Dimensioning Lofts

Ok, this is kinda off season stuff, but it is trouble we are having in class and are more or less just wandering if there is a way to do it.

We are working on making bottles for a project in our Inventor class and I just so happened to make it using a loft. I asked my teacher how we could dimension the curves, but he couldn’t figure it out either.

does anyone have a solution on how to dimension the curves on the side of a loft?


I would think about doing section views showing the shapes that make up the loft, and dimensioning them.

Section views are definitely the answer. Though, I might go about it in a different way. Instead of doing several section views of the shapes, consider doing one vertically through the entire bottle. (This only works if the bottle is asymmetric, though most bottles are.) I could help you more if you give a screen shot of your bottle in isometric. Also, keep this in mind for future projects. Though lofts look cool, if you can avoid them then I suggest you do. They are usually hard to dimension. Almost impossible to properly machine(for high school students anyway). Plus most of these jobs you can do with a combination of revolves and sweeps. I am sorry for getting off topic, just a little advice. I hope this helped somewhat.

As most have already stated, the correct way to dimension a loft is the same way you sketch it basically. lol I’m assuming you used one sketch around a center line, and then revolved that?

If that’s the case, simpley take a crosssection of the bottle as a section view, and dimension the arcs, and center points of said arcs from a central point on the drawing.

Using ellipses are a pain and a bit more tricky, but can be dimensioned as well.

For actual manufacturability of a bottle, certain areas are given dimensions, and left up to the manufacturer to make it “up to snuff” so to speak.

On a 2 liter soda bottle, there is a lot of engineering that goes into them to make sure they are the right strength so they actually hold the amount needed, and also so you have flat surfaces to attach a label.

For instance, the label area is predominatly a straight tube section, while the flow up to the cap, and down to the bottom (sometimes with additional features for design, or structural integrity added onto them (re: the bottom of a 2 liter bottle’s 5 points that make their “feet” so to speak.) is a loft type feature.

Btw, as a side note, if anyone in your class there does end up modeling a 2 liter soda bottle, I would love to get my hands on that model in a format I would be able to use in Solidworks. Let me know. I’m sure one of these days I’ll actually get around to make my own, but if you can provide me with one that would be awesome.

I’m not sure whether you’re talking about dimensioning the bottle (i.e. annotation) in a drawing file, or dimensioning the features in the part file in order to control the shape and size. If you’re talking about a drawing file, see above.

If you’re talking about changing the size and shape of the curves created by lofts:

When making a loft, you can make as many cross-section sketches as you want along the height of the bottle. Create work planes offset a certain distance from the bottom plane. When you choose the profiles for the loft, you can select the entire series of profiles instead of just the beginning and ending profile.

Alternatively, or at the same time, you can use “rails” to control the shape of the loft as it goes between each of the profiles. Create a sketch plane that cuts through the bottle in a vertical direction, then draw lines/curves to make the shape of the bottle’s profile (from top to bottom). The ends of that sketch should be contrained to the location of the beginning and ending loft profiles. Then, in the Loft dialog box, click to start a list of “rails” and choose that sketch.

I don’t know if you’re already doing one of these things, but I think Rails are what you’re looking for. You can constrain and dimension the rails to precisely control the path of the loft.

I hope that helps. If you post the Inventor file, I might be able to give a more concrete answer after I can see it.

One method is to Show Sketches (from the model) in the drawing. Of course with an organic design it is not possible to fully dimension - that is why it is powerful to be able to take your solid model data right to CAM software and then to CMM inspection software. The 3D model is the single source of truth.