Surface

Surface takes the whole stock top down flat with a wide endmill. Use it to flatten your spoilboard, or to face a board before cutting it. It needs no selection: click Surface (ribbon, OPERATION), or right-click a part, New operation ▸ Surface. On the command line, chipload op add-surface part.chipload.

A new surface goes first in the active part, since it faces the stock before anything else is cut. It takes the project’s widest endmill and 0.5 mm off the top in one pass.

How it cuts

• Back and forth along the stock’s longer side, in straight passes one stepover apart. Half the passes climb, half are conventional: usual for a shallow facing pass, and about half the time of cutting one way only.
• Past the ends: each pass starts and ends beside the stock, the tool’s edge just clear of it, so the tool goes down in the air, never into the stock. No ramp or helix is needed. Between passes it moves across beside the stock, without lifting.
• Past the sides: the first and last passes reach past the stock’s long sides by a quarter of the tool, so the edges come out clean even when the stock is a little larger than entered.
• Depths: with a step down smaller than the end depth, each depth comes back the other way, going down beside the stock where the one before ended.
• Once: the stock is faced once, even when the part has copies.

The setup sheet says how far the tool runs past the stock’s ends (its radius): keep clamps and fences clear of that.

Settings

• End depth: how much comes off, from the stock top. At most the stock thickness.
• Step down: the deepest each pass goes. Usually the whole depth in one pass.
• Stepover: how far each pass moves across, as a fraction of the tool diameter, from 0.1 to 0.9. A new surface takes 0.75.
• Feed and plunge feed: the plunge feed is for the moves down beside the stock.

The other operations’ depths don’t change: they still count from the stock top as entered. Facing 0.5 mm off means their first 0.5 mm cuts air, which is safe. A surface placed after other operations of its part gets a warning: it would face what they already cut.

Flattening the spoilboard

1. Make a project whose stock is the spoilboard’s area, Z zero at its top (Stock and work zero).
2. Copy your surfacing bit into the project (Tool library).
3. Add a Surface, with 0.3 to 0.5 mm off: enough to take out the dips.
4. Export, zero Z on the spoilboard, and run it.

In the file

"type": "surface" in the project file. Lengths are in mm, feeds in mm/min.