Making the Sextus clock

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ArtF
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Re: Making the Sextus clock

Post by ArtF »

Hi Dan:

>>I've tuned them many times in Mach but it's still a hair off; say about 1/8 to 1/16 which makes escapemen t wheels difficult . 

  You probably have a loose coupling making it sloppy, Mach will easily adjust for
two different motors with different step counts and rates. If you run the calibration on
it , it should adjust the counts so your less than .001 off typically.
  More likely mechanical though than count of motors..

Art
drezal
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Re: Making the Sextus clock

Post by drezal »

Certainly could be that too.  Or a springy coupler as well; they seem to have a little more play than I'd like.  It's a bummer when it comes to really tight tolerances.  What make CNC do you have and do you like it?  After building four CNCs from scratch and playing with this little 3040 I'd like a really tight machine.  One day.  When I can demonstrate to my wife that it is needed.  ;)

Dan
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Re: Making the Sextus clock

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My router is from way back in the earlier mach3 days, Chinese, but with cast iron gantry and nice ball screws. Very accurate. I think they were trying to learn how to make them cheaper but were still making them heavy at the time. :)

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kit
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Re: Making the Sextus clock

Post by kit »

Dan,
Nice to see the clock coming along and I always like to see other people's workshops. They always seem tidier and better organised than mine though I suspect that is what we all say.

I'm surprised you have such large errors on the CNC machine even after several re-builds. You can see that my own creation is not exactly an engineering masterpiece but it did well enough to get the Sextus working. I agree with Art that you problems are probably looseness in the mechanics, the software can be calibrated to get the steps per mm exactly correct.

Issues I've had include end-end slop in the leadscrew on the X axis (the Y axis is currently belt driven) which needs care to get rid of and flexing of the rails I'm using. The later is why I use shallow cuts (2mm or less) and slow speed (800-1200mm/min) to keep the loading on the tool down. The current upgrade is all about reinforcing the rails for both X and Y axes and making the whole gantry a lot more rigid.

Nice guitar playing too.

Kit

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drezal
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Re: Making the Sextus clock

Post by drezal »

Hi Kit.  Thanks.  Each of the CNCs I've built have been sort of odd.  Many of them are shown on my YouTube videos.  Great job on getting the Sextus clock working!  That is a really cool looking clock. 

This evening I took apart a few sections of the small 3040 CNC and found a few mechanical issues.  One of the bearings tends to stick ever so slightly causing a slight stutter.  There is also a tiny but measurable play in the Delrin bushing for the Y axis - I have the Y set up as the "long" run on the machine.   

I think we're all tougher on ourselves than we should be.  When I look at other people's shops and projects they always appear so much cleaner than what I make. 

Anyhow, always learning.

Dan
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