Reasons to convert a mill to CNC

A letter from John Stevenson

Model Engineering today is just as popular as it was years ago but other factors have changed.

Many of the older Model Engineers came from engineering backgrounds or similar. Many had come through the ranks of time served apprenticeships or learnt skills in the forces.

For the people not so fortunate there were a whole area of training establishments like colleges and night schools that threw open their doors and welcomed these people. There were also far more clubs that there are today. Around me there is only one club but years ago there were seven offering help and advice to budding Model Engineers.

The main crux of the matter is though, there was more time available. We didn't have all the current trappings we have today that need maintaining or require attention. Most people worked local and traffic was non existent so leisure time was greater taken overall.

It was not out the ordinary for the average Model Engineer to disappear into his shed or workshop most nights a week to carry on his hobby. Today given the pace of life it's a rare person who can get two nights to themselves what with modern pressures.

Whereas our intrepid hero would disappear for 4 or 5 consecutive nights to machine a tricky widget, usually right first time as he had the time and peace to do this, it's next to impossible today. Todays Model engineer is lucky to get two nights a week after late night shopping, going out for a meal and dare I mention Ikea? OK we won't mention Ikea.......

So that two nights now becomes a mad dash to get our scale model widget sorted. Because our modern ME now has no formal training or apprenticeship, limited club membership and attendance will use up one of these 'special' nights and the last college doing training in the arts of metal bashing and regurgitating is now teaching Chinese students the art of grabbing all the jobs. The result is that after two nights our widget is now undersize because of the rush.

Now we have to wait a whole week to start all over again. Next week we take a little more care and start again, two nights later we are half done and we wait again for our next time in the workshop.

This time we get a move on because two weeks is long enough to do what LBSC / Martin Evens / Duplex / E T Westbury [delete as required] would have done in a night. Result: we scrap that bugger as well.

Enter the house all sad and upset kick the cat and Gert say's something only women can say, something like "I don't know what you get up to in that shed of yours" Fortunately for the cat it's out of range. Why can't her indoors be attuned to the situation like the cat is?

So you are in the shower at night [this goes to show how times have changed, LBSC / Martin Evens / Duplex / E T Westbury {delete as required} would have had a bath, after removing the coal first] and you think to yourself "I wish I could get it right first time"

This is where technology comes to your aid, you can, it's called CNC, short for Computer Numerical Control where a computer actually runs a machine by following a code entered into it.

Basically you have a number of building blocks from various suppliers that when assembled make a complete CNC machine.

For starters we have a computer, just a bog standard office type PC that is loaded with a program to run the machine. This program is called the Controller.

From the PC via a printer cable the signals go to another building block called a Breakout Board. This is an electronic relay board that assists in the connection process but more importantly it acts as a buffer between higher machine voltages and the PC.

Moving on from the breakout board the signals then go to a driver box or board. You need one driver per motor. Some driver boards have multiple drivers on them but you still need one driver module per motor.

Feeding into the driver as well as the input signals from the Breakout Board you have a power supply that drives the motors through the drivers.

Then from the drivers you have the motors, you need one motor per axis so in the case of a mill you have three, X, Y, and Z

X is the long side to side bed axis, Y is the short back to front bed axis and Z is the up and down quill or head movement.

Some have a forth axis, usually called A that can control a rotary axis to perform work on circular items. If you need an A axis then you need 4 drivers and 4 motors.

Depending on who you buy your components from determines how well they work together. Many people have trod this path before and there is a wealth of knowledge on these subjects.

Once these components are all assembled and connected to your host machine you are ready to go. Depending on the controller software used, determines the next step.

Some can only work with pre written code, some can read in CAD drawing in a DXF format, some can work in conversational mode which is where you select a picture of the type of job you are doing and fill the blanks in and the controller writes the code. Some can do all three.

Now this is where we take over from LBSC / Martin Evens / Duplex / E T Westbury [delete as required]

We spend one night sat in the warm house doing our drawing and sorting the code out. [NOTE : This is an Extra night to one's hobby as if we are INSIDE we can't be accused of being OUTSIDE, so now we have three nights to play]

We do our job, sort what tools we want to use and watch the simulation on the screen, most times we even get a run time. When we are happy then we have a program that will run on the machine so the next free night we run this and get a perfect part off first time, well the first time after the learning curve has leveled off :-)

So now after a bit of experience we can churn out in two nights what it took the masters a week to do. I bet LBSC / Martin Evens / Duplex / E T Westbury [delete as required] are churning in their graves.

Brownie point note:-
These CNC machines are brilliant at doing engraving and a few gee-gaws and shiney magpie baits for her indoors will work wonders for the free time.
Note do not under any circumstances engrave RIP or In Memorial plaques for Mother in Law whilst still alive, for some reason this doesn't go down a bundle.

John Stevenson