Issues with Shapeoko Pro X-axis accuracy

[chrisCA (Christian Comtois)]

Hey guys,

I’m trying to problem-solve an issue I’ve been having with my Shapeoko Pro and looking for the communities feedback…read below for more context and my problem-solving attemps but the short n sweet question is: what kind of tolerance in the X-axis should I be expecting from Shapeoko Pro when cutting a pocket that is ~400mm in length?

I’m cutting a simple pocket in plywood using 3/16" bit that is 400mm x 6mm. After cutting the pocket, I measure it with a steel ruler and I’m reading 398mm in the X and just under 6mm in the Y. I don’t think my ruler is inaccurate and compared it to another one to be sure.
Is it reasonable for the Shapeoko to be 2mm under my required 400mm length…? I’m running the machine quite slow (~1000mm/min) and with 0.7mm D.O.C…I doubt this is aggressive to the point I’m skipping steps with these settings…

I don’t think my CAM is the problem either since I did the following test: milled two holes separated 395.225mm center-to-center by manually jogging the machine through Carbide Motion (and raising endmill out of way in between the 2 points). When you include the diameter of the bit, the extremities of the holes should be ~399.9875mm. I’m still reading ~398mm…

I also ran a .nc code from Fusion to machine what’s shown below. Vertical pockets cut first and then the long pocket. All pockets extremities line up exactly…all measuring ~398mm end-to-end…if I was skipping steps in the X, I would assume that the long pocket would be shorter than the extremities of the vertical pockets due to order of operations.

Is any of this normal or is there maybe a problem with the motor calibration of my system???

Thanks in advance,
Chris

[WillAdams (William Adams (Carbide 3D))]

Have you calibrated for belt stretch?

Calibrating the machines over long distances

The typical technique for machine calibration: https://my.carbide3d.com/faq/belt-stretch/ depends on precision measuring tools, and is limited by the reach of the tools in question. EDIT: It also depends on access to the MDI — if using Carbide Motion v6 it will be necessary to enable this in Settings | Options: [image] It should be possible to cut strips from a suitable blank of material, one along each axis — so we set up a square file which matches an available blank of material: [ima…

Is your machine mechanically sound? Per the machine operating checklist: Machine operating checklist , the basic points of adjustment for a machine are:

• Pulley set screws — verify that these are in-place and secure — for further details on checking them on a Shapeoko 3 see: http://docs.carbide3d.com/shapeoko-faq/shapeoko-3-how-to-check-the-pulley-set-screws/ — be sure to check all axes/pulleys (including Z on machines w/ belt-drive Z-axis, for an HDZ, check both coupler screws).

• (for the SO3/4, X- and Y-axes) V wheels / eccentric nuts: Tightening Eccentric Nuts - Carbide 3D

• (for the Pro, and SO4 Z-axis) Lubrication of the linear rails: Getting Started with Carbide Machines

• Belt tension (see the relevant step in your instruction manual, e.g., Getting Started with Carbide Machines) Note that the X-axis motor is held in place on standoffs and if those bolts are loose this can cause belt tension issues. Also, belt tension for the Y-axis stepper motors needs to be even/equivalent on each side — a significant difference can cause skipping on one side eventually resulting in lost steps on both. Measuring belt tension, squaring and calibration

A good video overview on setup:

Shapeoko 3 Squaring, Tramming, and Calibration Essentials - #159

Ensure that all screws are in place and secure, esp. on the linear rails on a Pro.

[chrisCA (Christian Comtois)]

@WillAdams I did not realize we needed to do X/Y calibration. I could be wrong but I don’t think the build manual mentioned anything about that…would be good to add this since the build isn’t complete until it is calibrated IMO…!
I went down a rabbit hole of videos talking about the subject so thanks for bringing it up. Haven’t fixed it yet but I believe I know how to. Will reply again if something doesn’t work out.

Thanks!
Chris