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Intermittent non-square issue

If you're having trouble with cuts that are non-square in the XY plane, this article details a known issue and workaround.

Intermittent non-square issue

 

A report has been received of an intermittent non-square XY cut in the field. Over a 2m x 1m area, diagonals were measured to have a 3mm delta on the diagonals of one cut, and negligible delta on the diagonals of another. We have examined this at HQ and diagnosed a potential cause for the error which lies in the physics of the square axis function.

Square axes function

Intent

The square axis  function drives the x beam against a hardstop of the machine. As the beam touches the square hardstop, the motors stall for a short period of time. This allows any discrepancy in the set of the beam to be evened out: a lagging motor would catch-up to the square deadstop point, before the motors get re-energised. The motors are then driven away from the deadstop simultaneously from the same hardstop position.

This function is only triggered once for each power cycle, and is included in the first homing procedure. Subsequent homing procedures do not include the square axis function.

Potential non-square case

On the approach it was witnessed that, during the stalling phase, the beam was bouncing away from the deadstop slightly. It is therefore feasible that the motors can re-energise in a sub-optimal configuration.

Immediate work-around

Firstly ensure that the wheels are set to yield as square a beam as possible under no load. See “How To Square the XY axes” here: https://www.yetitool.com/support/maintenance

On power cycling, the beam will auto-square.

The squareness of the beam can be checked against the legs using a set of vernier calipers.

Left side

Right side

If the beam is found to be insufficiently square, the squaring function can be repeated using a button in the settings screen:

 

(Note that normal homing, after the first homing sequence for the power cycle will not include a square axis function)

Mid-term fix

The “square axes” function will be re-analysed to improve the reliability on the first attempt. A new software version will be released which will include this fix.

Lizzie

Lizzie is the author of this solution

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Updated on Wed, 22 Jan 2020