Interview: Metal Stamping - Industrial Metallurgists

Interview: Metal Stamping

<a href=''>Interview: Metal Stamping</a>

This interview is with Rich Nielsen, Director of Engineering at IMS Buhrke-Olson, a metal stamping and assembly company. We discussed various aspects of stamping engineering. The interview is about 17.5 minutes long.

During the interview we discussed:

Rich Nielsen (left) and Mike Pfeifer






Interview transcription - metal stamping

Mike P.: Good afternoon. Hi, Rich.

Rich N.: Hello, Mike.

Mike P.: This afternoon, I’m with Rich Nielsen. He’s the Director of Engineering at IMS Buhrke-Olson. They are a metal stamper. Rich has been involved with metal stamping and fabrication his entire life. He worked for his father, in his stamping shop, and he’s been with Buhrke-Olson for a long time, as well. Thanks for joining me, Rich.

Rich N.: Certainly.

Mike P.: My first question is, what processes do you have at Buhrke-Olson?

Rich N.: We have metal stamping presses from 30 tons up to 600 tons. Almost all of them, with straighteners and feeders, so that we can run continuous from coil. Most, we’ll use a progressive die stamping method to produce a complete part, with every stroke of the press. These are all mechanical presses. They run off of a crankshaft, with a flywheel and clutch and brake.

In addition to metal stamping, where we can produce parts that are complete, we also have several joining methods available. We will do riveting, welding, toxing, staking, as well as resistance welding of studs or nuts to the stampings that we make. In that way, we can make not only metal stampings, but assemble them together.  Often, we’ll make five to ten metal stampings, and we’ll rivet, weld, spot-weld, whatever, MIG weld, or join them together.

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Mike P.: You work mainly for OEMs?

Rich N.: 90% of our work is automotive, and we work for the tier one suppliers that will deliver their assemblies direct to the assembly plants.

Mike P.: What materials are you typically working with?

Rich N.: Steels, red metals. Mostly cold-rolled steel. It can be anywhere from .1 millimeters thick up to maybe four or five millimeters, depending on the material thickness. They could be ductile steels that are made for forming. For example, draw steels, they sometimes are harder steels to form.

We do some work with red metals. It’s not a majority of our work, but we also do stainless steels and aluminum. We do a fair amount of work in aluminum, as well – cold-rolled.

Mike P.: Are there any materials that are more or less difficult to work with than others?

Rich N.: Sure, depending on what needs to be done to them, what shapes we need to create. In general, the materials that have a higher percentage of elongation are more forgiving, friendlier to the forming process.

Mike P.: What materials are those? This would be like deep draw steel?

Rich N.: Yeah, the deep draw steels. You just have to look at the percent of elongation, and the yield strength versus the tensile strength, and see what forces are required, and how much springback you can expect to see.

(2:46)  Mike P.: Is there sometimes any negotiation between you and the designer, over strength versus elongation?

Rich N.: Yeah. If we see a problem in forming a part out of a certain material with a low elongation, we will ask for and recommend using a steel with a higher elongation. But of course, that sacrifices some strength, and sometimes they’ve already looked at that and decided that they could not use softer material and more forgiving material, because it would have to be thicker, in order to produce the strength that they need.

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Mike P.: What ends up happening, then?

Rich N.: We have to either change the design to be formable, to be feasible, or in some cases, it’s adding to the design. In some cases, it may be introducing additional offline hits, in order to complete the part, because we would not be able to complete it in the progressive die.

(3:55) Mike P.: This gets to the having to do extra steps that might add to the cost of the part, because the part is not easily manufactured out of the material that’s been selected.

Rich N.:  What we’ve run into in the past year or so have been more and more parts to be made out of high strength and extra high strength materials. These are new products, that we’re not familiar with, so we’re in a learning curve. And often, I can tell that the designers designed it just as though it’s cold-rolled steel or highly formable stuff, and it’s not. Then, we’re all going through a learning curve.

We rely on forming simulation software, as much as possible, but that’s difficult to do, because in order to get a really true simulation, we need to design the tooling. That requires a commitment, and some time and investment right off the bat, before you can even really try it out and see what you can get. We have some forming simulation software that – I call it just a one-shot. It’s not for a multi-stage progressive die type simulation. That tells us some things, right off the bat.

