Delving into the tooling challenges for die and mould machining
by Tim Wilson
Die and mould machining comes with its fair share of challenges.
The industry is constantly changing, with new materials and industrial processes creating complex scenarios on both the design and the tooling side. More and more, the solution is to combine advanced CAD/CAM capabilities with the tooling itself. For that, innovative computing models are a must.
“A typical mould could easily have 30, 40, 50 CAM routines to calculate,” says Marc Freebrey, group marketing director at Vero Software.
“When producing large complex moulds it can be very important to distribute toolpath computation on to different machines.”
Although it is now common for CAD/CAM technology to be multi-threaded, allowing for three or four toolpaths to calculate at the same time, Freebrey says that Vero’s approach is quite innovative as it allows the operator to send individual toolpath calculations to other computers on a network. And die and mould shops are also innovating on their own. For example Garrtech, a machine shop in Stoney Creek, ON, has baked innovation into its mind-set.
“We are determined to produce moulds that give our customers a competitive advantage in terms of cycle time improvements, better finishes and more robust tooling,” says Tony Grossi, Garrtech’s president. “Right now we are beta testing a mould that has fewer parts, will last longer and, more importantly, run faster than our current tools.”
But Grossi says his company’s real innovation has been improving the flow through engineering and programming.
“We have invested close to 1,500 hours to develop design templates that allow our engineers to complete a mould design within a fraction of the time needed,” says Grossi. “These templates contain hundreds of attributes. As the designer changes the configuration of the template to suit the part design and customer specifications, the attributes within the templates adjust accordingly.”
Garrtech is now in the process of developing the same approach to CNC programming. It is using what it calls Feature Based Machining, in which various user-defined features in the mould design are quickly recognized by NX CAM software.
“For each feature, we have a predetermined machining strategy that has been optimized for speeds and feeds to achieve different surface finishes and accuracies,” says Grossi. “Early tests show that we will save a significant amount of time in programming.”
Aalbers Tool & Mould, Oldcastle, ON, is another die and mould company emphasizing the combined innovation of design and tooling.
“We have TopSolid 3D modeling software for the injection mould, and WorkNC as a servicing program for machining,” says Toni Hansen, president of the company, which focuses on the automotive sector. “The injection mould itself is then the tool, as is the die. On the machining side we have a variety of high speed CNCs from companies like Takumi, Okuma, and Kuraki.”
Aalbers Tool has put in place some aluminum tooling for production, but it mostly focuses on larger injection moulds with P20 tool steel, because aluminum won’t deliver to the required production volumes.
“The software helps give us a simulation of material flow,” says Hansen. “It can find areas with hot spots so we know where to add cooling to reduce warp. We can also simulate the mechanical function of a tool to look at all the actions that create a feature in a die-locked position.”
Tool and die is an area that many smaller shops can grow into. Alltype Machining in Brampton, ON, for example, has built up a diverse business that includes the automotive sector.
“We originally started as a job shop, a one man operation,” says Gurpal Bhamra, Alltype’s owner. “We slowly converted to a tool and die shop, making tools for the fastening industry.”
The operation is now quite advanced, using coordinate measuring machines (CMMs) and optical comparators to inspect the moulds.
“We are 100 per cent engaged with our customer for designing of the part,” says Bhamra. “Good cutting tool information is also important; we need to know cutting tool availability for different jobs, as it’s very important to finish the projects on time. On the machining side, we will provide suggestions to modify the part, within limitations, to improve the speed and ease of machining.”
Customers will often rely on CMM data to ensure the part is made to requirements. Though this is built into industrial specifications for high demand areas such as medical and aerospace, it is now a common best practice in automotive as well.
“When we build an injection mould we have to certify that it is built to data,” says Hansen from Aalbers Tool. “We pull the CMM report to verify that the steel was cut correctly. Once verified, we then have to determine if we need to adjust the tool to fit due to shrinkage issues.”
Variables will depend on the material and the part.
“Everything is great in theory, but it has to be practical,” says Hansen. “Automotive tooling is always changing. The demands are becoming higher–there are tighter tolerances for higher quality.” SMT
Tim Wilson is a contributing editor based in Peterborough, ON.