Combi-3: Home CNC Engraver

When engraving or tracking/drilling PCBs the 2000rpm top speed of the mill is too slow. The milling head is very unbalanced about the axis of the quill, which coupled with the regular and rapid Z-axis feeds needed in engraving creates un-necessary wear in the cast iron head/quill.

These problems are addressed by removing the standard 150w milling motor which is the heaviest component creating the out of balance moment on the quill and driving through the standard spindle from a remote, high variable speed (18000rpm) 150watt motor to a high speed spindle mounted directly below the quill and incorporating an integral collet chuck photo E2.

Optionally the Z drive can use a toothed belt (photo E4) or a leadscrew (photo E5). See also the gallery of high speed spindle options ranging from occasional hobby to commercial craft use.

The conversion from Mill to Engraver takes approx 10mins, involving unplugging and removing the milling motor (3-bolts). Plugging the 150watt suspension motor into the Sieg controller and suspending it by antivibration ligaments from the column (1-bolt). The heavy duty flexible drive from the motor passes through the locked Sieg spindle into the high speed spindle below it.

This configuration gives easy access for daily lubrication.

The motor/drive/spindle unit is powerful enough to offer light milling in non-ferrous materials, such as undertaken by jewellers, musical instrument makers, clock makers etc.

The Z-axis resolution for the Engraver in belt or gear drive is 0.01mm per step.

Note: The Z axis cnc motion uses belt or gear drive from the stepper motor. The absolute accuracy of the rack and pinion is less than that stated for repetitive positioning of 0.05mm. This means that for some work it may be necessary to check the final depths on the prototype and add Z-offsets to the program feature by feature.

Where absolute accuracy in Z is required 'straight from the drawing' a leadscrew actuated quill is offered photo E5.