Sienci Labs LongMill MK2, Assembly Manual

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With the machine together and moving, it’s time to tune its movement before we attach it to its work surface.
Most of these tuning steps will be the same ones you’ll use when performing maintenance on your machine.
Like other CNCs, and especially for hobby-grade machines, parts need to exist that can cancel out cutting
inaccuracies by compensating for wear over time and the initial user assembly. For the LongMill these parts
are the v-wheels, eccentric nuts, and the anti-backlash nuts. We chose these parts because they’re commonly
available and easy to use once you become familiar with them. Let’s start with the v-wheels and eccentric nuts.
Recall that during assembly each steel gantry was fitted with one set of firmly bolted v-wheels and another set of
loosely attached wheels with eccentric nuts, these loosely bolted ones are the ones we’ll be returning to to finish
tightening them up. For the Y-axis these are the top v-wheels (pictured) and for the X-axis these are the bottom.
We’ll work on these one plate at a time.
Eccentric nuts are ‘eccentric’ or ‘off center’ nuts and this means that by turning them you can change the
gap between the v-wheels attached to them and the fixed v-wheels on the other side of the rail. We call this
‘tensioning’, a system where the wheels can clamp onto the rails enough to not move around loosely but still
create smooth motion. You can see below what it looks like when an eccentric nut is all the way open (largest gap
between wheels) and all the way closed (smallest gap between wheels) for both the Y and X-axes.
Y-gantry Open Y-gantry Closed
Tuning Movement