Premachining Representation

[billzm]

Inventor 2013

I am trying to show a part in a drawing of three different configurations of a casting:

1) Rough as received from the foundry

2) Partially machined or rough machined

3) Final machined

What is the most basic bullet-proof way to show this? Three different models?

What is the procedure to change the representation to show changes in the model?

Why does suppressing a machining feature in one representation change all representations?

The rough part is brought into an assembly and the machining or removal of material happens in the assembly.

Bill

[michaeldavis7418]

Level of Detail ...or View presentation

[JDMather]

Used Derived Components.

Search here for previous discusions on machined castings.

[jtylerbc]

Derived components are definitely the way to go for this.

I've heard of people using assemblies to do the machining operations on castings before.  As someone who modeled cast and machined parts almost daily for 6 years, I think that's going about it the hard way.

Derived components will let you do essentially what the real-world manufacturing process is doing.  First you make the casting.  Then the rough-machined part uses the casting as a starting point.  Then the final machined part uses the rough-machined part as a starting point.

At all three stages, the model remains a part file.  This is much more logical to me than it suddenly becoming an assembly model just so you can make some machining cuts.  Each subsequent level is associative to the ones that came before it, so you can still update it to changes.

[billzm]

Ok, so now the search in on to use or create derived components. I have no formal schooling in Inventor, just seat of the pants and intuition.

Any great tutorials to point me in the right direction?

Bill

[billzm]

Can't edit after posting. Ouch...

The search IS on...

[jtylerbc · Accepted solution]

Well, after a quick search, I found lots of threads that discuss the method and it's advantages over other techniques, but didn't see any that actually described exactly how to do it.  It's fairly simple to do.

First, create your casting, just as you would normally.  Save it if you haven't already.

Next, start a new part (which will become your rough machined version).  On either the 3D Model or Manage tab (appears on both), pick Derive.  A File Open box will appear - browse to and select your casting part file.

You will then get the Derived Part dialog box, which will allow you to set various options for what you want to copy over during the derive operation.  Normally when I did this, the defaults were fine, but you may want to look through the options to see if there is anything addtional you need.

Once you click OK, you will have a single feature in your browser that represents the original base part (in your case, the casting).  You can then start modeling any machining features needed, on top of the casting geometry.

Once you have the rough machined version ready, you can repeat the process a second time to create the final version.  The only difference is that this time you'll pick the rough machined part file as your derived base. 

One catch I will warn you of is that the derive part technique does not automatically copy the material over from the original cast part.  You will need to set the physical material individually at each new part you create in the sequence.

[swhite · Accepted solution]

Derived parts are relatively very simple to create. Simply open a new part template, close any sketches and delete them if you wish. On the Manage Tab, on the Insert portion you will see Derive. Select this, navigate to the part you want to derive from. The Derived Part window will now open. If your part is a single body part with no seams, the first option is best. If it is a multibody part the third option works best in my experience. (Derive 1) Also be sure to open the parameter list and include any model or custom parameters, such as those that define your length, width and thickness. At this point you can choose to not include certain parts (if multibody). If multibody you must select each seperate solid to include.

You then use this derived part to begin your initial machining steps on. Once this part reaches the end of that process you create another derived part from this part using the same steps. This derived part is your final machining steps.

Any changes to the first part will reflect through the entire process, or changes in the second step will reflect into the third.

Included a quick example:

Edit: One warning, if you delete a face in a previous step that you placed a sketch on in a later stage, you might be forced to redefine the skecth location. Changes in dimensional geometry, such as changing width, length etc by using exsisting dimensions will not affect later sketches, they will resize automatically.

[blair]

There is a great example in the AU2012 if you have access.

[billzm]

Success!

Thank You, All

A derived parts is the best way to answer part of my first question without going thru the gyrations of drawing the base model each time:

"What is the most basic bullet-proof way to show this? Three different models?"

Bill

[JDMather]

You can go either way with the derived component technique.

