factor k development sheet.

[derrik]

hello to all.I also have problems with k not so much on the double fold but when there are more consecutive folds.
someone can explain to me how to insert tables in sw2011 not having office but a similar program as office starter. thank you very much for the help derrik

 

[ceschi1959]

Good morning to all,

I believe that the purpose of the forum, as repeatedly mentioned in this and other locations, is to provide, as far as possible, its experience to try to help other users who are in difficulty.
one of the obligations of those who intervene is to read the question carefully so that they can respond as accurately as possible.

the initial question of xxfast was:

'We suppose to draw a piece to l 50x50 by 2 mm and internal radius 2mm. then I cut it to the laser and piego in the workshop. I mix the piece and see that the l is shorter than 0.1 mm on each side. how do I understand the right value of the k factor to set up on sw to achieve correct development? '

translated is: how do I get the k factor to be inserted into the cad starting from experimental data?

(if I did wrong, I ask xxfast to correct me)

This question has been asked by many companies who fold in a day what mike has folded in a life.

the answer is in the pdf annexed to my intervention, in which I looked good at putting data because those depend on everything you try in the workshop. in my pdf there is no theoretical data but a calculation procedure.

I looked good at giving tables or values as others did because these are all to check with the equipment and materials that everyone has.

and now some punctualization:

citation of mike:

'the difference between real quota and theoretical factor k 'adjusted' them with the handle (= to attempts) inserting appropriate values in the field "factor k". '


sampom quote:

'look that you are saying the same things of all; in this case the per attempt is synonymous with experimental data. go to the workshop, do "tentatives" (proves, experiments) of fold to get the "experimental data" to return to the system cad.'

It doesn't seem to me that 'at attempts' in the two quotes is the same thing. for mike attempts is like: imposed k=x and I see that development is a little short.. Then I put k=x+0.01 and so on.


citation of mike:

'from your pdf you notice (who bended a few linear km of plates you notice immediately) that the fold radius is regular, tangent on the two sides... but in reality it is not exactly like this is a hyperbole, therefore the maximum of diametric irregularities. '

Do the plates have a hyperbolic radius in your drawings? Do you even put the knife in the radius?

citation of yorgioff:

'(cut) do the tests with the equipment that the operator (because then at the end it's him that counts) usually uses to bend the required thickness and set the k for every sheet thickness you will use. '


this is exactly the procedure explained in pdf, and you would have understood it if you had read it carefully.


'but with solid-edge I made templates for every thickness and material with set rays, k, weight, info for rendering etc. so as not to insert data each time. '

if by chance in progress in place of a sheet 10/10 you have to use a sheet 8/10 what do you change the template? Do you make the drawing again?


greetings

 

[enri09]

You're all saying the same thing, I don't understand why you're so excited.
for all:
the k factor depends on: material, sheet thickness, drawings used for bending.

said this is evident that each piece is history itself.

the procedure proposed by baskets1959 is a preliminary procedure: for each thickness, material and machine, it is obtained by measuring the fold finished the factor k of that particular combination.
is exactly the same way of proceeding from others called to attempts, or dictated by experience: by definition it is called experimental.

I find it a bit absurd to look for the tenth of tolerance on a folded sheet: tenth more or tenth less, usually these objects are measured by the meter and if it is not good it is from a "strisciata with the flexible"!

 

[maxopus]

Some considerations, there are several ways to bend the damn stuff called sheet metal.

In the context of structural profiles, (u, omega, c e l per carpenterie) and therefore subject to standard, there are strict rules.
Main rule: the inner radius of the fold must be 1,5 or 2 times the thickness (depending on the hardness of the steel).
for steels type s235jr the radius must be 1,5 thickness, for steels type s275jr the radius must be equal to 2 times the thickness.

to this can not be denied and to those who use smaller rays should be cut off the hands.
if I realize a smaller radius, I try to rinse the profile in the fold area and I compromise the characteristics of the profile resistance itself.
if I realize a wider radius I decrease the profile section and then I get a lower resistance.

