Guest
Recently I added an air cylinder to a manual lathe that opens the
half nut when threading by moving the proper lever.
For those who don't know a manual lathe that can cut threads has a
leadscrew that drives the carriage along the ways when a split nut-the
half nut-is clamped around the leadscrew.
When the carriage has traveled the desired distance the half nut
must be disengaged. The faster the carriage is moving the less time
you have to disengage the half nut. Failure to disengage the half nut
in time typically results in scrap parts or worse.
As I have gotten older my reflexes have gotten worse so I can't
thread as fast as I use to. So to move the lever I added an air
cylinder that is actuated by a solenoid valve that is switched by an
inductive proximity switch. It works very well.
But there is some drift after the half nut opens. I can set the
carriage lock so that it drags some while threading and the lathe will
stop repeatably within .004". But the faster the carriage moves the
more overtravel I get. Plus I don't like having so much drag on the
carriage.
So now I want to add another air cylinder that locks the carriage
for half a second or so whenever the half nut is opened. A 555
monostable timer seems to me to be the best option.
I have some questions though. Because of the way the proximity
switch works the trigger pulse to the 555 will longer than the time I
want the carriage lock to be actuated. This longer pulse won't be a
problem will it? My plan is to use the proximity switch to pull the
555 reset low whenever the switch is off. Then the switch will detect
the carriage, the reset will go high and the trigger pulse will
happen. Will this work? Do I need to just pulse the reset? I could do
this with another 555, or just use a 556 chip.
The whole reason for actuating the carriage lock for just a half
second or so is that the thread being cut requires several passes and
I want the carriage to stop and then be released so I can then wind
the carriage back and prepare for the next pass. I don't want to fuss
around with pressing reset buttons or anything. The way it is now
threading is seamless and reflexive, the lathe is operated just like
normal except I don't have to pull up on the lever to disengage the
half nut. I want to keep it that way.
Thanks,
Eric
half nut when threading by moving the proper lever.
For those who don't know a manual lathe that can cut threads has a
leadscrew that drives the carriage along the ways when a split nut-the
half nut-is clamped around the leadscrew.
When the carriage has traveled the desired distance the half nut
must be disengaged. The faster the carriage is moving the less time
you have to disengage the half nut. Failure to disengage the half nut
in time typically results in scrap parts or worse.
As I have gotten older my reflexes have gotten worse so I can't
thread as fast as I use to. So to move the lever I added an air
cylinder that is actuated by a solenoid valve that is switched by an
inductive proximity switch. It works very well.
But there is some drift after the half nut opens. I can set the
carriage lock so that it drags some while threading and the lathe will
stop repeatably within .004". But the faster the carriage moves the
more overtravel I get. Plus I don't like having so much drag on the
carriage.
So now I want to add another air cylinder that locks the carriage
for half a second or so whenever the half nut is opened. A 555
monostable timer seems to me to be the best option.
I have some questions though. Because of the way the proximity
switch works the trigger pulse to the 555 will longer than the time I
want the carriage lock to be actuated. This longer pulse won't be a
problem will it? My plan is to use the proximity switch to pull the
555 reset low whenever the switch is off. Then the switch will detect
the carriage, the reset will go high and the trigger pulse will
happen. Will this work? Do I need to just pulse the reset? I could do
this with another 555, or just use a 556 chip.
The whole reason for actuating the carriage lock for just a half
second or so is that the thread being cut requires several passes and
I want the carriage to stop and then be released so I can then wind
the carriage back and prepare for the next pass. I don't want to fuss
around with pressing reset buttons or anything. The way it is now
threading is seamless and reflexive, the lathe is operated just like
normal except I don't have to pull up on the lever to disengage the
half nut. I want to keep it that way.
Thanks,
Eric