Machine Shop Tour: Warren Screw Machine

A few months ago I had the opportunity to take a tour of Warren Screw Machine in Warren, Ohio. My guide, Craig Rossi, is an engineer for the company and was kind enough to let me take photos and to explain how the machines work.

Tell me a little about Warren Screw Machine. What do you make here?

Warren Screw Machine is a precision CNC machine shop. We handle both high volume and experimental parts focusing on the hydraulic and aerospace industries. Even though we primarily service those industries, we also get into a little bit of everything else. We are basically a CNC lathe shop, however we have more to offer than just CNC lathes and Swiss machines. We also utilize CNC milling machines, screw machines, broaches, gear cutting, grinding, and more. Our diversified shop gives us quite a bit of flexibility in running parts and keeps costs down by allowing us to perform most operations in-house. We have some of the newest machines on the market that possess amazing accuracy and blazing speeds, but we also rely on some older screw machines to stay competitive on simple parts.

What do you do for Warren Screw Machine?

My job is always exciting and changing. I get to work on all kinds of projects ranging from tooling improvements to helping figure out an entirely new way to run parts. I am a Lean Six Sigma Black Belt and mainly do continuous improvement projects at Warren Screw Machine. Essentially, my job is to find the most efficient way to machine parts. The improvements are mostly job specific, though sometimes I find general improvements as well. No matter what the project is, I work with operators and bring in the right outside tooling people so that we can figure out the problem at hand. We have had a lot of success over the past couple of years improving jobs, some by over 50% for cycle times while maximizing the capacity of the machines. It’s a lot of fun finding new equipment and pushing the limits of what can be done. In one project, for example, we ended up purchasing a machine that can hold accuracy and repeatability within .00008″, which is comparable to 1/25th of the width of a human hair. The only way to keep manufacturing in the US is to innovate and think outside the box. That is probably the main thing I do during the day, along with about 10 other activities.

Can you show us around a little?

This is a small sample of our raw material bar stock. We run everything from aluminum to steel to titanium. The material typically comes in 12′ lengths and will vary from round, hex, or square depending on our needs. All the material is tagged to show what type, when it was received, and its heat number. The green tags indicate a certified material that is a requirement for most military and aerospace customers.

Here you see a Brown & Sharpe Screw Machine, an awesome example of some WWII-era technology. Some of our machines that are still running have the old war machine stamp on them. This is a cam-driven manual machine, so instead of writing a program for how the part will run, a cam is created to manually control the tooling. These cams are complete and include the speed and feed of the tool, the turret position of each tool, the cut-off signal, and finally, the feeding out of new material. Since it does not have the ability to move the turret on the X axis, we typically have to use form tools to create the outside contour of the part. This machine might look old, and it is, but it can hands down create parts faster than anything else in the shop. It is just limited the complexity of the parts it can produce and tolerances it can maintain.

Our CNC Swiss machines are a distant cousin of the Brown & Sharpe Screw Machine. All of our Swiss machines have dual spindles—the main—and sub-spindles, which let us machine the front and back of the component simultaneously. Simultaneous machining greatly cuts down on our cycle times by minimizing the amount of down time in the machine. These lathes also have live tools which enables us to handle complex parts while maintaining repeatability and accuracy. Our machines also feature bar loaders so that we can continuously run parts without having to stop the machine to reload.

Here we have the OSP-P200L controller for our Okuma Space Turn LB3000EX. This machine is impressive. It is lightning fast and extremely accurate. The programing of the controller is standard M-code & G-code. You can see the line of code on the left that is telling the spindle, turret, tools, and everything else what to do. This machine has X, Y, C, M, W axis programing ability. The numbers on the right side of the screen are telling us the actual turret position and the distance to-go along with spindle speed. It has a full keyboard and touch screen. A cool fact about the Okuma Controls: if we have a major issue or something is acting strange, our service representatives can connect to it over the internet and remotely diagnose the problem.

This is the turret bed of one of our CNC lathes. On the bottom right you can see the center. This is sometimes used to stabilize or add rigidity to a long part or a part with critical dimensions. On some of our machines, instead of a center, there is another spindle that picks off the part and continues to machine on the back side. In the top center we have our turret. This is a 12-station turret, which means it can hold up to 12 tools. The focused tool is a center drill, with the stick tool above it being a turning insert holder. In the bottom left of the shot you can see the spindle. Some machines have automatic bar feeders while others either have a bar puller, or the bar is manually pulled to a stop.

This is a set of brass parts produced on one of our CNC lathes. This part is a good example of multiple tools needed in the turret. First, you have a center drill to line up the long drill that is needed for the center hole in the parts. The outside diameter gets turned with an insert tool, then a threading tool comes in after to thread the outside diameter. Behind the thread, a relief is created using a grooving insert. Just behind the threads and relief, you can see a flat. We have to use a live milling cutter to put the flat on the part. Finally, we will use a cutoff for the part once all of those other operations are done. My best guess is seven tools to do the job, but maybe more.

Thanks for showing us around, Craig!

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Matt Richardson is a San Francisco-based creative technologist and Contributing Editor at MAKE. He’s the co-author of Getting Started with Raspberry Pi and the author of Getting Started with BeagleBone.

View more articles by Matt Richardson


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