Thickness normalising before or after routing parts?

[Sgian Dubh]

Ive been making parts like these ...
Im working from rough sawn, and, sometimes the boards have quite a cup, so it requires thought to get the 18mm out of, say, a 1" board.
What do you think?

I'm struggling a bit to understand the problem. If you require material to finish at 18 mm and you're finding it difficult to get this out of rough sawn 1" (25 mm) stuff, I'd simply buy the next size up, i.e., 1-1/4" (32 mm) then face, edge and thickness the boards to 18 mm, rip to a width that suits the width of the part (plus some), and a length that suits a multiple of the parts including (plus some for the tool path between each part), and then place this on the CNC to cut out the requisite shapes. It looks like you could get somewhere between five and six lengthways on to a CNC platen that's 2440 mm long. I guess you could also lay three to five pieces widthways on to a 1220 mm wide CNC platen. So, at minimum, i.e., 5 pieces in length + 3 pieces in width you'd set up the machine to cut out 15 parts in one run of the programme. Once you've worked out how many pieces can be prepared and set out on to the spoil board it's just a case of having a means to put those blanks in the right place, turn on the vacuum, set the programme to leave locking tags to prevent the parts drifting as the cutter penetrates through to spoil board, zero the cutter and run the programme.

I guess the bit I'm struggling with is that you don't seem to be well set up to handle wood before you get it on to the CNC machine which is probably capable of knocking out multiples rapidly and efficiently. So, to fix the problem, there might be two solutions:

1. Buy some primary wood processing kit, i.e., a planer/thicknesser and bench saw, and maybe a chop saw, plus a means for extraction.
2. Sub-contract the basic machining to a woodworking business with tight specifications for the length, width and thickness of the basic blanks.

Above and beyond the bulleted points above you'd really need a means for final wood prepping and finishing, e.g., sanding kit such as a belt or drum sander and a random orbital sander, and the finish might be okay with a hand applied finish such as one of the oils, e.g., an Osmo product.

Of course, all of the above was written on the premise that you're getting orders for dozens or scores of these end panel things. If that's not the case and the orders are for five or ten pairs at a time then what I've written above probably isn't useful. Slainte.

 

[sploo]

This is along the lines of what i was thinking - rather than flattening the whole job, and removing more material than i need to, due to cupping etc, get the shape and THEN flatten, so as i get a flat surface but am able to maintain as much of the thickness as possible.

I have an axminster 106pt. Even with brand new blades, i always look at it as more of a roughing tool than a finishing one though. The trouble is, if it takes a scalp out of some bit of figured grain, its basically wrecked that job.

From what i see, drum sanders are more gentle, and less likely to write off a part in the blink of an eye?

A drum sander will be gentle, but they're not really suitable for reducing the thickness of a board.

What Jacob says about using concave surface down on a thicknesser (rather than putting the board over the top of a planer) is perfectly fine. Thin (bowed) boards might warp under pressure from the thicknesser rollers, but in your application you'll probably get away with it - especially with light passes.

Plus, taking light passes with a powered thicknesser should be OK on most grain; especially with sharp blades.

 

[TheTiddles]

Am, now I’m with you.

Design for your process. You have all the right tools to make them quick, for things like that I’d incorporate a feature that enabled you to hold the workpiece inside the cutting perimeter, like a few holes you can put some sub-flush screws in, then you can face and cut one side in one hit, having rouged the edge out on a bandsaw and thicknessed it down to within a mm or two beforehand. That’ll work well so long as your material isn’t on the move too much.

Aidan

 

[Jameshow]

I'd planer thicknesser first. Then CNC out.

You don't want to CNC and then PT only for the PT to mess up what you have CNC.

Just my 2 pence...

Cheers James