Cabling

Shielded multicore cable is used to connect the stepper motors to the power supplies.  In my case the stepper motor power units are mounted on a wall behind the lathe headstock end. From there cables are connected to the controller and stepper motors. They are then passed around the rear of the lathe behind the splash back and artistically draped on the floor, before reappearing at the lathe tailstock end.

Both stepper motors have a length of cable pre fitted and it was necessary to connect the multi core shielded cable using suitable connectors. These connectors are housed in robust boxes that will withstand handling during machining operations.

While the leadscrew cabling is static, the cross-slide cable is dragged about in use. So far this has not presented any problems.

In use, the whole set-up is easy to use and effective, provided certain steps are followed. One thing to note is that the controller only operates with metric units.  More of a pain than a problem!

Zero setting

This aspect is crucial to successful operation and consists setting zero points for the saddle and cross-slide powered by the stepper motors. The controller jog and step controls are used for this purpose and in practice the tool to be used for cutting is moved to touch the metal. I tend mark the metal with a marker pen then tool contact can readily be seen. The distances moved by the jog and step function are set as part of the system set-up. 

I currently have the step functions for both axes (X step and Z step) set at 0.005mm, so that the tool can approach the metal in steps of 0.005mm. When contact with the marked metal is made, for either X or Z and a faint line appears then either the Z0 or X0 buttons are pressed. This sets the zero position for either the cross slide or saddle.

It is important to make sure that backlash for the cross-slide and leadscrew is properly accounted for when setting the tool zero points. The backlash for these two is entered as part of the system set-up.

Input how much metal to remove

After setting the zero points, we then need to tell the controller how much metal to remove. Note, the CNC set up does not machine to a set diameter.

Setting up the controller for a particular operation generally requires three pieces if information:-

1. 1.The feed rate, F mm/rev
   

2. 2.The length to be machined, ZP mm
   

3. 3.The reduction in diameter, XP mm.
   

These are shown in photograph above. 

The values for ZP and XP are negative.  This is because they are relative to the zero positions, with negative towards the headstock and the centre of the lathe.

Hence, it is necessary to know the initial diameter of the stock to be machined.  The accuracy of the final machined diameter depends on the accuracy of the initial diameter measurement.

Once the above three pieces of data are set, the controller will set a number of passes (or cuts) to achieve the specified reduction in diameter.

This is shown in photograph above.  In the example chosen, the controller has set the number of roughing cuts at 36 plus 1 for a finish cut. These are decided from the initial setting up of the controller. However, the number of cuts can be altered with the controller rotary knob to a more desirable number if required. After the final cut, repeat cuts can be carried out to remove any flexibility effects.

Once the machine is set up can be left to get on with metal removal. A very useful feature!

The CNC controller requires the spindle to be rotating to function. This aspect makes the clutch fitted to Super 7 even more useful, in that disengaging the clutch during an operation permits the opportunity for those mid-cut size checks. This interruption does not seem to result in any operation, so far.

PART ONE HERE  PART TWO  PART THREE PART FOUR

PART FIVE  PART SIX