Reverse Engineering [using FreeCAD]

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.

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.

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 .

To give him his due ... I think he is trying to re-create a missing part, from someone else’s catalogue illustration.

MichaelG.

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

.

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.

Anyone learning Freecad may find this video helpful, other CAD users will find it of interest I'm sure.

**LINK**

Emgee

Most of the time if you're going to do something a bit goofy that isn't regular I've found a block much easier

A "bounding box" in post 2

Then carve out the bits you need

Drummond M series in progress

I always start with a block and remove volumes from it in a logical manner to create a machinable part. I have seen too many times parts with feature that cannot be machined, this is normally where a part has been built up using features. Working logically is always best using the knowledge of a Machining process you have, particularly if you are a beginner at machining.

Thanks, excellent tutorial on a complex shape. I found it very educational

I use a mix of methods, often for a fabricated part it is better to do it by drawing the individual bits that will make it up rather than starting with a block. This also allows you to think how you will fabricate it when in the workshop.

Starting with a block is often more suited to a part you are going to cut from solid. No real one way is right just use the e best method for the job in hand

On the first part Ady shows I would have set my intial "block" central so features could be mirrored rather than have it off set on one axis as it appears to be.

Edited By JasonB on 15/03/2023 13:49:22

I've had occasional issues with mirroring because everything has to be exactly right and I spotted small issues later on which may have been me or the software

So I prefer to be in control via sketches

If mirroring isn't a problem you can just put in a manual plane/axis