How Rafting Can Help Increase the Production and Profitability of Your Roll Forming Operation

Hello, my name is Brian Kopack and welcome to Formtek Talks. Today, I’m joined by Mr. Kevin Enos and Mr. Charlie Burgess of the Formtek Group. And we’re going to talk about rafting, and what rafting is, and why you want to consider rafting for roll forming.

I’ll go ahead and start. And I’ll say when we talk about rafting, basically what we’re doing is putting a group of roll stands on a raft, a steel plate raft, or a fabricated raft. And the number of stands we put on that raft can be anywhere from two, four, six, or even eight, depending on how big and how much weight we have to consider to put on that raft. And it depends on the customer’s capabilities of lifting the raft up. But we’re going to talk a little bit about the benefits of why someone would want to do this.

And Charlie, I’m going to start with you, please elaborate on why you think the main reason for rafting is required?

Sure. So, the main reason I run in roll forming is actually production, maximizing your production. If you have multiple products you’re trying to make on your roll forming line, you have to do tool change in order to make the various products. The non-rafted way is you get a pull, the rolls off the shafts that make up your roll former, and then put the new rolls back on, and you have to gauge things out. So, you’ve got the proper gaps between your top and bottom roll. This all takes time. And during this time you’re no longer making production. So, if you want to maximize your production, what you can do is go into rafting, where basically you have the stands on, as Brian said, a subplate. You’ll have one set of stands on their subplate, on the roll former making production, in most cases.

Then you’ll have a secondary set of stands and subplates that are offline. And while that line is running, you can tool up that raft set. Now, when you want to change products, you still have to shut down the line, but instead of going stand by stand and taking rolls off, also you’re doing is changing out these subplates. And as Brian said, you can have four or five, six, even three subplates with rafts on it that you’re going to have to change, but that’s going to be far quicker than going stand by stand and removing the rolls.

Right. I think in some cases, we’ve done time studies where let’s say you have a 20 pass roll forming system, and you have five sets of four pass rafts. Normally, it may take you 15 minutes per stand. You’re looking at 20 stands, that’s basically five hours. Just to physically change it over. Now you have additional time in gaping those stands and starting the thread material through and adjusting. You could be seven, eight hours in that change over time. If you’re doing rafts, general rule of thumb, is we figure 15 minutes a raft. Now you’re looking at five rafts. You’re just over an hour and 15 minutes. And in theory, what really makes this system work is, you’ve changed those roll stands offline, but you’ve also got them. You’ve also got them ready. You’ve set them up.

So when you make this changeover, there’s very little tweaking that you have to do to get the raft set ready. So, in essence, you’ve gone from seven or eight hours and you’ve knocked out at least 80% of that time. So, you’re down to one or two hours and you’re back up and running. So, obviously like you said, the production requirements or the production advantages are a huge, huge benefit. And there’s ways to even make raft changing even faster. But we won’t really talk about those. But another benefit that I think is really advantageous is the fact that now your roll forming line, if you have a second set of rafts. And by the way, we have some customers who have three and four sets of complete raft sets because some of their products, they never change. So, they just keep them tooled up offline, and maybe they designate one or two of the raft sets to be what we change overall the time, but they have a third and fourth of products they never change overall.

In line with that also brings to the point of expertise of operator. It’s hard to find talent these days to be able to gap properly a set of rules. It’s a skill. A lot of times it’s a learned skill. And keeping that talent can become difficult when you have dedicated rafts, as Brian was just saying. Once you’ve gaped those rolls correctly and you never change the rolls on those spare raft sets, basically when you take that raft set off and you set it aside, you run your other product, and then you bring that raft set, excuse me, back on, it’s set up. You don’t have to do any adjustments. It’s in the same position it was the last time it ran that product.

So, the requirement for having that level of expertise in operators is gone.

Right. Yeah. The other benefit that I was going to mention was the fact that from a maintenance perspective, if you lose a bearing, if something breaks on one raft set, in theory, you have another raft set. So, you’re not necessarily down, which is a great benefit as well. If you only have one set of roll stands and something breaks you’re down until you fix it, or maybe there’s a way to minimize that, but you’re down for some period of time. So, there’s that extra advantage of having raft sets. we can talk a little bit about what ways of changing the raft sets over and predominantly it’s Bay Crane. But if some customers don’t have Bay Cranes there’s options for forklifts and there’s things that we can do to make forklifts, to make it more easy to change the rafts over with forklifts.

