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4th Axis slotting

Vishrut

Aluminum
Joined
Dec 18, 2013
Location
India
Hey Folks,

We have a VMC with 4th Axis (whose axis is parallel to X-axis). Machine can work simultaneously with all the 4 Axis -- X, Y, Z and B.

We recently had a change in drawing. We do shaft that used to have 14mm straight slot in it.

But now customer has added another 30[SUP]o[/SUP] slot and a radius R5 where these slots meet...A bit confused with programming. I can always tilt rotary 30[SUP]o[/SUP] but not sure how can I accomodate R5.

I wonder if I can do that properly with moving all the three axes - Y, Z and B simulataneously.

Attached the lockshaft.jpgdrawing. Drawing does have another bunch of few drill & tappings which needs to be done at a particular angle with centre axis; not shown here.
 
Yes, because it is below center, you need to follow the tangent point of the radius around the rotation arc it makes as B rotates, which involves Y and Z axis.
 
I think this would take a 5 axis machine to do in a smooth sweep. I think you'd have to interpolate the curve if using a 4th axis unless you want to reposition the part (eccentrically) to put the center of the R5 on the same centerline as your 4th axis. If you do reposition the part eccentrically, you could still mill the straight parts of the slot in that setup.
 
Cut the slot with woodruff type cutter, the shaft vertical in v blocks or a fixture. Sometimes we make things too complicated.

The slot is 7.5mm deep with a 5mm radius at the bottom.. You would have to have a NEGATIVE 5mm shank
to do that.. And I don't think even Harvey tool makes key cutters with NEGATIVE diameter shanks.

I was thinking ball mill, that would be easy, but the edges of the slot are square.. Even if there is a
small rad permitted, it would take a tiny ball mill and a lot of wasted time...

Sinker EDM is what it looks like to me...

In reality, that 5mm rad probably doesn't matter for fuck all, and the part
would be perfectly fine if you ran in, rotated and ran out.. Or come in from
one side, then rotated and came in from the other side, the programming would be
easier.. The intersection would look like shit... But..... whatever...
 
The slot is 7.5mm deep with a 5mm radius at the bottom.. You would have to have a NEGATIVE 5mm shank
to do that.. And I don't think even Harvey tool makes key cutters with NEGATIVE diameter shanks.

I think you're looking at it backwards, the slot is 11.5mm deep. need about a 1.5" tool with a 1/2" shank, even less if its a woodruff keyseat cutter.
 
I think you're looking at it backwards, the slot is 11.5mm deep. need about a 1.5" tool with a 1/2" shank, even less if its a woodruff keyseat cutter.


Woops... You're right... I just looked quick... That makes it easy. Key cutter all the way,
though he did say there is a bunch of other stuff on the shaft also that isn't shown, so if
its up on the 4th anyways, might as well do it there...

Driving that rad isn't difficult.. G19 G2(or 3) Y?Z?J?K?A whatever... When I've had to do similar,
I've drawn it out, start rotation, end rotation and then at some point in the center, and come up
with a 3 point arc to get the values I need.
 
You're right Dandrummerman...slot is 11.5mm deep, sitting 2mm below the centreline of shaft.

Woodruff cutter, part vertically held.....that's exactly what I thought of initially.

But as earlier told, there are certain other features (that includes M3.5 CSK bolt drill/tapping, M8x1 bolt drill/tapping, another tiny slot parallel to X-axis etc. not shown in drawing), the angular position of all those are required at a certain degrees with respect to main 14mm slot. I am considering 4th axis to ensure everything being done in one setup and aviod multiple setups/fixtures.

Not to add to my woes, customer is demanding qty of atleast 7500 pcs every month !!:rolleyes5:
 
Woops... You're right... I just looked quick... That makes it easy. Key cutter all the way,
though he did say there is a bunch of other stuff on the shaft also that isn't shown, so if
its up on the 4th anyways, might as well do it there...

Driving that rad isn't difficult.. G19 G2(or 3) Y?Z?J?K?A whatever... When I've had to do similar,
I've drawn it out, start rotation, end rotation and then at some point in the center, and come up
with a 3 point arc to get the values I need.

Will the control even accept a rotary axis (amounts to a linear feed) move along with an arc (sinusoidal feed) command in YZ? I'd try that with a made up command first just to see if it alarms out.

Note, it also requires a very flat ended endmill to not leave a hump in the bottom of the slot when rotation is used. That is why the woodruff style cutter is a good idea. For 7500 pieces, it just makes fixturing the part on end that more justifiable, if even just taking a light clean up cut.
 
Note, it also requires a very flat ended endmill to not leave a hump in the bottom of the slot when rotation is used. That is why the woodruff style cutter is a good idea. For 7500 pieces, it just makes fixturing the part on end that more justifiable, if even just taking a light clean up cut.

Center-cutting tool for sure, but you really just have to take two or three passes to make it flat and square.
The tool should not be centered on part Y when you rotate the 4th... That will make the center of the groove flatter (and prevent effectively zero surface-speed there).

That initial pass will leave a slight elliptical corner to the slot due t the Y offset.

Assuming you're cleaning up each side of the slot, 3 passes:
Cut the first pass with Y=centerline - 1/4*R to Y=centerline - 1/2*R.
Then finish each side and rotate with Y=centerline

More specifically, let's say you have a 4 flute cutter with two flutes center-cutting and two flutes that aren't:
Measure the smallest radius where the edge of the non-center-cutting flutes start.
Add .020 (or .05mm) and use that as your Y offset from centerline for the slotting pass.

That method will ensure that you are using all four flutes on the face of the tool and avoid the zero surface speed condition when on center and rotating.

...I liked the woodruff cutter.
I would probably just write a second op for that with a block-skip on the tool-change to save time.
Put a couple of vises in the machine with aluminum jaws bored for three or more parts each standing on end.
Buzz three parts and cycle stop without a tool change is fairly fast.
 








 
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