It’s a simple equation for Slabe Machine Products (Willoughby, Ohio). If its spindles aren’t turning, the shop isn’t making money. Understanding this fundamental principle of the contract machining business and reacting to the just-in-time demands of its customers, Slabe Machine Products (SMP) has waged an all out war on machine setup time. The weapons the company has chosen in this battle have been multi-axis CNC Swiss-type lathes and turn-mill centers capable of dropping a part complete in a single setup.
SMP is an ISO 9002 certified component manufacturer that satisfies the micro-electronics, ultra-high purity and high pressures valve, medical, aerospace, commercial and automotive industries. Most of its customers come to SMP seeking parts with more complex detail made from alloys such as Inconel and waspalloy that are tougher to work with.
As the shop made the transition away from conventional CNC milling and turning centers and cam operated screw machines to more advanced machining, it quickly realized how critical efficient off-line CNC programming was to minimizing machine down-time during setup. Having invested in complex Swiss machines, including a Citizen L-20 and two Citizen M-32s as well as twin-turret, twin spindle turn-mill centers from Hardinge and Nakamura-Tome, SMP turned to PartMaker CAM software from IMCS Inc. (Fort Washington, Pennsylvania) 3 years ago to streamline its CNC programming off-line. The software assures SMP that when one part is completed the next is ready to run with an absolute minimum amount of setup time.
“As our work has been condensed to truly just-in-time lead times, we’ve been forced to change our entire business in order to generate much smaller volumes of components much faster at the same cost as the higher volume runs of years ago,” says company vice president of sales Brendan Slabe. “Without the combination of the machines we currently have and PartMaker software, the parts we make would be cost prohibitive.”
He cites a recent part run that required seven unique types of milling and turning operations, a part that could be completed in a single setup on the Swiss. However, the customer wanted only 100 pieces to meet its immediate needs, for the same price per piece as when it had purchased lots of 10,000 5 years ago. The ability to program and set up such jobs quickly means the difference between success and failure in an environment like this one.
“Once you lose machine time, it’s lost forever; you won’t ever get it back,” Brendan Slabe says. “Nobody pays you for setup.”
A Different World Requires Faster Programming
The trend of more complex parts being ordered in smaller batches is a common thread throughout the production machining business these days. The long production runs of years past are history in this shop’s eyes.
“The old days where you get blanket orders are over. The business has really changed. The only way to adapt is through technology. You’ve got to invest in technology because that’s the only way to make the parts cheaper,” says Edward Slabe, the company’s president.
In the face of this changing world, CNC Swiss has seen its traditional role of making only small, long, skinny parts change as well. For the example, the Citizen M’s at SMP come equipped with three tool stations, a gang, a turret and a separate slide for working only on the back of the part. These machines can cut parts with diameters over an inch and up to 32 millimeters, almost blurring the lines between the Swiss and the turn-mills.
Of course all this complexity needs to be programmed. In the case of the Citizen M-32, the machine actually requires three separate programs to be written to drive its 13 programmable axes.
As a result, CAD/CAM technology, too, has changed. Historically, CAD/CAM has been the domain of the CNC milling world for programming the complex free form geometries found in mold work. Only recently has CAD/CAM adapted to the needs of shops such as SMP to make the programming of complex multi-axis lathes easier.
The current market realities forced SMP to find out just how important a productivity tool the right CAM system is. What SMP has learned is this: The setup reduction achieved by having a machine capable of performing a number of turning and milling operations in a single setup instead of moving the piece to different machines in the shop can only be of benefit if that new complex machine can be set up quickly. A major part of setting up a CNC Swiss quickly is having a good, proven out program ahead of time.
“The amount of controllable axes on our CNC Swiss affords you the opportunity to do just about anything. But, you have to have something that lets you program efficiently and post process correctly to a wide variety of machines. You need a software package that can support a wide range of machines. PartMaker is a giant blanket over all of our machining capabilities,” Brendan Slabe says.
