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Spindle index slot dimension question..
« on: December 28, 2015, 01:28:28 PM »
Hey all,

I am Installing a new motor on my mill and it doesn't have an encoder like my BLDC did so I am making a single slot disk and using an optical sensor to read the single pulse per revolution.  I have done alot of research but haven't found hard data on the slot size itself.

Can anyone guide me on the slot size?  I have read it should be painted flat black to avoid reflection issues so I will paint it flat black.  The disk diameter is 2.9" and .1000" thick which gives it clearance but still fills the gap of the optical sensor about ~80%.  Any information on those who are running succesfully the single slot setup and their disk dimensions is greatly appreciated. Trying to do this once the right way..

I attached a screenshot of the disk with dimensions.. Tying to cut this today to move forward with installing the new motor so any guidance is greatly appreciated!

Chris





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Re: Spindle index slot dimension question..
« Reply #1 on: December 28, 2015, 02:08:16 PM »
Hi Chris,
  You can use the info below as a guide. Just use the WIDE slot dimensions and disregard the multiple smaller slots. Take into account your max spindle speed.
If in doubt, wider is better than too narrow.

Russ
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« Reply #2 on: December 28, 2015, 02:39:47 PM »
Awesome, thanks!  I wasn't sure of I should use those since it was pertaining to multi slot disks, but that helps a ton!

Do you know if a slot or angled section is better to use?  As in the degree from the calculation being drawn out from center point and the material between the two angle lines removed do the opening edge is parallel to the optical pickup? Or does that even matter at all?

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Re: Spindle index slot dimension question..
« Reply #3 on: December 28, 2015, 03:14:57 PM »
Also from what was written, it seems like maybe a larger slot is the way to go so if i just went with a 1/2" slot would this be ok or is there a negative for the slot being too large?

Thanks!


Chris
Re: Spindle index slot dimension question..
« Reply #4 on: December 28, 2015, 03:19:54 PM »
Angled or not is negligible. Won't matter.

.5" should be adequate.

It's a matter of time, so you have to consider the max rpm.

Russ

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Re: Spindle index slot dimension question..
« Reply #5 on: December 28, 2015, 03:36:22 PM »
The best approach is to make the slot 50 % of the circumference.   

(;-) TP
Re: Spindle index slot dimension question..
« Reply #6 on: December 28, 2015, 03:38:37 PM »
so a half disk basically?  now i'm getting confused....  i see the logic in that but it will cause some imbalance issues i would imagine.  is it truly the best method?

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Re: Spindle index slot dimension question..
« Reply #7 on: December 28, 2015, 03:58:48 PM »
Your mill spindle with its mass will never know it is there (;-)  assuming of course that it is an aluminum disc and NOT a 10 lbs disk (;-) .

(;-) TP
Re: Spindle index slot dimension question..
« Reply #8 on: December 28, 2015, 04:15:32 PM »
Ok.. i made it a 20 degree angled opening to be safe and it is a true angle not a slot so the pickup beam should have full exposure for the full 20 degrees of rotation.  I am balancing the spindle as well so having the 180 missing would be alot of imbalance to account for.

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Re: Spindle index slot dimension question..
« Reply #9 on: December 28, 2015, 05:35:28 PM »
I think you are over thinking it here BUT it is your call.  Consider making it out clear plexiglass then painting half of it black.   Not enough pulse time is the major #one cause of RPM problems with spindle indexing. I was just suggesting eliminating 100% of your future problems the first time out.


(;-) TP