CNC Software Helps Job Shop Produce More Complex Jobs in 1/3 the Time


Lyle Stahle purchased a 3-axis computer numerical control (CNC) machining center and several manual machine tools and started a prototype machining shop in his garage. At first, Stahle produced very simple parts that he programmed using conversational CNC on the control of his ProtoTrak machining center. Soon, Stahle was asked to take on more complicated and profitable jobs but found that they were difficult or impossible to program conversationally. Stahle began using FeatureMILL2.5D CNC programming software because it makes it very easy to program complex parts and provides many features to optimize machining time.

As an example, he recently programmed a complicated 20 inch square aluminum part with a pocket and a number of islands. “This part is so complex that I would not even have attempted it with using conversational programming,” Stahle said. “But it was a relatively simple using the pocketing feature of FeatureMILL2.5D. By machining a test piece to determine the maximum attainable feed rate and the machining optimization features of the CNC software, I was able to machine the part in one-third of the time required by the initial program.”

Machining jobs becoming more complex

Stahle does contract machining in the evenings and weekends to supplement his day job. His biggest competitive advantage is his ability to turn jobs around very quickly. He completes many smaller projects in just one or two days. When he first entered the contract machining business, Stahle primarily received very simple machining jobs. But as his customers gained confidence in his abilities, they began sending more complicated parts for him to bid on. Stahle was able to program some of these jobs using conversational programming.

“It took a long time to program these parts because conversational programming requires calculating and entering the geometry of each machine move,” Stahle said. “Another concern was that I was bound to make a mistake or two in programming a complicated program and often these mistakes meant that the first part of two that were run with a new program ended up as scrap.”

Searching for the right software

Then a customer asked Stahle if he could produce a very complex part in a hurry. Stahle wanted to take on the job but felt that the part was too complex to program using conversational programming. “The raw material for the part cost about $5,000,” he said. “I was concerned that without a method to verify my program before running it on the machine I was certain to ruin the material.” Stahle conducted a search for software that would allow him to more easily program the part. He downloaded trial copies of several different CNC tools and tried them out.

“I needed something very intuitive and easy to use because I had never used CAM software before,” Stahle said. “Meanwhile the deadline for producing the part was approach fast. Most of the programs that I downloaded were powerful but difficult to use. FeatureMILL is also very powerful but it is so intuitive and the programming process flows so well that in less than 30 minutes working with the demo program I could clearly see how to produce the customer’s part.”

Producing the CNC program

The part is machined from a 20 inch wide, 20 inch deep and 4 inch high piece of 6061 aluminum. Used in an automated assembly system, it has a pocket with many islands that need to be avoided. “Machining this part conversationally, I would have had to individually program each cutter pass over the islands,” Stahle said. “With FeatureCAM, I started by importing a DWG file the customer sent that detailed the geometry of the part. Importing the actual customer geometry saved time and provided certainty that I was working with the right geometry. I created the geometry of the block of aluminum that the part is cut from and overlaid the part geometry onto it. I chained the entities in the part geometry together to create a feature. Then I selected the feature, defined it as a pocket and entered its depth. The part was too large to machine in a single setup on my machining center so I divided it into two halves and programmed each half separately.”

After Stahle defined the feature, FeatureMILL automatically generated the toolpath required to produce the part. “The program generated all of the toolpaths needed to machine the part,” Stahle said. “I could have stopped there and produced the part but I wanted to optimize the cycle time on the machine.” FeatureMILL2.5 offers a variety of other features including holes, grooves, bosses and threads. The user has the option to apply draft angles, chamfers, and bottom radii to the walls of any milled features. The features can be machined with flat end, ball end and tapered tools. FeatureMILL provides an estimate of how long a part will take to machine and provides a range of tools to optimize the program to reduce machining time.

When Stahle first ran the program it defaulted to a ½ diameter square end mill running at 2000 rpm with a feed rate of 20 inches per minute. The cycle time with this cutter and conditions was about 135 minutes. Because the pocket was so large, Stahle decided to try a ¾ inch end mill. Using a larger, more rigid tool, makes it possible to increase the feed rate. He also ran experiments with a scrap piece of aluminum to see how fast he could run the cutter. He determined that with the larger cutter he could run at 4,000 rpm and 45 ipm. He also used the feed rate optimization feature of FeatureMill2.D which automatically adjusts the feed rate based on tool loads to minimize cycle time while evening tool wear. These steps reduced the cycle time to 45 minutes per side or 90 minutes for the complete part.

Using simulation to validate the program

“Once I was satisfied with the program, I used simulation to make sure the tool cuts the part correctly and avoids the clamps and other parts of the machine,” Stahle said. “I added hash marks to the part to indicate where the clamps would be positioned. I made a few tweaks to the program based on the simulation. When I was satisfied, I ran the postprocessor to generate G-code to run on the ProtoTrak machining center. The entire programming process took about 30 minutes from start to finish. I loaded the workpiece on the machine and the program ran flawlessly without any problems whatsoever. I delivered the finished piece to the customer on time.”

“I have used FeatureMILL2.5D on many projects since then,” Stahle concluded. “The software saves time on projects that I used to program manually and has made it possible to take on more complicated jobs that I could not handle in the past. I also have the confidence that if someone comes to me with a 3D part that I cannot do with FeatureMILL2.5D that I can upgrade to FeatureMILL3D and do the job. I’d like to mention that the people at Delcam have frequently offered technical support but I have always I turned them down because the software is so easy to use that I can figure it out on my own.”

For More Information

To learn more about Delcam’s  complete CAD/CAM solutions, contact Blaine Duke at 801-949-6769. For more information on quick turn prototype machined parts, contact Lyle Stahle at 720-319-3314.