made this premise, factor k depends only on the "hardness" of steel.
therefore every batch of homogeneous raw material to be used in production should be checked with special procedure (there are the hardness for this).
As for precision, I challenge anyone to maintain centesimal precision (or even a tenth of millimeter) in bending or profiling processes.
the more thicker and the size of the profiles, the more the scaling increases than the nominal size.
This is due to tolerances (quality and size) in steel lamination processes, tolerances in cutting machining, tool wear and tolerances in bending machining.

if we go into the field of sheet metal processing for non-structural use (furniture or components per pc or assimilar junk) the delirium is total.
knives and quarries are used at will.
3 mm thick sheets folded with 0.2 mm knives, steels without any control about quality (it only counts aesthetics).
when we work this way, we inevitably get ribs.
So much so that we always use low carbon steels to avoid cracking in the fold areas.
For this reason (control on raw materials and "unconventional" procedures on machining) it is necessary to empirically detect the behaviour of steels in different situations.

If we respect the rule that steel should not be ripped in bending, we would achieve much more homogeneous results at equal quality of steel and bending radius.

we say that with more ductile steel (low carbon content) corresponds to a lower k factor, as it lends itself better to compression phenomena of the structure in the inner part of the fold.
If, on the other hand, the steel is less ductile, as much as you can use narrow-range knives, he takes the inner radius he wants and if you insist as a damned giving him 1200 ton under the bending machine, he splits, and the phenomenon increases with the increase of thickness.

 

[giorgioff]

Good morning to all,


citation of yorgioff:

'(cut) do the tests with the equipment that the operator (because then at the end it's him that counts) usually uses to bend the required thickness and set the k for every sheet thickness you will use. '


this is exactly the procedure explained in pdf, and you would have understood it if you had read it carefully.


'but with solid-edge I made templates for every thickness and material with set rays, k, weight, info for rendering etc. so as not to insert data each time. '

if by chance in progress in place of a sheet 10/10 you have to use a sheet 8/10 what do you change the template? Do you make the drawing again?


greetings

I've described the working method I use and that according to my needs is the right one.:finger:
the templates I made them for themselves and I will also do them for sw because when design I know a priori that thickness to use to make a panel or a bracket, then if as you said, for various reasons I have to change thickness, I do not refer anything but correct in the properties of the single part the thickness, the radius and the k.:wink:

 

[Ste80vi]

Good morning, everyone.
I read all the discussion and I realize that I manage the "meaning values" a little differently than others. I personally use the k factor only when I have to calculate the developments of tubular or any geometric element obtained from flat sheet that present bent rays many times larger than thickness (from 15/20 times thickness). so the factor k is 0.5.
for folds made with punches having peak rays 1 or similar (i.e. those that are used) I provided to realize folding tables (instead of factor k) that are based on bending deduction. No one has ever talked about it here, but I find it very useful. they are based on the value to be removed (or to be added, regardless if the sides of the test shorten or on lengthen) on the basis of the thickness and bending radius used.
I have made tests (obviously experimental, and I think there will never be any way to do without) to determine the various shortening values according to:
- sheet thickness
- material
- Punzone/matrix combination (it may seem like a piece of workmanship, but if you notice the coupling of a punch r=1 with a 30 mm hollow matrix - although possible - you never use it)
At this point, for each test, I measured the inner radius of fold with a raymeter (note that value - distinctive for each punch/matrix couple) also provides the optimal value to properly operate the function "closed rod" and the shortening value. the shortening value will be calculated very simply considering the original length of the test and subtracting the length of the two sides. this value will be written in the bending table, so that solidworks will automatically withdraw it, thus calculating the development of the piece. I work with thicknesses ranging from 0,8 to max 3 mm, but having a good bending machine I assure you that, especially up to 2 mm, hold a tenth per fold you succeed without too many problems.
in case there are external factors for us not controllable, such as disuniform thickness, unscrupulous plate, etc. well, those are the risks of trade and the beauty of direct... every technology unfortunately presence its own unexpected.... I have a company and I teach balancecarpenteria also in a cfp of vicenza. once I ordered a pack of school sheets with a thickness of 15/10 and others from 12/10 and arrived - in addition to 12/10 - of the sheets with which I could not keep the measurements. when I checked the thickness of the theoretical 15/10, I found 1,35 mm thick... Nice story! lucky for a school it's okay but it was in the company? when you go to prepare folding tables or calculation systems like these of which you are talking, you must necessarily start from some constants, otherwise it is necessary to rely every time to a practical test realized for each piece that you have to realize, with the material that you will go to use, with punch and matrix that you will use for the work, even with the machine that you will use, because from machine to machine there can be slight differences. . This, although theoretically more than just, collides even with the times below which in production it is necessary to stand and that in order to remain on the market must be increasingly low... a tenth half on a 1.5 mm sheet corresponds to 10% error... It is as if instead of delivering a 1000 mm long tree, I handed it with a length of 1100 mm, or with a diameter of 55 instead of 50 mm.. Wouldn't you think they'd throw it on my pumpkin?
greetings to all and good holidays (for who does it)!

