EDM control system: Smooth surface finish and connectivity included
With a wire machine, it’s all about producing clean radii and smooth surfaces, especially inside the ejector holes. For mold maker BM Injection, that’s exactly what Makino’s U32j did right from the start thanks to a combination of rigid machine construction, thermal stability and Hyper-i control.
Established over 30 years ago, mold maker BM Injection operates from a 10,000 square foot manufacturing facility in Whitchurch, UK. Out of ten molds produced, eight are used for the on-site production of injection molded plastic products for many sectors such as aeronautics, automotive, household appliances, sports, security, optics and transport .
Before being finished and ready for use, each mold must visit both a die sink and an electrical discharge (EDM) machine as well as a machining center for hard milling. The proportion of time spent on each machine varies. In the production of BM Injection’s mold tools, unless some are hard machined on an on-site Okuma 3-axis machining center, all three production rigs used for mold making were built by Makino in Japan and supplied by the sole UK agent NCMT.
The last to be installed in May 2022 was a U32j wire EDM machine fitted with the same Hyper-i control system as a Makino Edaf 3 hot EDM machine which arrived in 2019, along with a Makino D200Z 5-axis machining center. from the same Japanese source.
The Windows-based Hyper-i dual touchscreen CNC system, with an intuitive interface similar to that found on tablets and smartphones, includes advanced features to help operators of all skill levels through every step of the process. machining process. The control contains an extensive library of cutting conditions that automatically optimizes the erosion process, even for sealed and low-flush applications. It also allows easy access and selection of power settings to produce accurate results in the fastest possible cycle times.
The control uses Hypercut technology, a process developed by Makino to produce surface finishes as fine as three Rz microns in standard tool steels in a three or four pass process. The machine commissioned by BM Injection Director Mark Combes was a high precision assembly with 0.05 micron scale feedback capable of producing extremely smooth surfaces down to 0.7 micron Ra if a process in 7 passes is adopted.
Ready for Industry 4.0
Of particular note is the Hyperconnect Industry 4.0 two-way network connectivity for remote machine monitoring and interconnection of all manufacturing information. This standard software provides cloud-based access to BM Injection’s Open Mind Opticam computer-aided manufacturing software. CAD/CAM information occupies the upper monitor of the dual screen control and can be viewed and operated as if on board, while Makino’s process control screen occupies the lower monitor.
Another noteworthy feature is the standard Crystal II machining functionality built into the Hyper-i control, which is effective in machining hard-to-polish shapes while improving surface finish for better mold release. It requires no special insulated jigs and is made with uncoated wire, Bedra 0.25mm diameter high zinc brass wire being the standard consumable from the Whitchurch factory.
The U32j is capable of using wire up to 0.07mm in diameter, however, smaller than most machines can handle. There will be a need for smaller gauges and the accompanying diamond guides for future production of BM Injection’s optical industry moulds. Combes points to a reduction in wire consumption coupled with an increase in cutting speed on every job done so far on the U32j compared to the nearly 20-year-old wire EDM machine that was replaced.
He continued: “When the time came to install new modern wire EDM technology, we looked at a number of options. We opted again for the Makino offer, not only because of the control and its synergy with our recessed CNC system, but also because of the impressive working volume of the U32j (370 x 270 x 220 mm) for the footprint (2,580 × 3,165 mm). We obtain a very compact machine while gaining 20 mm of additional travel in X, Y and Z. »
He was also impressed with the user-friendly design of the fixed-table, raise-and-lower tank, which provides access from three sides for efficient loading and unloading of components and for easy cleaning and maintenance. Reliable unattended operation is achieved throughout the night and into the next day, depending on the cycle, aided in part by the efficient, automatic, jet-less thread rethreading system. It uses the X, Y, U and V axes to unfailingly seek an optimal resuming position with the wire clear of the workpiece surface.
Another effective Makino technology is the Protech galvanic protection option, which helps prevent rust and oxidation of steel, carbide and aluminum. By placing an electrode plate in the bottom of the tank and giving it a positive charge, ensuring that the part is held at a negative potential constantly attracts positive ions and prevents oxidation.
Combes summed up: “Makino is a great product, but after-sales service is just as important to us. We have always received good support from NCMT since they delivered, installed and commissioned an Okuma 3-axis vertical machining center in 2016.”
In-depth product knowledge and the ability to pass this on to operators during training is even more crucial with EDM technology. Unless parameters are kept within tight limits, machining efficiency can drop quite quickly. “It is important that our staff know how to keep an eye on this. NCMT engineers provided a week of instruction initially and are always available online or on the phone for troubleshooting or if technical advice is needed,” says Combes.