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Constrained Geometry - Coordinate System Error
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* March 12, 2010, 03:47:39 AM
Hi all

I've got a problem with using constrained geometry which I just can't figure out. I was hoping someone could maybe shed some light on this situation for me. here's the details.

I have created the attached file, which I have been using to generate a cutting guide for folding corrugate cardboard boxes of varying dimensions. If you open the file up and have a look in the calculator panel, you'll see that there are L, W, H and BoardThick constrained dimensions. The idea being that if you type in the relevant internal dimensions of the box you want, and the thickness of the board, then Turbocad will draw a box with the panels dimensioned appropriately.

To quickly explain how the file works, there is an invisible layer named 'backing' which contains a centre line and all of the contrained boxes, which are aligned symetrically around the centre. These boxes change dimensions as different values are typed into the calculator panel. On layer 0 are a series of black and red lines (to Illustrate cuts and folds) which are aligned to the boxes on the hidden layer. As such, when you enter values into the calculator panel the hidden boxes are resized, and the visible lines (which make up what I actually want to print out) snap to them, giving you a perfect box cutter.

The file, although a little complex, does actually work pretty well, however i wanted to edit it in order to add four slots into the base panel (2 per side) rather than the current two slots. However, every time I draw a new box or line and try constrain it to the existing geometry I'm given the error message 'Invalid operation: Selected entities have different coordinate system'

As far as I can tell there are no differences between any of the coordinate systems so Im at a loss of what to do! Ive checked all of the properties and I cant see anything that is different between the two components. Im completely stumped! Does anyone have any ideas about what I might be doing wrong?


 - Martin


* March 12, 2010, 09:20:08 AM
That's gotta be the most sophisticated example of a constrained drawing I have ever seen.

Your problem might be Workplane-related. I made all layers visible in your drawing, set the current Workplane to "World," and applied Format|Place on Workplane. After that, I added an arbitrarily placed fully constrained rectangle to the drawing and applied constrained size and locating dimensions. I encountered no error messages; and editing those dimensions in the Calculator palette does update the drawing accordingly. (It is not at all unlikely, however, that I either have not fully understood your problem or have not really addressed it.)

Henry H


* March 16, 2010, 01:49:54 AM
Hi Henry

Thanks very much for your response to my question and for looking into it for me. Usually when I encounter problems like this it generally is workplane related, however by pure chance I managed to find out what was going wrong this weekend. I have no idea what the problem is, or why this fixes it but it works. Here's the answer:

When I drew all of the constrained boxes they were drawn around a vertical centre line which was placed in a random position on the page. Each new box was then drawn and constrained to this centre line. Once I was happy with the drawing, I selected everything I had drawn and moved it to (0,0,0) so everything was in a nice location inside the drawing. I did this by typing the co-ords 0,0,0 into the boxes at the bottom of the screen. When I draw a new box and try constrain it to the existing drawing I get the error message, however, if I draw a new box, move its position by typing new co-ords into the box at the bottom, and then apply the constraints, it works!

As I said, I have no idea why this works, but it does. Is this somehow related to TurboCad changing the co-ordinate system of objects when you position them manually? I dont know!

Anyway, thanks for looking into my problem for me. Not sure if what I've found will be of any help to anyone else but I hope so!