I have a process that gets blanks of steel that are bowed and I wanted to see if anyone else has dealt with blowed blanks of steel and what they have done to their process to help stamp a better part. The blanks size is 3.750" X 46.00". I want to see if any one has dealt with this and what they have done to make their process robust to handle the bowed blanks.

Hello Haueyman, Are you using flat sheets of steel or do you use coils? If you are using sheets and the sheets are not bowed prior to stamping, I would check the amount and type of oil that is being used in your process too much oil will cause parts to bow. If you are running steel off a coil you will have to check for flatness prior to running parts, do you use a flattener with the coils? I need more info to be of anymore help.:2cents:

Hello Haueyman, Are you using flat sheets of steel or do you use coils? If you are using sheets and the sheets are not bowed prior to stamping, I would check the amount and type of oil that is being used in your process too much oil will cause parts to bow. If you are running steel off a coil you will have to check for flatness prior to running parts, do you use a flattener with the coils? I need more info to be of anymore help.:2cents:

We get blanks from a supplier and the blanks come in bowed, what I want to know is, are there any things we can do to help elevate the bowing before it goes into the press? We get mis-hits and a lot of down time from this issue. Of course we are going back to our supplier but they can do only so much.

How thick is the material in question? What are you doing to the blanks? Are you piercing or forming? How much is it bowed? It would help to know.

We get blanks from a supplier and the blanks come in bowed, what I want to know is, are there any things we can do to help elevate the bowing before it goes into the press? We get mis-hits and a lot of down time from this issue. Of course we are going back to our supplier but they can do only so much.

Is there a specification for bowing? Did you mean you need to alleviate the bowing (rather than elevate)?

Is there a specification for bowing? Did you mean you need to alleviate the bowing (rather than elevate)?

That is correct, I wanted to see what others have done in their process to help with this.

Still need more info. Are these strips going into a progressive tool, or a single hit operation? You can set up a press with two blocks on the bottom and one on the top bring down the ram until the strip is as flat as you want it. You can run the strips thru rollers to flatten it. Again how thick is the material and what is the operation that is causing the mis-hits?

Still need more info. Are these strips going into a progressive tool, or a single hit operation? You can set up a press with two blocks on the bottom and one on the top bring down the ram until the strip is as flat as you want it. You can run the strips thru rollers to flatten it. Again how thick is the material and what is the operation that is causing the mis-hits?I think I'd also want to know the temper (soft, hard? actual Rockwell or Brinnell number?)

Depending on the operation producing the blanks (I interpret it to be a sheet or plate shear which needs adjustment), I would expect most producers would be able to produce flatter blanks.

Yep. I'm pretty sure we do not have anywhere near a complete story here.

The crux of ANY problem-solving exercise is to start with the root cause to determine if it can be eliminated. If the root cause is "unfixable," then, and only then, do we look for remedies or repairs. Seems to me this commentWe get blanks from a supplier and the blanks come in bowed, what I want to know is, are there any things we can do to help elevate [alleviate = ease] the bowing before it goes into the press? We get mis-hits and a lot of down time from this issue. Of course we are going back to our supplier but they can do only so much.has a strong odor of male bovine excrement wafting about.

That is correct, I wanted to see what others have done in their process to help with this.

Is there a specification?

We get blanks from a supplier and the blanks come in bowed, what I want to know is, are there any things we can do to help elevate the bowing before it goes into the press? We get mis-hits and a lot of down time from this issue. Of course we are going back to our supplier but they can do only so much.

If they're bowed on the length, you need to run them through a straightener. If bowed on the width, you can run them through a leveler. A leveler can take care of the lengthwise bow as well. How thick is the material?

The material thickness is .076" - .082" and and we use ASTM A1008/A1008M EDDS, we form and punch holes and add studs to the blanks. The problem that we have is when the blank is transfered to the press the equipment misses the blank. It has a traveler that takes the blank up to the first station to be peirced. The bow is in the blank, not width.

We do have the company coming in to talk with us next week and I agree with Wes that if it can be fixed then it should be but I guess I just wanted to see what others have done in their process to make it more robust.

