Many shops would like to do more electrical discharge machining (EDMing) but don't have the skilled EDM operators to run the machines. Mitsubishi EDM (MC Machinery Systems, Inc., Wood Dale, Illinois) recently introduced several new models, and the ones equipped with a new generation of control unit will appeal to shops in this situation. The EA8 is Mitsubishi's new low-cost, compact ram EDM, and the QA10 and QA20 are two new high-accuracy wire EDMs. All three are equipped with a new generation of 64-bit control units with a personal computer "front end."
The Windows 95 software in the personal computer is the key to making these machines effective and productive with operators who are not EDM experts. Windows 95 allows the operator to set up and program the machine based on choices presented as realistic graphical images. On the EA8 ram machine, for example, the user selects the type of workpiece, the type of electrode, whether it's a cavity or deep slot to be EDMed, whether multiple workpieces are involved, and so on. The user also indicates what finish is desired, how much time is allowed, and how much electrode wear is acceptable. According to the company, the software then automatically prioritizes these values and optimizes the settings to achieve these results.
During operation, the system's Fuzzy Pro2 control system monitors conditions in the spark gap and emulates the adjustments a highly skilled operator would make, the developers say. The EA8 is also equipped with a new, highly responsive drive system linked to feedback sensors with a resolution of 0.5µm, 10 times finer than the resolution on the EX series machines that the EA series replaces. The result is very smooth and accurate axis movement.
The machine's shuttle-type toolchanger has seven stations, making it less costly and complicated than some add-on automation units with more stations, but still allows the machine to operate in an extended unattended mode. The automatic rapid fill-and-drain work tank is also a feature productivity-conscious shop managers will appreciate.
Mitsubishi EDM characterizes the EA8 as a "low-cost, compact" unit. It appears that the builder has achieved this by designing this model for economical construction in its factory.
The QA series of wire machines also represents a design strategy that keeps construction costs down but enhances overall accuracy. The company did this by moving to a fixed table and traveling column design (the SX series wire machines, which the QA series supplants, used a moving table configuration.) The new machines use a rigid, liquid-cooled structure with a closed loop positioning system based on both precision linear scales and optical rotary encoders.
According to the company, one key feature of the QA's accuracy and fine finish capability is the design of the machine worktable. The one-piece table is supported by a one-piece, box-style cast base while four ceramic pads isolate and electrically insulate the table from the rest of the machine. This arrangement lends itself to the company's FS3 super fine finish option, which allows surface finishes under 4 Rae to be attained.
The QA series will appeal to shops involved in high-end mold and die work such as tooling for electrical connectors. These users will especially value the machines' ability to handle fine wire (as small as 0.002 inch) with automatic wire rethreading. Developers emphasize that automatic threading has to be highly reliable for unattended operation, and they say they have achieved this goal.
These machines feature the 64-bit control with Windows 95 PC software. Here again, the graphical qualities of the interface make stepping up to these machines relatively painless. For example, when programming tapers with different top and bottom shapes, the user sees a visual simulation of the opening that will be produced, instead of a wire frame showing only top and bottom shapes and a few framing lines. In addition, artificial intelligence in the control system optimizes parameters for fastest cutting, and the power supply's Micro-Pulse circuitry minimizes wire breakages.
The new control offers 10 megabytes of program storage, which is a plus for wire cutting gear shapes, splines, and other work involving extremely long tool path files.
On both the EA and QA series of machines, use of 64-bit control technology also opens the door to more advanced concepts such as shopfloor networking and Internet connectivity. Windows 95 facilitates network communication and simplifies the interfacing necessary for integration in automated cells. Internet connectivity offers many interesting options such as remote monitoring, diagnostics and trouble-shooting. For the here and now, however, making EDM programming and operation more of a sure thing when there aren't enough fully trained EDM operators to go around is a compelling prospect for most shops.