steak
Deputy

 

[stoccolma]

Bye.
to establish the fk we have tested with various materials and thicknesses.
the difference between real quota and theoretical factor k "adjusted" them with the handle (= to attempts) inserting appropriate values in the field "factor k".

I like it. Today you have given me a problem, I try it tomorrow and compare your theory with our equipment. I don't like the poor match between the cad model and the actual internal radius but I can fix it.
Thank you.

 

[jumpy]

with this http://digilander.libero.it/bonettig/lamiera/2009-10-28-calcolo_sviluppo_lamiera.pdf compute the k to have the development you want.

Hi.

g.

 

[c3kkos]

after reading and rereading this thread many things are not yet clear to me. . .

I reorganize mentally and share with you my experiences.



an operator of the sector, dedicated to bending, confided me the golden rule that, evidently, lives inside his workshop with his bending machine:

for each fold, for each mm thick sheet, you lose about 1/10mm


simple. Do I have to fold to "l" a sheet of 2mm thick? (material = iron, not aisi)

calculation 2/10 lost for each fold, in this case, one, unique.


we consider the internal radius close to zero and the external one close to the thickness of the sheet,
for one side 30 and 30mm, I consider the internal sides 28+28+(2/10) and I have the correct development for that workshop.

to achieve this result, in solidworks the factor k I have to set it to 0.35mm
development in sxw with this parameter is 56,24

if you disable the correction? remains 56,24... (argh!)


At this point I realize the mistake I made. .
on sxw, when using edge flange, the bending radius parameter is the internal radius, and not external. .

So I find my l with rest 4mm and 2mm

What happens if I put in 0mm?


It happens that I regenerate the sheet... but development with k 0,35 is 57,1mm

That is wrong!

without k to 0.35? always 57,1mm



What am I doing? will you have to take into account the radius of the punch?

in this situation the k that generates correct development of 56,2mm is "0,08"


igo snapshop...

 

[PiegatoreSolidworks]

with my punches and using real bent rays and the material from you indicated the correct development (for how I work) is 56.71mm.

p.s. I have 16 years of bending experience and about 6 of swx..

 

[c3kkos]

with my punches and using real bent rays and the material from you indicated the correct development (for how I work) is 56.71mm.

p.s. I have 16 years of bending experience and about 6 of swx..

thank you for the answer, God bless the experience.. :redface:


said this, the "my" golden rule was broken.. because calculations 7/10 more than internal measures. . .

You did 30, do 31! Could you quantify in this hypothetical case, your inner real ray?

 

[jumpy]

you have a 3d cad and you have to set the neutral k factor in your cad so that developments come out as the guy bending machine wants that it is 30 years that folds everything, even the wife when she comes home?

of all the discussion Czech laws (gift of synthesis) or my guide (trooopo prolissa e accozzaglia, but I do not have time to fix it).

only with formulas you can dominate the neutral factor of your cad 3d and make him find out the development you want
note well: the development you want, not what will go well in the world, development because the bending machine in production does not break the boxes. In short, like the accountant: Let's get along with it. :mixed:

and at this point you can make the attached document and you will receive the certificate of "neutral factor meter". :finger:
View attachment L_vari_R_e_vari_K.pdfg.

