Hi all !
I am new to using the sheet metal tools in Solidworks and I have a slight problem with a sheet metal cone that we have to manufacture. The cone will be rolled from 40mm thick mild steel (300WA).
The problem I have is that I don'y fully trust my settings in the flattening of the feature. I see that by adjusting the k-factor, I get vastly different results! I guess that the default of 0.5 is what I should be using.
How can I know for sure that the segment will come out perfect from the rollers if I cut the plate according to my Solidworks model?? (I won't be too popular if it doesn't......) Is there any way to check my results?
I will greatly appreciate any input in this regard.
Bye!
I use a K factor of .5 on all of our HRS and Stainless parts and have not had any issues. We roll a lot of round to rectangular duct transitions and have had the parts match up perfect. I have yet to try anything thiner that 12 ga. I believe you can check the machinery's handbook for a value based on your particular material and bending features.
Let me know what you find.
Joe
Here are a couple different methods to check your work. You can either sketch it out in 2D per this sample drawing, or you can trig it out. I included the trig equations in the sketch, and they are programmed in the excell file. Plug in the values for the two diameters and the height as defined in the sketch, and the spreadsheet will give you the two radii and the included angle for a 360 degree cone (or you can just get these values from a full scale sketch of your formed part). As your cone is less than 360 degrees, you will have to multiply the included angle by the percentage of 360 degrees that you want in order to get your specific sweep angle. Note from the sketch that I assume a K fact of .5 as I split the metal on both sides of the construction lines. This is how I figured out flat layouts before I had a computer at work, and actually trust it more than I do SolidWorks, as sometimes it seems SolidWorks doesn't take the metal thickness into consideration when calculating flats for sheet metal lofts.
Attachments
You didn’t say if this was an in house project or not, if it is not an in house project and the vendor will not give you the necessary information, I would make the pattern such that after rolling it is then trimmed to size.
If I needed to know exactly how the rolling affected the shape, whether it was going to stretch much or little, I would roll a sample of the same material.
Unlike bending in a press brake, rolling can be done in one pass or many, I would say the results you would get by passing it thru the rolls in one shot would differ from one that used many passes to achieve the desired radius, the reason is any work hardening of the metal should affect the K factor.
Large plates are rolled both cold and hot, this could change the K factor.
Rolling roll radius might affect the K factor.
I appreciate all the possible answers to my question, but I'm not yet satisfied. I was hoping to find a table with values, or a formula to calculate the k-factor. The whole idea is to use SolidWorks to draw or design a part, and then issue a drawing for manufacture. To waste time and money on trial and error problem solving is no option. I have many similar jobs to manufacture, so I need to figure out a way to get it right the first time.
On a conical job like this, the material length is not a real issue, because it will have to be manufactured in segments anyway, so to trim the lengths of the segments after rolling will not be a problem. (I need to allow roughly 200mm per side for manufacturing purposes). What is more important, is the inside and outside radius of the segment that has to be cut from the flat plate. On some of the bigger work pieces with diameters in the region of 2 meters and bigger, the k-factor has a significant effect on the results obtained by flattening, including the length, witch could then also become a problem.
I hope someone can solve this for me! If I could find a way of entering an accurate k-factor, SolidWorks could become a real handy (indespensable) tool in the manufacturing process. It is so quick to draw, flatten and print a drawing, it is almost unbelievable, but if the results are suspect.................
Martin,
Bending metal is inherently a trial & error process. It depends on what you are creating, what material you are using, the material properties of that specific lot of material and the manufacturing processes and tools/machines used by those that make the parts.
You will want to work with those that will be manufacturing the parts to come up with the correct k-factors for your specific parts. This will be accomplished by creating some test parts to calculate what the k-factors will be for your processes.
SolidWorks will give you very accurate flat patterns, but you have to do the work to find what the correct k-factors are for your processes/materials through your own test and evaluation.
Cheers,
Anna
I'm a little disappointed that the solution to my problem is not a simple question/answer scenario, but I think I know how I will approach this:
The first job is a cone with a 2493mm dia big side, and 2252mm dia. small side, and 466mm wide, 40mm thick. Since the job has such a big radius, I doubt if the k-factor will be far from 0.5. The elongating from the roll process won't be a factor, since I will allow for setting, witch will be cut of anyway after rolling.
Hold thumbs guys! (unless someone comes up with a better idea)
I'll keep you posted how it turned out.
Cheers.
On a side note...
I am trying to create a cone using your file as a guide. The difference being that my cone will have flanges. I have created my Revolve-Thin1, the next step is Sheet-Metal1. How did you achieve this? I have tried using the convert to sheet metal function, but it doesn't look like what you have on your feature tree.
Any help is appreciated.
I think you will find there will be to much deformation of the material for SW sheetmetal to give you a flat pattern.
Michael
Misty,
The best way to decipher someone else's part, is to start at the top op the feature manager tree, and edit the features one by one to see what parameters have been set in each particular feature to achieve a particular result.
In this case: Edit the "sheet metal 1" feature. You will see at the top on the left side of "Sheet-Metal1", the icon for insert bend appears. Take note of the edge selected on the model.
Here's how I did it:
Draw your part as a thin feature, then click 'insert bends", select the edge on your part, and accept to close. Next, select the "unfold" tool, select a fixed edge, and at bends to unfold, click on "collect all bends" and accept to close. Your part should flatten. To fold it back, just pull the history bar up to just above the "unfold" feature, or suppress the "unfold" feature.
Note that I never used the "convert to sheetmetal" tool.
I hope this helped!
Bye.
Martin.
Martin,
As you know the K-Factor is the position of the neutral fiber in relation to the inner radius expressed and percent of thickness, I believe that on 40mm mild steel and the process you descrived you can start with 0.45 to 0.5 (since you do not have actual data from testing with same material and part before), on the other hand as the material pass several times thru the rolling process it will harden and also will chage thickness so the K-Factor will change during the process. In fact it can be under 0.45 (but on a very large radius maybe it will stay between 0.45 and 5), but that as you know at the end will produce a little larger part (since you calculated for 0.5), in which case a god cutting torch will be very handy (you can cut, but you can not add :-) ). Any way, if you are an engineer, the production people will blaim you (and the entire engineering department) for every problem at the production floor... so what is new?
We fabricate large parts of heavy thickness (up to 150mm) for liquid natural gas for the oil industry and as you know those are formed in sections which are field welded, and after years of doing the same process, at the end we need to cut parts to fit exact dimensions which is part of the process of preparing the edge for the welding of the segments. The reason is that the bending parameters for those very large thick parts change from batch to batch of the steel we received form the supplier, and even when the proces is done by one operator or another even when the rolling machine is equiped with digital controls, the repetibility of the process is not achieved.