Automation Software and IMS in particular have done a lot to promote the idea that old machines are worth fixing up rather than replacing, however, there are always limits.

The first thing to consider is simple economics. It will rarely be true that it will be cost effective to do this kind of upgrade on a small machine. For example, including electronics, software, motors, drives, limit switches, wiring harness, etc., you are around $50K (minimum!). This is true regardless of size, because the incremental cost for bigger motors, larger gear boxes, more wire, etc. is minimal. Then recall that Sheffield's Discovery starts around $30K!

Also consider probe requirements. A manual CMM will have a manual probe. On a big DCC, if you will need to index your head, you really ought to get a motorized head. This will add an additional $25K or so.

Many CMMs were offered in both manual and DCC versions. If so, the OEM will have a slight advantage because all of the required hardware has already been engineered, and it is a matter of manufacture/assembly. A competitor or third party will have to do more or less engineering work, which will add to time and money, in addition to the manufacture/assembly. Some may not even be willing to do it.

Third parties are always risky - some will be around tomorrow, some won't. The best news - the odds are they'll be a whole lot easier to work with.

In my last job, I managed a project to upgrade a large manual Poli horizontal to DCC. I used a third party on my project - at that time, a lot of OEMs just weren't real active in this area. Fortunately, he had some links to Helmel, so his technology wasn't too far removed from the mainstream. Nevertheless, there was and is only one person in the world who can fix that machine! He still does the service as required, but otherwise, he's now out of the business.