If you know him, he doesn't kill you.

 

[c3kkos]

ho seen the look.

+1 for you :d

 

[PiegatoreSolidworks]

thank you for the answer, God bless the experience.. :redface:


said this, the "my" golden rule was broken.. because calculations 7/10 more than internal measures. . .

You did 30, do 31! Could you quantify in this hypothetical case, your inner real ray?

r real 1.5mm
♪
channel v12mm + blade r=0,8mm (20/10 iron).
Sorry I'm late.

 

[Cristian75]

Good morning to all,
I have read and read several posts on the subject, but unfortunately I have not yet found the solution.
technical office work for a precision carpentry (90% sheet 1mm to 15mm)
Our work in short is to build manufactured in customer drawing sheet.
Since most of our customers in addition to the tables also pass the step file, I would like, kindly know how and which table retreats set in sw. the treated thicknesses range from 1mm to 15mm and the degree of tolerance should not be excessive in the past with think I used only one k factor for thickness with a fixed radius.
coming sheet with different internal rays between customer and customer, I would have 2 solutions:
use only one radius type 0.1 to have no problems with its discharges;
use a table with a series of rays for thickness by entering type the factor k
I really hope someone can help me
Thank you

 

[c3kkos]

But if you read everything as you say, I think it's weird that you ask for such a generic help. . .

Moreover "precision footwear" without specifying the required tolerance.... nn fine :d

 

[Cristian75]

Good morning.
I read a lot of posts on the subject but by no one I caught how to solve my specific problem.... I'll be a bit of a pig! !
for precision carpentry perhaps I have a little bit deaf, I just wanted to say that we are a light carpentry, where we need tolerances in order of 2 tenths on the retreats.
being for us solidworks a software installed from a week only, I turned to qs forum with the hope that someone had to face my own problems and can guide me on how to set up and which table is best to use for my needs.
Thank you.

 

[c3kkos]

Christ,

as you will certainly read the topic is very "hot"; If you're looking for the magic solution, don't exist.

do you have to do with different thickness / bending ratios? you will have different k factors.
use the first quarry you find to make the folds and/or every time is always different? in this case the factor is kaos, not k.

practically the only advice I give you is: try to uniform everything, and leave the tables alone. If you can get down to 3-4 sp/rint reports you will be appropriate. (by experimentation on real folds)

 

[re_solidworks]

Good morning.
I read a lot of posts on the subject but by no one I caught how to solve my specific problem.... I'll be a bit of a pig! !
for precision carpentry perhaps I have a little bit deaf, I just wanted to say that we are a light carpentry, where we need tolerances in order of 2 tenths on the retreats.
being for us solidworks a software installed from a week only, I turned to qs forum with the hope that someone had to face my own problems and can guide me on how to set up and which table is best to use for my needs.
Thank you.

I do not use the bending tables as in all there is also the fold angle on which to apply the rule. as I do not bend to precise angles, but as it requires me in the project, for me these tables are not applicable. the factor k is, in my opinion, the best solution. in fact if we think of the rule said some post does of deduction, we strongly bind to the fold corner. with factor k you locate the neutra fiber and the game is made.
I do not have production, but a couple of sheet metal processing workshops gave me their radius values (inside) and withdrawal and experimentally went to look for the correct k factor. when the development with 10 consecutive folds gave a negligible error (less than 0.1 mm) I identified the factor k, in my case to 4 decimals.
now we have to cut the development of sheet metal directly (without any control/adjustment) on details with 12 non-parallel folds and which must be compared perfectly because they are details of finish.
to conclude: I recommend using invoice k and to charge it to each sheet. the table, if right, you can do it apart for reminder purpose.

 

[Cristian75]

Thanks to everyone, I know the subject is complex and customizable. . .
re_solidworks, I did a series of tests in production and I have a table with all 90° fold retreats and with various combinations of quarries.
You say there is a solution to find a unique k factor that can give me your results? How do I find the K factor with the information I already have? If you can tell what factor k you use?
You remember that I asked you about the choice between inventor and sw... and you advised me sw... well that's exactly what I installed a week ago.
Thanks again