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TOPIC: Geometry and Kinematics of Guided-Rod Sharpeners

Geometry and Kinematics of Guided-Rod Sharpeners 7 months 3 weeks ago #15880

  • AnthonyYan
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Hi Clay, Everyone,

More experiments with a CCD flatbed scanner (Epson V33). All of the images were scanned at 600dpi, and are un-edited except for being resized to 800 pixels for their long dimension. Using "adjust curves" one could have improved the contrast if needed. A clear transparency sheet was used to protect the glass platen.

Learn something every day: I was wrong about flat-bed scanners having absolutely no perspective effects! :ohmy: See below for details.


First I scanned a bunch of knives at once, hoping to save time. Cardboard background didn't work so well. Top to bottom, the knives are a Victorinox Pioneer Pruner (Silver), Spyderco Dragonfly Salt, Leatherman Wave, Kershaw Cryo, and a Spyderco Paramilitary 2 in M390.



Next, I tried the same thing with white graph paper as the background. Pretty reasonable, very usable, although the Swiss Army Knife is a bit dark.



At this point, I noticed something odd about the scan of the Blue Paramilitary 2: It is not a pure side view of the knife! You can actually see the top of the knife. So I tried scanning just Blue PM2 at several different positions in my scanner.


I'm using my flatbed scanner in "landscape" layout, and the scanner head is a vertical line that moves from right to left.


First, bottom of the landscape. You can see the top of the knife.



Next, mid way between top and bottom of the landscape. Looks good! Pretty much a dead-on side view.



Top of the landscape. You can see the bottom of the knife.



That was pretty interesting, so I tried the same thing going from the right to the left of the landscape.


Right side of the landscape. Looks normal for the most part.



Mid way between left and right of the landscape. Looks normal.



Left side of the landscape. Looks normal.



Conclusion:

In landscape mode, my particular scanner (Epson V33), has perspective effects going from top to bottom, but no perspective effects going from left to right. Pretty interesting!

So I think the moral of the story is:
For flat bed scanners, place your knife in the middle of the platen.

That being said, the distortion is probably too tiny to matter when we use a flatbed scanner. I suppose if you were absolutely crazy, you could scan a bunch of identical cubes (say 5mm per side) which were distributed over the entire platen, and then compare their images to measure the distortion. Personally, I'm too lazy to do that! So I'll just scan in the middle of the platen.

If any of you test your scanner, let us know how it went.
Last Edit: 7 months 3 weeks ago by AnthonyYan.
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Geometry and Kinematics of Guided-Rod Sharpeners 7 months 3 weeks ago #15881

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I am really enjoying this thread..... learning a lot but not too much to offer by way of help, but.....

The other night I was watching a gun review show on the Outdoor channel. Talking about a holster manufacturer, they showed how a holster for a new gun was introduced.

First, the gun is run through a 3D scanner.

Second, a sample holster is printed that fits it near-perfectly.

Third, minor adjustments made.

Fourth, production.

~~~~

Then, I thought about this thread. Scan a knife in 3D and then the program could perform near perfect calculations and placement, right?

I don't have a 3D scanner.

So, I was wondering if there are already 3D scans of many of the most popular knives?

I found this website: www.turbosquid.com/3d-models/global-knives-max/728173

The page refers to a 3D rendering of some Global knives.

So, there must be many sites that already have 3D knife files. Here's another one: grabcad.com/library?per_page=20&query=knife.

With 3D files already in a standardized format, can you import the dimensional data from those type of files?

~~~~

Perhaps, eventually, the Wicked Edge knife database will have programmatic elements on file about the knife so we can download the knife's precise settings!

Or, the program could be used centrally and the precise correct settings for any knife could be authenticated, approved and then published.

Sounds cool. Very, very, cool....
~~~~

For Now,

Gib

Φ

"Things work out best for those who make the best out of the way things work out."

"My goal is to be a good, practical knife sharpener. My dream is to polish molecules."
Last Edit: 7 months 3 weeks ago by GibCurry.
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Geometry and Kinematics of Guided-Rod Sharpeners 7 months 3 weeks ago #15882

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Wow, neat! :) Thanks for your post.

I don't have access to a 3d scanner, but that's a great idea.

It's certainly possible to import the data from 3d CAD files directly.

It's also possible to just take the 3d CAD file and use it indirectly: You could use computer graphics to render an orthographic side view of the knife. For example, you could have a white background and the knife silhouette is black. This image then could be easily traced either by hand, or by software.
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Geometry and Kinematics of Guided-Rod Sharpeners 7 months 3 weeks ago #15883

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You guys must have much better scanners than I .
I took one scan of my Edcs
Scan.jpeg


_MG_8232copy.jpg

with my HP then I took a photo using a Canon 50d with an EF 50mm lens.
I have to say the scan pictures were a waste of time clearly my scanner is no good
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Geometry and Kinematics of Guided-Rod Sharpeners 7 months 3 weeks ago #15884

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Gib,

That's great, thank you! We use 3D knives all the time in our renderings but we have to draw them ourselves and it's very time consuming. Having access to 3D files of some nice knives is great.
--Clay Allison
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Geometry and Kinematics of Guided-Rod Sharpeners 7 months 3 weeks ago #15885

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Messing around with a couple of cameras here. Knife is Spyderco Manix 2

length overall 8 " (203 mm)
blade length 3.375 " (86 mm)
blade steel CTS-BD30p
length closed 4.625 " (117 mm)
cutting edge 2.875 " (73 mm) weight 5 oz. (143 g)
blade thickness 0.125 " (3 mm) handle material G-10

First the Canon:

Spyderco---Canon-1.jpg


Spyderco---Canon-2.jpg
--Clay Allison
Last Edit: 7 months 3 weeks ago by wickededge.
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Geometry and Kinematics of Guided-Rod Sharpeners 7 months 3 weeks ago #15886

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Next the Sony:

Spyderco---Sony-1.jpg


Spyderco---Sony-2.jpg
--Clay Allison
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Geometry and Kinematics of Guided-Rod Sharpeners 7 months 3 weeks ago #15887

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Clay, those photos look great! :)
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Geometry and Kinematics of Guided-Rod Sharpeners 7 months 3 weeks ago #15889

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Here's one from my scanner. I just can't get any clarity from it:

Spyderco---HP2.jpg
--Clay Allison
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Geometry and Kinematics of Guided-Rod Sharpeners 7 months 3 weeks ago #15890

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Hi LeoBarr, Clay,

Wow, those flatbed scans of each of yours didn't come out very well. I see what you mean. btw, LeoBarr, nice camera!

Hmm... My guess is that your scanners use CIS sensors? That might explain the blurriness for everything not touching the glass.

Sincerely,
--Anthony
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