CNC Head Porting & Machining Centers – To Infinity, and Beyond

    One thing is certain, 5-axis CNC machining has brought the average machine shop light years ahead. In the past, these machines were reserved only for large manufacturing operations and thought to be unattainable for smaller, custom shops.

By Brendan Baker

   The fact that CNC machines have come down in price over the years, coupled with less complicated interfacing systems means that today they can be used by nearly anyone. You don’t have to relearn everything. You don’t have to take endless courses on how to make a tool change. Today’s machines are sophisticated and savvy enough to take over most of the legwork and let you concentrate on what you do best.

    These days, engine builders must get as much as possible out of every piece of equipment in order to make the investment make financial sense. And with the increasing complexity of performance and late-model production engines, some shops are forced to the edge of their older equipment’s capabilities. Shops looking to update older equipment have many choices today, but many engine builders have started looking for more than just an improved version of what they already have.

    New CNC machines – from head porting machines to full machining centers – can automate repetitive tasks with unmatched precision and, hopefully, pave the way to future growth.

    Millsite’s latest CNC machine, the Millport Super Red Rhino, incorporates a unique swivel head that rotates 45 degrees both left and right.This allows for the machining of those more aggressive port angles that weren’t previously possible.
The super Red Rhino was designed with versatility in mind, says Millsite’s John Trusty. “Our quick-change fixturing allows a rapid change from a 5-axis porting machine to a block boring and surfacing machine within minutes. It rapidly reproduces and modifies prototypes. Or just remove the head fixture and put a machinist vise in its place and begin general 3-axis machining.”

    Millsite offers two methods of digitizing: the old method, consisting of using a contact probe and recording data points along a surface; and the new method, which uses a white-light scanner to capture the desired surfaces.

    Millsite’s digitizing process uses 3D scanning from the old process of using a contact probe, and has drastically reduced data collection time while increasing accuracy and repeatability. The 3D scanning process digitally reconstructs and seamlessly duplicates your original hand-ground cylinder ports. This has resulted in the digitizing process, which used to take many days, now being complete in a matter of hours. The equivalent of about 4 million points are taken to achieve extreme accuracy.

    The art of hand-grinding ports and getting the perfect shape, along with the desired air flow results, gets more attention to perfecting the design instead of having to do every port, while maintaining symmetry. This process of redesigning ports to eliminate flaws and maximize the volume and velocity of air can be duplicated and automated.

    Included in the scanning process is the recording of a reference datum for locating the surfaces upon importing into CAD/CAM. The time spent struggling with data to accurately replicate the original surface has been drastically reduced to a matter of minutes, says Trusty. You no longer have to manually record data to create a “rough” surface to 5 axis digitize from. The 3D scanning process also eliminates issues such as: only recording center-point data, features being rounded-off by probe-tip diameter, having to offset the surface to achieve real size, and eliminates any “bad hits,” “shanking,” or “no hits.”

    You don’t have to worry about the probe getting stuck in small features and tough areas. You no longer have to patch two sides together, reducing the possibility of mismatch. And best of all, your machine is free to use instead of having to wait for digitizing to finish.

    Both processes begin with the hand-ground master ports. Using the probe, the next step is to use 3-axis with 4+5 positioning to record single curves at fixed locations. These curves will be used to make the rough surface. A 5 axis digitizing toolpath is created on that surface to drive the probe. The result is a collection of splines that create a wireframe for the port. Upon some manipulation of the resulting data, a cutting toolpath can then be created.

    Along with 5 Axis digitizing, the probe also offers such digitizing procedures as Radial Digitize, Grid Digitize, and Contour Digitize. The probe is also very useful for doing CMM work, can be used to check locations and positions of features and is a very useful tool to measure dimensions that would be difficult or impossible to reach with standard measurement tools.