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Author Topic: speed sensor/lathe threading  (Read 3515 times)

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speed sensor/lathe threading
« on: June 14, 2013, 04:25:10 PM »
What are some available options to add a speed senser so I can thread with my lathe.  I am using a breakout board via parallel port and have a couple inputs available.   
Thanks,
Don

Offline Hood

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Re: speed sensor/lathe threading
« Reply #1 on: June 14, 2013, 04:52:21 PM »
When using the parallel port I had good success with a slotted disc and an Optek OPB917B

Hood

Offline RICH

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Re: speed sensor/lathe threading
« Reply #2 on: June 14, 2013, 10:22:12 PM »
Have used a slotted disc but now use a Hall Affect Sensor which is easier to mount but would be more costly than what Hood
suggested.

RICH
Re: speed sensor/lathe threading
« Reply #3 on: June 17, 2013, 08:25:32 AM »
Thanks guys I have been checking them out.  As long as the sensor works with the 5vdc any reason not to have the sensor tied directly into the board just like the prox switchs I use for homing?  I see prices all over the board, will a simple optical or hall effect sensor work?  I see some cheap ones on ebay. With either one input per rev the best for general use?  I just need it accuated enough to thread and have a max spindle speed of 2800.
Thanks,
Don

Offline RICH

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Re: speed sensor/lathe threading
« Reply #4 on: June 17, 2013, 09:01:42 AM »
Both will work and a simple optical along with one slot in a disc with basic dimensions of the disc slot and diameter per info in the Mach manual. A disc made from a CD and painted black saves time.

The Hall Effect I used actualy has two sensors and only one is used. Sensors have a response time so be carefull if purchasing a Hall Effect and also don't use reed type sensor since many of them don't have the response time /
are not fast enough for higher rpm's. Attached is a pic of the Hall effect sensor mounting showing that adjustment
and mounting can be easy if your space limited.

Multiple slotted disc's / input are not supported and there is no advantage to it for threading.

There is write up in Members Doc's called Threading On the Lathe and suggest you may want to have a
read.

RICH

« Last Edit: June 17, 2013, 09:04:15 AM by RICH »
Re: speed sensor/lathe threading
« Reply #5 on: June 17, 2013, 09:34:45 AM »
Thanks Rich, I never knew that section of this forum existed now my head is spinning.  Couple questions, how did you mount the magnet?  Thinking I could bore a recess then epoxy it in.  How do I figure out the resonse time required?  Also I was thinking I could mount the magnet or a piece of steel (depending on the type of sensor) to the cats head (which is aluminum) and just mount the sensor to the gear box door since the cats head is on the outside.  Any recomendations on a senser available in the states?  I did a yahoo search of the opt sensor Hood speced out but everthing that came up was from overseas.  Ideally a sensor that worked off reflective tape or paint would be the easiest but the few I found work off usb and I doubt the timing would be accurate enough for threading.  I see CNC4PC has an optical sensor type with a board, any advantage of the board over a sensor tied directly into an input on the breakout board?  I don't thread much, figuring out all this stuff almost makes me want to put the gearbox back on the lathe.  But eventually I am going to replace the acme leadscrews to ballscrews and I never seen a halfnut for that, but that's another issue to come later. For the meantime backlash comp seem to be working out relativaly well for the accuracy I need at the moment.
Thanks,
Don

Offline RICH

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Re: speed sensor/lathe threading
« Reply #6 on: June 17, 2013, 10:52:30 AM »
how did you mount the magnet

Crazy glue and you will / can adjust the clearance and location of the sensor from the magnet ( just an 1/8" diameter and high approx and Radio Shack had them)

Some have purchased the CNC4PC board and it worked fine with a slotted disc, I have one but never used it.
Probably cheaper than a Hall Effect.
CNC lathe threading is great and you can do things that makes manual threading antiquated.

Threading, for that matter any lathe work, will only be as accurate as you lathe SYSTEM. Ged rid of the backlash so there is no need for BC ( worth the effort).

RICH
Re: speed sensor/lathe threading
« Reply #7 on: June 20, 2013, 09:27:54 PM »
Ordered that board from cnc4pc along with a new pwm speed board.  I'll see how it works. I'm sure I will be asking some more questions when I get everything.  As for the backlash, this is a self funded project, so as the machine earns me some money I put it back in the machine.  Keeps me from getting in over my head.  Hopefully I can get some ballscrews to replace the old leadscrews as funds arise.
Don