Guest
Show Posts
5691
Show"N"Tell ( Your Machines) / Re: CNC CONVERSION - 6" ATLAS LATHE
« on: September 26, 2009, 10:07:09 PM »
INDEX PULSE – MOUNTING / USING A HALLS SENSOR
Got the index pulse all working. I used a Hall sensor instead of a slotted disc.
Readout is dead on from the 53 – 2400 rpm of the lathe and doesn’t vary. Components amount to a rare earth magnet which is was super glued to a gear inside the spindle housing. The sensor ( SMC D-F7NC )
was mounted onto a steel strip and attached to the casing. The sensor actually has two sensors in it and only one was used. The sensor also has an indicating light to show when it is triggering making for easy alignment and visual confirmation other than using the diagnostics. The sensor components and mounting are shown in figure # 55.
What was really nice was that it could be mounted in close quarters. I didn’t have many options for
mounting a disc and this did the trick. The sensor works from 5 to 24 volt and I already had the wiring inside the controller setup for a 5 volt supply which saved some rewiring. Why did I use this particular
sensor? Well, as a friend pointed out, look in your “junk box” because we have a few of them ( always like to have a spare part !) and there they were. A little guidance from another friend on the pull up resistor and life is good. I didn’t check the generated pulse with an o’scope so I can’t say how good it is, but frankly,
it works, and that’s what is important.
In the last post I showed a ruined ½ - 20 thread. Now I can use the proper chuck and test out some heavier
threading. The ½-20 was again tried ( 863 RPM / 43 IPM and .006” cuts) and was done with ease. I tried a few more threads to build the confidence level up and all was fine.
Picture # 55 & 56 show the results for a ¾-13. It was cut at 115 RPM using flank cutting ( 15 degree ),
.010” first pass / then .003” passes / and I spring pass. The steppers have a lot of torque at that speed and in back gearing the motor has plenty of torque. This is a rather deep sharp vee thread ( 0.0662” )
so the cutting is rather heavy. The RPM / feedrate never changed. The resultant threads pitch and profile
is very good. An increase in RPM and lighter cuts along with a few spring cuts would probably improve finish. But I was interested in timing, rpm and cutting ability.
The next tests will be with longer threading to see if the lead is going to change over the length.
This is a problem that plagues a number of folks when doing threading. Stay tuned!
RICH
Got the index pulse all working. I used a Hall sensor instead of a slotted disc.
Readout is dead on from the 53 – 2400 rpm of the lathe and doesn’t vary. Components amount to a rare earth magnet which is was super glued to a gear inside the spindle housing. The sensor ( SMC D-F7NC )
was mounted onto a steel strip and attached to the casing. The sensor actually has two sensors in it and only one was used. The sensor also has an indicating light to show when it is triggering making for easy alignment and visual confirmation other than using the diagnostics. The sensor components and mounting are shown in figure # 55.
What was really nice was that it could be mounted in close quarters. I didn’t have many options for
mounting a disc and this did the trick. The sensor works from 5 to 24 volt and I already had the wiring inside the controller setup for a 5 volt supply which saved some rewiring. Why did I use this particular
sensor? Well, as a friend pointed out, look in your “junk box” because we have a few of them ( always like to have a spare part !) and there they were. A little guidance from another friend on the pull up resistor and life is good. I didn’t check the generated pulse with an o’scope so I can’t say how good it is, but frankly,
it works, and that’s what is important.
In the last post I showed a ruined ½ - 20 thread. Now I can use the proper chuck and test out some heavier
threading. The ½-20 was again tried ( 863 RPM / 43 IPM and .006” cuts) and was done with ease. I tried a few more threads to build the confidence level up and all was fine.
Picture # 55 & 56 show the results for a ¾-13. It was cut at 115 RPM using flank cutting ( 15 degree ),
.010” first pass / then .003” passes / and I spring pass. The steppers have a lot of torque at that speed and in back gearing the motor has plenty of torque. This is a rather deep sharp vee thread ( 0.0662” )
so the cutting is rather heavy. The RPM / feedrate never changed. The resultant threads pitch and profile
is very good. An increase in RPM and lighter cuts along with a few spring cuts would probably improve finish. But I was interested in timing, rpm and cutting ability.
The next tests will be with longer threading to see if the lead is going to change over the length.
This is a problem that plagues a number of folks when doing threading. Stay tuned!
RICH
