SOLIDWORKS SHEET METAL - What is K-FACTOR?

In today's power moves #tootalltoby shares a #sheet #metal #tutorial on what #bend #deduction #bend #allowance and #k-factor all do - and how these tools can help you calculate a sheet metal flat pattern length.
Lots of great training content at www.TooTallToby.com/training
0:00 What is BEND DEFORMATION in sheet metal?
2:45 SolidWorks Training with Toby
3:50 Bend Deduction in SOLIDWORKS
5:45 Bend Allowance in SOLIDWORKS
7:27 What is K-FACTOR in sheet metal?
10:32 Is Bend Deduction better than K-Factor?
11:56 Final Thoughts and Advice
Leave a comment with any questions or suggestions you have for this series.
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[@ZbigniewAlejster]

This is probably the simplest and best explanation of the "K factor" I've seen so far! Thanks! Well done!

[@TooTallToby]

Awesome! So glad this helps!

[@TooTallToby]

Here's a comment I got on Reddit with regards to this video. This guy shares some great insights about how the team on the other end (the manufacturing/shop team) might prefer to receive sheet metal designs, from CAD designers/engineers. These are some GREAT POINTS and the TLDR point here is: Always work with (or talk to) the manufacturing team and find out what works best for them - it can save you a TON of time, since you won't have to waste time coming up with a good flat pattern - just let them do it (if that's what they want) 🙂 ======================================================= REDDIT COMMENT from Joaquin2071 I think this is a very good explanation for beginners going into sheet metal, however, if you are engineering and not actually manufacturing, it’s important to know that you shouldn’t be messing with these as it is up to the engineers at the manufacturer to determine the bend deduction based on their machines and their dies, especially when air forming. As someone who is an engineer in manufacturing, my job is a lot easier when the customer does not give a flat pattern and even better when they don’t dimension off of a flat pattern because 99% of the time, whatever k-factor/bd they are using is going to be way different than what we use. As far as the way I see k-factor, as someone who works directly with the brake department and has a gigantic table of bend deductions for all sorts of material and thicknesses, I see k-factor as a dependent variable that is found after doing live bend tests, finding the bend deduction by solving for how much the material shrunk. then, when plugged into the formula for bend deduction, you solve for the k-factor. That k-factor can then be used for that material, thickness, and radius to solve for non 90deg angles. The only time I ever use k-factor built into solidworks is for hems, and from there we proof the flat to show a bend deduction and then that is given to the brake operator. Just my little 2 cents from working in mfg for almost 5 years now (learning from old heads lol). P.s. A tried and true k-factor that is used a lot though that will almost always work is .4469. Especially for aluminum when air forming. That’ll get you pretty dang close P.p.s always dimension to the virtual exterior tangents, thank you :)

[@acesvaba330]

Guys, K-factor is not a thing you come up with, when you design in a certain material, the vendor of that material has the K-factor value into the data sheet. Let's say you have 2mm thick AISI 304 sheet ordered, in the documentation of that order you will find the mechanical parameters, including the K-factor. The value changes from softer to harder material and from thinner to thicker thicknesses. If you have to enter a value, it should never be 0.5, that means that you are bending diamonds, as a bench mark, softer metals like copper or aluminium are 0.38+/-0.02 and harder metals like stainless steel is 0.41+/-0.4. Do your research before you start designing something you intend to produce. Selection of material is one of the first things you need to do, thus, the K-factor should be there. Awesome video Toby, amazing as always!

[@TooTallToby]

Great insight - thanks ace!

[@amoplantalexei]

Excellent explanation and much much better format in 12 mins, then in shorts. Not too long (20- mins), not too short (1- min).

[@TooTallToby]

Nice thanks Mr Alex! Great feedback!

[@MrRick76]

Default K-Factor in most software is 0.440 If you use this number you are going to be very close. A larger K-factor increases material & a lower number reduces material. Example. Stainless Steel 1.5mm Standard Pressbrake Tooling V12-30 Bend Allowance = 3.10mm Internal Rad =2.50 External Rad=4.0 K-Factor=0.413 A great utility is available online called Bendworks V1.1 from 2003! but it works fine on Win11. You can reverse the k-factor by doing a bend test & measuring it. Cut a blank 100x100 bend it to 90 degrees & measure it accurately. Good tutorial Toby, I work in sheet metal & some of the customers need more training! Cheers

[@MarkSummersCAD]

Agree with the Bendworks program comments. The app is very handy and the attached PDF (The Fine Art of Sheetmetal Bending) is a great reference with topics I teach in my Manufacturing Engineering classes at ACC and TXST.

[@TooTallToby]

thanks Mr Rick these are some great insights and the community very much appreciates them!

[@TooTallToby]

Awesome thanks Mark!

[@chrisrobinson2172]

Great explanation. What finally really helped me was to understand that the K-Factor is a percentage of the thickness of the material. In other words, the total thickness of the material is 100%. A K-Factor of .4 then is for all intent purposes 40% of the material thickness; your offset basically.

[@TooTallToby]

Awesome thanks chris and glad this helped!

[@JernD]

Wow great video and shout out to the other commenters sharing their time tested wisdom!

[@TooTallToby]

YEah what a great community!

[@akashrathod6134]

Visual explanation really helped to understand concepts.

[@TooTallToby]

Awesome glad this helped!

[@KaushalPrajapati-ku6bi]

Finally, I understood the concept of K factor. Thanks for sharing.

