What's new
What's new

How are we feeling about the machinability of this model geoemtry?

Seen many fixtures in my day, never any with small inside radii like that.
Whoever said bury a 1/8" endmill in there and clear it has the right idea.

Almost looks like the guy just used the mold cad for the fixture cad ??!!
I think they mentioned as such, just gave them CAD of the mold cavity, and kind of a fix it.
Hope the CAD they gave was pre shrink, or even better shrink modified from actual parts.:confused:
 
I think they mentioned as such, just gave them CAD of the mold cavity, and kind of a fix it.
Hope the CAD they gave was pre shrink, or even better shrink modified from actual parts.:confused:
I'm by no means a professional at this stuff, but it seems like a good idea to look at the structural geometry of the part and select the best points for location and support--with FEA if you're an overachiever--and leave clearance everywhere else. Making a simple relief of the part is begging for interference.
 
I think they mentioned as such, just gave them CAD of the mold cavity, and kind of a fix it.
Hope the CAD they gave was pre shrink, or even better shrink modified from actual parts.:confused:
I missed that. In that case drill 1/2" holes from the side thru all the corners. Cut it to a 1/4 ball !
 
I'm by no means a professional at this stuff, but it seems like a good idea to look at the structural geometry of the part and select the best points for location and support--with FEA if you're an overachiever--and leave clearance everywhere else. Making a simple relief of the part is begging for interference.
FEA wont help because the parts fluctuate on their size based on running the parts, unless climate controlled and strict specs. and monitoring of parts during running.
even still.
Usually the least geo. is best, and on the largest surfaces, and the process part is being held for, I think in this case they said welding, sometimes inserts pressed in.
 
Attached is a screenshot of a part im working on. It's a 7"x2"x2" workpiece, and it's half of a nest to hold injection molded parts for RF welding. I have a 3 axis VMC with the Mastercam 2d license. This gives me access to optirough and single surface 3d toolpathing. The longer i look at it the more i get discouraged about my abilities to finish this part with what i have. Some of this geometry doesn't seem possible. Some of the smallest radii are .02", and I can't think of any ways to follow the geometry surrounding that center boss. Should i have my boss send this part off to an actual tool and die shop, or is it possible to achieve a good result with what i have? Ordering tooling to match some of these radii is an option but upgrading my mastercam license does not seem to be

Well, nobody has asked... so I'll dive in:

What is the injection molded part made from? If the material can tolerate "some" temperature...

Have you considered making a couple of simple "half boxes" (the "halves" probably defined by the parting line in the mold) that have a few contact points so that each "half box" would position the part appropriately. Then fill one half with low melt temp bismuth alloy. Repeat the process on the other half. Might not even need to completely fill each half -- as long as the outer boxes have a feature or two that will repeatedly and accurately index them together.

In simple terms: "pour" the two halves of the holding device for your RF welding process.

PM
 
Last edited:
Almost looks like the guy just used the mold cad for the fixture cad ??!!
that's exactly what they did. pretty sure they used the shell feature, cut it in half, and called it a day. I'm having a hard time making any changes to the solid model because of it as well, since its hollow and there are no real features i can change geometry on. A lot of pretengineering here
 
Well, nobody has asked... so I'll dive in:

What is the injection molded part made from? If the material can tolerate "some" temperature...

Have you considered making a couple of simple "half boxes" (the "halves" probably defined by the parting line in the mold) that have a few contact points so that each "half box" would position the part appropriately. Then fill one half with low melt temp bismuth allow. Repeat the process on the other half. Might not even need to completely fill each half -- as long as the outer boxes have a feature or two that will repeatedly and accurately index them together.

In simple terms: "pour" the two halves of the holding device for your RF welding process.

PM
I'm not really involved in the engineering process. I can run these ideas by the engineers, but if it isn't done our boss's way then its wrong. Because these parts are medical, im not sure if bismuth is a material we can use. I appreciate the tip and will put it into my mental toolbox as i further my carreer
 
I also agree with the "do what's required only" approach to making a fixture to enable a process. Do you actually have access to the part(s) that fit in this fixture/ and can you determine what is required to hold them together to make the welds? Having the actual part design info will help guide the fixture design. Eliminate everything that isn't needed. Use of the datum surfaces on the part itself will be the clearest way to get the fixture put to bed.
 








 
Back
Top