PC based CNC machine tool controllers are starting to become the trend in CNC machining. Retrofitters and OEMs are looking toward the PC as the new machine tool controller platform to accommodate today's need for "high-speed" machining. More and more retrofitters and OEMs are starting to switch from a pre-fabricated controller to a PC based CNC controller for a variety of positive reasons. The most common reasons are described below.
PC based CNC machine tool controllers are less expensive than pre-fabricated controllers. You can replace your existing pre-fabricated control with a PC based controller at a fraction of the cost when compared to replacing your control with another pre-fabricated controller. This cost savings is accomplished because a PC based CNC controller uses a standard Windows based 95, 98, ME, NT or 2000 personal computer, motion control board, digital I/O card and CNC machine tool control software, which are relatively inexpensive components.
If you don't want to build your own PC based CNC machine tool controller, you don't have to. Today, there are several different companies manufacturing various ready-to-go, bolt-on professional PC based CNC controller enclosures. Most of these controller enclosures include all the hardware and software necessary to control your machine including the amps and motors. Users can also purchase separate high-quality hardware and software components and use their own personal computer.
PC based CNC machine tool controllers are easy to install. The idea behind advanced PC based CNC machine tool controllers is to eliminate the need for tracing wires to the PLC or write ladder logic. Rather, the computer becomes the PLC and does the logic thus eliminating the need for PLCs and writing ladder logic. PC based CNC machine tool controller software generally comes equipped with several ready-to-go operator screens to choose from and even customize for ease of use and to get you up and going in minimal time. The software generally allows you to mix and match physical buttons, knobs, gauges, switches, lights and displays with virtual ones.
PC based CNC machine tool controllers are also easy to use. A well designed PC based CNC controller software package generally has the ability for a user to fully customize the control's user interface without being a C++ or VB programmer. For example, the control's user interface is able to be designed by dragging and dropping control objects around the operator screen and then setting each control object's size, caption and functions with fill-in-the-blank or check boxes within Windows. The user interface can be as simple or as feature rich as the operator desires. Control operators are no longer subject to the rigid design of pre-fabricated controllers. PC based CNC machine tool controllers also offer various programming styles such as G code, conversational or CAD to motion.
PC based CNC machine tool controllers are quickly retrofitted. Most companies cannot afford to take months off to get a machine on-line and productive. A good PC based CNC machine tool controller's learning curve is only about 1/5 of the time needed when compared to most controllers that still use PLCs. On average, installation is capable of being done in three days for the most common types of knee mills, bed mills, lathes, lasers, water jets, plasmas and punch presses.
PC based CNC machine tool controllers are capable of stilling running a customer's old G code programs. A state-of-the-art PC based machine tool controller, for example, allows flexibility to run a Fanuc G code program in the morning and then an Allen Bradley in the afternoon. Definable G code and M code tables are generally built into the control to allow configuring the new controller to understand pre-existing programs.
Real time solid modeled or wireframe tool path simulation while the machine is cutting is one of the features a good PC based CNC machine tool controller contains. Being able to perform tool path animation and CNC verification prior to pressing Cycle Start is also an important feature. Simulation provides step-by-step control over each move graphically, moving the light source, solid model rotation and viewing angles.
PC based CNC machine tool controllers are user customizable and are considered an open system. The best software allows screens to be customized without having to be a VB or C++ programmer. Typical Windows-style fill in the blanks and check boxes are used on well-organized screens so that even novice Windows users can drag and drop objects into place and set their properties. More advanced users are able to configure the controller routines to support new processes and new technologies with well-documented software application program interfaces (APIs) made available to all customers as well as source code for ActiveX and DLLs.
All good software supports the ability to integrate third-party applications. PC based CNC machine tool controller software contains, at a minimum, machine maintenance software, remote diagnostics via a modem, self-diagnostics and remote machine tool monitoring via RS232, ActiveX or a Network card. This includes automatic collection of manufacturing data in real time without operator intervention as a standard feature.
PC based CNC machine tool controllers are fast and can easily accommodate today's "high speed" machining requirements. With over 200,000 motion cards shipped to date these cards can achieve 62.5 microsecond servo update times per axis, which result in cutting feedrate velocities of up to 122,000 IPM. Some digital I/O cards can detect a change of state at rates in the 10 KHz range. DSP microprocessors close the servo loop using dual 32 bit micro processors to increase productivity, feedrates, accuracy and cut quality. Multiple events and multiple position motions can happen simultaneously. 3D profiles can even be cutting while the tool is changing. The extra processor on the motion card is not only the best way to close the servo loop with the motors, it is also the fastest method known to date to produce the fastest block-to-block cutting speeds.
With PC based CNC machine tool controllers, maintenance and repair are no longer an issue. Machine operators are now the masters of their own machine. Self-diagnostics are generally a part of every system. When it comes to parts, off-the-shelf Windows 95, 98, ME, NT or 2000 personal computers and brand name hardware purchased from local sources can be used. Are your parts now either so proprietary or hard to find that they do not exist anymore? How long can you be down? PC based CNC machine tool controllers eliminate the need to rely on others. Machine operators can learn how to service, support, maintain and upgrade the complete control and replace any part themselves.
PC based CNC machine tool controllers help eliminate downtime. No more waiting for proprietary parts that can only be obtained through the control's manufacturer. Generally, there is a terminal strip and cable that connects the machine wiring to the computer. All that needs to be done is to unplug the cable from the computer. This will not disturb the wiring to the machine. Next, restore the screens, G codes, M codes and logic files within 10 seconds from a saved backup on a floppy disk. The backup file is also small enough to be emailed. If the problem is the motion or I/O card, either of these can be replaced by anyone without disturbing the wires. If a control breaks, swap out another computer to replace any control for any machine type at anytime.
PC based CNC machine tool controllers are easier and quicker to service. Manufacturers of PC based CNC controller software hire qualified technicians to immediately answer technical questions via phone, fax or email. If application assistance or custom logic is needed, the PC based CNC controller software manufacturer has qualified in-house staff and local reps that can fulfill these needs either on-site or via the internet. Also, most PC based CNC machine tool control software manufacturers do not detach themselves from the hardware boards and takes responsibility for all of the hardware boards they sell.
PC based CNC machine tool controllers allow use of your existing motors and amplifiers. This holds down the cost and labor plus ensures that the motors and amps are sized right for the machine. Good hardware can control existing motors that are: Brush or brushless, AC or DC, servo, stepper, PWM or hydraulic. The amps or drives can be either current driven or velocity type. Spindle drives use current mode or inverters. Feedback can be closed or open loop. Closed loop systems use encoders or resolvers. There are a number of companies that also make digital I/O cards. Touch screens are also available.