How CAM Software Helps
In the case of the PartMaker suite of products, the software supports all of SMP’s machining capabilities, including its CNC Mills, two-axis lathes, eight-axis turn-mill centers and CNC Swiss-type lathes. To address the unique challenges in the programming of its Swiss-type lathes, SMP uses a module called PartMaker SwissCAM.
“Before [PartMaker] we had a milling package and a turning package; we didn’t have anything that explicitly supported our mill-turns, so any type of special features typically had to be programmed at the machine, which was agonizingly slow. On the Swiss we also did a lot of manual programming, which is about as ancient as when we were doing trig with a calculator in front of the machine, dimension by dimension. PartMaker allows us to program all the machines in one shot in a uniform manner,” Brendan Slabe says.
PartMaker is a visual programming system that operates from graphical representations of the various faces of the part. The system breaks a complex part into a set of faces. The faces can be planar or rotational, and each can contain various machined features such as holes or j-slots. A specific machining function such as turning, polar milling or cylinder milling is assigned to each face. A dedicated window, referred to as a face window, contains a workspace for the graphical representation of the face features.
A built-in drawing capability lets the user draw a part from a part print or import geometry directly from virtually any engineering system.
A dialogue box associated with each face window contains a pictorial representation of the machining operation to be performed, the location of the face boundaries, and the positioning of the face relative to the machine coordinate system. According to SMP’s programmers, this visual programming makes PartMaker very intuitive and easy to use.
“When you start to look at more complicated programming such as milling and radial moves, deciding how all the axes are going to work together is probably the toughest part. With the complexity of our machines, I don’t think anything we do anymore is simple,” says Jeff Hoyga, a CNC programmer at SMP. “The software’s approach lets us break down these complex parts and express our ideas about how the part should run very easily.
“I would estimate to write programs manually for our parts would take 8 hours. We can get the same program finished in PartMaker in an hour, complete. This includes drawing the part, choosing tools, writing the program and optimizing it.”
For Swiss, as each part feature is created, the user has the opportunity to verify a tool path as well as watch the stock evolving through the guide bushing.
The software includes an integrated tool database that contains data for each of the tools used on the machine being programmed. A dialogue box is associated with each type of tool (drills, end mills and so on). A graphic representation of each tool type and a list of each tool’s parameters are also provided. Once the tool data are entered, they are permanently stored in the database for the life of the tool.
For repetitive operations such as center drilling, drilling, tapping, boring, chamfering and so on, the programmer needs only to create the cycle one time. The cycle can then be stored in a cycles database, which is linked to the tools database. The graphical user interface makes creation and modification of cycles a simple task.
The software comes with an extensive materials database, with recommendations for average cutting parameters. Feed rate and spindle speed are computed based on tool geometry (size, number of flutes and so on) and machinability data.
Rather than create a job plan in a conventional sequential manner, the programmer describes the placement of groups of part features on the surfaces of the machined part. Once the part feature description is entered into the computer, the software automatically generates an optimized job plan. The results of the job plan are summarized in a process table window. The table lists tools and cutting conditions for each process. Feed rates, spindle speeds and cycle time are automatically calculated and displayed.
Point And Click Process Synchronization
Once generated, the Process Table allows the programmer to easily synchronize operations being performed simultaneously. This is where the software shines, because it allows the programmers to choose the type of synchronization strategy being performed from graphical diagrams. For example, if the user wants to cut with one tool on the main spindle while cutting with another at the same time on the subspindle, he or she merely chooses a diagram corresponding to this type of synchronization by just pointing and clicking.
These visual synchronization strategies are applied to every process on the part. Because the software knows the architecture of the machine being programmed, it checks that the synchronization strategies used by the programmer will actually work. If the programmer tries to synchronize operations in a manner the machine cannot handle, the software indicates where the error has occurred.
When synchronization has been completed, the software displays a balanced cycle time, showing how much time is being spent on the main spindle, how much time is being spent on the subspindle and the total machining time, taking into account all concurrent operations. At this point, the programmer can see if additional cycle time reduction opportunities exist and make the changes accordingly, right at a PC.
