Y-rails bowing slightly as gantry moves

So I’ve started making measurements of my Shapeoko Pro to see what can be tweaked and modified to get better results. I’ve checked things like runout, and stepper intervals. My stepper intervals might be a bit off but they’re so close I think the error is in the noise of my measurements and my current capabilities of measuring. I do have some issues with runout but I have a VFD spindle on the way so I’m not particularly concerned with that right now.

One measurement that I’ve done so far that seems to be really off is how Y-rails bow as I slide the gantry across. The gantry seems to be pulling the Y-rails in and their position relative to the table where I have the indicator mounted will drifty by 0.1mm as the gantry moves closer. I’m not sure that this is actually causing any problems but it kind of shocked me that it was bowing by that much given all the other measurements I’ve made being well below 0.1mm, even my worst ever runout measurement was 0.08mm (I think the collet, bit, and router were clocked really bad there).

Is it normal to see this kind of bowing? Is there a screw that I can lossen and gently retighten to improve my shapeoko pro?

Could you send a photo showing how you’re doing this measurement in to support@carbide3d.com ?

Have you tried a test cut?

I’ve cut lots of stuff on it, the gantry moves fine and I get aesthetically fine results out of it. The Y-step seems fine.

I’ve just started to see what the accuracy of the machine is like. I have some materials coming that I want to do test pockets on later but everything has worked fine in wood so far. I’ve also cut aluminum and other materials that all worked out but nothing I could measure.

The general guideline is that the tool used for measuring should be one or preferably two orders of magnitude more accurate than the precision/accuracy to which you are trying to measure.

I have a flat steel wrench clamped down onto the hybrid table, and a Mitutoyo magnetic indicator holder held onto that. That’s holding a 0.01mm Mitutoyo indicator dial that has less than 10 um of error over its full 10mm range according to the certificate. I’ve used it to measure smal gauge blocks and it can correctly distinguish the larger of 1.005 and 1.007 mm gauge blocks as well. I trust my eyes to at least 0.005 mm with it but the markings on 0.01mm apart. This bowing measurement repeats very well I’ll also add.

I’ve uploaded pictures of my setup at 3 different gantry positions so that you can see that the y-rail is being pulled in closer as the gantry comes closer (this works at all positions not just this corner but corners let me move the gantry further and I see a bigger deflection than I do in the middle).



I’m sending this to support along with a video of me sliding it in real time.

BTW, I contacted support and they said this kind of deflection is inconsequential. I have yet to see a consequence so that checks out!

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