How to machine blade like this.

[slavkok]

Hello...

I looking for solution how to mill blade such this.
I have 3 axis CNC. So how to do that design on "basic" cnc.

How to make Gcode? (for now I use freeMill/visualMill). The blade is quite small up to 30cm (1') as this size windmill can be puted to windtunel for test.

And how to clamp it.... Until now I use double sided tape or screw direct to MDF top.

[christinandavid]

Suggest you remodel part to incorporate some level bosses around outer profile, through which you can locate and clamp component.

Orient component so that all areas can be machined in two set-ups. Rough each side, then finish each side using a simple plate for a fixture, with a couple of bolt holes and a couple of dowel holes to locate holes in bosses.

Remove bosses on the final operation, for which you could machine a 3D fixture and clamp to support the blade. Or, if acceptable, bandsaw them off and hand-dress the edges.

DP

[slavkok]

I'm not shure what you mean with level bosses. I suppose you meann some studs to support. I don't think that this can work. As the blade itself is realy thin (just few milimeters in the center of radius) I think the support should be bigger as few studs.

I'm thinking in the way I machine top side to finish and after that to just flip in some fixture (probably vacum) to hold and support until bot side is miled. Just isn't shure how to machine support to proper align work.

[christinandavid]

What's the material? Could you start with a rectangular block, stick dowel holes in opposing corners for location purposes, then Z-level machine the component from either side, but not quite all the way through...

This would leave the part encased in a thin wall of material to support it, which you can then cut away at the end - bit like an airfix model...

DP

[slavkok]

The stock is laminated wood. I intend to glue aprox 5mm thick pieces together. So the stock is aprox 5mm thicker on every place than needed. This cut down the roughting pass and laminated wood doesn't bend so much. The bottom side is flat.
For top side I intend just to doubletape the stock on machine. Seem's good idea to make Z offset so the bottom side is elevated 1 or 2 milimeters. And to model some pegs to help aligning the bottomside carving.

I have no clue how to fix so thin blade. I try the vacum but thin wood like this is just to much porous. Doesn't work..

[penot]

If you want to use vacuum for hold down thin (or thick) pieces, you could try to paint the bottom side with an air tight paint or lac

[RomanLini]

Carve side1 out of the sheet, then set it in block of hard wax, turn over and carve side 2.

The wax will support it, then when finished you just melt off the wax.

They do similar things in some rapid prototying machines. You can machine very thin structures then melt away the support later.

[slavkok]

I gonna try with scrap wood and small scale.

I'm just finished top side machining. So that's easy part. (side )
I don't want wax method. As wood is porous the wax removal is in question.

My plan is to route some fixture with "negative" of top side and try to use double sided tape to fix part. (this part was fixed with it.)

But now I got the problem.
How to route inverse of STL file (eg mould)?!?
The STL file is output from bladedesigner software. So here no cad is involved. The freemill is used to generate Gcode.

Is there some software to make moulds from (inversions) from STL files?

And there is result from some scrap wood.

[slavkok]

Well Here is completed blade.

It's done in three pass (routhing) process.
1. Machine one side of blade on blank anywhere in CNC table.
2. remove routed part.
3. Put next blank on CNCtable (anywhere)
4. Route negative image (mould) of same side of blade as already routed part is.
5. Doubletape glue routed blade to just routed mould. (do not remove mould from CNC as we need precise reference point)
6. Route other side of blade.

That's all....

As I find no tool to make "mould" negative I just write few lines in my blade design software to output just top sheel of blade in separate file. Even if sheel is invalid STL file the FreeMill and all other programs I try all opens it.

In foto below the ugly cut's are done by just jogging machine. As I cut mould I can't fit blade into mould as cutter radius leave to much material. So I remill all sharp edges where I have excess material by just jogging.

Slavko.

[eSilviu]

Well Here is completed blade.

It's done in three pass (routhing) process.
1. Machine one side of blade on blank anywhere in CNC table.
2. remove routed part.
3. Put next blank on CNCtable (anywhere)
4. Route negative image (mould) of same side of blade as already routed part is.
5. Doubletape glue routed blade to just routed mould. (do not remove mould from CNC as we need precise reference point)
6. Route other side of blade.

That's all....

As I find no tool to make "mould" negative I just write few lines in my blade design software to output just top sheel of blade in separate file. Even if sheel is invalid STL file the FreeMill and all other programs I try all opens it.

In foto below the ugly cut's are done by just jogging machine. As I cut mould I can't fit blade into mould as cutter radius leave to much material. So I remill all sharp edges where I have excess material by just jogging.

Slavko.

I had the same idea: mill the inverse image for the top face of the blade. You will support better the blade on the inverse image than on 2-3 points...