Hi,
Just saw an interesting comment by @TheCADWhisperer in a thread and thought it might be a good
request for the Devs, if it hasn't been made already.
In Fusion we can design stuff to exact tolerances and it doesn't care. We can make a revolute joint and
if there is any interference it doesn't matter. In the real world it DOES matter. If we have a shaft and a
bearing, there will usually be one part of the bearing that allows the shaft to rotate, and one part that
is fixed. In addition to this, bearings wear out and need to be changed so we usually don't want the
bearing fixed so tight it cannot be moved in the future. This is why we would normally look at a Fit Chart
like this one to work out our tolerances.
So my suggestion to the Devs is:
On the Joints menu we could have a check box for a "Fit" and a drop down menu for the type
of fit. Fusion could then take our choice and display it as our standard size, but in our drawings and on the
manufacturing side, modify the shaft and hole sizes by the the Standard from a similar data chart. This is
what happens already with standard threads. There would also be an option to set up a non-standard
fit if necessary.
For example, using an H7/p6 press fit on a 50mm diameter:
- H7 (hole) tolerance range = +0.000 mm to +0.025 mm
- p6 (shaft) tolerance range = +0.042 mm to +0.026 mm
- Potential interference will be between −0.001 mm and −0.042 mm.
This example from Wikipedia could mean that I design my shaft and bearing in Fusion at 50mm and it
will be displayed as a 50mm shaft and hole. The Joint Icon has a small modification to indicate it is a
Fitted Joint. This could be a normal blue icon for a non-fitted joint, and a green icon for a clearance fit,
a yellow icon for a location/transition fit, and a red icon for an interference fit. The actual fit would be
automagically calculated by Fusion based on a menu choice, say a sliding fit or close running.
Under the hood of Fusion the actual tolerances would be set and used for manufacturing. So for our 50mm
shaft with a press fit, we might have a required tolerance of 0.02mm and the applied tolerances for the
press fit would use an actual shaft diameter of 50.01mm and hole diameter of 49.99mm. This could be modified
to a set tolerance if necessary but otherwise these would be numbers that Fusion would use.
I don't know if this is on the Dev Roadmap already, but if it isn't I think it should be. I have seen comments more
than once in this Forum that we need to take this into account the differences between the Fusion world and the
Real world where we actually make what we design. This would make fusion do the work at the design phase and
not at the manufacturing stage where often these fits are hand calculated and then applied. As more and more
fabrication is taken over by software being directly uploaded to CNC, this would be a great function to have.
Cheers
Andrew
