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zelo, make your stepgen maxaccel higher than your regular max accel

To expand a little on Aciera's response...

Starting/stopping the sub-spindle is pretty straightforward, but as I've recently found there aren't many sub-spindle lathe configurations posted on the forum (or other places), so setting one up isn't really a simple cut-paste from someone else's config.

There are a couple of considerations if you are retrofitting (or building) a sub-spindle lathe:

• Spindle direction and main-sub synchronization
  • To make programming easier, the sub needs to rotate opposite the main when the sub is sent an M3 command.  If not, then back-working tools (for the sub) would need to all be programmed opposite than main tools.
  • This makes synchronizing the main and sub for a parting hand-off a little more complicated than just setting them both to "M3 Sxxxx".  I won't post the gory details right now, but on my DIY lathe (with sub) I created an M-code activated 'switch' that basically sends the main spindle's inverted position feedback to the sub's command input.
  • Result - when the synch M-code is activated, the main spindle is programmed and the sub is slaved to the main - both rotate at the same speed and direction until the de-activate M-code is triggered.
  • Both my main and sub motors are servos controlled via step & direction; I don't know how accurate 0-10v (or -10/+10v, or Ethercat, etc.) would be during a main-sub synchronization attempt.  
• Sub axis naming
  • LinuxCNC doesn't allow (as far as I know), axes to have an 'alias' applied.  If you're used to programming a sub's linear axis as "Z2" you'll have to get used to using a different letter.  LCNC can control up to 9 axes, but since the Z-axis is already (likely) the turret, then the logical letter for the sub's linear axis is 'W,' since UVW generally represent linear axes parallel to the primary XYZ axes.

Note that my lathe isn't finished yet and I've not done much cutting, but the main/sub config appear to be working OK... so take the above with a large grain of salt.

Hello cornholio,

I'm actually building both types of boats: model (1/4 scale) and real-sized; the first being a prelude to the second.

The RC boat starts with a "short kit" bought off of eBay - just the frame members (laser cut). I just have to put a skin on it.

I would dearly love a laser CNC machine to cut out the frame members for the real boat but many boat plans are not digitized (like mine) so the first thing I need to do is to turn a CNC machine into a giant "digitizer". Does experience doing that exist? It does seem doable and if I create the files I might be able to find someone to laser them for me for a price.

Thanks,
Tom

The MPG encoders are part of the inm module, so in halshow,
select hm2_7i96s.0.inm.00.enc0-count

Note that these are just raw counts and would need
the scale component to scale to position.

It might be easier to have some normal encoders brought out on the
parallel expansion connector since standard encoders have scaling built in.