PATTERN INSTANCE VARIABLE

john_faraci

I have many rails of different lengths that all have holes equally spaced along the length. What I am trying to do is model one of the rails and then use a variable to control the number of holes in the pattern. For instance, all rails have a hole .625" from each end then they have holes spaced 1.25" between those holes. I want the variable to take the distance between the holes at each end then add the correct number of spaced holes determined by the length between the end holes? Does this make sense?

Thank you for your help.

NeilCooke

Sounds like your rail length is governed by the holes rather than the other way around? If that is the case then it makes it easier than trying to calculate the length of the rail first before adding the holes.

https://cad.onshape.com/documents/d748a4ebc28ac8c465b2eba6/w/4a867cab21e46273c6c1a05b/e/0b90dcb3487744b7bd94971b

john_faraci

Thank you Neil.

I see how you did that. In our case the rail length is the known factor, therefore I was hoping to have it function by being able to change the rail length and then the number of holes would adjust.

mahir

@john_faraci, try this example. It takes as input the rail length and hole spacing. It then automatically calculates the number of holes. All this is done via variables and equations which drive feature dimensions. In this example the edge spacing is variable in order to keep the holes centered on the rail, but this could easily be modified to make the edge spacing static.

https://cad.onshape.com/documents/57acdfaae4b005c413ed9b6f/w/3fd585a46d3af1b3ba413c53/e/691a7028f1006301aa47baa0

NeilCooke

@john_faraci - I think it depends on what is important. Presumably the hole spacing is fixed, so therefore one of the end spacings must be variable? Or is it like @mahir said where the holes are centred?

mahir

Realistically, it works more like @NeilCooke suggests. I made my rail as an example of how to use equations to back out an integer number of holes from a variable length. But (non-custom) off the shelf rails don't usually come in fluid lengths. You have specific lengths available in whole number increments of the hole spacing. So even if you're ordering rails by their length and not the number of holes, it's the number of holes that drives the lengths.

NeilCooke

If the lengths are predefined, use configurations.

john_faraci

Gentlemen, thank you very much for the assistance. As you may have gathered, I am new at variables and was trying them out with something familiar. I appreciate all of your comments and suggestions. After thinking about it a little bit I realized that having the lengths and doing a little math I can come up with the number of holes easily enough. 

Configurations will be my next challenge.