Cast to machined follows the real world process, but -

as designers

we usually know the finished dimensions first, so you can from machined backwards to casting. (sometimes this takes a little more thought)

[JDMather]

---

@billzm wrote:

"What is the most basic bullet-proof way to show this? Three different models?"

Bill

---

When I worked in industry these stages would have 3 different part numbers.
Do three drawing sheets, either in one file or in 3 files.

[swhite]

I think 3 is best personally, unless your machining process requires more. The finished part will be inserted into your assembly, if such is required, depending if you just manufacture individual parts or need to show all parts fitting together, the other two will only show on the drawing to make the part.

Of course you could if only the part needs to show place all 3 in an assembly all constrained in the same place, then use view reps to suppress the others in turn. This might help others be aware that derived parts exist for the other steps, so they dont accidently re-create them again. Plus you can edit in-place and see the results instantly, without having to individually open each part.

[blair]

That's how I would do it. My finished machined parts, then derive to get my casting where I have added material that would have been machined off.

Started working this way prior to iParts

[jtylerbc]

---

@Anonymous wrote:

You can go either way with the derived component technique.

Cast to machined follows the real world process, but -

as designers

we usually know the finished dimensions first, so you can from machined backwards to casting. (sometimes this takes a little more thought)

---

My usual process was to start by making a rough model of the finished version, which I used to work out the design and get approval to proceed.  Often there would be several versions created, particularly if we were trying out multiple concepts.  These models were generally built and revised many times in a relatively short span, and were often done quickly and with less-than-perfect modeling practices.

Once the final geometry had been settled on, I built the cast and machined model set as a new, clean model.  Since a crude version of the final part had already been created, it was available for reference.  The "good" copy of the models would typically come together very quickly.

It sounds like extra work building the model twice like that, but I found it to be a good method for me.  It allowed me to model "quick and dirty" while minds were still being changed often, and then do things properly once a direction had been settled on.

[swhite]

Yes, I do alot of prototyping and do that myself a lot, It is too cumbersome trying to always do the best geometry and constraints when everything is in constant change. Once the prototype is finished I can usually recreate it fairly quickly and with proper techniques and most times even shorten the number of steps needed to complete the model, (one sketch instead of 5, etc.

[JDMather]

I nearly always consider my first attempt (or two or three) simply an exercise to understand the geometry.

Then I start over from scratch creating a clean and robust model.

I have seen too many cases of users fighting a poor initial attempt with the response, "I have too much time in this, it would take too long to start over from scratch."  I have found that it is much faster to start over from scratch even on a complex model than to try to fight a model that was flawed from early on.

[graemev]

---

@Anonymous wrote:

... I have found that it is much faster to start over from scratch even on a complex model than to try to fight a model that was flawed from early on.

---

Testify!  Sometimes the baby needs to go out with the bathwater.

[IS200]

Am I the only Inventor user in the whole world who uses Weldments? Why would anybody want 3 parts to describe something as simple as this?

Just put your part (casting) into an assembly and convert to a weldment.

You can use the 'Preparations' section to add any cutting features - i.e; your 1st machining step.

Then you can use 'Machining' section to add more cutting features - i.e; your 2nd machining step.

All you have to do now is put the weldment on a drawing sheet, select which step you would like to show (Preparations or Machining), select your part from the dropdown box and voila!

You can make a drawing of the original casting, one of the 1st step, and one of the 2nd step all from one part and one assembly (weldment), they can even have the same filename because one is an assembly and the other is a part.

Now, can anybody out there tell me, is there anything wrong with this method? I have been using it ever since weldments came to Inventor and I have never had a problem with it.

I ask the question again, am I the only Inventor user out there who does this?

[swhite]

Apparently so :). Sounds like something I will be checking out. Was not personally aware that the other steps in the weldment procedure would not affect the original. Thanks for the info though! Of course have not had much call for weldments in the past. Our company uses a weld reference, so only unique welds are ever called out, so was never much use for weldments. Seems have found one now 🙂