Published 4/3/2019

From-Scratch CNC Post Processor Lets Dual-Toolhead Mill-Turn Shine

A dual-toolhead multitasking machine made coordination of tool paths difficult, if not impossible. A new post processor for use with Mastercam Mill-Turn resulted in smooth programming of tight-tolerance tool paths using both toolheads.

Edited by: MMS Editorial Team

Process Engineer Shaun McAlevey stands in front of one of the Mazak Integrex 300-IIIST machines that that benefited from the new Mill-Turn post developed by CNC Software Inc.

This photo shows a view of the upper and lower turrets of the Mazak multitasking machine. Here, you can see a transfer between the main- and subspindles while being parted off with the upper turret. This is programmed with Mastercam Mill-Turn. But before a new post was developed (a six-month process), it was impossible to really coordinate the tool paths for both toolheads.

This is one of the first parts that was made in one operation using Mastercam 2019 Mill-Turn with the new post. This part has extremely tight tolerances and a custom spline on the end.

One of the final problems to address in the development of the post was trying to get tools to cut contours on a tipped plane on the subspindle while using cutter comp (not easy to do on the Mazak Integrex). The team, composed of staff from CNC Software Inc., Cimquest and PMSI, had to go through a lot of testing and revisions to get the code to come out the way they wanted. Here is the finished part.

PMSI currently has five-axis mills, standard mills, 11-axis Mazak Integrex machines, and dual-spindle, dual-turret lathes. The shop also has three DMG MORI NMV 3000s, which handle between 32 and 115 pallets with 320-tool carousels. The shop employs 70 people, with 36 machinists and six process engineers on hand to develop machining processes and write programs.

Every part that PMSI produces has extremely tight tolerances—some within 50 millionths of an inch, with true positioning in the thousandths of an inch. These parts are manufactured in a clean, climate-controlled environment. The PMSI team works with a range of materials: exotic aerospace metals; 410, 440, and 416 stainless steel; Inconel; titanium; aluminum and magnesium (a dangerous material that requires special coolant to avoid catching fire).

The shop uses its Mazak Integrex 300-IIIST 11-axis milling and contouring machine to machine complex components and prototypes. Developing the machine’s post processor or “post” was challenging, however, due to the machine’s dual toolhead construction. The top and bottom toolheads each required separate tool paths, and coordination between the two to create a post proved impossible: One tool path canceled out the other, creating a CNC post processor that reflected only part of the machining process.

Process Engineer Shaun McAlevey reached out to his Mastercam reseller, Cimquest, and to CNC Software Inc. for help in creating a post processor that would work on the machine. Cimquest’s Mike Slajka and CNC Software’s Pedro Sanchez, Keith Goodrich and Quanwen Du joined forces to see what could be done.

Developing a Post Processor from Scratch

Mr. Sanchez says that there were more than just a few complications inherent in the task. One of the biggest concerns he had before starting was that whatever post processor they created would need to work on all similar machines. He wanted to avoid writing code that only ran on a customized machine or that only worked with how one person ran their machine. “If we go with how the machine needs to run, then it’s generic across the board, and if we give it to another customer, it’ll run,” he says.

Even though everyone involved was dedicated to completing the task at hand, PMSI’s existing contracts had to be delivered on time. “That’s the dual challenge there as well. How can we do the post with the time the shop has available?” Mr. Sanchez says. The assignment took approximately six months to complete.

Mr. Sanchez knew from the beginning that it would not simply be a case of tweaking an old post processor. “We have a new Mastercam Mill-Turn product, so we couldn’t take the old-style post from a new engine and just convert it to a new platform. We really had to develop the whole thing from scratch.” The CNC Software team spearheaded the effort to create a brand new post processor, with Cimquest assisting and Mr. McAlevey testing and correcting their code on the Mazak machine. The crew ran tool paths as they were being formulated to check for errors, and mistakes were fixed until the post ran flawlessly.

The resulting base post processor incorporates both toolheads seamlessly and drastically reduces programming time for PMSI. It can be adjusted to work with any machine on the same platform, even for older controls. CNC Software released the Mazak Mark III post processor at the end of September, and it is currently in high demand, according to the company.

Mr. McAlevey says the machine now runs smoothly with his CAD/CAM software for cutting tough features. Mastercam now enables him to program and simulate the machining process, then get the code exactly how he wants it with minimal effort, he says.

Dynamic Tool Paths Times Two

PMSI does optic machining work for the military and was recently contracted to make lens housings with specific, complex geometries. Machining these intricate parts involves tipping the tool about 30 degrees along the Z and B axes and uses a variety of end mills. Because the process strips away layers at an angle, the material undergoes high levels of stress. Parts have deformed and moved under machining in the past, making constraining the parts difficult but essential.

Mr. McAlevey depends on Mastercam’s Dynamic Motion technology to avoid excessive loads on the material while machining at high rates. Dynamic tool paths use algorithms to constantly monitor both the tool and the material. Mr. McAlevey uses mainly Dynamic Turning and Dynamic Contour to keep the chip load constant during very precise cuts where consistency is key. The PMSI team can now use smaller end tools to machine small parts with complex geometries and tight tolerances.

PMSI can feed its nine-axis machine at 300 inches per minute now. At those rates, it is imperative that the tool paths are error-free. Mazak’s Smooth platform and Mastercam’s Verify feature work together to this end. Verify enables the programmer to preview the finished part and check for any mistakes in code before machining begins.

Mr. McAlevey also uses the simulating options in Mill-Turn. Mr. Sanchez explains that Mill-Turn lets users visualize the product and the cutting operation. Using it has allowed the PMSI team to generate code and restructure their machining to better accommodate the two separate toolheads. Now the upper and lower tool paths are programmed side by side.

“I save a day or two when programming jobs just by using Mill-Turn. Working side by side with Quan and Pedro took years off of post development. It literally changed the game,” says Mr. McAlevey, though he claims that it was a team effort. CNC Software and Cimquest visited the shop twice to work alongside Mr. McAlevey while writing the post processor.