We still need to know how much of a bow you have, does the blank slide over the nesting pins, or does it jump up over them when the ram is engaged? Does your P.O. or print have a flatness requirement? You can set up a press with two blocks on the bottom and one on the top bring down the ram until the strip is as flat as you want it. You can run the strips thru rollers to flatten it. Or you can tell your supplier you want it flat w/in .005. If you do not show a requirement for flatness, there are industry standards that allow for bowing. Too many unanswered questions.:(

We still need to know how much of a bow you have, does the blank slide over the nesting pins, or does it jump up over them when the ram is engaged? Does your P.O. or print have a flatness requirement? You can set up a press with two blocks on the bottom and one on the top bring down the ram until the strip is as flat as you want it. You can run the strips thru rollers to flatten it. Or you can tell your supplier you want it flat w/in .005. If you do not show a requirement for flatness, there are industry standards that allow for bowing. Too many unanswered questions.:(

The variation in bowing is different and it can be an inch to 4 inches, varies from lot to lot. The PO states that the blanks must be flat but as I looked there is no call out other than MUST BE FLAT. Being that we don't have a spec seems to be causing a problem.

We have a machanisim the 'hook' that takes the blank up a rail and places it into the die. If the blank is bowed the hook misses the blank, if the operator holds the blank down for the hook to grab it once the blank is set in the first operation and gets two peirced holes for locating but now the part is off to one side or the other because of the bow.

The variation in bowing is different and it can be an inch to 4 inches, varies from lot to lot. The PO states that the blanks must be flat but as I looked there is no call out other than MUST BE FLAT. Being that we don't have a spec seems to be causing a problem.

We have a machanisim the 'hook' that takes the blank up a rail and places it into the die. If the blank is bowed the hook misses the blank, if the operator holds the blank down for the hook to grab it once the blank is set in the first operation and gets two peirced holes for locating but now the part is off to one side or the other because of the bow.


Thanks for the info, 1" to 4" is way above industry standards. I think the best thing for you to do is flatten the remaining blanks you have either with a press or a flattener and use them, and your next P. O. should reflect that you want them flat w/in .050 or what ever will work for your process.:2cents:

1" to 4" sounds an awful lot of bow to me. It might be worth conducting an audit at their facility to see how they are producing these blanks.

Dean,
May I ask what is the ASTM Standard you are ording to:

What is the tolerance you are ordering to +/-0.003 etc.

This is a must and they have to hold this if it is a ASTM standard.
There is a call out that states per customer specified demensions per P.O.

I think your best bet is go through this with your supplier. We don't know yet (or did I miss it?), whether these blanks are cut from coils or plates. Cut from coils, in the rolling direction, this could be coil memory, and maybe the supplier needs to add a straightening step. If these are cut in a transverse direction to rolling, it sounds like something caused by their cutting. How are the cuts made? Shear, laser, plasma?

There are just way too many variables at play for anyone here to hazard a guess. But as you stated you wanted to see how we'd handle it if it happened to us, I would say that I would carefully work through a corrective action process with the supplier and not jump to any conclusions. It could be caused by your supplier, their supplier, even how the blanks are transported to you. You've eliminated the possibility that the problem is not caused at your end, no?

If your supplier is good, they will want to find the cause too. Good luck, and keep us posted, OK?

Get your supplier's azz in you plant asap.

Get your supplier's azz in you plant asap.See! That's not what I'd want. I would want to observe the supplier's process from receiving raw stock to packaging and shipping blanks to me. That means my azz at his plant!

See! That's not what I'd want. I would want to observe the supplier's process from receiving raw stock to packaging and shipping blanks to me. That means my azz at his plant!

If you feel a need to see an incumbent supplier's operations due to a product problem, it's too late for it to help much, imo. Suppliers should be trusted to take care of their own issues. I've always favored having suppliers come to my building to discuss NC issues, for a couple of reasons:

There's something akin to home-court advantage in customer-supplier relationships, and I want to play on my court whenever possible. Supplier representatives aren't going to be distracted by the goings-on in their own shops, and things are focused better.
If I do visit a supplier, I don't want it to be perceived as something negative to the people on the shop floor whom I'm bound to encounter. I want them to be glad to see me.

