can linux cnc can cut a thread using only breakout board without using mesa card

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7 years 3 months ago #139113 by Dinuka_Shehan
I think you have the code for the PP for threading .

What is PP?

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7 years 3 months ago #139114 by Clive S
PP = parallel port. I think you said you using one with a simple bob

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7 years 3 months ago #139417 by andypugh
You probably can use the 2000 count encoder for threading with the parport + BoB but only at low speed.
At high speed you will lose counts.
This might be acceptable, threading is often done at low speed.

But, if you are going to fit an encoder, it is probably best to have one that works at all speeds.

But most lathes make it difficult to fit an off-the-shelf encoder, as the spindle is so large, and a home-made slotted disc is an easier solution.

There is a class of encoder called an "elevator encoder" that can have a very large through-bore suitable for a lathe spindle, if you can find one cheap.

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7 years 3 months ago #139472 by Dinuka_Shehan
Hi,
Thank you for help and your valuable information.

I am going to make a slotted disc for myself and it will be cut on a 2mm thickness piece of acrylic or 5mm thick ebonite disc.
I planned to fix it on my spindle thread which used to tighten the taper roller bearings of spindle.
It is 33.5mm of major thread diameter.slotted disc will placed between two locknuts.

Slotted disc will have 60 slots and only one tooth cut too deeper for index pulse.
slot size wiil be 3mm wide and depth of 4mm and only one tooth depth for 6mm to index.
PCD(pitch circle diameter) of (3x3)60/3.1416=114.59mm.
diameter of disc will be 114.59+3=117.59mm.

I am using two optocoupler speed sensors to detect the index pulse and phase A.
its slot wide 6mm and height of 7mm.

is this well enough for my setup?

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7 years 3 months ago #139474 by Dinuka_Shehan
No eBay APP ID and/or Cert ID defined in Kunena configuration

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7 years 3 months ago #139486 by tommylight
You can find a lot of those sensors on old photocopiers or printers, although they should be fairly cheap.

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7 years 3 months ago #139557 by andypugh

DinukaShehan wrote: is this well enough for my setup?


Yes, that will work well. I ran with exactly such a system for years.

You could consider adding a phase B, it will give you the ability to rigid tap.
Or use a two-sensor detector for A and B.

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7 years 3 months ago #139569 by Dinuka_Shehan
but I cannot use Phase B on my bob.
It just 20khz.
so I searching for a new bob for cheap price for my purpose.

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7 years 3 months ago #139571 by Dinuka_Shehan
I have already got some old photocopiers optocoupler switches but the problem is I can not figure out the pins of those switches.
any ideas?

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7 years 3 months ago #139572 by andypugh

DinukaShehan wrote: but I cannot use Phase B on my bob.
It just 20khz.
so I searching for a new bob for cheap price for my purpose.


20kHz is an (approximate) parallel port limitation rather than a limitation of the BoB.

What is your base period set to in the HAL / INI files?

60 slots / 4x quadrature / 20kHz is 5000 rpm....

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