Z-depth variance along X-axis

Assembly questions and answers for the Shapeoko 3 CNC Mill
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jeybee
Posts: 2
Joined: Sun Jul 26, 2015 1:43 am

Z-depth variance along X-axis

Post by jeybee » Tue Jul 28, 2015 3:53 am

I've been putting together some calibration patterns (I don't know much about this so making it up - overlapping squares, concentric circles, parallel diagonals etc.) and it was clear I needed one for z-depth since on the few jobs I've run there's been obvious differences between the same Z value at different points on the X-axis.

For the test I did a variety of depths of lines so I could measure them with calipers.

For the deepest cut (0.3"):

x=0" y=0.304"
x=5" y=0.290"

So it's clear there's an issue, but I am not knowledgeable enough to know how to fix it. I'm guessing the problem is that the 2 y-bars are not parallel, but I have loosened them and tried to pull them as high as possible but it didn't make any obvious difference. Halp?

LTEPM
Posts: 271
Joined: Tue Jan 06, 2015 4:34 am
Location: no where near the end of the rainbow

Re: Z-depth variance along X-axis

Post by LTEPM » Tue Jul 28, 2015 4:52 am

Others have had to drill out the frame holes on the Y axis to adjust properly.

Tools I consider necessary for proper setup. NOTE: I consider this a tool and to achieve the desired precision certain tools will be required. I had all of this equipment on hand for my other machine setups.

Digital Calipers
dial Indicator
Machinists Square
Straightedge
1-2-3 blocks
Good tape Measure
Flashlight

First, use a straight edge to ensure your MDF base is flat side to side, front to back, corner to corner.
Use dial calipers to ensure Y rails are same height above MDF
use Machinists Square to ensure rails are perpendicular to MDF
Use same method for X-axis, use 1-2-3 blocks if necessary for digital caliper.
Use two 1-2-3 blocks on the base to ensure your spindle mount is parallel to the MDF base. I set the 1-2-3 blocks and jog Z axis until the mount rests on the 2 1-2-3 blocks.
Use dial caliper onZ Axis to check overall flatness of base.
Use the flashlight to shine behind the straight edge and square to check for gaps.
After rails are parallel and perpendicular, check frame for square. Square the frame corner to corner if necessary if your test cut is not square.

You'll need to determine which tolerances you can live with for the type of work you are performing, materials, and level of work you wish to produce.

jeybee
Posts: 2
Joined: Sun Jul 26, 2015 1:43 am

Re: Z-depth variance along X-axis

Post by jeybee » Wed Jul 29, 2015 1:03 am

Thanks @LTEPM, that's exactly the kind of detailed instructions I was hoping for! I'm going to gather a dial indicator and small machinist square and will report back on how much difference I make.

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