When trying to mill a job with any offset other than Centerline, the following message is displayed:
One or more layers with tool offset has open curves.
Open curves will not be produced.
Do you want to move open curves to a new Centerline layer?
Press No to continue and ignore open curves.
If you click OK, i-cut will automatically change your tool offset to Centerline and take you through to the Production Manager. If you then run the file, your job will be produced over/under sized.
Solution
This is caused because the file you are trying to run has open curves. Without being closed, i-cut cannot define an inside or outside. To resolve, close any open curves.
Click Edit > Apply Import Options.
In the Import Options, ensure that the Connect Open Curves check box is selected.
i-cut would have now connected the open curves. Check the Tool Path Preview to ensure that you have selected the correct tool offset.