The same robot, three different accuracies: how Doosan's spec sheet moved under a fixed model name

A catalogue entry is a snapshot of what a manufacturer says today. Set the same page side by side with its own older versions and the snapshot turns into a record of how a company's confidence in its product changed. Doosan Robotics launched with four collaborative arms - M0609, M0617, M1013 and M1509 - shown together at Robot World in Seoul at the end of September 2017. All four are still on sale under exactly the same names. Their declared repeatability is not the same as it was. In October 2018 Doosan's own product cards gave every one of the four an identical figure: plus/minus 0.1 mm, whatever the arm's length. By 2020 the cards had split: 0.05 mm for the 900 mm M0609 and M1509 and for the 1300 mm M1013, 0.1 mm still for the 1700 mm M0617. Today the pages read 0.03 mm for both 900 mm models, 0.05 mm for the M1013 and 0.1 mm for the M0617. Read as a series, that is a threefold tightening on the short arms across eight years, and no change at all on the long one. It is also the origin of a pattern this catalogue described earlier: across Doosan's current twelve cobots, declared repeatability tracks reach and ignores payload. That rule was not there at the beginning. In 2017 the company published one number for the whole family; the fan-out by arm length appeared later, as the declarations were revised model by model. What the manufacturer does not do is explain why. The product pages carry no revision history, no note of a hardware change and no reference to a measurement standard. Three explanations fit the evidence equally well: the arms were physically improved, the test method changed, or Doosan simply grew confident enough in a mature product to publish a tighter figure. Nothing on the page distinguishes them. The practical lesson is for anyone comparing robots on paper. A specification sheet is dated even when it does not carry a date, and a model name is not a guarantee that the machine behind it - or the claim in front of it - has stayed put. This catalogue records the current figure as the specification and the older ones as history, and says which is which. The four M-SERIES arms now have profiles in wujec.ai.