OD CNC Grinding: The “Non-Round” Way
Rob Titus 03.06.2013
A few months ago I wrote a blog post about CNC Grinding vs. Hard Turning. By now you’re all aware that Okuma has a full line of Cylindrical OD and ID CNC Grinders. But did you know that Okuma also has an OD Cam Grinder? The GC-34NH CNC Cam Grinder can grind a variety of “non-round” shapes on the OD of a part, such as ovals, flats, triangles, and even squares.
A Common Non-Round Challenge: Changeover Time
For all of you motorheads and race fans, let’s take a look at the example of an aftermarket camshaft. A common challenge facing aftermarket camshaft manufacturers is changeover time. Typically these companies are running a very low quantity of a particular camshaft, or during R&D they may want to slightly tweak the cam lobe design to achieve maximum horsepower. Additionally, many of these companies have top-notch camshaft designers who can change the cam lobe design in a matter of minutes. But it may take a CNC machine programmer hours to develop a program that applies these changes to the CNC control.
Forget Hours, We’re Talking Minutes
The Okuma-developed PC-APT-CAM-G cam software addresses these challenges. Camshaft designers create a cam data lift file that is charted out in 1-degree increments for a full 360 degrees around the cam lobe. These data files are carried out to at least 7 decimal places. This data is then entered into the PC-APT-CAM-G software, and within 1 minute they have a file created that can be transferred into the GC-34NH CNC Cam Grinder. The file created produces approximately 2000 data points that synchronize the X and C axis for the full 360 degrees around the cam lobe. The time to change from one cam lobe design to another and be back up and grinding is less than 10 minutes.
Software Compensates for Burn
Another challenge that aftermarket camshaft manufacturers face is the potential for burn in the ramp areas--the area between the base circle and the nose of the camshaft. This ramp area can be almost a straight line which means there is more grinding wheel contact to the cam lobe in this area than there would be on the base circle. More contact area creates higher temperatures. The PC-APT-CAM-G software accounts for the increase in contact area and slows the rpm of the camshaft down in this ramp portion of the cam lobe to reduce the material removal rate, which in turn reduces the temperature generated by the grind.
Speeding up changeovers and the ability to quickly change cam lobe designs during R&D are vital to the success of aftermarket camshaft manufacturers. Okuma’s GC-34NH CNC Cam Grinder and user-friendly PC-APT-CAM-G software streamline these processes, and can be used in many other non-round CNC grinding applications as well.
Do you have a CNC grinding requirement that involves a “non-round” shape? Comment below, or contact us, or your local Okuma distributor, and we’ll help you find the best solution for your application.
Click this link to see a video of the GC-34NH Cam Grinder in action.
Rob Titus is Applications Engineer - Grinder Products, Okuma America Corporation