Re: [CAD_CAM_EDM_DRO] Digest Number 690
Posted by
Andrew Werby
on 2000-09-09 12:14:41 UTC
Message: 15
Date: Fri, 08 Sep 2000 21:16:14 -0000
From: ballendo@...
Subject: Re:Lathe threading
Andrew wrote:
<snip>spindle encoding very simply- just attaching a small magnet to
the spindle head, with a reader to register it as it flew by. That
done, a fairly simple circuit can control the speed of the toolpost.
He's getting ready to sell kits for between $100-$200. I couldn't
get him to subscribe to this list, but if someone's looking for a way
to do this, they might contact
him- he's Jim Lewis jimlewis@m.... ]
Andrew Werby
Andrew, the way you describe this he has created a ONE SLOT encoder.
Although you could monitor the spindle speed from the magnet, and
calculate the speed necessary for the toolpost(at this spindle speed)
and then issue a start toolpost moving, stop toolpost command with
this setup, I imagine it could get pretty dicey, pretty fast. A lot
of variables to creep in. I'd like to know how repeatable he has been?
[You'd have to ask him. It certainly doesn't add up to a fully-automatic
threading operation; you'd still have to engage and disengage the threading
cutter by hand. But it does make it possible, which is something,
considering the price. ]
Maybe an air cylinder to move the tool slide in and out quickly,
could be an add-on?
[Except the air cylinder has a fixed stroke length, right? Would you count
on the air pressure to hold the cutter into the material so it didn't jam
up? I suppose this could be adjusted for, but it might take a few tries.]
Adding magnets improves the situation, but pretty soon you'd be
better off just using an encoder.
[For this sort of thing, do you really need to keep track of fractional
spindle revolutions?]
Just doing threading on a lathe does not require a PC for control,
and he's taken an interesting approach. I might suggest using a real
encoder and some simple divider circuitry or s/w (this IS a PIC type
project). One encoder for the spindle, one stepper for the carriage,
and a hand calculator size "black box" to set TPI.
(metric/TPmm??;Hey! you guys across the pond, how do you write
this?).
[I think that mounting the encoder would present some problems in this sort
of machine. The magnet solution sounded a lot simpler. ]
Sherline is already most(if not all)the way to this already.
But it could make an interesting product???
Ballendo
[I haven't seen a Sherline threading attachment anything like this- is
there any info about it on the web? I thought the way they did threading
was by using change gears.]
Andrew
Andrew Werby - United Artworks
Sculpture, Jewelry, and Other Art Stuff
http://unitedartworks.com
Date: Fri, 08 Sep 2000 21:16:14 -0000
From: ballendo@...
Subject: Re:Lathe threading
Andrew wrote:
<snip>spindle encoding very simply- just attaching a small magnet to
the spindle head, with a reader to register it as it flew by. That
done, a fairly simple circuit can control the speed of the toolpost.
He's getting ready to sell kits for between $100-$200. I couldn't
get him to subscribe to this list, but if someone's looking for a way
to do this, they might contact
him- he's Jim Lewis jimlewis@m.... ]
Andrew Werby
Andrew, the way you describe this he has created a ONE SLOT encoder.
Although you could monitor the spindle speed from the magnet, and
calculate the speed necessary for the toolpost(at this spindle speed)
and then issue a start toolpost moving, stop toolpost command with
this setup, I imagine it could get pretty dicey, pretty fast. A lot
of variables to creep in. I'd like to know how repeatable he has been?
[You'd have to ask him. It certainly doesn't add up to a fully-automatic
threading operation; you'd still have to engage and disengage the threading
cutter by hand. But it does make it possible, which is something,
considering the price. ]
Maybe an air cylinder to move the tool slide in and out quickly,
could be an add-on?
[Except the air cylinder has a fixed stroke length, right? Would you count
on the air pressure to hold the cutter into the material so it didn't jam
up? I suppose this could be adjusted for, but it might take a few tries.]
Adding magnets improves the situation, but pretty soon you'd be
better off just using an encoder.
[For this sort of thing, do you really need to keep track of fractional
spindle revolutions?]
Just doing threading on a lathe does not require a PC for control,
and he's taken an interesting approach. I might suggest using a real
encoder and some simple divider circuitry or s/w (this IS a PIC type
project). One encoder for the spindle, one stepper for the carriage,
and a hand calculator size "black box" to set TPI.
(metric/TPmm??;Hey! you guys across the pond, how do you write
this?).
[I think that mounting the encoder would present some problems in this sort
of machine. The magnet solution sounded a lot simpler. ]
Sherline is already most(if not all)the way to this already.
But it could make an interesting product???
Ballendo
[I haven't seen a Sherline threading attachment anything like this- is
there any info about it on the web? I thought the way they did threading
was by using change gears.]
Andrew
Andrew Werby - United Artworks
Sculpture, Jewelry, and Other Art Stuff
http://unitedartworks.com