This post was prepared for a friend who will like to know how to accurately scale imported 3D model in Autodesk fusion 360. It is a known fact that fusion 360 can import files like step, .prt, .dwg, .3dm and many others from similar cad software. The files imported can also be edited to meet the required needs.The method I am going to explain works for both in-house built and imported models.
To accurately scale 3D model file, select a length of the imported file and take the measurement for reference purpose. This you will want to compare later with the proposed length in order to arrive at a scale factor. Let say the original length is 10 mm and you want to change the original length to 13 mm (the proposed length). Note that with most cad software, when working with scale command you are required to supply a scale factor. If there are few multiple objects to be scaled, you may select one after the other while holding the ctr key. When you have numerous objects to be 3D scaled, select the first object, scroll down to the last object. Then select the last object while holding the shift key. This action allows you to select the first and last objects, plus every other in between. Then you will go to the Modify menu, and select the scale 3D model option from there. At this point, you will be prompted to enter the scale factor. In addition, you will be prompted to select a reference point to scale 3D model. Enter the calculated scale factor and select the reference point (this could be any point highlighted on the model.
By completing the a fore mentioned tasks, your model would have scaled accordingly. From the above assumptions. The scale factor for scaling 10 to 13 is going to be 1.3 (dividing the proposed length 13 mm by original length 10 mm. Once again, the scale factor is calculated by dividing proposed length by the original length. I hope this answer your question?