There’s things that we can do there. There’s also been a lot of applications where automated raft changeover systems have been developed, where there’s carts that come in and move the rafts. And this is applicable to not only roll foaming, but tube mills as well, where cart systems come in and change the rafts and move the rafts for the operator. It all comes down to the level of automation. All of that comes at a price, obviously.

Yeah. And also the aspect of storage.

Right.

If you do want to have dedicated rafts, you got to have floor space because you’re going to have to put these -nonoperational rafts somewhere while the current set’s being run. So, you also have to take that in consideration if you want to go with dedicated rafts. You do need the storage.

As a person less familiar with rafting, are there limitations or standards for the number of stations on a raft?

Yeah, we tend to typically pick even numbers. There’s no big reason for that other than it’s simplicity. Two, four, six, eight on our smaller mills with smaller roll stands, we can get as many as six or eight stands on a raft set. On the larger mills, we tend to settle on two or four. And it’s just really weight. It’s the amount of weight that raft set has. Because now if you have eight stands, you have eight stands at tooling. You have the raft plate itself. If a customer says, “Hey, I have a Bay Crane, but it’s only five ton and this is a big line. I may be required to only have two stands on a raft, just because of weight.” If you have a forklift and you’re using a forklift way of changing the rafts over, they may say, “I can only lift 5,000 pounds with this forklift.”

So, then even on a smaller mill, we may go to a four pass raft, because we can get the weights down. Now obviously, the more rafts you have and if you’re figuring 15 minutes a raft to change a raft over, it takes you a little bit longer, but compared to changing a roll stand over, it still saves you a lot of time because you can… Essentially you’re changing that roll stand over in 15 minutes and you got 20 of them. It can take a while.

You mentioned larger mills and it struck something in me. That’s another application for where you might want to consider rafting is, you get into the larger mills like the… Excuse me, the three inch, the three and a half inch diameter shaft mills. You got pretty sizable rolls there. And for a man to be able to go in and pull that roll off the shaft, carry it over, set it on the table, bring the next roll over is not easy. And with today’s limitations in the workspace and safety and such, sometimes you just need to go to rafting simply because you’ve got a sizable set of tooling that you really don’t want a person to handle. My mind that’s like three to three and a half inch and I really I think start [crosstalk 00:10:23] diameter shaft. When I get to that set of products-

It could be 7 to 10 inch roll.

Right. I tend to try and quote or push the customer into a rafted application at that point in time.

Right. Another thing to understand is, there are times where we’ve been able to retrofit the rafting method to older mills. It’s not only limited to brand new mills. It tends to be more cost effective if we’re doing it on a brand new mill, but we can retrofit older mills with raft sets. It’s not 100% guaranteed. We can do it every single time, because there’s certain mill designs that it’s just not easily possible to do that or it becomes really costly to do it. But if you’re talking about Yoder roll formers and style, and obviously QBW style, we can retrofit old end styles with rafts and usually make that work where a customer can buy another set of rafts.

So now they’ll have two to interchange in and out. Something else to think about when it comes to the rafting is maintaining the raft and keeping things clean. I mentioned that if something breaks down, obviously if you have another raft set, you can pull it over, but cleaning the raft, it can begin to make sense where you can have a raft changeover area. And in doing something like that, you could have a wash station where you could wash that raft down. You could get all the mill scale and grease and gunk off it, so that you can… It makes it easier for the operator to change those rolls out offline separately, and put new rolls back on it. And now things are clean and easy for them to work with. So, there’s something else that you can do offline.

Along those lines, one of the markets I get into quite a bit is flux-cored wire. And it’s a very dirty environment and they’re basically taking powder, pouring it into a U-shaped tube, closing it up and reducing it down. And now it’s weld wire, but that powder goes everywhere. And a lot of times when they use the M style, which again, a little technical, but the gearing is actually on one of the stands, but with the rafted style QBW, the gear boxes are actually removed from the workspace by the distance of a spindle. And getting that distance away from that work area helps [crosstalk 00:13:05].

Mitigate the dust getting everywhere.

Yep. Because they have a horrible time with their gears and everything getting chewed up because that dust got into the M style gear box. And they also like to do wash downs, as you were saying, and taking that raft over to a wash down table is quite convenient for them. So, yeah. Environment can also be another reason why you would want to go with rafting.

Any other things that we can think of with rafting?

