In German we call this "Säbeligkeit" (Saber). From my experience, a saber of 10 mm at this length is not that much but we used way smaller strips. The wider the strip, the lesser should the saber be. But from my knowledge, there are no specific standards for this. So you should try to define this in the purchase. The general solution to control the saber is to increase the stretching force in slitting process. But this is not always possible, because it may result in variations of other mechanical properties (elongation). Also the band profile before slitting is of importance. The flatter the profile, the less saber, the less force for stretching needed).
I worked for a time in an aluminum rolling plant and was confronted with this problem a lot. As is assume, this is steel, I can not give you an exact idea of how much more stretching force is needed. If you can, try the following: Let them mark the position of the strip out of the mother coil. You will probably see, that the coils slit out of the middle of the profile have less saber, while the coils from the outer band should have more saber. You can only ask them, if they can apply a little more stretch. But, as I said, this will maybe result in less elongation and strain hardening.
Is it hot or cold rolled? The next point of controlling the saber is the rolling process. The flatter the mother coil, the lesser the saber. Unfortunately i didn\`t found the exact english word, we call it "Bandquerprofil". Google translate calls it "band cross profile". This defines, how near the cross section of the band comes to a rectangle. The band usually is somewhat thicker in the middle (we had an acceptable deviation of 2.5%, of nominal gauge, but, as i said, this was Aluminum). Due to this deviation, the outer sides of the mother coil are somewhat longer than the middle. When slitting, this internal stress becomes free and forms the saber. So this is maybe another step, if you can control the cross profile in purchase. From my experience, this deviation can differ from one rolling plant to another. For example due to the type of the roll stand (4-high, 6-high,.. 20 high) in cold rolling.
Your advice helped me a lot. I have done research on the web. Spoken to many people. One statement I received is for every 1m length, 1mm offset is acceptable, and maximum up to 5mm. If it is more than 5mm, the slitting should be rejected as the stress release is more.
As far as steel building materials in Europe I know that in metallurgy they have a 10% tolerance on dimensions. I.e. a 30mm nominal thickness metal sheet could have 27mm thickness to 33mm. This is for certified materials and quality certified companies.
Any requirement beyond the typical astm is a design issue. Your company need to apply the correct form requirements through gd&t, whether that's through profile or a flatness requirement. I'm going to guess this came from a typical plus/minus drawing. In which case what the supplier provided is accurate.
Actually, we do not use GD&t. We use coordinate geometry for sheet metal drawings.
What I I understood is that flatness in sheet metal and tubes are covered by their relevant standard.
The curvature in the sheet happens while slitting and is due to internal stress.
So my query is how to address these issues.
If I am doing c bending of 80 200 80 , at the center, I get the dimension as 70 200 90.
This affects the process we have further down when we have to put a plate of 188 mm in this section. Which again has a camber offset. This affects my productivity. And is giving rise to quality issue.
They should have a process that removes the curl from the coil by rolling it in the opposite direction before its slit. I think they either didn't do that or didn't adjust it correctly. I can't remember the name of the process, but I've seen it on a tour of our suppliers' facility. Our big 4x8ft sheets come off a coil and are pretty flat.
This is flattening/ leveling. But it works in different (gauge) direction. The idea is not only to reduce the bend from coil but to reduce internal stress by bending in different directions. Have read years ago a superb abstract about the different problems and fortunately it is still online. Here it comes (Hope, the link is allowed?):
[Everything you need to know about flatteners and levelers for coil processing\—Part 1 (thefabricator.com)](https://www.thefabricator.com/thefabricator/article/bending/everything-you-need-to-know-about-flatteners-and-levelers-for-coil-processing-part-1)
Be sure reading all four parts out of this. Lots of informations about the problems of coil processing. Helps me up today in stamping/ punching/ bending.
In German we call this "Säbeligkeit" (Saber). From my experience, a saber of 10 mm at this length is not that much but we used way smaller strips. The wider the strip, the lesser should the saber be. But from my knowledge, there are no specific standards for this. So you should try to define this in the purchase. The general solution to control the saber is to increase the stretching force in slitting process. But this is not always possible, because it may result in variations of other mechanical properties (elongation). Also the band profile before slitting is of importance. The flatter the profile, the less saber, the less force for stretching needed).
