Why Not Create Using Mirrors?

[merrill.rosenow]

Hello everyone,

Most of the replies I received about the assembly pattern thread detailed that people tend to avoid creating mirrored parts whenever they can. I was lucky in my case to find a work around. I am curious though, why does the community try to avoid creating a part using mirror?

The reason my company uses it is to reduce error. When you make a part that is a left hand, or right hand formed part from the same flat pattern they are symmetrical to each other. Instead of creating two independant models for the same part, my company creates one of the two, then makes a geometrically dependant model based on the first. This ensures that changes made to the original also changes the mirror.

Why do people try to avoid this and create two independant parts? Ideally I would be able to create the left and right hand versions in the same model, using different instances. However, changing a formed angle from +90º to -90º also changes the dimensions since the form is based on one side and you will be out a material thickness. Is there another way to do this using family tables? It would be great if both left and right hand parts were part of the same model, in a family table.

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[dgschaefer]

I do use mirrored parts as you describe for the reasons you mentioned. If the design intent is for the two parts to be mirror images, a mirrored part captures that intent perfectly. It does create some other challenges in terms of assembly at times, but the benefits of having consistent data and avoiding the risk of a change being implemented in one part, but not in another outweighs the extra work in assy mode.

I'd be interested in the downsides as well.

Doug Schaefer

[A_CASHEN]

We do not use mirror because more often than not, 2 parts that start out as symmetrical become non-symmetrical as the design evolves. At least that is the case for us.


Amy Cashen
Engineer II
The Delfield Company
Manitowoc Foodservice
T 800.733.8821 x12634 | F 989.773.1588
Integrity, Commitment to Stakeholders, and Passion for Excellence.

[dgschaefer]

I've found that minor differences like a hole in one but not the other can be fairly easily handled with the mirror. If the design evolves to the point where the mirror no longer makes sense, then you need to model the part from scratch, but you would have done that at the beginning anyway.

Doug Schaefer

[kevinb600411]

The company that I am currently assigned to has the procedure of:

* If it is an Identical Mirror of a sheet metal part, it is OK. Create the first part and the flat pattern, then mirror to generate the mirror.

* If it is a Identical Mirror of a Machined part we are to create them independent. For some reason Pro/Man does not like the first feature being a mirror and then will not generate the G-Code.

We have also run into an issue where there is a family table of similar parts (holes or spacings different) if these are mirrored then the next level up assembly has to be regenerated twice in order for the correct instance to show up. This causes issues in ProductView since if it can not regenerate the first time it crashes (an will not generate an image for the drawing).

Just my two pence!

Best of luck which ever way you decide to do it!

Kevin Brandt

Independent Contract Engineer

[jer3d1]

Another method that may be of interest to the community discussion (until the PTCUser wikis come through... Hint, hint :)) is using published geometry. Using published geometry, you can easily share and mirror geometry in a way that respects what is common between both parts and still maintain both associativity AND independence.

Here's how you do it:

Build Part A up to the point where the geometry is common between both parts. Now, copy and publish all of this geometry (Copy Paste all solid surfaces and then publish using Insert --> Shared Data Publish Geometry - Select the copy quilt, OK) Nice work, everything that happens to Part A after this feature will stay with Part A.

In a brand new part, we'll call it Part B, bring in the shared geometry (Insert --> Copied Geometry, Under references, choose the published geometry from Part A, OK). Now that the surfaces from Part A are in Part B, you can select the quilt and mirror it how you would like. With the geometry mirrored, select the mirrored quilt and solidify it. From here you can add whatever features you like to part B making it as independent as you want it to be.


It is not as fast as building a mirrored component through an assembly, but it doesn't have the drawbacks either. Not to mention any of the other possibilities available using this powerful feature with others. Also, if you're admin enough, you could create a mirrored component start part that already has these features built in making it easy for your users.

Best wishes,
Jered

[jer3d1]

WildFire 4 allows you to create a mirror part directly from another component without the assembly (File -->New...). As in the assembly method, you can choose whether or not you want feature independence. It seems as though this method would accommodate most mirror needs.

[lelande]

In addition the all the other methods, have to tried making the the two
parts as a family table? You need to set the table to allow negative
values, but then both parts are made from the same flat pattern.

Leland Erickson
SpecSys Inc.

[merrill.rosenow]

That is an excellent idea. I have tried making the parts from one family table. The problem is, when you input a negative value for an angle, the material forms on the other side of the sketch line. This means that mirrored parts are off by one material thickness per form. This would be the ideal method of making left and right hand parts, since not only would they be geometrically dependant on each other by they would also be the same file (different instances).

That is of course, unless someone knows a way to work with this?