Panel rail spacing error

[trontoby]

Prerequisites

• I have read FAQ
• I have searched existing issues (including closed ones)
• I use KiKit at least version 1.6.0 (older version are not supported)

KiKit version

1.6.0

KiCAD version

8.0.5

Operating system

Windows 11

Description

While panelising a design I usually use these frame settings as required by PCBWay:

type = railstb (top and bottom)
vspace = 1.6mm
width = 5mm

I would then expect that the space between the rail and the boards be 1.6mm. However, when looking over the panel I discovered that actual vertical spacing between the rail and the board was 1.601mm as shown.

The offset error is also observed within the .pos file for component placement.

This erroneous behaviour also appears with the frame type set to left and right rails, but does not appear when whole frame is selected. I have confirmed that an older revision of this board from October 2023 doesn't exhibit this error, I am unsure what version of KiKit was used at that time.

I am aware this is a wee bit pedantic, but whole metric number make brain happy :)

Steps to Reproduce

Kikit JSON preset:

{
    "layout": {
        "hspace": "1.6mm",
        "vspace": "1.6mm",
        "rows": "6",
        "cols": "4"
    },
    "tabs": {
        "type": "fixed"
    },
    "cuts": {
        "type": "mousebites",
        "drill": "0.55mm",
        "spacing": "0.9mm",
        "prolong": "0.9mm"
    },
    "framing": {
        "type": "railstb",
        "vspace": "1.6mm"
    },
    "tooling": {
        "type": "4hole",
        "hoffset": "2.5mm",
        "voffset": "2.5mm"
    },
    "fiducials": {
        "type": "3fid",
        "hoffset": "5mm",
        "voffset": "2.5mm",
        "opening": "1.7mm"
    },
    "text": {
        "type": "simple",
        "voffset": "2.5mm",
        "text": "RAZFL-244HMCF - LEVEL SHIFTER PCB R2.1 - 4 X 6 = 24"
    },
    "post": {
        "millradius": "0.8mm",
        "origin": "bl"
    }
}

Input board:
input_board.zip

Generated Panel:
panelised.zip

[yaqwsx]

No need to feel guilty about being pedantic. The board should be placed precisely, this is a bug in KiKit and I will look into it.