But the problem we have is that in order to really determine if we can successfully make the part, we either have to build a tool and try it, or we have to design a tool, and run those stations and the tools through a simulation that’s capable of doing that high level multi-step processing of the simulation. We don’t have that software. It’s very expensive

But I can outsource it. In some cases, some our tool shops, our tool vendors may have it, and they will do some of that for us. But that’s presenting a problem, because in the case of dual-phase steel, this stuff is designed to harden as it’s formed, so that it absorbs energy in a crash. Well, that’s what we’re doing when we’re forming it. We’re crashing it. We’re crushing it into a different shape.

So, it’s resisting being formed, and it’s absorbing a lot of energy and giving us a lot of springback, so it becomes very challenging to make parts using that material.

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(6:14) Mike P.: So, someone has to make a commitment to you, for you to be able to get the tooling to do the experiment, so it’s not risk-free for them either then, is it?

Rich N.: Correct. What we’ve done in some cases, when it’s possible, we have made some temporary tryout tools, to just trying forming it, either just in a small press, or even a screw press or something like that, or a hydraulic press, so that we can actually measure the springback in certain conditions. We’ve had to introduce a lot of tricks to fight the springback, and to accommodate that.

We’ve found that for these really super high strength steels, that 90 degree bends are hard enough. But when it’s a complex drawn, highly complex geometry, it’s nearly impossible to predict. We’ve had to add, for example, ribs on a formed flange of a part, in order to form it without having it turn into a potato chip.

This part here is very recent. This is dual-phase 980 steel, very tough stuff. High springback, real high springback. You can kind of see what’s happening along this drawn edge. You see the wrinkling that’s happening there, and the stress and the high pressure marks. What this did was – yeah, we can form it. It doesn’t really come out to a full straight 90. There’s too much springback.

But the result of trying to form that creates an unflat condition, not flat condition, on this     surface, which they need that flat. So, we ended up actually having to put ribs all along here, to gather up some material. It wants to wrinkle anyway, so what we did was we just gave it a place to wrinkle to, and control that, but that took so much extra time and effort and money that was just not at all something, that was planned for.

8:17  Mike P.: If the design engineers had come to you earlier in the project, could some of the problems been avoided?

Rich N.: Yes. We’ve had other customers that have come to us and said “We know this is going to be a tough job, so what do you think? What can we do? What can you hold? What kind of tolerances? Where do you need to open up tolerances, and where can we keep them tighter, and how can we achieve this? Would you recommend any changes?”

This was one that was kind of dropped in on us. They were already months late, so there was no time to do anything, much less have a reasonable discussion. I think one of the biggest things that you need, one of the most important things that’s needed for this kind of part with this kind of material, is an expectation that we may have to change the part, and time to do that. That’s what’s sorely lacking, many times.

(9:10) Mike P.: What’s the typical process for a customer working with a company like yours?

Rich N.: We’re tier two automotive. Our customers are tier one. They’re the ones that have designed the seatbelts or the airbags, or the seat construction , or whatever it is – radiators or whatever the component is. They’re the ones that design that whole component, to be ready at the assembly line, for the car manufacturers. That’s tier one.

Then, they will design all their parts. Then, they have to go to their supply base, which is us, for stamped metal parts, or another supplier for plastics, electronics, whatever it is. They have to contract us to design and build tools to make those parts, and to make those components for them. So, we work directly with those tier one guys.

In some cases, they have good experience in metal forming, and they know where the pitfalls might be. In other cases, they have no clue.

In the best case scenario, they have designed the assembly and the components they want us to make, and they come to us early enough to have us have face-to-face or online evaluations with their designers and their engineering team, to identify and address potential issues with forming the part, like I talked about. If that’s done early enough in the whole process, then there’s time to address those things, and they’re willing to listen, either because they’ve had prior experience and they know they’ll do better if they listen, or because they know their knowledge of it is not as deep as ours.

(10:57) Mike P.: What about the case when someone doesn’t ask for your help or input?

Rich N.: We give them our input, whether they ask for it or not. What happens is when we get a proposal and we have to quote on it, and it looks like it’s getting serious, then we will mark up drawings or prepare a PowerPoint presentation, with views of the part, and maybe some data from a simple forming analysis, a forming simulation, and let them know, or try to give them the data behind why we think there would be a problem in a certain area, why we need to change something, or why we need more tolerance for one item or another.

