Pattern accuracy

[woodhead1]

I am modeling a heatsink. I created the base, then the first fin. I patterned the fin using a directional pattern. The base is 1.102" wide. The fin is .030" wide. I need 15 fins. That means the pattern spacing needs to be (1.102-.030)/14=.076571428. When I enter this value or even the formula the pattern dimension defaults to 3 decimal places (.077).


Is there a way to change the accuracy of this value. I searched config.pro and could not find anything that looks like it would affect this. I changed the model accuracy value with no affect. Any ideas?


View attachment 3022

 

[oldman]

Would it help to add more decimal places to the .077 dimension?

 

[woodhead1]

That is the problem. I can type in .076571428 or .07700000000 or any number of decimal places and it rounds down to 3.


I found this in the PTC knowledge base but it didn't help. https://www.ptc.com/appserver/cs/view/solution.jsp?n=129485 Ichanged the value of default_dec_places to 8 and it still rounded to 3.


BTW, I am using WF2 date code M180. I forgot to mention that in my original post

 

[ReinhardN]

does a relation like increment=length/number_of_cuts work ??
ReinhardN

 

[pjw]

You can easily set your number of decimal places by modifying the the dimension properties. But why would you want to work to 9 decimal places? You couldn't manufacture to this. In imperial terms the most precise we work to is 0.001". Anything more precise than this is unrealistic. In metric measurements we would work to the nearest 0.01mm.


Phil

 

[woodhead1]

Yes, a relation does work. The increment distance is now correct. There is absolutely no offset between the last fin and the base which means the relation carried the decimal to thefull9 places (.076571428). When I edit the dimension though it only shows up as a 4 place decimal (.0766). I suppose that is OK since all that really matters is that the model is correct.


I still think there should be some way to do this without a relation.

 

[woodhead1]

Thanks PJW, editing the dimension properties is the way to do it. You can't change the properties in the "edit definition" mode. Only in the "edit" mode.


What you are saying about manufacturing to 9 decimal places is true.The first step,however, is to get the model built correctly. My drawing would just indicate 15 equally spaced fins, and not the actual dimension value, except maybe as reference.
Edited by: woodhead1

 

[dr_gallup]

You can set these config options to control your default accuracy.

default_dec_places 3
default_ang_dec_places 0
sketcher_dec_places 3

Accuracy just depends on what industry you are in. We make fairly high precision machined parts. In inches we routinely use 4 decimal places and on critical features we may need 5. It is possible to specify and measure to these accuracies, it just costs a lot. Precision optics needs better than that.

 

[ReinhardN]

you could create a parameter number_of_holes and enhance your relation to
increment= length(number_of_holes-1)
ReinhardN

 

[jeff4136]

I don't guess I've ever created a pattern that wasn't relation driven.
That's a bug. The program should never munge input without warning you.
It would be interesting to see the documentation if it's "as designed".


Give this a try:
Create the pattern as you have.
Select the pattern, RMB -> Edit.
Now enter (1.102-.03)/14 and regen.
(There is no relation created.)


While you're about it note the d#.
Crank up the Relations dialog and Evaluate d#.
It'll return .076571.

 

[woodhead1]

RMB -> Edit enter (1.102-.03)/14 and regen does work. If you try and input the same math in the "Edit Definition" mode it doesn't work. That iswhat my problem wasoriginally. Ido think it is a bug that it won't let you do it on 'Edit Definition" mode.