Circular tool path error

[Anonymous]

Hi all

I am having a strange problem when using circular tool paths as part of a CAM setup for a guitar neck. All other operations have been executed well and correctly, but the circular tool paths are about 1mm off on the x axis.

I have used 3D roughing strategies, 2D contours, scallops, and parallel operations that have all worked perfectly. My X and Y coordinates remained constant throughout the entire operation, centred on the stock and the model.

I used a 6.35mm flat end mill to rough out the headstock angle (which was correct) and then proceeded directly to the circular operation to cut the tuner holes. I then ran various other operations, all off which worked as expected and cut to the correct coordinates. It wasn't until I had completed the finishing pass with a ball end mill that I realised that all 6 tuner holes were about 1mm too far in the positive direction on the x axis.

When I simulate the circular tool paths, they are correct. Is something happening in post processing? Could it be something to do with the compensation type? Has anyone else ever experienced anything like this before?

Looking for a bit of guidance so that I can avoid this in the future. I need to decide whether to put the part back in the machine (feels risky) or try to relocate the holes by hand (imprecise). Either way it will be a bit of a squeaky bum moment...

Any thoughts and guidance would be much appreciated.

Cheers

Matt

[seth.madore]

Is it possible that your machine lost any steps or may be loose in some aspect?
9 times out of 10, when an issue presents like this, the error is found at the machine level. 
What is your machine and post processor?

[Anonymous]

Hi Seth

Thanks for your message. I have the Ooznest Workbee 1000 x 750. The post processor is the one provided by Ooznest for the machine. I don't think that there are any mechanical issues with the machine, as it has successfully milled all of the other parts of the strategy. This isn't the first time I've noticed the issue with circular tool paths, just the first time that I've put two and two together. It would be too coincidental for the machine to be losing steps only when milling circular operations.

If I run a circular tool path, it will be incorrect. If I then run any different kind of tool path (same tool), it will be correct. Then if I run a circular tool path again, it will be incorrect.

Could there be an issue with the Ooznest post processor?

Cheers

Matt

[seth.madore]

And what happens if instead of a Circular toolpath, you use a 2D Contour? Will they be in different spots?
Can you put your nc file and your post processor into a zip file and attach it here?

[Anonymous]

I think a 2D contour would be in a different spot. I have some fillets in a parallel operation that should be located directly over the holes. The fillets are in the right place but the holes in the wrong place. I've attached the 2 nc files and the post processor here.

Cheers

Matt

[seth.madore]

Could you also share your Fusion file?

File > Export > Save to local folder. Return to thread and attach the .f3d file in your reply

Merging the two files together and running it through a backplotter do seem to indicate that there is something amiss:

[Anonymous]

Fusion file attached. Thanks for helping me out with this. Looks like you're back plotter has the files mismatching on the y axis though, which is interesting...

Cheers

Matt

[seth.madore]

Turns out that's not an error, as your toolpath is also shifted like that in Fusion:

That's not actually a mistake there, as it's showing the cusp of the tool.

Are you using the same tool throughout?

Does your machine have a work offset table, what do you do in between tools to establish the new length?

 

[Anonymous]

Hi Seth

It could well be user error, as I am a novice. I'm not sure what a work offset table is. If I change the tool, I leave the X and Y home position the same (as it is centred on the model and stock) and I use a touch probe to reset the Z axis.

In this case however, I used the same 6.35mm flat end mill to cut the rough contour of the neck, adaptive roughing and finish contour. These operations were undertaken both before and after the circular tool paths and they are all correct. All other operations (whether with the same tool or a different tool) are correct, which makes me suspect the circular operation. Having accurately measured this morning, I can see that all circular holes are shifted 0.75mm too far positive on the X axis. This occurs with all tools and isn't exclusive to the 6.35mm flat end mill.

Cheers

Matt