Length error : sum of sub-elements larger than the "total length"


#1

Hi There,
I’m new with Sketchup and the 1st issue I face is that drawing a rectangle of 15 mm length, dividing it in several elements the total length obtained by adding up the elements is 15.1 mm.
I am not sure where the problem is coming from & any suggestion would be appreciated.

Best

PS: I could not see how to upload a file but in case the drawing can be of any use it can be access with the following dropbox link


#2

That’s not unusual when you have Precision set as coarse as you do. Increase the precision (and disable length snapping while you’re at it) and you should find the numbers come in much closer.

Window>Model Info>Units

Having the SKP file was a big help in identifying your problem. You can use the Upload button–7th from the left in the row of buttons immediate above the window where you typed your message.


#3

Hi Dave,
Thanks for the tip. Unsnapping and 0.000 mm does work better.
10^-3 is a bit extreme especially as the minimum step I could reach is 0.03 mm. Not sure how/if it can be adressed but that should do for the time being.
Thanks again & Best Wishes
PAscal


#4

I only chose the highest precision to show you it’s possible and to show you how far out your dimensions are. You can choose what is appropriate for your application although I think it’s generally better to work in SketchUp at higher precision than you will use in the real world. One reason is exactly what you showed in your file.

the fact that the dimensions between lines are close to but not on any reasonable dimensions makes me wonder how you went about placing them. Even with precision set as coarse as you had it, there’s no reason you have to have those errors when setting out the lines except if you were just eyeballing their placement.


#5

Many thanks again, I restarted the drawing from scratch with a 10 times higher precision compared to what is needed in the real world… it ran all smoothly and at the next design step I realised I should definitely get this higher than reality precision as a reflex… Thanks for the trick.


#6

You’re welcome.

Most of my projects are done in fractional imperial units. I have the default precision set to 1/64" in my template. I would never intentional make dimensions with 64ths as the fraction’s denominator but it is a good troubleshooting tool. One quick way I use it is to run a cutlist from the model and examine the dimensions. If I see 64ths or ~ with any dimension, it raises a red flag for me to inspect for errors. I rarely have problems with my own models and when it happens, it’s more likely due to a part that is angled in the model. I use the same process on models from others, too. I tend to find many more issues


#7

I would add that when I encounter this sort of problem in my models it is almost without exception because I sized or moved something by dragging with the mouse instead of typing the exact value and I failed to notice the “~” when clicking to set the position. The best way to avoid the problem is to get into the habit of always either typing values explicitly or making sure you are getting an inference snap to a known, good entity.


#8

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