a technical expertise, which is unmatched in the industry. Sheet metal forming massachusetts institute of technology.
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. The kfactor in sheet metal working is the ratio of the neutral axis to the material thickness. Changing any of these things can change the kfactor of a bend. Calculate k factor, bend allowance and y factor for sheet. Bending is a manufacturing process that produces a vshape, ushape, or channel shape. We can calculate the leg length 1 and 2 as follows. Let me make it clear that it is a very important term used in sheet metal design.
Sheet metal characteristics elongation the capability of the sheet metal to stretch without necking and failure. Introduction to fracture mechanics david roylance department of materials science and engineering massachusetts institute of technology. Kfactor is a ratio that represents the location of the neutral sheet with respect to the thickness of the sheet metal part. Thereby forming a certain angle and curvature shape. Or yfactor in the case of proe where yfactor kfactor. Material type, grade, thickness, forming method, tooling, bend angle, etc.
It is used to calculate sheet metal flat length flatpattern. When working in solidworks to create sheet metal designs, we will often need to know three important values. The line where the transition from compression to stretching occurs is called the neutral axis. Input material thickness and and inner radius to get the data of k factor, y factor, neutral layer. You can easily modify the material thickness, inside radius and k factor for each thickness at. Learn what a k factor is in sheet metal forming, learn how k factor is used, and learn how to calculate k factor in this video. K factor is defined as the ratio between the material. The main reason that i compared it ti the appearance ui is that it clearly has a standard library, you custom items, and also shows what is unique to the document. When a piece of metal is being formed, the inner portion of the bend compresses while the outer portion expands see figure 1. Best way to calculate k factor in sheet metal is by reverse engineering.
Creating featurespecific bend allowance using the bend allowance tab of sheet metal tools when available. Prosheetmetal will subtract from the actual length of the material to compensate for the elasticity. The y and kfactors affect how the part stretches when transitioning from a flat pattern to a finished piece so it is important to understand their values. I extensively work on sheet metal and i use the value k factor 0. How to set up sheet metal gauge tables engineers rule. In the sheet metal industry one of the most important stages in m anufacturing is the accurate. Calculating bend allowance, bend deduction, and kfactor. The yfactor is used, as far as i know, solely by ptcs proengineer, now known as creo elementspro.
The bend deduction is the amount the sheet metal will stretch when bent as measured from. Calculate k factor, bend allowance and y factor for sheet metal bending. In sheet metal, the kfactor is the ratio of the neutral axis to the material thickness. I had a question on k factors for our 3d modeling software. Or y factor in the case of proe where y factor k factor. Avoid large sheet metal parts with small bent flanges. Bending is a stamping process that uses pressure to force the material to plastically deform. When sheet metal is bent, the inside surface of the bend is compressed and the outer surface is stretched. In sheet metal design, the k factor is used to calculate how much sheet metal one needs to leave for the bend in order to achieve particular final dimensions.
Mathematically k factor value is equal to the ratio of position of neutral axis and sheet thickness. Calculate k factor, bend allowance and y factor for sheet metal. The steel and aluminum used for ductwork is a high achiever in the 21stcentury move toward sustainable buildings because of the high recycling rates and cleanliness. When you select kfactor as the bend allowance, you can specify a kfactor bend table. Commonly used bends include vbend, zbend offset bend and hemming bend etc bending height. Thiscritical stress intensity factor isthenameasureof. In fact, sheet metal use in hvac is greater than all other materials combined. It is essential that you used the measured values for the thickness and not the published values also, go here and run the search for k factors. The kfactor approximations given below are more likely to be accurate for air bending. The formula according to which developed length is calculated is. The sheet metal bending height should be at least 2 times the thickness of the sheet metal plus the bending radius, that is, h. Now, you may be thinking, where this k factor is used. Kfactor is actually the ratio of the offset t of the neutral axis from the inside bend and the thickness of the sheet t when a piece of sheet metal is bent. Figure 2 illustrates the sheet that is bent with the bend angle of 90 degrees.
Sheet metal k factor user modification i also thought about referencing the parameters ui, which would work well also. Somewhere in between the thickness of material lies neutral axis. For example, a flat sheet of aluminum is less stiff than that same sheet of aluminum bent into a v cross section. The k factor is the ratio of the neutral axis location t to the material thickness mt. When you bend sheet metal, the neutral axis shifts toward the inside surface of the bend. The inside radii are based off of a standard air bend force chart.
When metal is bent the top section is going to undergo compression and the bottom section will be stretched. Department of mechanical and production engineering. From there we can calculate the k factor and the bend deduction. The kfactors at the lhc are similar to the kfactors for thesame processes at the tevatron, but have a tendency to be smaller. Minimum bend radii are typically specified in terms of sheet thickness t such as 1t, 2t. So if the thickness of the sheet was a distance of t 1 mm and the location of the neutral axis was a distance of t 0. The bend allowancebend deduction of the sheet metal specified in k factor by configuring and utilizing a sheet metal gauge table, we can speed up the process of selecting the correct wall thickness based on gauge value and selecting. I have idea to use sheet metal to avoid bend part option in standard modeling please imagine that i have curve which consists of 10 arcs, then i need to make 10 bending operations to get the wished shapethat is the reason why i am trying with sheet metals, but k factor makes a problems with material extension. The difference between k factor, bend allowance and bend deduction in solidworks duration. The kfactors tend to be closer to unity if either the same nlo pdf is used for both the lo and nlo calculations, or equivalently, if the cteq modi.
Design for manufacturability sheet metal guidelines. The k factor is nothing more than a multiplier that can give you an accurate value for the relocated neutral axis. Here is a good explanation of k factor and a spreadsheet for helping you determine the ones for your equipment and processes attached. What is the best answer for kfactor and yfactor in a sheet metal. The k factor depends on many factors including the material, the type of bending operation coining, bottoming, airbending, etc. The below chart is for even numbered gauges 8 through 24 and has a default k factor of. In sheet metal, there is a powerful bend constant known as the kfactor.
It ultimately allows you to estimate the amount of stretch without. Setbacks, bend allowances and k factors are somewhat. The k factor in sheet metal working is the ratio of the neutral axis to the material thickness. What is the best answer for kfactor and yfactor in a. The k factor is fundamental to designing precise sheet metal. Design for manufacturability sheet metal guidelines bends for the ease of manufacturing, multiple bends on the same plane should occur in the same direction.
This change in sheet length depends on the position of neutral axis or k factor. Pdf the study of design constants in sheet metal forming. The y and kfactors affect how the part stretches when. Line within thickness that is neither compressed nor stretched. Many cad programs, however, also work out bend allowances automatically by using k factor calculations. The kfactor is the ratio of the neutral axis location t. Blank development for formed sheet metal parts there are many systems employed by a variety of industries aircraft, electronics, architectural, automotive, etc. After bending the sheet we need to do some measurements as shown in figure 2. Once you know the k factor, you can use it to predict the bend allowance for various angles.
In low carbon steel sheet metal, the minimum radius of a bend should be onehalf the material thickness or 0. Bend allowances are calculated using a k factor as follows. Somewhere in between the thickness of material lies. When sheet metal is bend, the inside bending surface is compressed. K factors are a great tool for developing flat blanks for sheet.