Another use for Comp3key is as a hardware test facility. As it requires no additional computer programming, one can enter manual mode and check feed directions and feed rates before setting the machine up for 'real' CNC.

When used under a modified drill with XY table, will centre and pilot drill all holes accurately, and repetitively.

When used on a vertical mill, will generate curved / angular shapes using a small cutter, that would otherwise need a larger machine and rotary table. Program allows multiple LOOPS increasing the depth of cut by a programmable amount on each pass. This allows low powered, un-supervised machines to remove relatively large amounts of metal. Particularly useful for die-sinking work as reverse lettering can be input to your program from CAD, moulds for wheels or model tyres might be of interest. ? The combination of CAD + Compucuts multipass facility, makes those "difficult" jobs such as turbine blading, and aero wing rib machining an interesting project. Straightforward examples are the machining of sheets of scale chequer-plate and raised letter nameplates for model locomotives.

When used on a lathe, will generate complex angles and curves that would need to be form cut, or need a copying lathe. Program allows multiple passes, automatically increasing the depth of cut on each pass, i.e. screwcutting. Allows smaller machines to tackle larger jobs, by virtue of multiple passing, and generating rather than forming all curves and angles. The compressor and front casing for a gas turbine can be profiled this way.

Using a 20 TPI leadscrew, and a 200 step / rev motor, each unit of feed is 0.00025 inches which offers acceptable accuracy form most amateur projects. The program accommodates any pitch of leadscrew, and motors of any angular resolution.

When used on old or home built machine tools, the user can produce a calibration file, from which Compucut can, if required, "dynamically correct" the errors in the leadscrew pitch to +/- 1 step. This feature is unique to the Compucut system. 1000 corrections for each of X, and Y are stored in a calibration file.

WHAT DO I DO? (An overview to give the sequence of operations)

(First time computer users, build a simulated 3-axis machine, for a cost of £10-£15, details included, and follow the step by step examples in the manual, which even covers testing your "car boot bargain" P.C.).

Using any ASCII text editor or word processor (DOS5 edit is fine) the user types a "PARAMETER" file which contains the non dimensional data for the machine such as feed rate, rapid feed rate, port address, scale factor etc, his this file is saved to disk as PARAM.nnn where nnn is your 3 digit identifier. (First time users; use the default PARAM.000 file.)

The user then types a "CONTROL" file which is the list of operations needed to complete the job, chosen from a "language" of 22 command types. This file holds the dimensional data, and is saved on disk as YOURJOBn.con where "yourjob is your identifier for this machining job. E.g. CONROD2.CON

(First time users; use the demo control files)

The machine is set up, the cutter set to "datum" position, the motors are switched on, and the program is run. The computer "beeps" at the completion of the work, which could have been many hours of continuous cutting. (While learning, follow the numerous examples given in the guide).

Anyone who has watched the movements of carriage and copy slide of a copy lathe turning an angular or curved profile might be thinking that the programming for complex shapes is very mathematical. NOT SO! (Or rather it is, but we don’t do it). The computer is often being asked to perform the equivalent of this X-Y function when it outputs the design produced using a Computer Aided Drawing (CAD) program to a PLOTTER. We can borrow this facility to produce the data for our machine program. The "industry standard" language for driving X-Y plotters is the HEWLETT-PACKARD GRAPHICAL LANGUAGE. (HPGL). Using the CAD package DraftChoice draw out the job required to scale and save the work as a plot file. That is it, the X, Y program data is complete, you now edit in the Z axis data, add screen prompts for cutter changes, dimensional checks etc, which is fully described in the manual.

IF YOU CAN DRAW IT YOU CAN MAKE IT

THE COMPUTER CAN EVEN HELP YOU DRAW IT

You do not need an expensive computer for machine tool control (typical cost £50 - £100). You do not need previous programming experience. The results of mistakes are trivial when you prove programs by milling polystyrene wallboard, which is cheap and kind on the kit, even if you decide to rapid traverse towards the table! However once proved and saved on disk these programs become part of your tool kit and are always on hand to produce duplicate pieces in the future.

The on disk help covers the following:

What you need to know to operate the package, and how to select, and connect suitable stepper motors.

A selection of typical jobs in drilling and milling, supplied as drawings (JOBn.DCH), together with the associated plot files (JOBn.PLT), the control files (JOBn.CON) and cutter path files (JOBn.CUT) which are then used to illustrate the step by step procedure from drawing thro' programming, and proving, to setting up and cutting the work.

A SECONDARY BUT IMPORTANT OBJECTIVE IN PRODUCING THE COMPUCUT TUTORIAL SYSTEM IS THE PROVISION OF ACCESS.

Access for the established engineer, who may well not be a programmer, to the field of computer aided workshop technology

Access to small-scale engineering for young computer programmers who may well see this as an interesting peripheral hobby, or school project leading to the building of a suitable machine.

COMP3KEY is also useful as an introduction to the COMPUCUT system, when used with a machine tool simulator (details provided). It is easy to simulate the 3 axes with 3 small cheap stepper motors, plus a small dc motor to simulate the cutter, and four bell pushes or micro-switches to simulate the limit switches on X and Y. This simulator is only an evenings work and costs about £15. Once the user has gained an insight into the use of the PARAMeter file, mini programs can be entered and checked by watching and counting the turns of the X, Y and Z steppers. The simulator can run from a car battery charger to keep the costs down while the user assesses how best to integrate this new technology into his/her workshop. If you have not used CAD before, the simulator can be observed to 'machine' and prove your designs. Inserting a pause at the completion of each step of your program, allows checking off each feature against the computer printouts of your design and your control file. No swarf means that this can be practised inside, in the warm, during the winter. This could provide an instructive insight for the NON-computing members at your local ME club night. (For new features included in version 2 see news page)