Article From: 9/15/2002 Production Machining
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Command Tooling (Ramsey, Minnesota) thought it was doing more work than was acceptable for the results it was getting and was searching for a way to save time each month. The company manufactures precision CNC toolholders—primarily end mill, collet, and shell mill holders—that are designed and manufactured to deliver the extreme gripping pressure that ensures precise tool centering and rigidity.
Most of Command's products are machined on Okuma and Mori Seiki lathes. In many cases, quite a bit of metal must be removed from the stock piece to create the desired holder. The company has implemented four-axis lathes to speed this process. Four-axis lathes use two cutting tools simultaneously, inherently doubling the productivity of the machine. Programming the four-axis turning process was difficult, because the company's CAM system did not support four-axis machining. Command's programmers got around this by using the system to generate two separate two-axis programs, one for each of the cutting tools. Then they manually edited the M-Codes to combine the two programs into a single program that controlled the four-axis operation. This process was time consuming, as well as prone to error because it was easy to make typos while editing.
These drawbacks led Brad Hughes, Command's lead programmer, to IMTS where he evaluated a number of different CAM systems. His main criterion was support for four-axis turning, because that would reduce the time and errors that resulted from manually combining separate two-axis programs to get four-axis operations. In addition, he was looking for a CAM system that would permit access to the post file. Command's programmers were already skilled at manipulating post files. They believe post file manipulation is the simplest way to adapt a program to a new machine, for example, or to allow a program to support a new indexer. They didn't want to lose this ability with the new software.
Mr. Hughes found only two programs that supported four-axis machining, and only one, Esprit from DP Technology (Camarillo, California), provided the ability to manipulate the post file. This CAM system also featured knowledge-based machining, which allowed it to capture information from a company's programs and original designs and helped build a database of knowledge to augment its own set of rules. "Adding knowledge to our programs would save time because it wouldn't be necessary to determine things like which tool is needed for a particular operation each time we program a part," says Mr. Hughes. "This capability was also appealing because it would give us more consistent programs. Each time a programmer worked on that particular part, the software would ensure that the preferred tool was used."
A demonstration of Esprit helped convince Mr. Hughes that it would suit Command's needs. "I asked an engineer from our parent company to perform all the tasks that I had seen cause problems for other CAM packages," says Mr. Hughes. "He was able to get this program to do anything I requested, and he had only been using it for 3 months." One additional factor that sold him on this software was its programming language, a comprehensive language with logic, loops, variables and so on that is similar to C, which is familiar to company programmers.
New toolholders are designed in the CADkey CAD system, usually in 2D. When the product is ready for manufacturing, the first step is to run a CADkey macro that automatically removes the text from the CAD file, rotates the model 90 degrees and outputs the file in DXF format. The DXF file is then imported into Esprit. There, a CNC programmer uses the CAM software's modeling tools to remove the shank end of the tool. The shank and the nose ends of Command's toolholders are manufactured in two different operations on two different machines. The shank portion has already been programmed, so all that remains is to program the nose end. This programming begins by manually creating the sequence the tool will follow. The task is done graphically, drawing the cutting sequence on top of the part geometry. Next, the programmer indicates the rough contours. Because the part will be turned on a four-axis lathe, it will be roughed out with two cutting tools simultaneously. The programmer chooses the option within Esprit for balance roughing the outer diameter, which splits the roughing operation between the two tools. Then a finish pass is added.
Since most parts get drilled, bored and tapped, the next step is to select these options from the software's Motion page. When the programmer selects on "drill," for instance, the software displays the drilling operation page, which is where the programmer identifies the appropriate drilling tool. However, as programmers have been adding knowledge to the software, more of these choices are already made. "I have the software set up so that each part has its own tool list with the correct speeds and feeds already specified," says Lyle Isaacson, programmer. At this point, the programming is complete and the programmer signals the software to generate the tool path. The time from when the CAD file is loaded into Esprit to when programming is complete takes 5 to 30 minutes. Command Tooling repeats this process between 400 to 800 times per month because much of the company's business involves custom products. Thus, reducing programming time by 50 minutes per program yields an overall time savings of about 250 hours per month.
To save even more time, the company has also written Esprit macros that automate the programming of certain standard products. For example, one macro generates a CNC program for a collet holder in only 1 to 2 minutes.
The purchase of CAM software that supports four-axis machining has significantly reduced programming time at Command. Simply having software that can generate code for multiple cutting tools operating simultaneously is a big improvement over modifying a two-axis G-Code file. This improved software capability has reduced programming time from 1 hour to a range of 5 to 10 minutes. The development of macros that automate toolpath generation is shrinking it even further. With up to 800 tool paths being programmed each month, this reflects a significant time savings.