design strategy for tweezers

Hi,

I'd like to model a pair of tweezers. What is the best SW design
approach for this? Pair of lofts? Sweeps? Extrusion with various
types of filleting? How would the surfacing experts do it?

SWX 2004

Thanks in advance,
MT

 

Well, to start with do you have an image of what it looks like, say a
napkin sketch or something? What mfg process will you use to make it?

wrote in @o13g2000cwo.googlegroups.com:

 

The plastic tweezers will be molded and right now I believe they will
look similar (though not exactly) to tweezers you'd find thru
McMaster-Carr.

Thanks in advance,
MT

 

Do they have to be shown open and closed?

A variable cross section sweep comes to mind.

 

They should be shown in an open configuration.

 

wrote in @o13g2000cwo.googlegroups.com:

Are you constrained as to how complex the mold can be? If so, you
will need to design the part so it can be pulled out of the mold
easily with only two sides of the mold. With plastics, you can do
almost anything you can afford. To be a good plastic part designer,
you really have to have an understanding of how molds are built and
work.

For most of the tweezers I've seen, I would probably use a sweep,
with some additional features to shape the ends. It would be a
shame to simply recreate a metal tweezer with plastic, since there
is so much more you can do with plastics. Did your product
development or marketing dept give you any sort of design criteria
for the new product?

 

I have designed a number of plastic replacements for metal, and indeed
the design must be reconsidered almost from square one to take into
account the exact end need of the product.

Plastic is just so much more flexible than steel or aluminum, that
extra care must be taken to design the right amount of stiffness for
the job, and acknowledge the limited pinching ability of jaws in
plastic and the nature of thin jaws to deform due to both contact
pressures on the nibs and from finger actuation pressure.

Tweezers are simple, but I have seen plastic tweezers in both
industrial and medical applications that basically suck.

Bo

 

Think about how you are going to mold them. Where do you want the parting
line? How much draft do you need? Are there areas that can't have any draft?
Where do you want the gate? How will you eject them?

The simplest approach would seem to be to extrude a profile, with or without
draft, then cut the plan view. Does that work well with the answers to the
questions above?

Jerry Steiger
Tripod Data Systems
"take the garbage out, dear"