CAD question

[Your Old Dog]

This is a general question of common terminology used in CAD software of all types.

Lets say I have drawn a 10" long rectangle and bored several holes thru it of various sizes and spent 2 days doing so. Now I discover it needs to be 5" long with all the holes moved to there new relative positions and sizes. Do most CAD programs offer a feature to simply reduce the size to what I want?

I have searched all through ViaCad and have been unable to spot any commands in the search engine that might address the problem.


Am I stuck with redrawing everything?

[Evan]

The command is normally called "scale". Make sure the drawing is a Group and scale the entire group.

Example: scale x,y,z

scale .5,.5,.5 will scale to half size in each dimension

[moldmonkey]

I only know basic AutoCAD and I read it as you are making a half-size part and not scaling the drawing (which is a bad idea, scale in paper space. the model should 1:1) so:

there is a MOVE command to move the holes to a new location. If the holes sizes need to changed that can be done in the PROPERTIES box or with SCALE.

The rectangle can be reconfigured by picking the vertices's and moving them.. SCALE would result in a the width being changed by the same factor as the length.

There has to be a way to do it in your program. Being able to easily modify a drawing is one of the main points of CAD.

Edit: On rereading if everything is half-size then scale everything. Unusual scenario though. Usually th ehole sizes wouldn't be half.

[fdew]

In the 3D cad systems I am familiar with it depends on how you made the part.

If you knew that you might change the length then you would set up the holes to move with it. (Let's say you had 3 holes in it, equally spaced, if they were dimensioned at 2.5 in apart then they won't move until you move the dimension, If they were set at total length / 4 then they will follow the length.

Another example, let's say the whole pattern needs to be 1 in apart, and centered in the part. This center relationship is easy to set up and will stay no mater what you do to the length.

Worst case, you need to open each sketch and make a change, but you never start over in 3D CAD

My answers are based on SolidWorks but many programs are similar.

[Your Old Dog]

Okay, thanks for the help. I suspect Evan's suggestion is my best course in this case.

I have one more question. I frequently get a "curves not planar" error message. As an example, I just drew half the profile of a .5 x 1.5 pin or axel with straight lines. I included some square notches on the length near both ends. These were to be used for C clips once I made the drawing 3D by using the "lathe" tool. Instead of making my part for me I get the curves not planar message when I try to lathe the part. I don't understand what they mean by that and a search of their PDF instruction manual makes no mention of it "curves not planar"?

[John Stevenson]

All depends on the CAD system, some are more intuitive than others.
A decent 2D system can be more user friendly than some of the 3D modelling software packages that require you to jump thru hoops because everything is restrained to make it parametric, ie change one thing and the whole drawing updates.

I read the OP to read scale positions but leave holes the same.
My CAD program, a little known program called Fastcad, has the ability to use Boolean logic in selection.

You can select then futher select by and, or, not then further select by range



Then further by type



These commands can be nested up to 256 times if needed.

Circles and dimensions can be edited based on a specif size.



A very powerful package.

[Your Old Dog]

Thanks Evan! That was it.

Learning this type of software isn't too easy without some background in serious math. I don't understand many of the terms but it's been better then working crossword puzzles for me.

Now I'm hoping one of the files ViaCAD will export can be handled by a less expensive home use CNC machine. Anybody know if any of these export files are useful for the home hobbyist where CNC is concerned?


ViaCAD
DWG/DXF
IGES
STEP
ACIS SAT
EPS
CGM
FACET
VRML
RAW
FACT
BMP
STL
ADOBE ILLUSTRATOR
TEXT
Viewpoint Media


edited:
John, thanks for all the effort. You must have been posting while I was typing. Will any of the above export files work on the setup (home CNC) you have been developing?

[Evan]

DXF is the standard for converting to g-code.

[Stepside]

For CAM

Every CAM producct I have worked with will read .DXF for 2D work and .iges for 3D work.

If I understand your question about planar : It is telling you that your lines describing the notch/groove are not parallel. They should be parallel and if extended would pass through the axis of the shaft. If you could look straight at the end of the shaft, you should see only one line. If the bottom of the groove is flat, both lines describing the sides should be the same length and connected by the line describing the bottom profile.

[loose nut]

Another example, let's say the whole pattern needs to be 1 in apart, and centered in the part. This center relationship is easy to set up and will stay no mater what you do to the length.

.

This is true if you do the drawing right, using your mid line grips, could be called something else in a different program, to locate the hole to the center of the block BUT if you position the hole in the center of the block by drawing lines from one or more sides to find the center , these lines have a dimension that will not change in some instances (this is dependent on how each program works) and when you scale the block to it's new size the hole will not move because it's position is set by a dimension from the side (setting a center point of a circle by drawing a line 1" towards the center from the side of a 2" square, if you scale the square to 4" the hole will still be 1" from the side).

3D cad programs are frequently "associative" which means if two or more parts are linked associatively, if one dimension is changed the others are also changed to reflect this, if the parts are not linked then the other parts don't change. This associative ability can be turned on or off as necessary and will allow you to scale a part as a whole or selectively as you need.

Hard to explain without a demo.

[Your Old Dog]

Thanks again guys. Stepside, you hit it on the head. I redrew the part and made sure to follow the "on line" and "perpendicular" prompts and it worked just fine. I've been dealing with that error message forever not knowing exactly what they meant by it. This will help a lot.

Loosenut, I'll watch for that on subsequent drawings now that I know it's something I have to be carefull of.