Unit Substitution (as opposed to conversion)

paul_bunnell

When changing the work space units, an existing dimension will change from (for example) 10 inches to 254 mm.  The request is to add an option that will make 10 inches turn into 10 mm.  In an ideal world the user would always remember to set their units before they start but mistakes happen (especially among students who are just learning the system). 

lougallo

@paul_bunnell That is not really how parametric systems work.  All geometry is in the real size, not a unitless body.  Since this is not something that is common there is not way to do that unless you scale the body.  In any event, this is not really an option we are going to consider at this time.

paul_bunnell

I appreciate the reply.  The need for this is less about fulfilling a design purpose but rather that if a person makes the mistake of forgetting to change the work space units at the beginning there is no way to rectify that mistake. I am teaching high school students (and I teach them to always set the work space units as their first step, but of course, mistakes are inevitable in the learning process).  The way of implementing the request that I am imagining is akin to doing a "find and replace" within the code text, changing all instances of "inch" to "mm."  (Maybe it's not that simple, but I was hoping it would be). 
On a broader note, it looks like OnShape is pushing to attract educators in addition to working engineers, and I think that is a savvy business move.  But to do it well, you may need to consider features that are geared toward educational use even if they are less relevant to industrial use.  Whether this is one of those, is of course, is at your discretion.

Jake_Rosenfeld

@paul_bunnell

Note that you can change your default workspace units in the user settings:


As long as your students are not switching between metric and imperial, just have them set this once and you'll never have to think about units again.

I see how this can be somewhat frustrating because sketches do not display their units, but it should be pretty obvious when making the first solid feature that the units are not what you desire:



Our users have the opportunity to bake a lot of design intent into their specifications of parameters.  For example, for an extrude depth, you could enter "1ft + 2in + 3mm":



This expression is preserved in the system.  You'll actually notice that if you go back and try to edit that "254 mm" value from your initial question, when you click on it to edit, it will revert back to "10 in" (because this is how initially specified the value to the system).

If the user who entered the "1ft + 2in + 3mm" extrude parameter were to then execute some "switch all units" command, its difficult to tell what they actually want.  They were very specific about what they wanted, should we destroy all that design intent and just apply a scale factor on the result of the expression?

billy2

@paul_bunnell

Onshape is based on meters. The engineer chooses which units they want to work with which is stored in the template. The geometry is never converted based on someone's units.

I'm always designing in mm so I'm never having the forget issue that young students have.

In the instance when a mistake is made, do a transform and scale the geometry to fix mistake,  then never do it again.

brucebartlett

I think in Onshape currently, it is very obvious which units you are in as default as it appears at the end of the dialogue as "mm" or "in"  when typing in any number or taking measurements. If there was a mess up by a student that would be a good learning experience and I belive the best way out would be going though and coverting each input after the overall default was changed.   

billy2

@brucebartlett that'd train the muscle memory, put'm to work. You can always build it faster the 2nd time.

We all make mistakes somewhere in the process of the design:
-Creating drawings of part studios vs. assemblies
-Inserting part studios vs. assemblies (my biggest blunder)
-Type " vs. in for units

I guess this is part of the learning process.