4th Axis Rotary struggles

[mrramsey1969]

Greetings All!
Over the past day or so I have begun testing my 4th axis. I have to be over looking something simple but I cannot figure out what.

I designed a very basic model of a cylinder in SketchUp. The diameter is 2.95" and the length is 5.375", there is also a small ringed lip at one end with a diameter of 2.75".
My process as follows:
1. I create a new rotary project in v-carve with a diameter of 4.95" (the cross dimension of 3.5" square stock) and a length of 8".
2. I set the z0 on the axis and the origin at the center.
3. Open the modeling tab and import the model. The model imports and the diameter and length of the model are shown at 2.95" and 5.375" as they should.
4. I generate a roughing tool path and a finish tool path

I let the program run on my machine and it cuts but my finished dimension diameter is about .33" smaller than it should be at about 2.62" +/-. Any ideas of what is happening are appreciated.

[Rcnewcomb]

Can you upload your .CRV to the forum?

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[SteveNelson46]

What is your depth of cut? For those dimensions, it should bi 1". to get a final diameter of 2.95" As said many times before, upload or put a link to your project. Otherwise we are just stabbing in the dark.

[SteveNelson46]

I did it here with a spiral toolpath. I'm not sure of why you need to import anything to get just a cylinder.

[mrramsey1969]

Can you upload your .CRV to the forum?

Here is the file...

[SteveNelson46]

In my humble opinion, you don't need to import a model and use a 3D toolpath. It may work but a rounding or spiral toolpath using a flat bottom or surfacing bit would be much faster and cleaner.

[SteveNelson46]

Here is an example using a rounding gadget and a profile toolpath for the lip.

[adze_cnc]

Looking at the 3D model preview all the cut depths, material remaining, etc. are correct dimensions based on object size, material size, and cutting parameters.

As this is your first project the question to ask is: if the rotary attachment calibrated properly? If you try to round a square piece to a cylinder using 2D methods do you get the right size?

[mrramsey1969]

Looking at the 3D model preview all the cut depths, material remaining, etc. are correct dimensions based on object size, material size, and cutting parameters.

As this is your first project the question to ask is: if the rotary attachment calibrated properly? If you try to round a square piece to a cylinder using 2D methods do you get the right size?

Adze, Thanks for confirming that the model I imported and the toolpaths I set look to be correct. I manually set the XY0 to the center of my material then set the z0 to the center of the axis. Which I believe would be correct. Could this be a post processor issue? I have two options depending on which axis I have the lathe set up on. Interestingly enough I do get a dialog box in Vcarve when I select one of them but not the other.

[TReischl]

........ Could this be a post processor issue? ,,,,,,

The simple answer is NO. You are not the only person using that postprocessor.

My guess is that you may have set the Z axis centerline incorrectly or you need to check your Z calibration. Another possibility is that you are losing/gaining steps on Z.

My rule of thumb is to never blame the software first. This stuff has been around a long, LONG time. Blaming the software results in not being able to fix the "issue" because we cannot fix the software, someone else has to do that. So the idea is to eliminate absolutely everything else before pointing a finger at software. You will get your issue solved much quicker.