Author Topic: CNC 4th Axis  (Read 2454 times)

Offline kvom

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CNC 4th Axis
« on: May 11, 2015, 11:15:37 PM »
I decided to upgrade my CNC mill by adding a 4th axis.  They're very useful for gear cutting, and potentially other jobs.  Unit is basically your Chinese 8" rotary table with the manual handle replaced by a stepper motor. My mill's controller already had the electronics to drive it, so it was pretty much plug and play.  Novakon provided me with a Mach3 profile that had the basics for controlling it, and I just needed a few configuration mods to get it moving.

First job is to mount a chuck to the table.  With the table mounted horizontally I centered it under the spindle.



That turned out to be a waste of time since I found that I didn't have enough Z space to use the same center finder with a rod held in the chuck.  So went to plan B using a DI to center the chuck, which I just moved from my old manual rotab.



Managed to get it aligned to less than .001" all around, so quite happy with that.  Then set it vertical.



As can be seen, the motor extends out a long ways.  I might need to turn it the other direction because the tailstock wants to point from the left:



I suspect that once the aligned the tailstock can be operated OK with its back to me.

Offline Tennessee Whiskey

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Re: CNC 4th Axis
« Reply #1 on: May 12, 2015, 01:20:55 AM »
If y'all keep on with CNC stuff you are going to cause Stan to spend 6 or 8 months of his tool allowance on one of those VMC thingies and then he is going to convince me how much fun they are then here we go.  On second thought,  keep it up,  we both just need a good excuse  :lolb:.

Eric

Offline Dave Otto

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Re: CNC 4th Axis
« Reply #2 on: May 12, 2015, 01:36:36 AM »
The VMC thingies are a lot of fun and you can make some really cool stuff with them; I'm fortunate to have have one in my cube at work and I'm able to use it for my own projects after hours and weekends.  :ThumbsUp:

Kvom, when I built my new control box for my knee mill at home, I added everything that I need for the 4th. I haven't decided what I want to do for the hardware yet; but it will be servo driven because that is what the other 3 axis are, I added a 4th Gecko 320X for the A axis.

Interested to see how this works out for you.

Dave

Offline kvom

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Re: CNC 4th Axis
« Reply #3 on: May 12, 2015, 12:47:30 PM »
The first project I have in mind is to mill the profile for the frame spacers for the Coventry engine.  My thought is to repeatedly mill the profile on some round rod advancing the A-axis 20 degrees after each pass.  That would result in 18 facets, but then I could sand the corners down on the manual lathe.  Essentially using it as a very slow CNC lathe, but each of the spacers would be nearly identical.

Before I do that I need to source some 7/16 diameter brass rod.

Offline Jasonb

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Re: CNC 4th Axis
« Reply #4 on: May 12, 2015, 01:16:41 PM »
Can't you just hold the spacers in the mill spindle and mount a lathe tool onto the mill table, move teh table in and out as the table goes up.

Offline kvom

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Re: CNC 4th Axis
« Reply #5 on: May 12, 2015, 02:45:28 PM »
Can't you just hold the spacers in the mill spindle and mount a lathe tool onto the mill table, move teh table in and out as the table goes up.

Yes, you can do lathe work on the mill as you describe, and I've done so in the past.  The restrictions there are:

1) No tailstock support
2) Stock must fit in R8 collet
3) CAM program needs to support lathe G-code generation

Aside from these, the issue with this part is that two separate lathe tools would be needed to cut the profiles, and getting them into registration would be tedious at best.