Thermoforming with FDM Rapid Prototype tooling

[mjfengineer]

I am looking to have a thermoformed catheter tray made. The tray is 40" long 5" wide. The material is HIPS.

I need about 150 trays and then I know the design is going to change. I really don't want to invest much in tooling, so FDM tooling seems like a good option in theory. I have been told though that they only generally get 10 parts out of the tools. I haven't had a good explanation of why the tools fail.

The RedEye website makes FDM tooling sound great.

http://www.redeyeondemand.com/APP_FDM_Thermoforming.aspx

It sounds like everyone is using ABS, when polysulfone might be a better option. I am looking for some advice on making low volume reasonably large thermoformed parts. What are the limitations of FDM tooling?

 

[KENAT]

Do you have a thermoforming house/supplier in mind? What do they say?

I talked to my vendor about this a while back and seemed they'd only just started to look at using rapid manufactured tools.

On the tool failing I'd guess is was from the thermal cycling.

I'll be interested to see what others say as the volumes they claim for this tooling on redeye is in our ball park.

Your part is on the large side for making the tool in one place by FDM, you may have to make it in 2 parts and join together which may be a weak point.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[patprimmer]

I have not seen it done, but if the prototype could be laid over a wooden platform or chassis it might hold up better.

If it is ABS, heat will be the thing that kills it. Cooling between cycles might help for low volume.

It should also be possible to cast a mould in epoxy or thermoset polyester using the FDM model as a plug. If this was incorporated in the original plan, the FDM could be sized to correct for mould shrinkage that occurs when making the mould.

If it's a simple part it might be just as easy to fabricate it out of wood and forget about high tech.

Polysulphone will make a substantially stronger prototype.

There was some time ago a rapid prototype technique that UV cured epoxies. SLA or stereo lithology I think.I think.



Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[KENAT]

Pat, FDM is similar to Stereo Lithography but with higher grade materials.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[patprimmer]

If you are going to thermo cycle it, I doubt ABS is higher grade than UV cured epoxy.

I agree FDM usually can offer materials more in keeping with the material to be used for the final product.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[mjfengineer]

I am still looking for the right vendor.

I was really hoping that vendors would know more about rapid prototyping approaches to tooling. Or at least give me an understanding of when it is appropriate.

The mold would definitely have to be two pieces as the largest build size is 24" I believe.

$4000-$5000 for a tool I am going to scrap after 150 pieces is expensive for packaging.

 

[KENAT]

I'd find a vendor to talk to.

I had one thermo form vendor that was quoting Al tooling in the price range you're talking about (assuming US $) for parts in your size range.

Some might be able to splash a wooden mold with epoxy or similar for the volumes you're talking about for less money.

(Pat, 'higher grade' was perhaps a poor choice of phrase, sorry. More robust or/tougher or production representative may have better.)

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[HDS]

Find the right vendor for the production parts and have them machine a prototype mold out of wood or renshape. You can easily make 150 parts on a mold like that depending on the geometry. One of the beautiful things about thermoforming is the cheap tooling for prototypes. I could usually have 10 thermoformed prototypes off of a wooden mold faster than a RP model could be built.

The surface finish of the FDM model will show up in the parts. A machined part will give you a better finish.

The nice thing about FDM molds is that they are porous and you don't have to drill holes.

 

[KENAT]

HDS, you sure about that life on wooden tools?

My most recent experience they only lasted about 5 units before showing serious damage.

That said, they were layered MDF, not real wood, so maybe the adhesive in the MDF was more prone to damage.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[mjfengineer]

So I will probably end up going for aluminum tooling. I quoted some FDM molds through RedEye and they were almost as expensive as the aluminum mold for parts this size. I wish there was a better option. FDM might work if someone had a nice pre-made frame so the plastic mold could be more minimalistic.

 

[KENAT]

talk to vendors, some have quoted wooden molds with epoxy coatings and similar for low volume work, may be cheaper than Al.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[mjfengineer]

Yes, some vendors will do resin based or wood tooling, which is about 20-30% less than aluminum. If there is a lot of machining required, prices are fairly close. There is also the risk of resin or wood molds failing that is eliminated with aluminum tooling.

 

[patprimmer]

I have seen wood moulds last thousands of cycles when thermoforming plastic signs. I think they where coach wood. They where certainly fairly hard and had a tight uniform interlocking grain. There was a clear finish on them. The one that specifically springs to mind is Taxi signs.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[HDS]

MDF requires a coating to make it stronger. But for thin molds the porosity sometimes lets the vacuum though.

Freeman sells lots of grades of hard and soft wood for tooling as well as foams. They even sell giant pieces of MDF that don't have to be layered. The life also depends on the geometry of the tool.

 

[patprimmer]

It also depends on temperatures and cycle times and how gently or otherwise you handle it. I have seen epoxy inserts stand up for hundreds of shots injection moulding cellulose propionate spectacle frames. That is a lot more aggressive process, but great care was taken.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules