Another carved seat issue

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sbouloc
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Another carved seat issue

Post by sbouloc »

Hello all,

I finally started carving my seats, with some great help from rscrawford fixing the design issues.

The blank is 516 x 503 x 40 mm
I am only carving the seat and the nose on the CNC, the contour is done with regular woodworking tools. So I started the rough cut with a 0.25 straight uncut bit. So far so good. Then I changed to a 0.25 ball nose bit (https://www.amazon.com/gp/product/B0070 ... UTF8&psc=1) but the bit is too short. I thought it would be fine since I rough carved it, but the smoothing carve starts at a place when there's full height (see picture). It is trying to go full depth and the collet hits the top of the material. Any idea how I could fix this?

Thank you.
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martin54
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Re: Another carved seat issue

Post by martin54 »

Can you run the roughing cut with the same ball nose bit your using for the finishing cut since both are 1/4" ? I do this sometimes just use a different stepover for both, saves me having to tool change plus I can send both toolpaths as one file & machine just gets on & does the job :lol: :lol:

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Re: Another carved seat issue

Post by LittleGreyMan »

Martin,

I don't think it will change anything as the 2 tools have the same diameter. It's probably a machining allowance issue: the roughing tool can't simply reach the angle because there is not enough space for the diameter + allowance.

Can't be sure without the file.

sbouloc,
before cutting, analyse your toolpaths. Simply run a simulation (preview toolpath) and you will see this issue. You can then adjust your tooling or you design to avoid problems. Aspire simulation is very reliable and accurate.
Best regards

Didier

W7 - Aspire 8.517

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rscrawford
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Re: Another carved seat issue

Post by rscrawford »

If I have a 3D area where it will plunge too deep (around the edges of my seat) I'll make a 'border model' that sticks out from the seat 1/2" and is just lower than the seat model where the two meet. This keeps the bit from plunging down off the edge of the seat model.
Russell Crawford
http://www.cherryleaf-rustle.com

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Re: Another carved seat issue

Post by mtylerfl »

rscrawford wrote:If I have a 3D area where it will plunge too deep (around the edges of my seat) I'll make a 'border model' that sticks out from the seat 1/2" and is just lower than the seat model where the two meet. This keeps the bit from plunging down off the edge of the seat model.
+1 on that. Several of the Projects of the Month use that technique. I typically label those components as "Bit Stop" or "Bit Stop Plane"
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martin54
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Re: Another carved seat issue

Post by martin54 »

mtylerfl wrote:
rscrawford wrote:If I have a 3D area where it will plunge too deep (around the edges of my seat) I'll make a 'border model' that sticks out from the seat 1/2" and is just lower than the seat model where the two meet. This keeps the bit from plunging down off the edge of the seat model.
+1 on that. Several of the Projects of the Month use that technique. I typically label those components as "Bit Stop" or "Bit Stop Plane"
Can you share with us which projects they are Michael, not sure I fully understand Mr Crawfords explanation so would like to look into this a little further, hopefully all will become clear if I look at the project files :lol: :lol: :lol:

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Re: Another carved seat issue

Post by mtylerfl »

martin54 wrote:
mtylerfl wrote:
rscrawford wrote:If I have a 3D area where it will plunge too deep (around the edges of my seat) I'll make a 'border model' that sticks out from the seat 1/2" and is just lower than the seat model where the two meet. This keeps the bit from plunging down off the edge of the seat model.
+1 on that. Several of the Projects of the Month use that technique. I typically label those components as "Bit Stop" or "Bit Stop Plane"
Can you share with us which projects they are Michael, not sure I fully understand Mr Crawfords explanation so would like to look into this a little further, hopefully all will become clear if I look at the project files :lol: :lol: :lol:
Here's just a few recent projects off the top of my head that use merged planes as "stop planes"...

• Yummy Cake Pedestal

• Weathered Slat Clock

• Faceplant Planter

• Seahorse Corbels (I merged and baked the bit stop planes and individual components for public release - you can view it in the 3D preview, but not as separate components)
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sbouloc
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Re: Another carved seat issue

Post by sbouloc »

rscrawford wrote:If I have a 3D area where it will plunge too deep (around the edges of my seat) I'll make a 'border model' that sticks out from the seat 1/2" and is just lower than the seat model where the two meet. This keeps the bit from plunging down off the edge of the seat model.
Thanks for the feedback rscrawford. Sorry for the dumb question , but how do you achieve that? Zero plane?

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Re: Another carved seat issue

Post by LittleGreyMan »

LittleGreyMan wrote:Martin,

I don't think it will change anything as the 2 tools have the same diameter. It's probably a machining allowance issue: the roughing tool can't simply reach the angle because there is not enough space for the diameter + allowance.

Can't be sure without the file.

sbouloc,
before cutting, analyse your toolpaths. Simply run a simulation (preview toolpath) and you will see this issue. You can then adjust your tooling or you design to avoid problems. Aspire simulation is very reliable and accurate.
Discard this, I completely misread your posts.
Best regards

Didier

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Re: Another carved seat issue

Post by martin54 »

Thanks Michael, will have a look at those when I can find a bit of spare time :lol: :lol:

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Re: Another carved seat issue

Post by mtylerfl »

I think in some of the video tutorials the term "Limit Plane" is used. Same idea..."limits" or "stops" bit travel when and where required.

Yes, you can start with a Zero Plane and add thickness for some situations. Or, create an Offset vector and create your own custom shaped plane that extends beyond a model, as mentioned earlier.
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Re: Another carved seat issue

Post by rscrawford »

sbouloc wrote:
rscrawford wrote:If I have a 3D area where it will plunge too deep (around the edges of my seat) I'll make a 'border model' that sticks out from the seat 1/2" and is just lower than the seat model where the two meet. This keeps the bit from plunging down off the edge of the seat model.
Thanks for the feedback rscrawford. Sorry for the dumb question , but how do you achieve that? Zero plane?
I'll look and see if I still have your file and I can add a plane.

Basically, I follow the contour of the edge of the model, and just make another model 1/4" lower that sticks out from the original model (overlap the models and 'merge' them). It just gives something to stop the bit from plunging all the way down to the spoil board if it goes off the edge of the model (which is often possible with these 'pixelated' type models that Aspire uses - they are superior in many ways to NERBS based models, but inferior in other ways, particularly at the edge of your models).
Russell Crawford
http://www.cherryleaf-rustle.com

sbouloc
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Re: Another carved seat issue

Post by sbouloc »

Now I remember you put a zero plane on some previous carved seat you shared on the forum. I didn’t understand why you did that at that time. Thank you for helping me out again.

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