If you feel a need to see an incumbent supplier's operations due to a product problem, it's too late for it to help much, imo. Suppliers should be trusted to take care of their own issues. I've always favored having suppliers come to my building to discuss NC issues, for a couple of reasons:
There's something akin to home-court advantage in customer-supplier relationships, and I want to play on my court whenever possible. Supplier representatives aren't going to be distracted by the goings-on in their own shops, and things are focused better.
If I do visit a supplier, I don't want it to be perceived as something negative to the people on the shop floor whom I'm bound to encounter. I want them to be glad to see me.My primary aim is to solve a problem, not create a psychological advantage over a supplier. In most cases, I already have that by being able to reject nonconforming material and cancel contracts. What I TRY TO DO IS SEE FOR MYSELF WHERE THE "ROOT CAUSE" INVESTIGATION IS BOGGED DOWN. If I go in a spirit of helpfulness instead of calling a supplier on the carpet, I have done a great deal toward treating a supplier as a partner, rather than an adversary.

(AS MOM USED TO SAY
You catch more flies with honey than with vinegar!")

Dean,
May I ask what is the ASTM Standard you are ording to:

What is the tolerance you are ordering to +/-0.003 etc.

This is a must and they have to hold this if it is a ASTM standard.
There is a call out that states per customer specified demensions per P.O.

I am not ordering to any standard. I am merely saying that the OP can order his material with a flatness call-out and the supplier should be able to meet that requirement. I have not worked in metal stamping for some years now but I recall we used Industry standards for how much bow could be in material for instance .008" per 20" ( depending on thickness and width) of material (this is just an example I do not recall exactly what it was we went by). But I know if I recieved blanks that were bowed 1 to 4" and they were only 46" long I would not accept them.:2cents:

See! That's not what I'd want. I would want to observe the supplier's process from receiving raw stock to packaging and shipping blanks to me. That means my azz at his plant!

You must not have ever worked in the auto industry. :nope:

I bet you wouldn't even charge them for your plane ticket and buy them lunch too. Get them to really like you lots and then maybe they might fix their problem.

Now...back to the real world.

You must not have ever worked in the auto industry. :nope:

I bet you wouldn't even charge them for your plane ticket and buy them lunch too. Get them to really like you lots and then maybe they might fix their problem.

Now...back to the real world.As a matter of act, I did briefly work in the auto industry as a direct supplier of prototype parts for Ford. It was a lovely relationship. Ford paid electronically when bar coded package hit their dock - I had usable money faster than if I had a driver collect cash and bring it back in a pouch. I had zero nonconformances. A Ford SQA visited one time and spent a whole half hour before approving us as a supplier. Our total sales were a very paltry $100,000 because we did not choose to bid on production quantities. So to say I have no experience screwing up with an automotive supply chain, you are absolutely correct!

45 years ago, I earned a large part of my college money working nights at a steel service center. I ran sheet and plate shears, bar stock saws, and plate burners.

In a shear, when cutting narrow strips (less than 4 inches), three major defects (distortions) can occur (assuming the blade is sharp and is actually shearing, not breaking the stock):
camber
twist
bowAll of these three are directly affected by the rake angle of the upper knife. If the rake angle is too high, the material is being bent during cutting. If the shear is underpowered for the thickness or hardness of the material, more bowing and twisting will occur and even adjusting the rake angle will not eliminate the problem on an underpowered shear.

Almost every shear manufacturer can troubleshoot such problems even by phone, but certainly with emailed photos of the bowed product and closeups of the rake angle setting.

When I said I smelled male bovine excrement, I meant it. The material dimensions and physical properties are such they should not be a factor in such extreme bowing - the situation is caused by the cutting process. Other things besides rake angle can affect the bowing, but such things as poor hold down of the material would also manifest in terrible burrs and most likely variation in width of the strip from one end to the other.

With such extreme bowing, my guess is someone needs a refresher course in setting up the shear for optimal operation.

As a matter of act, I did briefly work in the auto industry as a direct supplier of prototype parts for Ford. It was a lovely relationship. Ford paid electronically when bar coded package hit their dock - I had usable money faster than if I had a driver collect cash and bring it back in a pouch.

Is this the same Ford that I know?

I don't know Wes, it doesn't sound like you where in the automotive manufacturing "chain". You are playing with the big boys when supplying production parts. ;)

I don't know Wes, it doesn't sound like you where in the automotive manufacturing "chain". You are playing with the big boys when supplying production parts. ;)Yep. I followed my own advice. I paid attention during Contract Review. Prototyping contacts were VERY lucrative. Production contracts were not. I was not about to subsidize an organization that spent more on just electricity in one hour throughout its enterprise than I spent on my entire operation - rent, utilities, maintenance, capital equipment leases, etc. in one year.