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Reverse Engineering [using FreeCAD]

Horologists at play ...

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Michael Gilligan20/10/2020 10:12:03
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16632 forum posts
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I am about half way through watching this video, and thought it worth sharing:

**LINK**

Already, I can see oddities in his process [and I don’t even have a copy of FreeCAD yet], but he’s doing a grand job !

Comments from the cognoscenti would be appreciated.

MichaelG.

blowlamp20/10/2020 11:33:46
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As a quick starting point, I'd measure the width and height of the part with my calipers and use those dimensions to make an accurate bounding box in my CAD system. That would help give access to hole centres and provide reference lines to work from.

Martin.

JasonB20/10/2020 11:37:47
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Sorry Michael, I gave up after a couple of mins with all that faffing about sizing the grid. In Alibre I just click on two points and enter a known distance, in this case just clicking on the ruler lines and entering 1mm sets the x scale. For Y as martin says a known measurement can also be entered .

rolex2.jpg

Michael Gilligan20/10/2020 11:53:14
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To give him his due ... I think he is trying to re-create a missing part, from someone else’s catalogue illustration.

MichaelG.

SillyOldDuffer20/10/2020 15:36:48
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I found it useful. As a tutorial it's unrehearsed, hence the grid fiddling and other mistooks, but in a way that's useful. A problem with many tutorials is they're too slick, so when the poor old beginner misses a small detail he comes off the rails and is confused. In this one, he makes and fixes a few common FreeCAD mistakes, which is valuable. For example, the need for all the lines to join before an object can be cut or extruded isn't obvious, and the driver has to look really closely at the joins.

Tracing parts is a valid technique, though in this case I'd use caliper measurements as Martin suggests. The important dimensions are the two hole diameters and their centres; everything else can be eyeballed to shape, which is probably how the original draughtsman did it. Tracing is useful for replicating more complex shapes though so worth knowing how it's done.

He misses a trick, perhaps deliberately. It's only necessary to draw one half of a symmetric part because sketches can be mirrored. Half the work, and they're guaranteed identical!

Later the video describes how to set up tool paths for CAM, which is a mystery to me. I shall watch that part again.

Dave

Edited By SillyOldDuffer on 20/10/2020 15:38:22

Michael Gilligan20/10/2020 17:18:56
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16632 forum posts
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Posted by SillyOldDuffer on 20/10/2020 15:36:48:

I found it useful. As a tutorial it's unrehearsed, hence the grid fiddling and other mistooks […]

He misses a trick, perhaps deliberately. It's only necessary to draw one half of a symmetric part because sketches can be mirrored. Half the work, and they're guaranteed identical!

Later the video describes how to set up tool paths for CAM, which is a mystery to me. I shall watch that part again.

Dave

.


I agree on all three counts, Dave

... The non-use of mirroring came as a shock; but I do like the ‘reality’ of it all, for the reasons you discuss.

Regarding the CAM side of things: That’s how I found the video ... it supports a series of articles, commencing issue 82, available here: **LINK**

https://www.bwcmg.org/timepiece

MichaelG.

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