Notes on rapid positions and wasteboard leveling

Wrote up a bit on this here:

Filled in the numbers for an XL — if someone has an SO3 or XXL and is using CM4, I’d be glad of confirmation of the other values for it there (they were made by halving the steps on my XL and configuring it to be an XXL and if you have an XL, a comparison to how things map on your machine would be welcome).

Based on the above, I created a wasteboard level program for the XL:

Updated file based on further numbers/commentary:

SO3_XL_810x350.c2d (19.5 KB)

(please verify before using — it would want adjustment for example if using the Carbide 3D T track setup)

I hope it’s obvious how the sizes and positioning of the C2D file are set up based on the numbers / measurements — if anyone needs any assistance, please let us know!


Finally taking the time to revisit this with other machine sizes.

For a Shapeoko 3 the rapid coordinate positions are (assuming one has set the origin at the SW rapid position point):

NW = 0, 350 N = 200, 350 NE = 400, 350
W = 0, 215 C = 200, 215 E = 400, 215
SW = 0,0 S = 200, 0 SE = 400, 0

which yields:

It is possible to move 5mm to the left along X on a Z-Plus machine, and 65mm towards the front of the machine, and the Southernmost Rapid Position Points are aligned ~3mm in front of the front edge of the MDF on a machine which was not calibrated for belt stretch.

From the NE position it is possible to move 9mm right and 9mm to the rear.

The rear edge of the front edge plate is ~10mm from that front edge, which is ~3.5mm thick and 722mm wide.

Drawing in that we get:

and we have a possible cutting area of 414 x 424mm:

(plus the diameter of the endmill used)

which is a bit more than 16.25" wide, and 16.625" deep (switching to Imperial 'cause it will make life a bit easier for me in cutting it out, and I figure the slight reduction will make any belt stretch issues easier to deal with).

Then, for reference we import a version of the SO3 wasteboard file so that we can see where all the hardware is relative to things:

(note that the origin is set at the SW rapid position point)

and lastly, draw up a mounting system for fixtures which @Luke suggested:

which then requires that the stock being cut for the middle layer threaded insert board be slightly extended:

(the previous dimensions will be used for the spoilboard)

In case anyone wants the file (updated per below): SO3_rapid_position.c2d (368.7 KB)

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A slight adjustment — we want the blank to be aligned against the front endplate, so we slightly increase its size and reposition it:

One further adjustment is we need a slot to allow the board to lay flat over the endplate.

Duplicate the rectangle which stands in for the endplate, and drag it into alignment with the original, set its width to match the stock being used, select it and the rectangle which stands for the stock and mirror it from top–bottom:

Assign a suitable toolpath to the rectangle and the 3 holes for the fixture which are at the front. (1.1 KB)

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Adjusted my X-axis homing switch to center the positioning as best I could and then cut by securing the stock with blue painters tape:

Next up is flipping it and then cutting the front two holes using the same technique.

Once done, flip and cut the actual front holes:

front holes (846 Bytes)

then drill holes and install threaded inserts to install. The two holes at front will require removing the MDF baseplate to drill them through and install threaded inserts from underneath.

Add features either by machining from the top while installed, or flipping back as was done for drilling the initial holes and machining the slot to machine things from underneath.

Install with M6 or 1/4-20 threaded inserts and hardware (flathead countersink machine screws would probably be easiest — need to get some):

@WillAdams On the standard Shapeoko 3 where is X0 Y0 actually located on the machine bed? If the dimension was taken from the front left hand corner of the machines waste board what would its X Y position be?

X0 Y0 would be wherever one would want them — in the diagrams above I positioned the origin at the SW rapid position point.

@WillAdams I’m not sure if I worded my previous question in the clearest manner, I’m interested in the location of the work area on the wasteboard, so if the right rear corner of the 400mm square work area was X0 Y0, what would that point be in relation to the front left corner of the wasteboard? I chose the front left corner as on the wasteboard print it is where the ordinate dimension zero is located.

I tried to draw in the boxes and describe them systematically — please try recreating them on your machine to see how things map to it.

Revisiting this using the Pro XXL I just received w/ Carbide Motion build 547 on a Raspberry Pi.

Default Travel Dimensions are:

  • X: 865
  • Y: 850
  • Z: 95

Installing a 1/4" probing pin and trying to configure the BitSetter results in this falling a bit short of being able to center on the BitSetter button, so we increase the Y-axis travel dimension to 860 (855 would probably suffice) so that we can configure this at the center of the button.

Initializing the machine with the new settings:

  • X: 865
  • Y: 860
  • Z: 95

and moving to the SW position and setting XY zero there results in the following positions:

NW = 0, 779 N = 422, 779 NE = 844, 779
W = 0, 429.5 C = 422, 429.5 E = 844, 429.5
SW = 0,0 S = 422, 0 SE = 844, 0

The machine is pretty much centered along the X-axis, but Grbl is not calibrated for belt stretch:

Since I have a pair of calipers which will measure a bit over 100mm, we draw up:

and add 3 circles:

to which we add drill toolpaths using a V endmill is is less acute than the tips of the calipers:

100mm calibration-bottomleftorigin.c2d (11.5 KB)

and we write out G-Code:

100mm (517 Bytes)

We cut the holes and do the math, and send the new values for $100 and $101, then re-cut the holes to verify — with the new holes both measuring at 99.99 we call it close enough.

Next, in CM move to the SW point and set XY origin there.

Then we load a drawing of the hybrid T-tracks:

Hybrid T-track slats - XXL.c2d (110.5 KB)

(it would be great if someone would measure the slats on a standard/XL size machine)

and simplify and rotate it and set the stock size to match the rapid position points:

Now we move the machine to determine the location of each MDF filler strip, and position copies of the MDF filler strip graphic appropriately — the easiest/most accurate way to do this is to put CM into machine coordinate position by clicking on “Position” which then shows the origin as being X -855, Y-780 (there are tiny decimals due to the calibration for belt stretch which we are ignoring)

We then probe for each MDF filler strip origin using a probing pin and a BitZero v1: X -811.26 Y -830.618 for the first one:

and we repeat for each and make a layer to put them on:

and make a layer for the rapid position points as well as the BitSetter:


For surfacing, here’s a zig-zag pattern for a #201 on a Pro XXL (should also work for an SO4):

surface_slat_pro_xxl_origin_front_left_0_001mm.c2d (12.2 KB)

v7 file:
surface_slat_pro_xxl_origin_front_left_0_001mm_v7.c2d (44 KB)

Just set the origin at the front left of each slat and run it — I mark each w/ a zig-zag pencil pattern, use a level to pick which one is lowest and start w/ that one for Z then I jog over and only change the X origin for each other slat. Repeat until all pencil marks are gone.

Would you mind sharing this file for the PRO XXL like you did with the SO3 earlier in the discussion? Thank you!

to be clear, I am asking for “Shapeoko Pro XXL T-track layout.c2d”. Thanks in advance!

My apologies, saw your message when I was away from the computer which had the file.

Shapeoko Pro XXL T-track layout.c2d (319.8 KB)

Please verify it against your machine — there will be minor variations based on homing switch placement/positioning, the setting for homing switch pull-off, &c.

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