“The process table is beneficial to the point of reducing cycle times. When we can prove that tools can run at the same time on the computer, that means the up time on the machines is that much greater,” Mr. Hoyga says.
Once the programmer has optimized the process satisfactorily, the software displays a full 3D machining simulation of the process. This simulation verifies that the process will run without any tool collisions or crashes and shows the synchronized operations being carried out on both spindles simultaneously. For a CNC Swiss, the position of the bar stock relative to the guide bushing is shown throughout. This visualization shows if there is ample support being provided to the piece during machining by the guide bushing collet. Finally, a 3D solid model of the completed component can be viewed and analyzed.
Edit Free Programs
When the programmer is satisfied that the process is crash-free and the part is visually correct, he or she selects a post processor to generate a CNC program for a particular multi-axis lathe. Multiple programs with “wait” or “sync” codes automatically inserted are generated for machines that require a separate program for each set of programmable axes. At SMP, the Citizen L and the turn-mills require two synchronized programs while the more complex Citizen M requires three. The software eliminates any need to manually edit the generated NC program.
“The productivity improvements the software provides are definitely seen the most in setup. You can literally watch the part run in simulation. If I do not like what I see, I can change it before it ever gets to the machine. So all the setup guy has to worry about is putting his tools in, touching them off correctly and pressing cycle start. Because the post processors are correct, the machine’s not going to crash, it’s not going to make a bad move, and the program’s going to be right,” Mr. Hoyga says. “As a result, the programs we write are not getting changed at the machine.”
Unique Programming Challenges
As SMP delved further into the capabilities of its CNC Swiss, its programming staff realized something had to be done to speed up the process. It saw its parts becoming more and more intricate and complex. Programming manually simply made setup too long.
Doug Paoletta, whose primary responsibility is programming the bank of Swiss machines at SMP, recalls setup being a very time consuming process, before adopting the automated approach to programming. When programming manually, Mr. Paoletta would have to rely on physically inspecting a machined part to ensure that programming had been done correctly. This process usually involved running the first piece, viewing it on a comparator and then going back to the machine to make the needed adjustments. This process would iterate a number of times until the part were correct. Needless to say, the machine was not running while this back and forth inspection was going on.
With the software, Mr. Paoletta is able to draw his part (or import its geometry if the customer has provided it) and visualize the entire process on screen. Instead of waiting until he gets to the machine, he can now perform the time consuming first piece inspection at the PC and be confident that the part program is being generated correctly.
A recent, particularly difficult job programmed with PartMaker bears out just how much time the software has saved. The particular part had a number of intricate features, including a hole whose depth was 36 times its diameter. Mr. Paoletta had a program ready to run within a few hours of picking-up the print. Previously, he estimated such a part would have taken 2 days to program and another 2 days at the machine to prove out.
“Now, there are no people yelling at you because you are doing a setup and its taking you forever and because you are trying to fix this or that. Ninety percent of the time the program is right the first time,” Mr. Paoletta says.
Programming with a CAD/CAM system, versus manually, has also let SMP’s programmers take better advantage of the unique cycle time saving features of their Swiss machines.
“The software has definitely let me be more creative with what I can do on the machines. It’s been the case many times where I’ve thought of a part one way, programmed it, looked at the time on it and watched it run on screen and said ‘This isn’t right,’ completely reversed the part and cut down the cycle time by looking at it another way,” Mr. Paoletta says.
Productivity Is Key In A Tough Market
The more productive approach to programming has also helped SMP maintain its level of customer service despite difficult market conditions. Now when customers order parts, they want them immediately. That means if the machine their parts were initially slated to run on is busy, the parts have to be ready to run on another machine very quickly, according to Nick Valetta, SMP’s shop supervisor.
“Because the market is slow, customers demand that their jobs be delivered immediately. If you don’t supply them, they are going to go somewhere else. We have to change machines quite often to accommodate these demands. We could have a program ready to go for one machine, but the parts have to go on a different machine to meet our delivery schedule. We then have to put the job on a different machine,” Mr. Valetta says. “We can go into PartMaker and change a couple tools and we’ll be ready to go in 10 to 15 minutes.”