Need advise on CNC production.

[JONEK]

Good day.

I have a design that I need produced but I am clueless to the production side using CNC. I need to sort out how to produce this at high volume. I may begin with about 50 to 100 pieces. however, if the design proves itself for further production, I may need several thousand.

Firstly, I have no idea what CNC process to use - 4-axis / 5-axis? I designed the wood piece in Fusion 360.

Also, I should add that I am wanting to use solid wood - preferable birch - at 6.5mm thick.

As you can from the layout, there is the general shape - but with the additional drill holes that need to be accurate.

Would love some advice!

Jon

 

[deema]

First off, wood isn’t going to enable you to machine to those dimensions, I appreciate you haven’t given any tolerances, but assuming you really need position and hole diameter to be specified down to 10 microns I’m assuming a suitably tight tolerance are also required.

 

[Kayen]

I'm not quite sure what you're asking for exactly - do you have a CNC, or are you intending to buy one?

If you haven't already got a CNC I would suggest outsourcing the manufacture - off the top of my head I would have thought a fiver each, which is a lot less of an investment than the £2000 minimum for a small but accurate CNC.

Why solid Birch? I don't think it's as readily available as other woods like Ash (strong and stable) or maple (hard and light).

I don't know what tolerances you're working to, but 89.94 could be 90.27 the next day!

 

[ChaiLatte]

Is the hole in the top face supposed to be central?

It is dimensioned 11.09mm in one view and the overall width is given as 22.33mm.

 

[--Tom--]

Would be easier laser cut but you’d get a burnt finish. If you need those exact measures I imagine most places would decline.
What’s it for out of interest?

 

[Ollie78]

You could do this on a cnc but as said above it won`t stay that accurate because its wood.

Looking at it I would be inclined to use the cnc to cut the outer shape out with a spiral compression bit then make up an accurate jig for the pillar drill to do the holes.
The reason being the holes and chamfers will require tool changes and 2 fixtures because of the hole on the end.

On a "normal" 3 axis machine this job would need 4 different setups.
1: outer cutout and hole on top side, chamfer first then cutout and hole so one bit change.
2: hole on side 1, chamfer then hole
3: hole on side 2, chamfer then hole
4: hole on the end, chamfer then hole.

There is often more time setting up the job than running it. To cut out the outer shape would probably only take one minute each to actually machine. I would likely do the chamfer first then the cutout.
Also they wont be perfect out of the machine because of the direction of the grain on the rounded parts, even if you do a final pass in the opposite direction you will probably have to sand it a bit.

 

[JONEK]

I'm not quite sure what you're asking for exactly - do you have a CNC, or are you intending to buy one?

If you haven't already got a CNC I would suggest outsourcing the manufacture - off the top of my head I would have thought a fiver each, which is a lot less of an investment than the £2000 minimum for a small but accurate CNC.

Why solid Birch? I don't think it's as readily available as other woods like Ash (strong and stable) or maple (hard and light).

I don't know what tolerances you're working to, but 89.94 could be 90.27 the next day!

i don't have a CNC - and so yes - i would be interested in outsourcing. i am in iceland so i have to take that into account - shipping and import fee costs.

if you have any recommendations that would be great appreciated.

birch is native and quite common here in iceland and is revered culturally.

this will be part of a tool that will go into mass production - so outsourcing for accurate tolerances is preferred.

 

[JONEK]

Is the hole in the top face supposed to be central?

It is dimensioned 11.09mm in one view and the overall width is given as 22.33mm.

ha yes - sorry. the dims are not completely accurate in this DWG. i was having issues with fusion 360 with the layout - so i exported as vector and dimensioned elsewhere.

though they don't show accurate in this drawing - i was more wanting to capture the scale and detail. the original design is accurate.

 

[JONEK]

Would be easier laser cut but you’d get a burnt finish. If you need those exact measures I imagine most places would decline.
What’s it for out of interest?

it will part of a hand tool design.

 

[JONEK]

maybe i ought to consid

I'm not quite sure what you're asking for exactly - do you have a CNC, or are you intending to buy one?

If you haven't already got a CNC I would suggest outsourcing the manufacture - off the top of my head I would have thought a fiver each, which is a lot less of an investment than the £2000 minimum for a small but accurate CNC.

Why solid Birch? I don't think it's as readily available as other woods like Ash (strong and stable) or maple (hard and light).

I don't know what tolerances you're working to, but 89.94 could be 90.27 the next day!

maybe i ought to consider another wood though. would ash prove to be a better species for this design then?

 

[--Tom--]

maybe i ought to consid

maybe i ought to consider another wood though. would ash prove to be a better species for this design then?

If your outsourcing is go with what they recommend/can get to work/is available from a supplier in sizes close to your required dimensions. Sheet goods are often used as judging a whole sheet on a machine bed gives you one set up for all the pieces you can get from an 8x4. Small pieces massively increases the setups and costs for larger runs- and is going to impact viability. More of a consideration for the thousands than the handful of prototypes though

 

[deema]

I’d suggest you go back and review the design. You’ve designed a very expensive part to make irrespective of the material used. So, assuming tge hole pockets are to clip something to it, review the design to make them into pockets. This would allow them to be machines from the top requiring only one clamping. Take a good look at your dimensions, and consider creating a design that allows the largest tolerances and simplify the actual values. A dimension that’s say +/-1 mm is far easier and quicker to produce and check than one that is +/-0,01. Lastly consider tge material and its dimensional stability. Wood cannot be machines to 0,01mm and to remain to that tolerance. So, if you’re looking for mass production and not one offs, I can state with absolute confidence your design will fail as it’s presently conceived. The old rule of thumb was that a change on paper cost X, every step towards full production that was taken and a change was needed would cost between 10x and 100x. So you could have design, prototype, testing, revised prototype, revised testing, ore production and production, each stage with a 10~100X multiplier to make a change.

 

[ChaiLatte]

Sheet goods are often used...

As his finished item is solid wood, what sheet good would provide this specification?

Can you provide a link to an 8' x 4' sheet of solid anything that is 6.5mm thick?

You are absolutely correct in the general thrust of your question. At some point in its past, that finished item would have been a tree standing in a forest. How it gets from tree to sitting on the bed of a CNC router will be an important factor in the overall cost.

Should we also consider the knotty (?) question of grain orientation in the piece?

 

[Ollie78]

maybe i ought to consid

maybe i ought to consider another wood though. would ash prove to be a better species for this design then?

No issue with Birch specifically, it is a nice wood. Perhaps birch ply would be good for reasons of stability and ease of machining big sheet at once.
The production using boards of solid wood would involve making up a bunch of specific sized blanks which is another process.
Each process adds cost.

My other observation would be that the thickness of the board is 6.5mm and the holes on the side are 4.1mm there is a very small amount of material above and below the hole. If this part of the design requires any strength whatsoever you are asking a lot of just over 1mm of wood.