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Stiffness and Deflection Testing on the LongMill MK2

The LongMill MK2 is an exceptionally rigid machine. By optimizing the design, we’re able to build and design a capable machine at an affordable price.

It seems rare for CNC companies to share this sort of data and testing, so it’s difficult for consumers to be able to compare apples to apples on different hobby CNC machines. Hopefully, this is a good start for our industry to work towards bringing better, more rigid machines to the market.

Based on our results, a LongMill experiencing regular cutting forces of 10N, which we’ve determined to be representative of a normal cutting load on a hobby CNC machine, we see that the total deflection is under 0.1mm on both the X and Y axis. Given that 0.1mm is roughly the thickness of a sheet of paper, users should expect a very high level of accuracy for their machines.

We created these tests to show users that even though the LongMill is substantially less expensive than other hobby CNC options, it still offers a highly competitive level of rigidity and that customers are not missing out on something just because we’re so affordable.


(Tested at 10N)X Axis DeflectionY Axis Deflection
48×30 Longmill MK22.8 thou / 0.072mm3.2 thou / 0.080mm
30×30 Longmill MK22.3 thou / 0.057mm3.0 thou / 0.076mm
12×30 Longmill MK21.9 thou / 0.049mm3.0 thou / 0.076mm

We also did an additional run at 25N, the results are as follows.

(Tested at 25N)X Axis DeflectionY Axis Deflection
48×30 Longmill MK214.2 thou / 0.361mm20.7 thou / 0.525mm
30×30 Longmill MK212.3 thou / 0.313mm18.5 thou / 0.470mm
12×30 Longmill MK213.0 thou / 0.330mm18.2 thou / 0.461mm

For the full report, including my commentary, please read the report below.

Raw data: