Adding a 4th axis?

#1

I’d like to add a 4th axis to the Nomad. I have a couple of sweet Oriental Motor geared servo motors, 30:1 gearboxes with no discerable backlash.

It would be easy to make a chuck for this gearmotor but I have no idea how I’d interface it to Carbide Motion to enable MeshCAM 4-axis code.

I can handle the actual driver cirtuitry, it’s only controlling it that is the issue…

Randy

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(Mark Bellon) #2

Neat! No scale… how big is it?

mark

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#3

About 3 fingers, Mark. :smile:

Seriously, about 2.7" square over the geabox by about 5.7" long plus the shaft.

I’m sure I could work out a workflow that would avoid the tool sensor…

Randy

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(Mark Bellon) #4

Not sure if there are any stepper controls free on the existing boards. If there are, perhaps it can be used; if not, Nomad organ and brain transplant? :smiling_imp:

mark

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#5

@mbellon, the stepper board (in the Nomad Classic at least) is 3-axis and all 3 axes are in use. :slight_smile: The board in the Shapeoko3 has four drivers, but two are slaved for the Y axis. But even if it were reconfigurable it would not help me. My gearmotor is actually a servo.

I’m thinking the easiest way to implement rotary indexing might be to clamp a 5C collet block to the table against pins to register in the X and Y axes. The 4-sided block would give 90-degree increments, done manually in between the individual gcodes. The 6-sided block would need a tall fence to register in Y, but would give 60-degree increments.

http://www.shars.com/products/toolholding-workholding/collet-fixtures/5c-collet-block-set is a typical set.

Even the Shars block is claimed to be within .0005" squareness, so finding the axis in Y and Z would be very easy–edge find the block, touch down in Z and adjust each coordinate by half the block’s size.

I’ll need to add my voice to the requests for Rob to implement round stock when doing a 4-axis part…

Randy

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(William Adams) #6

I’ve been considering getting a second Azteeg X5 mini and attaching the one I have to my Shapeoko 1 and experimenting w/ adding a 4th axis there.

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(Mark Bellon) #7

@mbellon, the stepper board (in the Nomad Classic at least) is 3-axis and all 3 axes are in use. :smile: The board in the Shapeoko3 has four drivers, but two are slaved for the Y axis.

That’s what I suspected - all full. That it’s a servo means it wouldn’t go anyway. :wink:

Ah! I see you’re idea. I like it! That’s 4 axis indexed machining. I’m used to doing 4 and 5 continuous machining; indexing is just a subset… but you’re scheme is more accurate/precise for indexed machining since I have to have all the general motion uncertainty and then have to deoend on the uncertainty of a lock at a fixed angle.

I’ll need to add my voice to the requests for Rob to implement round stock when doing a 4-axis part…

YES!

mark

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#8

On my Interstate 5C collet block set, the square block is 1.723" square, giving a center height of 0.8665" above the mounting surface. Interestingly, the hex block is 1.782" across the flats, giving a center height of 0.891" above the mounting surface.

@mbellon, MeshCAM only supports indexed 4th axis machining, but not continuous. So the collet block is a reasonable way to index.

Sherline has an 8-sided collet block, threaded for its own chucks and endmill holders, but I have not been able to find a 5C 8-sided block…

Randy

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(Mark Bellon) #9

On my Interstate 5C collet block set, the square block is 1.723" square, giving a center height of 0.8665" above the mounting surface. Interestingly, the hex block is 1.782" across the flats, giving a center height of 0.891" above the mounting surface.

I can’t wait to see this thing! :joy:

@mbellon, MeshCAM only supports indexed 4th axis machining, but not continuous. So the collet block is a reasonable way to index.

Makes perfect sense to do it that way you’re doing then. :grinning:

Once my Nomad arrives I’m going to work up a BobCAD-CAM 5 Axis Mill Pro post processor for it. This package is capable of 3 axis work, as well as 4 and 5 axis indexed and continuous machining… and it is total overkill… but it will be fun!

By-the-by, Fusion 360 is capable of 4 and 5 axis indexed machining currently. They have plans for 4 and 5 axis continuous but the timing has not be announced.

Another CAM package that is capable of 4 axis indexed machining is DeskProto.

mark

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(Rob Grzesek) #10

If we’re just speaking theoretically then Carbide Motion could be modified to move a 4th axis connected to a separate USB port. This would not be coordinated motion, it would be 3+1 for positioning, not “true 4 axis”.

I can’t say this has moved beyond the “Hey wouldn’t it be neat if…” stage but we’ve considered it.

-Rob

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(Frank Zhao) #11

I just looked at my Nomad 883 Pro’s circuit, there’s 4 stepper drivers, 3 in use, a spare Y driver that’s not connected.

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(William Adams) #12

If it’s the same board as the SO3, then the 4th connector is driven in reverse to the other Y-axis connection.

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(Frank Zhao) #13

Ah so it is a Shapeoko 3 board, I found some pics on the Shapeoko wiki. But is it tied by hardware or can a firmware change unlock that axis?

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(William Adams) #14

It’s a hard wired reversing. You’ll need a different Microcontroller and board for a true 4th axis setup, or some other mechanism for controlling the additional axis.

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(Frank Zhao) #15

Let’s say that we swap out all the brains and software, what are your opinions on adding one of these

onto a bed extension of some sort, aligned with the Y axis, and sticking out the front of the Nomad a bit?

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(Jonathan K) #16

sauce for said device?

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(Frank Zhao) #17

Ebay has plenty of similar things when you search for CNC 4th axis. A couple hundred bucks.

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