Curved Sides flat Bottom large dish

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Barrie123
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Joined: Sun Oct 06, 2019 1:57 am
Model of CNC Machine: ELE1316

Curved Sides flat Bottom large dish

Post by Barrie123 »

Good afternoon
Is anyone able to assist with the program for cutting out a 1000 mm Long x 200 mm wide x 75 mm oval dish'
The requirement is to have a flat inside bottom 15mm thick
Curved sides down 60 mm, to the flat inside base.
See drawing attached
Cut out Board 02 01 2021.pdf
(9.94 KiB) Downloaded 107 times
This the first one of these projects that I have tried,
Still fairly new to CNC
Looking for some very much appreciated help
Thanks
Barrie

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adze_cnc
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Re: Curved Sides flat Bottom large dish

Post by adze_cnc »

I do modelling outside of VCarve (in my case) so I can’t really help there.

If you do model this in 3D you could get by with 3 toolpaths:
  1. pocket toolpath using the inner oval to get the 60mm deep flat area
  2. 3D roughing toolpath between the two ovals
  3. 3D finishing toolpath between the two ovals (if I was using beech as the wood then a 3/8” ball-end cutter with 0.025” step-over would give me a finish that would require little sanding)
As a variant this could be done without any 3D modelling using the previously mentioned pocket toolpath and two moulding toolpaths. See this “Salt box” post: viewtopic.php?p=232042#p232042 for a sample file.

Steven

4DThinker
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Re: Curved Sides flat Bottom large dish

Post by 4DThinker »

Looking at the provided vectors, the Moulding toolpath would be a challenge to use as the length of the inside curve varies around the flat bottom. You could get close using a circular array of vectors and the fluting toolpath. Pocket out the center to the 60mm depth. Set the moulding toolpath to o 60mm deep. All the vectors should run from the outside vector to the inside, but be offset inward 1/2 the diameter of the end mill used.
Long eliptical bowl 4D.jpg
4D

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adze_cnc
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Re: Curved Sides flat Bottom large dish

Post by adze_cnc »

4DThinker is quite right about the moulding toolpath. Viewing the PDF file on my iPad only showed the long sides and I was too lazy to zoom out to notice that the two ovals weren’t merely offsets of each other.

I like the fluting solution. One day I’ll have to explore that toolpath more fully.

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dealguy11
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Re: Curved Sides flat Bottom large dish

Post by dealguy11 »

You can model this with a 2-rail sweep. I've attached a file with the vectors but not the components as it gets very large with the required resolution.

1. When you set up the job, hold the "shift" key when clicking on "New". This will give you the option of creating the file with "Maximum" resolution, which is necessary because of the size of the bowl. Or just use the one I attached.
2. Create your 2 ovals. Also create the sweep vector. Remember it has to have a "leg" on one side. See attached file
3. Go into node editing mode and make sure the start point for both ovals is the same (the start point nodes will be green). If not then adjust one or the other as necessary
4. Open the two-rail sweep tool. Select your drive rails. I did the outside first, then the inside, but if that comes out backwards, you may have to do it the other way. Check the arrows on the rails to make sure they are going the same direction. If not, right click on one and change its direction
5. Select the sweep vector
6. Select "Sweep between spans" and "fill center of inner closed vector rails". Do NOT select "Scale cross section with width"
7. Choose the "Merge lowest points with previous components" combine mode (furthest to the right).
8. Click on "Apply". In the 3d view you should now have a bowl shape. If not, then go back to step 3 and select the rails the other way.
9. Click Model | Create Component | Add Zero Plane on the toolbar at top to create a zero plane
10. Go to the modeling tab, select the zero plane and move it to the bottom of the list
11. Double click on the zero plane to open component properties, and set the base height to 60 mm
12. In the Toolpaths tab, click on "Material setup" button. Set the Model Position in Material to the top of the material

At this point you have your model appropriately positioned in the material block. I would probably use a 2d pocketing toolpath to hog out the center, then use a 3d Roughing Toolpath with a z-level roughing strategy, followed by a 3d finishing toolpath with a large ballnose bit (like 1/2" or 12mm). The bits will need to be long enough so that the collet will not hit the side of the bowl while carving.
Attachments
bowl vectors.crv3d
(33.5 KiB) Downloaded 73 times
Steve Godding
D&S Artistic Woodworking http://www.dsartisticwood.com

Barrie123
Posts: 8
Joined: Sun Oct 06, 2019 1:57 am
Model of CNC Machine: ELE1316

Re: Curved Sides flat Bottom large dish

Post by Barrie123 »

adze_cnc wrote:
Sat Jan 02, 2021 8:55 am
I do modelling outside of VCarve (in my case) so I can’t really help there.

If you do model this in 3D you could get by with 3 toolpaths:
  1. pocket toolpath using the inner oval to get the 60mm deep flat area
  2. 3D roughing toolpath between the two ovals
  3. 3D finishing toolpath between the two ovals (if I was using beech as the wood then a 3/8” ball-end cutter with 0.025” step-over would give me a finish that would require little sanding)
As a variant this could be done without any 3D modelling using the previously mentioned pocket toolpath and two moulding toolpaths. See this “Salt box” post: viewtopic.php?p=232042#p232042 for a sample file.

Steven
Steven
Thank You, I will try to draw in 3D and see what comes using your suggestion
Regards
Barrie

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adze_cnc
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Re: Curved Sides flat Bottom large dish

Post by adze_cnc »

I had a better look at the PDF file. You do know that the height of the curved wall is only 45mm and not 60mm? If you want 60mm deep you’ll need to stretch the profile vertically.

I rethought the toolpathing strategy I’d use (I rarely cut bowl-like objects with flat bottoms). In the following I’ll presume the 45mm overall depth of cut for the flat area based on the vectros presented:
  1. 3D roughing toolpath using the outer oval as boundary using z-level roughing. I’d use a 90 degree angle so that the cut will be parallel to the gantry. This ensures that the gantry is not moving back and forth excessively. Plus cutting across the grain prevents running tearout.
  2. Preview this toolpath. Hover the cursor over the desired flat depth to figure out how deeply the roughing toolpath went. (Let’s pretend it’s 37mm)
  3. Pocket toolpath using inner oval as boundary. Start depth from #2 (37mm in my supposed case). Cut depth 8mm (45mm - 37mm again in my pretend case)
  4. 3D finishing toolpath between the two ovals.
My rationale for roughing out using only the outer oval is that doing a pocket toolpath first would remove material that the roughing toolpath could easily do. Also, by only roughing between the two ovals you might end up with a case near the bottom where it’s making these short little movements. This new way allows the machine to maintain a good speed as the cutting area decreases.

Steven

Barrie123
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Joined: Sun Oct 06, 2019 1:57 am
Model of CNC Machine: ELE1316

Re: Curved Sides flat Bottom large dish

Post by Barrie123 »

Well, with a lot of help and great info from the Vectric users I have finally completed the Curved Sides flat Bottom large dish
It finished 1030mm long, 230mm wide, 75mm high
Made from a single piece of French Oak an I used Osmo Oil for the Finish.
It was cut out with one router bit
120mm long, 12mm Shank, 75mm cutting side and a taper down to 4mm. I used a 10% stepover and a cutting speed of 14000RPM at 4.00 Meters a minute. Total machining time was 5.00 hours
Once again thanks for all the assistance
Curved Sides flat Bottom large dish.JPG

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