Thread: Sieg C6 lathe - electronic leadscrew

Hi Geoff,

Originally Posted by snowyskiesau

While getting most of the electronic components I need for this from eBay is not a problem, the time take for free shipping is annoying - not enough to actually want to pay for shipping but still it slows things down.
PCB's are on their way, should be here this week. I still need to order the encoder,

It may be worth investigating a computer mouse for the encoder wheel or a scrap inkjet printer. There is usually a very salvageable encoder wheel and photo optic sensor on them.

Encoder_Disk.jpgIgnore the centre punch propping up the back edge

At least there has been some progress on the mechanical side. Thanks to PDW, the pulleys have been bored and fit like a treat.
The last image shows the pulleys fitted and the stepper motor where I hope it will be. As the stepper is a close fit where it's shown, there's no room for adjustment so I hope I can get a belt with the required number of teeth. I've ordered a NEMA 23 motor as a replacement which is 3mm smaller than the NEMA 24 shown so it might be adjustable enough.

I've found that the shaft where the larger pulley is attached is not actually the lead-screw shaft. There's a 1:1 gear drive from this shaft to the lead-screw, presumably to provide an offset so the gear will fit into the side housing. The gears involved are not tight and have a large amount of backlash. Hopefully the software can compensate for this

I've also been looking at this Myford project as a model for my cross slide modification.

A mouse encoder wont do the job unfortunately as the rotary encoder has to provide a quadrature signal as that's what the controller expects. It also has to provide an index pulse, once per revolution, so the controller knows the position of the spindle.
A quadrature signal will also indicate direction of rotation.

This one looks like a good fit. 1000ppr (pulses per revolution) which give a resolution of 4000 pulses per revolution using quadrature. Index pulse too. Only $30 -$40 on ebay.