[@TooTallToby]

Awesome very glad this helps!

[@EduardoSantosf5Gwx]

That was new to me too! Home run!

[@TooTallToby]

Awesome thanks Eduardo! Glad this helped!

[@kalvinglennsaul873]

For someone don't have the knowledge in sheet metal just like me this is a great lesson, Thank you

[@TooTallToby]

Awesome glad this helped!

[@Ryohgantz]

Thank you for the lesson

[@TooTallToby]

My pleasure and glad this helps!

[@asif.a15]

This is well explained Toby!

[@TooTallToby]

Thanks!

[@amirshay]

Excellent, thanks!

[@TooTallToby]

Thanks Amir!

[@adrinelu3977]

Well explained, thank you!

[@TooTallToby]

Awesome glad this helped!

[@franklaurent80]

Awesome , this is the best explanation I've ever heard for bend allowance, Thank you

[@TooTallToby]

Thanks Frank!

[@bjh9501]

great explanation

[@TooTallToby]

Thanks!

[@jelasukmawan2359]

Hello, I have been looking for a video about unbend / flatness for determining blank size dies for a long time. I want to ask how to make blank sizes from neutral format parts such as STP, x.t, etc. Apart from using logopress and autoform If the solidwork format such as sldprt can still be unbend using the sheet metal feature,

[@TooTallToby]

Sure I can make a video on this - the short answer is: use INSERT>SHEET METAL>INSERT BENDS or use INSERT>SHEET METAL>CONVERT TO SHEET METAL

[@Chimney_bbx]

They had us writing pages worth of reports on this shit. Im saying you spend 12+ hours grinding and they give you the report back at C- or D+ on a good day. Those engineers dont mess around.

[@TooTallToby]

lol for reals! FLAT-LENGTH off by 0.5mm across 2m? NOT GOOD ENOUGH!!

[@EngineerAAJ]

Why it isn't always K-factor = 0.5? Working with NURBS modelling in the shipbuilding industry, we are used to extracting the midsurface from the bends and using that as the surface to be flattened out. Being bend sheet metals like you showed in the video, or just curved panels used to build the hull.

[@TooTallToby]

Take a look at some of the other comments - there's some great stuff in there about K-factor value - but the TLDR is: The K factor will be different depending on the material, material thickness, bend radius, and bending process.

[@garramiro]

it used to be a line of Wilson tennis racquets

[@TooTallToby]

The K-Factor generation has four main components (K)arophite Black, (K)onnector, (K)ontour Yoke, and (K)ompact Center. Nice

[@jamesjefferson8916]

Where did the 0.35 K-factor come from?

[@TooTallToby]

The correct K-factor value is determined by a variety of things: Material, Thickness, Bending process, Bend Radius, and trial and error (working with the shop floor). If you are completely unsure, you can use a value between 0.35 and 0.5, and you'll usually be pretty close, but you'll want to make sure you discuss with the manufacturing team before proceeding.

[@jamesjefferson8916]

So the Q number in the table is bend deduction, isn’t it?

[@TooTallToby]

Yeah that would be used with the BEND DEDUCTION option in SolidWorks, since you're measuring to the virtual sharp

[@MrMemusashi]

I completely understand what k factor is and I use it almost all the time. However I do not understand how to know what is the correct k factor or how to go about figuring out what the correct k factor should be. I just always use .5 since I almost never use metal thicker than 14 GA. I can't be that far off. But I would like to know how to figure out the right k factor for me.

[@MarkSummersCAD]

K-factor is a function of several items, such as material alloy and condition, type of bend (air, bottom, etc.), bend radius, ambient temperature, etc. The best way to determine the K-factor is to do a test bend with known parameters and reverse calculate the K-factor. For most aluminum alloys and thin steel sheets, K-factor of .44 will get you pretty close. Look into Bendworks application for some good reference material.

[@TooTallToby]

Excellent answer thanks Mark!

[@MrMemusashi]

@MarkSummersCAD thank you. What is "bend works application"? Is this a website? Or an app?

[@MarkSummersCAD]

​@@MrMemusashi​, it is a downloadable app for Windows. Just google "BendWorks_V1-1_Setup.zip"

[@MrMemusashi]

@@MarkSummersCAD thanks again.

[@DRIFTMOTIVE]

so how is kfactor calculated for different thickness and radius?

[@bjh9501]

I believe it is found by practical experiments using test pieces in the workshop.

[@TooTallToby]

The correct K-factor value is determined by a variety of things: Material, Thickness, Bending process, Bend Radius, and trial and error (working with the shop floor). If you are completely unsure, you can use a value between 0.35 and 0.5, and you'll usually be pretty close, but you'll want to make sure you discuss with the manufacturing team before proceeding.

[@BobPhelpsRRIowa]

Spot on but you didn't explain that K-Factor is just the percentage of the material thickness. The line/depth that doesn't change length throughout the bend. All the material on the inside of this line gets compressed and all the material on the outside of this line gets stretched. In the real world with steel and aluminum a K-Factor of .4 is a good baseline until you run samples or prototypes. And your shear size is smaller than the outside bend flanges combined.

[@TooTallToby]

Nice thanks for the feedback Bob - Great stuff!

[@maz1988]

If bend radius is greater than 3x material thickness, k-factor would usually be 0.5

[@TooTallToby]

Nice - great insight - thanks!