Any Tips or Tricks to Shell

[colombo75]

Hi to all,

I seem to have problems shelling my part....is there anyway I can loosen the tolerance in the shelling so it can swallow all surface that are to small....

When I was working in I-Deas Master series, loosening the tolerance would usually do the trick...I do i do that in Solidworks?

Are there any tips or trick some of you can give me....

Thanks

Colombo75



Industrial Designer
SW2005 SP3.1

 

[CorBlimeyLimey]

Not that I know of ... SW doesn't use the "tolerancing" concept like I-DEAS & Pro/E.

Can you post an image to explain better what you are trying to do? faq559-1100


Making the best use of this Forum. faq559-716
How to get answers to your SW questions. faq559-1091
Helpful SW websites every user should be aware of. faq559-520

 

[CADGemini]

A couple things to try:

First try to use the multi-thickness setting in the shell feature. (giving certain faces a different thickness will sometimes fix the issue)

Another possiblility is to move the shell feature before fillets. (sometimes fillets can create very small faces which are undesireable to the shell feature)

Can you post a picture of what you are trying to shell so that we can try to help you further? (also include the feature tree in your post)

Best Regards,
Jon

Challenges are what makes life interesting; overcoming them is what makes life meaningful.

Solidworks 2005 SP3.1

 

[Heckler]

I downloaded these rules from some guys website but can't remember whom.....so I can't give them credit.

-Writing a set of rules that applies perfectly in all situations for design with plastic parts is impossible. Below is a set of guidelines that I try to use when I'm working on plastic parts. Sometimes you have to bend the rules, and sometimes you have to throw them away altogether, but for most situations, these rules of thumb for plastic part design should serve you well.

-Fillets cause many of the conflicts with other types of plastics features.

-Fillet order, with respect to the other features, is critical.

-Small convex fillets cause problems with shells, and any fillets between faces prevent multi-thickness shells.

-Fillets running perpendicular to the direction of pull cause problems with draft

-Large fillets should be applied first.

-Vertical fillets that can be tapered can go before the draft.

-Fillets to be applied between the draft and shell:

-Large, non-tapered fillets between faces of equal shell thickness.

-Fillets to go after the shell:

-Fillets with a radius smaller than the shell thickness.

-Fillets between faces with different shell thicknesses.

-Fillets that should not be transferred to the inside of the shell.

-The most common cause for the shell command to fail is that there are fillets on the model that have a smaller radius than the thickness of the shell.

-Use Tools, Check to find minimum face curvature, geometry errors or short edges.

-Severely sharp, pointy geometry may also frustrate the shell.

-Cut away sections of the model that look suspicious and retry the shell, then narrow in on the problem area.

-Existing bad geometry may cause a shell to fail for no apparent reason. Use Tools, Check to find bad faces or edges.

-It is recommended to add small fillets after the shell.

-Draft can come before or after shell. Remember that if
it comes after, you will also have to draft all the interior faces.

-Drafting a face that is adjacent to a fillet that runs perpendicular to the direction of pull will not usually give acceptable results, even if the feature does not fail.

-All tangent faces should be drafted the same amount.

-Be aware of how draft changes the wall thickness of parts.

-Draft is sometimes not required on faces that will pull away from the mold due to shrink. It is always best to consult the tooling engineer before doing this.

-Drafting a fillet running parallel to direction of pull results in a tapered or variable radius fillet. The alternative is to apply the draft before the fillet.

-Draft features can be applied to faces which already have draft on them (draft is not “cumulative”).

-Draft can even be applied to straighten out curved faces when axis of curvature is perpendicular to direction of pull.

-Scale should be added to the engineered part as a separate configuration.

-Scale does not change the size or position of sketches or planes.

-In assemblies, avoid making incontext references or mates to unfinished plastic parts, unless you are sure that the face or edge being referenced is not going to be consumed later by a draft, fillet or split line feature.

-Mates to drafted plastic parts may be best handled with planes.


Best Regards,

An apathetic slacker Gen Xer

 

[davidinindy]

I had issues when designing some thermoformed parts and resorted to just shelling the part to the thickest it would go without failing, and noting the actual thickness of the plastic used on the print.
I worked doing that for 8 months because I never could find a true solution.
Sorry I couldn't be more help.

David

 

[Theophilus]

This is essentially a logical problem most of the time. The big things are not to have faces on the outside of your form that cannot be offset inward to create your inner walls. Fillets and chamfers are often to blame for this.

Rollback your part and try the shelling at different points to isolate the problem. Once you identify the problem, figure out a different way of performing the problem feature, or put the feature after the shell feature.

Sometimes you can shell at the point of failure and use the multi-thickness shell to keep your features as they are. However, this is not normally the best way to mold a part (for injection molding) if you can avoid it--it's better to keep relatively consistent thicknesses on your walls.

Check out all the posts above this one. Great advice.


Jeff Mowry

http://www.industrialdesignhaus.com

Reality is no respecter of good intentions.