A tip for Tool Changes for REST machining
Posted: Thu Feb 01, 2018 6:30 pm
I have a project where I use 4 different tools to refine the details.
I start with a 1/4" tool, then 1/8", then 1/16" and finally a 1/32".
All the tool paths smaller than 1/4" use the REST method to reduce machining time.
The detail is fine enough that it is really important to get the Z0 value for each tool to be the same.
I use the following method to achieve this.
Create a set of tool paths that are used just to calibrate the Z0 settings.
One tool path is a long profile cut in a straight line. The rest are short cuts across the first one.
When the tool paths are created they can all use the same tool - any tool will work.
They all need to be in a waste area of the material.
When actually cutting the part, do the following steps.
Run the long line tool path with the first - largest - tool. This establishes the base depth for the rest of the cuts.
After changing to the second tool and zeroing it, run one of the short line tool paths - lets call it A.
Inspect the intersection. If the new tool is too high or too low, adjust the Z setting using the control panel.
If the original cut was to shallow, then you can run the A tool path again. If it was too deep, use the B tool path.
Inspect the new cut. Repeat as necessary until the bottoms of the cuts line up exactly. And repeat for each tool change.
The 15 toolpath picture shows 5 different tools with the first cut too deep, the next just right and the third too shallow.
The first tool is a 90 degree V bit - the same tool used to make the first long cut.
The second tool is a large ball nose bit. The third is a square end mill. The fourth is a 30 degree V bit.
And the last is a very small ball nose carving bit.
The Preview with 3 toolpaths shows the 90 degree V cut too deep on top, just right in the middle, and too shallow at the bottom.
If you load up the Aspire file, you can tilt the previews to see the differences more clearly.
The long cut is 1 mm deep. The bad cross cuts are only 0.1 mm different but the error is apparent.
I hope this is useful to others who take advantage of REST machining techniques.
I start with a 1/4" tool, then 1/8", then 1/16" and finally a 1/32".
All the tool paths smaller than 1/4" use the REST method to reduce machining time.
The detail is fine enough that it is really important to get the Z0 value for each tool to be the same.
I use the following method to achieve this.
Create a set of tool paths that are used just to calibrate the Z0 settings.
One tool path is a long profile cut in a straight line. The rest are short cuts across the first one.
When the tool paths are created they can all use the same tool - any tool will work.
They all need to be in a waste area of the material.
When actually cutting the part, do the following steps.
Run the long line tool path with the first - largest - tool. This establishes the base depth for the rest of the cuts.
After changing to the second tool and zeroing it, run one of the short line tool paths - lets call it A.
Inspect the intersection. If the new tool is too high or too low, adjust the Z setting using the control panel.
If the original cut was to shallow, then you can run the A tool path again. If it was too deep, use the B tool path.
Inspect the new cut. Repeat as necessary until the bottoms of the cuts line up exactly. And repeat for each tool change.
The 15 toolpath picture shows 5 different tools with the first cut too deep, the next just right and the third too shallow.
The first tool is a 90 degree V bit - the same tool used to make the first long cut.
The second tool is a large ball nose bit. The third is a square end mill. The fourth is a 30 degree V bit.
And the last is a very small ball nose carving bit.
The Preview with 3 toolpaths shows the 90 degree V cut too deep on top, just right in the middle, and too shallow at the bottom.
If you load up the Aspire file, you can tilt the previews to see the differences more clearly.
The long cut is 1 mm deep. The bad cross cuts are only 0.1 mm different but the error is apparent.
I hope this is useful to others who take advantage of REST machining techniques.