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Weiss VM32 CNC Conversion

slow-poke said:
Options, options, so many options.........
A couple to consider:
1) 3D print disk with many slots or holes
2) To avoid the power drawbar, use the rotary encoder linked to the motor pulley and just do the ratio conversion in software.
Click to expand...
I 3D printed a disk for my Gingery to use with 3 slotted sensors. I had to paint the black PLA with metalic paint. The senso IR went right through the PLA. I tried different colours. No difference.

I'd post a picture but we're at YVR waiting for our flight.

For my mill I cut slots in 16g aluminum.
 
Sorry @DavidR8 - I am lost. I should just keep my nose out of it. But maybe a few stupid questions from the back of the class can bring more clarity to the teacher.

Are you suggesting that you will NEVER do regular threading? If so, then fine. You will only need to coordinate advance (z) with x & y.

But if you plan to do regular threading at some point in the future, the rate of advance is the thread pitch which depends on where the spindle is in its rotation.
 
Susquatch said:
Sorry @DavidR8 - I am lost. I should just keep my nose out of it. But maybe a few stupid questions from the back of the class can bring more clarity to the teacher.

Are you suggesting that you will NEVER do regular threading? If so, then fine. You will only need to coordinate advance (z) with x & y.

But if you plan to do regular threading at some point in the future, the rate of advance is the thread pitch which depends on where the spindle is in its rotation.
Click to expand...
If by regular threading you mean chucking a tap in a collet , running the spindle at some low rpm and manually advancing the tap into the work then no because I won’t have the ability to manually control the Z axis advance at the rate dictated by the spindle speed and the pitch of the tap.

The Z axis is going to be controlled by a servo motor which is why to do rigid tapping an encoder is required on the spindle. The encoder tells the CNC controller exactly how much/far the spindle has rotated so the CNC controller can calculate how much to advance the Z axis.
 
DavidR8 said:
The Z axis is going to be controlled by a servo motor which is why to do rigid tapping an encoder is required on the spindle. The encoder tells the CNC controller exactly how much/far the spindle has rotated so the CNC controller can calculate how much to advance the Z axis.
Click to expand...

I see. Well if you ever want to do rigid tapping, I think you will need a lot more sensing locations (pulses per rev) on the rotational encoder. But you might be able to increase the number of pulses by adding more sensors in a phased "or" array (any one generates a pulse) instead of adding more slots. They don't have to be located all around the perimeter. They can all be in one phased cluster. It's a handy way of improving resolution without changing the number of slots.
 
Susquatch said:
I see. Well if you ever want to do rigid tapping, I think you will need a lot more sensing locations (pulses per rev) on the rotational encoder. But you might be able to increase the number of pulses by adding more sensors in a phased "or" array (any one generates a pulse) instead of adding more slots. They don't have to be located all around the perimeter. They can all be in one phased cluster. It's a handy way of improving resolution without changing the number of slots.
Click to expand...
Yes that is what I’m learning.
It’s all a bit moot at this point though because I’ve discovered that the CNC controller I’m using doesn’t accept the g-code commands that are required for rigid tapping.
So thread milling is how I will be cutting threads.
I’m completely fine with this because it allows for more control over thread fit because I can specify how deep the thread is cut.
 
Another option for tapping on a cnc mill is a "tension-compression" head. this allows for a deviation to a degree between the commanded z travel and the actual amount the tap enters the work. I used one for the first time a few weeks ago, nerve wracking but exciting, and sure was faster than figuring out threadmillling and 20x faster than hand tapping. I'm still trying to figure out threadmilling, its easier if you buy a threadmill for the specific thread and pitch, but I'm trying to use an inexpensive metric threadmill (M6 x1) to cut an imperial thread (1/4-20). I think in theory it seems like it should work but I ran out of play time to keep tweaking it,
 
Mike R said:
Another option for tapping on a cnc mill is a "tension-compression" head. this allows for a deviation to a degree between the commanded z travel and the actual amount the tap enters the work. I used one for the first time a few weeks ago, nerve wracking but exciting, and sure was faster than figuring out threadmillling and 20x faster than hand tapping. I'm still trying to figure out threadmilling, its easier if you buy a threadmill for the specific thread and pitch, but I'm trying to use an inexpensive metric threadmill (M6 x1) to cut an imperial thread (1/4-20). I think in theory it seems like it should work but I ran out of play time to keep tweaking it,
Click to expand...
In the above vid I am using a 1.0mm pitch threadmill to cut a 1”-27 thread. Big advantage of threadmilling is that with a single thread cutter you can do many different and weird threads and hole sizes.
 
Mike R said:
Another option for tapping on a cnc mill is a "tension-compression" head. this allows for a deviation to a degree between the commanded z travel and the actual amount the tap enters the work. I used one for the first time a few weeks ago, nerve wracking but exciting, and sure was faster than figuring out threadmillling and 20x faster than hand tapping. I'm still trying to figure out threadmilling, its easier if you buy a threadmill for the specific thread and pitch, but I'm trying to use an inexpensive metric threadmill (M6 x1) to cut an imperial thread (1/4-20). I think in theory it seems like it should work but I ran out of play time to keep tweaking it,
Click to expand...
By tension-compression head do you mean a tapping head like a Tapmatic or something different?

Edit: found what you meant with a bit of googling
 
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