PDF's L-cheapo ignition

[awake]

Also very interesting.

Again, my only 3d experience is with FreeCAD. In that program, very often it is better / easier to sketch something without actually using dimensions. Here's a simple example. Let's say I want to put a hole in the center of the face of a rectangular part (by sketching a circle in the center of the rectangle, then pocketing it out). Rather than locating the center of the circle using X,Y dimensions, I just tell it to constrain the location to be equidistant from two opposing corners of the rectangle. Boom - the circle is centered, and I didn't have to remember the dimensions of the rectangle, divide them in half, etc. Later if I change the size of the rectangle, the circle re-centers itself, with no intervention on my part.

Now, when I make the drawings/plans, I don't want to show how I sketched it - yes, I could say, "put it equidistant between the corners," but what I'd rather do is have it show me how far the hole is from each edge - or maybe how far the hole is from some other feature of the overall part (maybe the rectangular face is only in one area of the part). No problem - FreeCAD will happily calculate any of that and produce the dimension(s) I need.

It may be that I am using FreeCAD all wrong ... though the sort of thing I describe above is what I learned and had reinforced from countless tutorials. But at least with how I am using it, most of the time, it would not be particularly useful to expose the build dimensions - how it is "built" in the CAD program is not at all how it will be built or machined in manufacturing.

How does the above compare to other programs? I hadn't thought it was at all unique to FreeCAD ... ??

 

[Charles Lamont]

In Onshape tutorials they refer to thinking about the sketch in the way you are doing as a matter of 'design intent'. Of course in doing the drawings you place dimensions (from datum features, and without redundancy ) as required to provide all the information the machinist needs.

 

[Mike Whittome]

Mind, the XLS files attached are the converted from XLSX some functionality may have been lost.
The files were made for my use only so some of the mental gymnastic may not appear obvious to someone else, as a matter of fact sometime I wonder myself "what was I trying to accomplish here?"
Accuracy is pursued only to the end of getting the part done, details that are obvious to me like for example the drill for a threaded hole or its depth are not displayed.

Why did we not all think of that - - - Brilliant

Mike.

 

[tornitore45]

When you draw in Excel, can you then take dimensions directly from the drawing, or vice-versa, have a dimension (say in a cell) adjust the drawing automatically?

NO NO, In Excel There is no relationship between graphic size and numerical dimension, is like sketching with pencil and paper you can dimension a square as a 20 x 2 and the program does not complain.

What I do I set the cell grid to look like small square and I say each square represents a 0.1" x 0.1" or whatever is appropriate then when I need to place a 1/2" circle I make sure that it occupy a 5x5 grid.
Sounds like a Mikey Mouse approach? YES.
I never said it was elegant, like a CAD, but as I said I am very good at and learned all the tricks to speed up the process and it works for me.

Of course if you change one dimension and all other are recalculated the graphic does not change and the graphic is no longer scaled correctly but all dimension are still consistent. Small changes are OK, large are not. But when you design a part you are fiddling with adjustment and compromises you are not changing shapes substantially.

 

[awake]

I thought that might be the case. But very often, I don't really need the drawing to change; I just need the dimensions to update so that I machine it correctly. Of course, in a 3d CAD program, it is hard to have one without the other!

 

[JohnBDownunder]

This recent discussion is interesting even if a side track off the original topic.
I get frustrated with some drawings / plans where you have to calculate from the given dimensions just what the missing dimension might be.
I have very limited experience messing with metal. A textile dyer most of my working life this making swarf is my hobby in retirement.

Oh, plus I work in metric so there is a lot of multiplication or division by 25.4 going on as I don't care whether dimensions are in imperial or metric. Thank goodness for the drill or thread conversion app on my phone when it comes to them there bits of the drawing tho.
John B

 

[awake]

This recent discussion is interesting even if a side track off the original topic.
...
Oh, plus I work in metric so there is a lot of multiplication or division by 25.4 going on as I don't care whether dimensions are in imperial or metric.

Oh yes - what was the original topic, again??

FWIW, my metalworking machines are all inch-based, but my 3d printer is metric-based, and much of the software I use defaults to metric. And when I am making my own designs, often I opt for a metric part (especially when it comes to bearings) because they are more cheaply available. So gradually this old dog has learned new tricks; I can't say that I am quite able to think in metric fully, but I have gotten very comfortable going back and forth freely. After all, at the end of the day, it's just a number on the DRO or dial.

 

[JohnBDownunder]

Not to worry awake,
I'm on my 79th orbit of the sun so grew up with imperial. Still look at 100mm, 150mm, 75mm and think 4", 6", and 3" respectively so I can get a rough mental image.
Really, as far as I am concerned we are aiming for a model (Hopefully one that works) and how we get there is half the fun. Specially when I mess up and learn stuff doing a work around rather than re-make the part. Of course sometimes I actually learn that it would have been easier to have just re-made the part. Oh well!

 

[tornitore45]

I spent my first 28 years in metric Italy, mechanical and electrical design occupy all my life, after a couple of years in the US I was equally comfortable with both system. The only thing that still slow me down is the fractional system ... what wrench is next size down from 5/32nd? I have to think 10/64 - 1/64

 

[awake]

Hah - I grew up with inches and as noted above, all my machines are inch based ... and I have to do the exact same thing to think of the next size down. Or just look to see which drill is next in the drill index!

 

[JohnBDownunder]

Spanners seem to be grab a few and try to me. I do try to avoid the universal spanner, AKA shifting wrench or crescent wrench is it over there?? Whatever you like to call it they are definitely a last resort unless you want rounded nuts or bolt heads.

 

[RonW]

Spanners seem to be grab a few and try to me. I do try to avoid the universal spanner, AKA shifting wrench or crescent wrench is it over there?? Whatever you like to call it they are definitely a last resort unless you want rounded nuts or bolt heads.

In Canada they're called Newfie verniers.
Ron W

 

[ron]

I spent my first 28 years in metric Italy, mechanical and electrical design occupy all my life, after a couple of years in the US I was equally comfortable with both system. The only thing that still slow me down is the fractional system ... what wrench is next size down from 5/32nd? I have to think 10/64 - 1/64

 

[JohnBDownunder]

Ron W,
Well that's another name I have never heard of, Should ask my model engineering club if anyone there knows what a Newfie Vernier is. Could be interesting.
Sometimes I get intrigued that we speak the English language and have so many variations in so called common items.
Still, as a whole English speakers will import and adapt any word from other languages that suit our purpose.

 

[johnlaudano]

Bluejets, I'd like to build a few of your circuits. Is there a supplier that can provide all of the components?

 

[tornitore45]

My go to supplier for electronic is digikey.com

 

[johnlaudano]

Thankyou