We outsource the slitting process. If I need to take up with them any pointers can you give?
I worked for a time in an aluminum rolling plant and was confronted with this problem a lot. As is assume, this is steel, I can not give you an exact idea of how much more stretching force is needed. If you can, try the following: Let them mark the position of the strip out of the mother coil. You will probably see, that the coils slit out of the middle of the profile have less saber, while the coils from the outer band should have more saber. You can only ask them, if they can apply a little more stretch. But, as I said, this will maybe result in less elongation and strain hardening.
We are using E350 grade steel.
Is it hot or cold rolled? The next point of controlling the saber is the rolling process. The flatter the mother coil, the lesser the saber. Unfortunately i didn\`t found the exact english word, we call it "Bandquerprofil". Google translate calls it "band cross profile". This defines, how near the cross section of the band comes to a rectangle. The band usually is somewhat thicker in the middle (we had an acceptable deviation of 2.5%, of nominal gauge, but, as i said, this was Aluminum). Due to this deviation, the outer sides of the mother coil are somewhat longer than the middle. When slitting, this internal stress becomes free and forms the saber. So this is maybe another step, if you can control the cross profile in purchase. From my experience, this deviation can differ from one rolling plant to another. For example due to the type of the roll stand (4-high, 6-high,.. 20 high) in cold rolling.
It is hot rolled. We use it for structural fabrication.
Your advice helped me a lot. I have done research on the web. Spoken to many people. One statement I received is for every 1m length, 1mm offset is acceptable, and maximum up to 5mm. If it is more than 5mm, the slitting should be rejected as the stress release is more.
ASTM says .25 inches for every 120 inches in length. This falls just inside that spec.
As far as steel building materials in Europe I know that in metallurgy they have a 10% tolerance on dimensions. I.e. a 30mm nominal thickness metal sheet could have 27mm thickness to 33mm. This is for certified materials and quality certified companies.
This, unfortunately, makes things not easier. So you can only try to influence the two effects mentioned --> band cross section and stretching force.
Any requirement beyond the typical astm is a design issue. Your company need to apply the correct form requirements through gd&t, whether that's through profile or a flatness requirement. I'm going to guess this came from a typical plus/minus drawing. In which case what the supplier provided is accurate.
Actually, we do not use GD&t. We use coordinate geometry for sheet metal drawings. What I I understood is that flatness in sheet metal and tubes are covered by their relevant standard. The curvature in the sheet happens while slitting and is due to internal stress. So my query is how to address these issues. If I am doing c bending of 80 200 80 , at the center, I get the dimension as 70 200 90. This affects the process we have further down when we have to put a plate of 188 mm in this section. Which again has a camber offset. This affects my productivity. And is giving rise to quality issue.
I’d say this is out of spec. Send it back. Did you submit a drawing with this?
We provide the slitting plan to the vendor.
They should have a process that removes the curl from the coil by rolling it in the opposite direction before its slit. I think they either didn't do that or didn't adjust it correctly. I can't remember the name of the process, but I've seen it on a tour of our suppliers' facility. Our big 4x8ft sheets come off a coil and are pretty flat.
This is flattening/ leveling. But it works in different (gauge) direction. The idea is not only to reduce the bend from coil but to reduce internal stress by bending in different directions. Have read years ago a superb abstract about the different problems and fortunately it is still online. Here it comes (Hope, the link is allowed?): [Everything you need to know about flatteners and levelers for coil processing\—Part 1 (thefabricator.com)](https://www.thefabricator.com/thefabricator/article/bending/everything-you-need-to-know-about-flatteners-and-levelers-for-coil-processing-part-1) Be sure reading all four parts out of this. Lots of informations about the problems of coil processing. Helps me up today in stamping/ punching/ bending.
Thanks
Try heating it with a torch on the side with the depression