topic Re: Create negative from part in Inventor Forum

Create negative from part

Anonymous — Sun, 31 Jan 2016 13:53:17 GMT

I have seen that this has been asked previously, but none of the replies I have seen have helped me to achieve the goal I am after.

Basically, all that I want to do is create a "plug" from a part file, so I can use this as a fibreglass mold.

For the life of me I cannot find a way to do this, but that is probably because of my limited skills with the more advanced tools, like derive, sculpt and split, which I assume are the things I should be using.

Attached is the part file I am working with. What I need is a plug of the inside of the step well, along with the bits that stick out beyond the floor (upper rectangular surface).

If someone can give me a bit of a step-by-step that would be greatly appreciated, as I am getting really frustrated currently.

Re: Create negative from part

Mark.Lancaster — Sun, 31 Jan 2016 14:17:26 GMT

For furture reference (especially when posting a file).. ALways indicate the version of Inventor you are using. ALthough we can determine it after downloading the file (Inventor 2015 file). It just saves time up front if we knew..

@Anonymous Also welcome to the community.. I would also recommend that at some point you upgrade to Inventor 2015 SP2 and update #3. You are currently at SP1.

Re: Create negative from part

Anonymous — Sun, 31 Jan 2016 14:25:50 GMT

I'll put that on the "to do list", thanks.

Re: Create negative from part

JDMather — Sun, 31 Jan 2016 15:46:24 GMT

This angle is not measurable (by inspection) and not manufacturable.

What is the design intent?

Re: Create negative from part

Anonymous — Sun, 31 Jan 2016 23:32:56 GMT

That angle dimension is irrelevant. It is what Inventor generated when I used the auto dimension and constrain feature.

I do not understand why when I add all of the dimensions required to manufacture a part, sometimes it does not fully constrain the sketch, but it doesn't.

There is a slight draft from the floor section to the bottom step. From my personal experience in manufacturing fiberglass molds/parts, this is sufficient to allow for the release of the part. I should add that this is not a finished design, mearely an example that shows the "concept".

My main concern at the moment is how I create a new solid that fills the area of the step well. If I can create that then I can move forward.

Attached is an image showing of the area I need to create a negative of.

Re: Create negative from part

WHolzwarth — Mon, 01 Feb 2016 07:32:12 GMT

Let's hope, that I understood it well (2015 file)

Walter

Re: Create negative from part

Anonymous — Mon, 01 Feb 2016 10:30:16 GMT

Firstly, thank you very much for the attached file Walter.

I have expanded the model tree to see what you did, but I am having a bit of trouble figuring out how/why you actually did specific things.

To be honest, it seems like a lot of work to achieve what should be a relatively straight forward task. Maybe I am naieve in thinking that, I don't know.

Assuming that I can recreate what you have done (personally, I am a bit sceptical), how would I isolate that surface and make it into a new solid part?

Re: Create negative from part

WHolzwarth — Mon, 01 Feb 2016 11:05:10 GMT

Here's another way of doing. Perhaps it's more transparent to you.

There are now 2 solids in this multibody IPT. You can get separate solids with the Make Components command.

Re: Create negative from part

Anonymous — Mon, 01 Feb 2016 11:14:53 GMT

Thanks again.

I will have a look and see if I can work it out.

Will let you know how I go.

Re: Create negative from part

Anonymous — Tue, 02 Feb 2016 10:20:58 GMT

The way you did it in the second file was definitely easier to follow. Thank you.

I don't think that I did it exactly the same way as you did, but I was able to achieve the desired result

This is what I did...

Created a mid point plane between the two sides of the step
Created sketch on plane
Projected geometry of steps
Finish sketch
Extrude to next as a new solid
Mirror solid

Turns out that it was not that hard to do, when you know what to do. 🙂

Your help is greatly appreciated.