Custom CNC Coftware | CNC Control Software

Custom CNC software - computer numerical control - column

Golden E. Herrin

Custom CNC Software

Custom CNC software - users clamor for it, machine tool builders often get stuck with writing it, control builders try to avoid it and independent software firms welcome it. When custom software cannot be avoided on a new CNC machine, who is responsible for writing it? To adequately answer this question the software must first be divided into its basic categories and each category addressed individually.

CNC Executive Software is the software embedded in the CNC providing the architectural framework and basic features of the control. This software is supplied and maintained by the CNC builder as part of the CNC unit and is considered proprietary by them. In fact, the source code for the executive software is not available from some control builders. With others, it is available under very restricted licenses agreement.

Even if the user is able to obtain a copy of the source code, they may find it of minimal value except for the secure feeling they get from ownership. The secure feeling may change to frustration if a user attempts to make modifications. They quickly discover that personnel must be trained in the proprietary architecture of the specific executive. Then the required compliers and computer hardware must be obtained which are often custom or proprietary from the control builder. In addition, any existing control warranty would be voided and future software enhancements from the control builder would most likely not be compatible with user modified software. These obstacles usually make it impractical for anyone but the control builder to make changes to the executive.

The requests for executive software changes are generated by both the user and the machine tool builder and cover a wide range of requirements. Frequently one control builder will be asked to provide a feature similar to one that is offered by another. Typically, features of this type are: 5-axis tool lenght compensation; 5-axis cutter diameter compensation; zero shift in cycle; solid tapping; retrace and so on.

Request for features may also come from the machine tool builder as a result of a unique requirement generated by the machine design, or as a result of the user's special requirements. Features which fall into this category are: more axes error compensation points than the basic control offers; two error compensation tables for a given axis; an axis address not offered in the basic control; split or parallel axis in a control that does not provide it.

How willing are control builders to make these kind of changes? A lot depends on the market potential of the features, how many machines involved, and how much influence the user and the machine tool builder have over the control builder. Also, how responsive a control builder is to creating special features depends on whether they are a high-volume standard control builder or a low-volume custom control builder. In some cases, it may become necessary to switch control vendors in order to get a required new feature.

Application Software is provided by the machine tool builder to marry the CNC to the machine tool. It normally resides in a special partition of the CNC which functions much like a programmable controller. The basic functions performed by application software are: axis homing sequence, pallet shuttle, toolchange cycles, as well as the logic for all machine pushbottons, lights and limit switches. Today's CNCs, however, provide considerably more capability than just the basic functions. Most CNCs now provide the machine tool builder with the capability to create M codes, G codes and mnemonic codes. Also, with the power provided by subroutines and math capability, the machine tool builder can provide custom cycles for a variety of functions including custom milling, drilling, boring and probing cycles. Machine tool builders are generally very flexible when it comes to designing custom software for special machines. They are less likely to commit to changes on a standard machine.

Front End Software is a term applied to the software dealing with the management of data in and out of the CNC. It consists of such functions as transfering part programs, collecting and analyzing status information, or the matching up of unlike communications protocols. This software normally resides in a personal computer located external to the CNC. However, an increasing number of controls are providing built-in personal computer front ends which can be used by both the machine tool builder and the user.

The suppliers for this type of custom software are considerably more abundant than for other types of software providing an environment for competitive bidding. Suppliers consist of: independent or third party software houses; the machine tool builder; and in some cases, even the users own internal software department. Front end software is generally capable of being clearly defined in terms of functional requirements making it a good candidate for an independent design task.

There's a possibility that custom software in one or more of the above three categories may be required on your next CNC machine. Whatever the reason may be for requiring custom software, it does provide a valuable service for meeting the changing requirements of manufacturing in today's market.