Threads for Rapid Prototyping

[Hochiki]

Hi all,

I've used solidworks for years to design parts for CNC manufacture, but I'm now having to 'embrace' rapid prototyping as apparently its the future... so I'm having to re-learn some of the features I've never had to use on Solidworks.

When putting a thread into something that is going to be converted to IGES to be sent for prototyping, I am assuming I can't just use the 'Hole Wizzard' as I would if the part was to be opened by a CAM software- I assume I have to do a thread pattern?

Also, does anyone know how the price of a rapid prototype model is calculated? Does it cost more to radius edges and make it look nice? Should I leave non critical things as square edges?

Thanks for your help and advice in anticipation!

[dpryor]

You are correct, the hole wizard will not do the trick. You will need to physically model the threads, driving the thread profile around a helix.
Radii shouldnt really affect the RP cost. It is pretty much based on the amount of resin, time in the machine, and finish (sanding) operations.

[Hochiki]

Thanks Doug. No more being lazy with threaded holes then!

[keebler303]

The rapid prototyping I have been involved with has been priced based on volume. Different colors, support media, etc. may change the price too. Really depends on how the outfit you work with does things.

Another option for threads would be to use brass inserts. Mcmaster has inserts that fit onto a "soldering iron" and you push them into a hole, melting their way in and locking in place. I used them in PP and they worked fine for what I was doing. I doubt you will get very good threads in the smaller sizes due to the resolution. I am assuming FDM here as there are technologies which can produce extremely fine detail.

Matt

[Hochiki]

Thanks for your advice guys.

I think what I might do for my first go is just put a hole in drill sized and manually tap the holes required- that way if they don't work I can drill it out and use a thread insert. I might also try modelling a threaded hole in a non critical place as an experiment to see how it comes out! I'm expecting to have to chase the thread at least... but we will see.

We use a company called CRDM for the things the other guys have had made, and they seem pretty helpful, but everyone else has just avoided putting thread in things... its just my luck that the first thing I want to prototype doesn't have any choice but to have a thread in it.