No, I think sometimes we got into that bottom shaft adjustable with the XW, which-

Yeah, that’s the roll stand feature.

That’s a roll stand feature, but predominantly on just the rafted type setup.

Yeah. Currently with our rafts, the big thing with the raft is you have to be able to disengage what I’ll call the drive mechanical from… You have to be able to disassemble that to some degree. And we’ve developed methods that make that a little bit easier so that you’re not necessarily grabbing a wrench or anything to break that apart. Also, just as a safety precaution, we always make our rafts where they bolt onto the base, but there’s hydraulic lifts or hydraulic locks. There’s all sorts of features there that we can add. But usually, the simplest thing is just to put a bolt in and give a guy an air ratchet and he can buzz that in five seconds.

And now we’re locking the raft down to the base and it can’t really come up. Now, you could argue that the weight of the raft, it’s not really going to come up, but from safety’s sake, it’s probably always a good thing to lock them back down to the base. Something else to think about though is, with our raft sets, obviously alignment with regard to the center line of the product or center line of the process. We do have key ways in our rafts that we keep that alignment very, very tight. It doesn’t go off. And the keys are chamfered so that it’s easy to get the rafts on and off. So that’s something important to keep in mind that we have to do with raft sets so that there’s a positive location, so it doesn’t affect the product being run. So, we do take care of those things. It’s built into the rafting process, but it’s something to consider, especially if you’re retrofitting.

That was going to be my question. How do you ensure when you’re changing from one raft to another that you’re locating it in the proper spot?

So, that’s actually a very good question. In most cases, we like the rafts to always have its home based on, if this is pass one through four, it always sits in that area, one through four, and then pass five through eight… And it’s appropriate area. The tooling will dictate that, because you can’t put… If you tool it up with passes one through four and then five through eight, you can’t put five through eight in the space of one through four because the tooling won’t let you… That won’t work. So, you have to keep that in its correct chronological order. Now, there are cases where you can… If you have a 20 pass mill, you don’t have to utilize all 20 passes. You could run a product that only needs 12. Where do you put those rafts on now?

Do you put them at the raft position one or do you start at raft position three? Because that’s all you need. In theory, when we align those rafts, they get aligned in the position that they’re in. So the best, most accurate place for it to go is in back into that position spot. We’re very accurate on machining our keys. There is some tolerance band there. So, if you do move a raft that’s in position three into position one, you’re going to have a small deviation. And we have measured as much as anywhere from two to 10,000s. Now, depending on the type of product you’re making, that may not make a world of difference at all. But what’s more important to understand is, obviously you want the alignment from raft to raft to be as good as possible, but what’s even more important is alignment from pass to pass.

And if that raft has so many passes on it, that’s never changing. So, that’s really the… That in essence is our cushion factor that we… Passes one through four or if it’s one through eight, if that’s how many passes we have on that raft. Those passes are aligned to that raft and they can’t go go back. Now, your transition from one raft to another raft and tooling, because it’s in a different position on the mill bed, that could affect your overall tolerance. But usually it’s very small. It’s very small. But again, when we align it in theory, if you had a perfect key, it would always be right. But we all know there’s manufacturing tolerances. And in some cases on very long mills, we may have three or four beds that are all keyed together. And when you look at all keys added up and all the key ways, you can have from one end to the mill to another 40,000s.

And when we align those rafts in those positions, we’ll clean that 40,000s up so that it’s only plus or minus two from shaft to shaft. But it’s when you move that into a different, a position, that’s where you could get into a difference.

Another advantage I thought of, and it is more in line with the rafted design of the drivetrain and… Because you could have rafted or non-rafted, is the fact that you can do single output with the rafted design drivetrain, meaning that you’ve got a double allow put gear box that’s off the main base of the mill. And on heavy gauge applications, you don’t always need to drive the bottom and the top shaft.

You can drive one or the [crosstalk 00:19:42].

You can drive. Yeah. Just the bottom. And so, from an economic standpoint, that’s advantageous because with the other style mill, the M style mill, that Formtek makes, you automatically drive the top and bottom shaft. You’ve got all that gearing in there, regardless of whether you need it or not based on gauge. But with that rafted design, you can save some money in the drivetrain by going with a single output, but typically that’s only on heavy gauge applications.

All right. And I think we’ve covered our topic of rafting and why you’d want to do it or why you may not do it on behalf of Charlie and Kevin, I thank them. And thank you for joining us for Formtek Talks, Brian Kopack, I’m signing out.