| Gallery, Projects and General > How do I?? |
| Another daft idea, electronic lead screw. |
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| John Hill:
First off, I know a lot of people have done this and I know there is much debate as to it being a worthwhile project but I would like to at least dip my toe in the water with regard to the subject of CNC. I have a nice stepper which might be big enough for the job and I have been looking under the cover of my generic Chinese 12x36 lathe. The idea is to mount a stepper with a pinion to engage with the 120/127 compound gear when the banjo is swung away from the spindle pinion (no issues then of having electronic and mechanical drive engaged at the same time!). That bit looks simple enough. Then I need a spindle encoder but fixing anything to the spindle might be a challenge due to the big hole that has to be kept clear right through the middle! There is the pinion that turns at spindle speed and normally engages the 120/127 compound gear but fixing anything to that would be a nuisance when using the normal mechanical drive scheme. There is another option and that is to attach an encoder to the drive pulley which is geared to the spindle. It turns at a more or less constant speed of about 700rpm. If I used that to mount my encoder the encoder would be turning faster for most (all?) threading operation and slower than spindle speed when high speeds are selected. Obviously my software would have to be told what drive gear was engaged. There is so much to think about! : :scratch: |
| Manxmodder:
You could consider a one to one ratio toothed belt drive from the spindle to the encoder,should be pretty simple to design and would give you greater flexibility as to where to mount the encoder.....OZ. |
| John Hill:
Good idea Oz, I wonder how many steps I need per revolution of the spindle? |
| Manxmodder:
I don't have enough experience to know how many steps would be most suited but I would have thought the more the merrier. Another possibility arises with the toothed belt method in as much as you could use a 2:1 encoder to spindle ratio and effectively double your step count simply by selection of appropriate pulley sizes :smart:.....OZ. |
| John Hill:
I have been thinking about this and it seems like more indexes than enough would make the computer software less reliable, but how man is enough? :doh: |
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