For a while now, my bender, has been complaining about my sheet metal developments and has to fiddle constantly to keep his dimensions. So I ask him to simulate a typical part on his very recent AMADA folding machine (only 3 years old the beast). In short, to get back to the press that the machine gives it, I have to change the K factor to 0.45.
On the forum many posts say that the K factor of 0.33 is valid for thicknesses from 0.5 to 5 but in our case for steel and on our machine, it turns out that the best compromise up to 8mm tested would be 0.45.
I would like to have your opinion on this subject.
Another point, for the same part programmed on the CN AMADA, The developed between S235 steel and 304 stainless steel is different, which seems strange to me. By the way, we haven't done the test in real life yet but the difference is quite important and from memory the elastic limits of these materials are not so far away.
For the part, folding is really a world apart. The development will always be only theoretical because there are really too many variables, quality of sheet metal (hardness tolerance; the harder it is, the more material is needed because of the small bending radius and conversely for sheet metal a little more "mole" bending radius larger therefore less material is needed, thickness (tolerances according to standards) direction of cutting in the sheet metal (rolling or fiber)..
The unfolding depends on the size of the vee, the type of material, and even the direction of folding in relation to the direction of rolling. we can go as far as the presence of paper and even lubrication. And even the temperature of the sheet metal. I almost forgot: and if the thickness of the sheet is in the upper or lower tolerance.
It all depends on the requirements. so sharp make tests and modify accordingly.
Folding is indeed a world apart when you don't know it.
We cannot determine a developed only with a factor K. Each bending machine has its own values, The ideal is to fill in the SOLIDWORKS bending tables once and for all with a reading made on the machine. So we forget the K factor and we put the "Folding Template" option on the Folding Zone. You need at least 1 table per subject. But the ideal way to cover all the possibilities is to have one table per material + 1 table per reference of vee + punch. This is the b...
In each table will be entered the thickness and the bending radius, values read directly on the folding machine.
With us I have k-factor values for each thickness and material (with variants for the different V's available). Just spend an afternoon bending to retrieve the developed data from a simple angle iron with all your thicknesses, materials and V, and find the k-factor that corresponds to all of this. We put it in a table and we're good! I did this once, since then my folds are impeccable. If you are really a perfectionist you can note the k-factor values for several angles (90,45,135°), but personally I take the k-factor at 90° even for different angles and the result is more than correct. We achieve precision to the millimeter at home, which is more than enough for us.
Thank you for your answers, we are currently doing material and thickness tests. I'll tell you more in a short time. I understand that there can be different values depending on all these parameters but I have to find a K factor per material to apply so that it doesn't become a gas plant in the BE.