Without getting into specific simultaneous and positional multi-axis machining techniques/strategies and efficient cutting tool utilization...
While I entirely agree that the practice (and benefits) of simultaneous 5 axis motion in many dental applications could be argued, I would have to disagree when this statement is applied to milling abutments.
During the development of our abutment machining strategies we found a wide range of cases that would require significant machining concessions on several abutment design characteristics commonly found "in the wild" that would significantly affect quality, machining and post-processing time; particularly when applied to both the emergence profile and the chamfer region.
More can be found in the "Abutments" section on the Gallery page of our website.
Relative to the "clean up line" previously mentioned:
Due to a common abutment design characteristics, simultaneous multi-axis motion is required to quickly and easily produce high-quality abutments in timely manner that require minimum hand finishing. Design characteristics include:
- Subgingiva under-cuts
- Margin-to-chamfer transitions containing concave regions
- Modeled retention grooves presenting "less than ideal" manufacturing conditions
- and more (can't give away the store ya know)
In these cases 4-axis simultaneous motion is a minimum requirement with 5-axis simultaneous motion being the best choice since it will greatly expand the range of designs that can be tackled easily.
Some examples of more "complex" abutment designs we handle easily with our solution are shown in a slide show on our website (if you can get through the first few frames):
https://www.axsysdental.com/Implants.html Of course effectiveness and quality of the product "as machined" depends on fixturing techniques, machine and CAM software capabilities. As with all manufacturing, many times there are trade-offs that dictate one approach over the other. Examples might include:
- Improved surface finish (less post-processing)
- Sharper Margins
- Less tool wear
- Tool breakage
- Speed
I agree that simultaneous 5-axis machining can be over-utilized and can frequently reduce the overall machining/manufacturing efficiency. However when applied to abutment manufacturing, the selective usage of simultaneous multi-axis motion can and will help to produce a superior product.
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