4th Axis Question

OK; I've had my 770 for over a year and I'm just now getting around to using my 4th axis.

I'm wanting to mill some flutes on a small specialty Reamer but, I'm not sure how to reference my part once it's mounted in the chuck of the rotary table.

I figured out how to set it up in my SprutCam software and the simulations look like I have good tool paths but, I just need to know exactly what reference points to use for my tool offsets.

Is the top of my part the "Z" reference point the same as for milling a rectangular part?

If so, does that make the "X" axis reference the Right-End-Point of my part and the "Y" reference the side of the part closest to me just like it would be if I were referencing a part in a vice?

I know these questions may sound ultra-newbie to some of you but I want to mitigate the chance of crashing my machine. I did enough of that the first couple of times I turned it on.

Thanks for your help.

MetalShavings

All of your axis setup would be exactly the same except you now have A to set as well. The only thing I usually run into is that Z is set to the radius of the part and not zeroed on the top of the part generally.

Set your Z to the center of rotation, then set your safe height to the maximum radius of your work piece + .1 or there abouts.

Thank you gentlemen:

I actually asked this same or similar questions a few months back when I was initially gearing up to use my 4th Axis rotary table for first time. I even got a little help from Eric over at tormach.

Things got a little hectic back then so I never even un-crated my 4th Axis unit.

I've since forgotten everything I learned about setting up my part for machining with the 4th Axis so I thought I'd ask all over again.

Using the "Search Feature" I even looked up all the replies I got previously when I asked my 4th Axis questions. I'm not very good at applying knowledge I've learned in the past unless I've been applying that knowledge all along.

I see that I'm going to have to start from scratch. After viewing a couple of videos on the subject it looks like my reference point will be the center-axis of my cylindrical part for the "X" and the "Y" axis'. The "X" axis reference point will be at the right-end of my part.

Since this is a cylindrical part that will be rotating to four different positions, the "A" axis can be zeroed at any position to begin with.

Does this sound correct?

MetalShavings

I don't use SprutCam but normally the reference points for the tool offset on the machine will be the same as the reference points in the CAD/CAM program. When the CAM produces the gcode it did it based on a set of reference points set in CAD. The reference point for the x. y, z and A axis will be wherever the zero point for that axis was relative to you part in CAD.

Phil:)

Quote:

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Originally Posted by MetalShavings

After viewing a couple of videos on the subject it looks like my reference point will be the center-axis of my cylindrical part for the "X" and the "Y" axis'. The "X" axis reference point will be at the right-end of my part.


Does this sound correct?

MetalShavings

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Quote:

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Originally Posted by philbur

I don't use SprutCam but normally the reference points for the tool offset on the machine will be the same as the reference points in the CAD/CAM program. When the CAM produces the gcode it did it based on a set of reference points set in CAD. The reference point for the x. y, z and A axis will be wherever the zero point for that axis was relative to you part in CAD.

Phil:)

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Hi Phil:

I see what you mean. The reference points in my CAD software are in the center of my cylindrical part with the X axis being referenced on the far right end of the part.

When I go to index my part to set my tool offsets that means I'll be touching off on the top edge and the side of my part to establish my measurement to the center of my cylindrical part/stock. The center being the point where the X and Y axis' are zeroed.

For example: if I have a .75" diameter cylinder that I'm indexing and the Z axis reads, .650" when the tool touches the top surface of my part, that means that I would enter 1.025" in the Z axis text field before I click "Enter". Correct?
(.650" + .375"= 1.025") (half of .75 equals .375")

If I'm using a .5" end mill and the Y axis reads, .250" when the tool touches the side of the cylindrical part, that means that I would enter .625" in he Y axis text field. Correct? (.250" + .375" = .625")

Trying to give explanations with the written word tends to make things seem far more complicated than they really are some times. This may be one of those times.

I hope what I'm trying to ask or say makes sense. I also hope it's correct. If it's not please let me know.

MetalShavings

Wrong and wrong. All you need to do is tell the machine where the tool is relative to the X, Y, Z and A axis reference (zero) points.

So if the CAD/CAM has the Z axis zero at the center line through the part and the part has a diameter of 0.75" then you touch the tool of the top of the part and then enter 0.375" and press enter.

With X and Y you tell the machine where the spindle axis is relative to the part reference points are by touching of the end and side of the work respectively.

When touching off the side of the part the tool reference would be half the part diameter plus half the tool diameter. You need to make sure whether the offset is + or -. If you touch of the back side of the part then the offset will normally be plus.

when touching off the end of the part the offset will be half the tool diameter.

Providing you are starting with a part that is blank and symmetrical (a plain shaft) then you can just zero A and press enter as it will not matter where on the circumference the cut starts.

Always cut air to check the tool behaves as expected before you do it for real .

Phil:)

Quote:

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Originally Posted by MetalShavings

For example: if I have a .75" diameter cylinder that I'm indexing and the Z axis reads, .650" when the tool touches the top surface of my part, that means that I would enter 1.025" in the Z axis text field before I click "Enter". Correct?
(.650" + .375"= 1.025") (half of .75 equals .375")

If I'm using a .5" end mill and the Y axis reads, .250" when the tool touches the side of the cylindrical part, that means that I would enter .625" in he Y axis text field. Correct? (.250" + .375" = .625")

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Hi Phil:

I see where I went wrong in my last reply.

The numbers I put up included random numbers I get when I reference my tools to my part by using a little Starret sliding block.

I use this little sliding-block gadget that Starret makes for measuring the distance of the end of my tool to the edge of my part. I can't remember what the technical name of this little do-hickey is but, essentially;

You bring the tool down close to the surface of the part to be milled, then rather than actually touching the part with the tool, you put this little Starret block between the tool-end and the part and slide it open until it fills the gap between the tool and the part. You then measure the width of that gap using the sliding block plus half the diameter of the cylindrical part to give you the zero position.

With this Starret tool between the tool and the part, the readings on the Z, Y and X axis' are either added or subtracted from the overall measurement when referencing my tool offsets.

So I think I was correct but I'll double check anyway just to be sure. The problem was the way I wrote my down my question.

I appreciate your help Phil. Thanks for the confirmation.

MetalShavings

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Originally Posted by KrausMotor

Set your Z to the center of rotation, then set your safe height to the maximum radius of your work piece + .1 or there abouts.

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+1... this is how I do it too.. otherwise I forever seem to be second guessing the a-axis.