Spoilboard for 3018 CNC Mill

This is a 3D printed 3-section spoilboard for a 3018 CNC mill, with threaded inserts for workpiece hold-downs.

Each of the three sections is identical, with six counterbored holes for M3 Allen head screws to clamp it to the machine bed. Top (and bottom) faces are printed at 2.5 mm thick allowing plenty of stock for milling the surface flat and square following installation. The top of the Allen head screws (with flat washers) is ~ 4 mm below the top surface before milling.

Milling my spoilboards required removing about 0.6 mm of stock from the highest spot, leaving almost 2 mm of top surface in the thinnest area after machining the plates flat.

There are nine shouldered pockets in the underside of each panel for M3 brass threaded inserts for workpiece hold-downs. Those install from the bottom before the boards are mounted to the mill bed. They don't require heat to set them; pull them in cold with a screw until they're shouldered. Twenty-seven hold-down holes for clamping workpieces should provide plenty of flexibility for most any operation.

I've included a file for T-nuts with a pocket for M3 hex nuts to hold the plates down. I used a prick punch to upset some of the plastic around the nuts to hold them tightly in the pocket without using glue. It makes installation easier if they don't fall out of the pockets while trying to install the screws.

M3 screws are smaller than typically found for 3018 mill hold-downs but they seemed plenty strong for machining the tops of the spoiilboard panels and should be OK for clamping items to be machined.

This is not a trivial print; each of the three sections requires about 45 meters of filament. Expect to use nearly half a spool of filament.

Installation Tip:

Place the six T-nuts for a panel in the slots in approximately the correct positions with a piece of M3 threaded rod sticking up from each. Place the panel over the threaded rods until all six are in the holes - it's a little tricky but so is trying to get the T-nuts precisely aligned to receive the cap screws without using the threaded rods. Holding the panel at a slight angle allows starting one threaded rod at a time until all six are through the plate.

Once a panel is down on the bed with the threaded rods protruding through it, carefully remove the rods one at a time, installing a flat washer and the cap screw in place of each before moving to the next. Don't tighten any until all six screws are installed.

Bill of Materials:

3D Printed Parts:

Spoilboard Plate (qty. 3)

T-Nut (qty. 18)

Hardware

M3 X 16 mm Allen head cap screws (qty. 18)

M3 flat washer (qty. 18)

M3 hex nut (qty. 18)

M3 Threaded brass insert - M3 X 3 X 5 mm (qty. 27)

https://www.amazon.com/gp/product/B07D683Q26/

Printing Notes:

PLA

0.3 mm nozzle

2.5 mm top & bottom

0.8 mm shells

16% infill