Ultimarc Mini-PAC Enclosure – Parametric Case with Wire Slots (OpenSCAD)

A clean, practical enclosure for the Ultimarc Mini-PAC USB arcade encoder, designed to protect the board inside an arcade cabinet, bartop or control panel while keeping every screw terminal easy to wire.

KEY FEATURES

- Two-part design: a base tray and a flat screw-on lid

- Full-length wire slots along both long sides, so wires from all 34 screw terminals (player 1 and player 2 rows) go straight in without threading through holes. The slots are open at the top, and the lid closes them off.

- Mini-USB cutout sized for the cable's overmold, not just the connector

- Small window in the lid above the status LED, so you can see the board is alive without opening the case

- Four standoffs that match the board's M3 corner holes, with 5 mm of clearance underneath for the through-hole solder joints

- Mounting ears on both short ends for 4 mm wood screws, to fix the case inside a cabinet

- Countersunk lid screws for a flush top

- Fully parametric OpenSCAD source included

DIMENSIONS

- Outer size: approx. 115 × 56 × 23.5 mm (144 mm long including mounting ears)

- Board size used in the default model: 94 × 50 mm, with M3 holes 3.75 mm from the short edge and 4.75 mm from the long edge

IMPORTANT – CHECK YOUR BOARD BEFORE PRINTING

Ultimarc has made several revisions of the Mini-PAC, and I could not find an official dimensional drawing. Please measure your own board with calipers and compare it to the values at the top of the .scad file before printing. If anything differs, change the parameters and export new STLs (see "Customizing" below).

Tip: print a quick test of just the floor with the four standoffs first, to check the hole positions before printing the full case.

HARDWARE NEEDED

- 8× M3 heat-set inserts (Ø4.0 mm hole, 5.7 mm long, e.g. Ruthex M3): 4 for the PCB, 4 for the lid

- 4× M3×6 cap screws: PCB to standoffs

- 4× M3×8 countersunk screws (DIN 965): lid

- 2× 4 mm wood screws: mounting ears (optional)

No inserts? Set use_inserts = false. The holes become 2.7 mm pilot holes, and M3 screws will cut their own thread in PLA or PETG.

PRINT SETTINGS

- Material: PLA or PETG (PETG recommended if the cabinet gets warm)

- Layer height: 0.2 mm

- Walls: 6 perimeters with a 0.4 mm nozzle (the walls are 2.4 mm thick)

- Infill: 20–30%

- Supports: none needed

- Orientation: print the base open side up. Print the lid flat with the countersunk side facing up.

ASSEMBLY

1. Press the heat-set inserts into the four PCB standoffs and the four corner bosses with a soldering iron (about 220 °C for PLA, 240 °C for PETG).

2. Place the Mini-PAC with the USB connector facing the USB cutout, and fix it with 4× M3×6.

3. Wire the buttons and joysticks. The wires drop into the side slots.

4. Plug in the USB cable through the end cutout.

5. Close the lid with 4× M3×8 countersunk screws.

6. Optionally, screw the case into your cabinet through the mounting ears.

CUSTOMIZING (OPENSCAD)

Open minipac_case.scad in OpenSCAD. All the important values are in the first sections of the file:

- pcb_l, pcb_w, pcb_t: board size and thickness

- hole_off_x, hole_off_y: mounting hole positions

- under_clear, top_clear: space below and above the board

- usb_y, usb_z, usb_open_w, usb_open_h: USB position and cutout size

- led_window, led_x, led_y: LED window on or off, and its position

- use_inserts: heat-set inserts or direct screw holes

- mount_ears: mounting ears on or off

- wall, floor_t, lid_t, gap: wall thickness and tolerances

To export, set part = "base" and render (F6), then export the STL. Repeat with part = "lid". Use part = "assembly" to preview everything together with a dummy PCB.

FILES

- minipac_base.stl: the base tray

- minipac_lid.stl: the lid

- minipac_case.scad: parametric source

Designed by De Ronde Engineering. Not affiliated with Ultimarc. "Mini-PAC" is used only to describe compatibility.

Feedback, remixes and photos of your build are very welcome!