Users often run into this situation, and unlike scan service providers, don’t have multiple scanner systems available in-house. The first option is to have the parts that don’t fit your scan system capabilities outsourced. Sometimes it is the fastest and most affordable option, especially if this is only an occasional event.
The next option is to look at the most flexible system you can afford. Whether you are considering arm-based, handheld, or fixed scan systems, purchase the model with the widest range feasible. Handheld scanners are often marketed as the most flexible. While this may be true for freedom of movement, the size limitations are determined by the design of the unit, and since this is a permanent feature, you would need to purchase additional models to expand capabilities.
One reason I use a fixed scan system so often, is that it offers the ability to scan a wide range of different part sizes, with one system. This is achieved by simply changing lens sets, and doing a quick automatic calibration. The system is now optimized for that particular part size, but can be quickly and easily changed to match the next part that comes in, without sacrificing accuracy. All without investing in separate scanners and software. The lens sets can also be purchased as needed, so you only purchase the components you actually need.