We’ll do that, regardless of whether we’re asked, just because it gives us a leg up on it. It doesn’t always change their minds. It depends on who you’re talking to. Sometimes we’ll just hear “This is what we need. We have to have it.”

(11:55) Mike P.: In that case, what happens?

Rich N.: If it’s a serious enough problem, we may back away and say “We’re just not capable of making the part the way you want it.” Most often, what will happen is we agree that we will get as close as we can, and we’ll discuss it again after we get the tool made, and we’ve fine-tuned, we’ve debugged the tool to the extent possible. Then, we’ll see them.

“We can’t hold the tolerance you did want, but we can hold this. How about this?” Then, we’ll negotiate a new tolerance, on the basis of that. If everyone is working in good faith, that works okay.

( 12:40) Mike P.: It’s interesting that you mentioned the thing about having to back away from a project, because the ease of fabrication is just not going to be there. When you’re quoting things, and you’re assessing the materials that have been selected and the design, does ease of fabrication influence what you’re going to end up charging per part?

Rich N.: Yes, it does, insofar as we will have an extra charge, or will include extra money, if we know there is going to be a high degree of development, a lot of time to develop the tool, a lot of trial and error, or a lot of outside expense for either making prototypes, trial and error that way, or outside expense for the high level of forming simulation that we might have to outsource.

Another thing that we may do is we try to quote parts as often as possible, on what we call “prog complete.” That is out of a progressive die with many, many stations, that’s progressively pierced and formed and crushed into shape, and finally the part is complete, at the end of the tool. That’s the most cost effective way to make these parts. That way, you’re really making best use of the economy of metal stamping by progressive die method.

If we think there’s a chance that we might not be able to get that tolerance or that bend, or whatever it is, we may include a secondary offline re-strike of the part, which of course, is physically handling it in and out of the tool much slower than getting it complete, off of the progressive die. In that case, we would have the cost of the progressive die, the cost of running it and all the materials, but we would also have the cost of an additional step or multiple steps, that may be needed to complete the part.

If there’s no budging on it, we would have to either – like I said – back away, or include extra steps, to try to make it. We have to be careful what we promise.

(14:36) Mike P.: Does this apply to all materials?

Rich N.: Some materials are more friendly to forming than others, so we really have to watch closely what materials are selected by the customers, and another suggestion might be a different material.

(14:54) Mike P.: Different materials have different ease of fabrication. There’s a tradeoff between strength and ductility or elongation, and also there’s work hardening, too, because different materials work harden at different amounts. Some materials are very easy to work with, because they don’t work harden a lot. They have high ductility. Other materials are more difficult. It could be because of their strength, or it could be because of their composition.

Rich N.: Yeah. And these materials, they’re designed and created for certain purposes, so they suit a certain function. But that doesn’t mean they’re easy to work with.

15:32 Mike P.: Yeah, it’s important for designers to think about not just the mechanical properties for a component’s application, but also think about ease of fabrication, regardless of the fabrication processs. From a project management perspective, it’s important to have discussions with a stamper early in the design process. That can have a big impact on preventing problems and mitigating risk.

Rich N.: Unfortunately, I don’t have an engineering degree. I didn’t go to mechanical engineering school, but I’ve been told that in those courses, in that course of study, they may spend a month or something covering metal stamping. Of course, they’re going to be exposed to some basics, some very basic knowledge. But if you try to design stamped metal parts with only that kind of exposure, you’ll be very limited and you could quickly get yourself into trouble. As opposed to – I’m an old guy. We used to have high schools where you’d make some stamped metal parts. You’d do some casting, you’d mold some plastic and weld some parts.

So, there was a little more hands-on understanding of what was involved in some of those processes. So, I think a little clearer understanding of the limitations, as well as the capabilities, often that’s where we have to fill in the gap.

(16:50) Mike P.: I think that’s where it requires the designer understanding the limitations, or their limitations in terms of knowledge, and reaching out to you or to whatever stamper they’re working with, to get the input required, in order to make sure that things go more smoothly. We can’t be experts in everything.

Rich N.: No, we certainly can’t. Right. So, we have the best results when we do just like you say. We have a good conversation and understanding of what the challenges will be on a particular part.

(17:26) Mike P.: Alright.  I think that’s it, Rich.  Thanks a lot for meeting with me. That was a great discussion.

Rich N.: You’re welcome. I enjoyed it, too. It was good talking to you again.

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