3D Printed Mold for Rubber?

[FatgadgiParticipant @fatgadgi]

I want to make a nice looking rubber part for a REMAP job I’m doing (covers a bracket for safety).  So, 3D printed a mold & tried pouring 2 part polyurethane rubber into it.

Not my best effort 😕

I included a hole to pour the rubber into, diameter 5mm, which was far too small.  The riser was 4mm diameter.  Just couldn’t get it to fill (I even cut my losses and drilled filler hole 10mm on the hoof).

Next attempt I will make a long, big aperture to fill it and heat the rubber slightly to make it more runny (?).

Any experiences to help me ?????

Cheers Will

[renardiere7Participant @renardiere7]

Hi Will,

 

Another REMAP engineer here. I’m only a recent adopter of 3D printing however I know one of our other REMAP engineers is working on a project where over-printing of ?TPU was not working so he 3D printed molds and cast a two part PU compound successfully. He was experimenting with rubbers of different duromers to optimise the effect.

 

We have our case review meeting next week, I can ask him then if he has any tips.

All the best

Alan

[Dave SParticipant @daves59043]

Can you make the mold open on a flat surface?

direct printing in a suitable TPU might also be a viable option?

 

Dave

[FatgadgiParticipant @fatgadgi]

Hi Alan, yes please, any hints would be brilliant, thanks!

I didn’t consider overmolding – I assume it was the bonding to the substrate that was the issue.  Again, for future reference, any info about what worked or didn’t would be most welcome.

Dave – until a few moments ago, yes, I was wondering the same thing, to open the mould up.  It wouldn’t give me the shape I want to hold the finished part in situ, but there may be a compromise if I can’t get what I want.

I say a few minutes because I’ve just opened the cured first attempt.  It only half filled, but the filled half was surprisingly good, so I’m going to concentrate on that for attempt #2.

cheers Will

[FatgadgiParticipant @fatgadgi]

I should also have said, Dave, having read about the difficulties people have with printing TPU, it wouldn’t be my preferred route – I once tried printing a filled nylon, and I’ve still got the scars!

[Dave SParticipant @daves59043]

TPU prints fine on my Bambu with the default settings.
The other option might be to print a syringe like reservoir on the runner that you can force the rubber in with.

I assume you have a decent amount of vent holes to let the air out

Dave

[FatgadgiParticipant @fatgadgi]

Hi Dave – still not (quite) desperate enough to try printing it yet 😂

Have your TPU prints had supports?

I did have what I thought was a decent diameter vent hole at 4mm, but my next attempt will have just a big slot.  And a big funnel to hold the liquid as it drains down, similar to your syringe idea.

Cheers Will

[Dave SParticipant @daves59043]

Phone cases mostly. Small amount of supports, but not very much.

what shape is this thingy?

 

Dave

[FatgadgiParticipant @fatgadgi]

Dave – I’ll post a picci when I can, in a couple of days.

Cheers Peter

[renardiere7Participant @renardiere7]

Hi Will,

I spoke to my colleague tonight about your moulding problem. In general terms his advice is make the entry aperture for the liquid PU large, maintain a head of fluid in a funnel or large syringe with the plunger removed.

You must have a bleed hole to allow air to escape from the far end of the mould and could consider applying suction to that hole for example with another large syringe.

Speaking from my own experience as a veterinary surgeon I would recommend using feeding syringes for this as they have large tapered nozzles, about 6mm at the small end and can be got in large volumes. I’ve got a bag full of out of date ones in my workshop or garage so if you want a couple let me have your address and I’ll post them out to you.

[FatgadgiParticipant @fatgadgi]

Hi Dave – rubber boot looks like this, about 70mm wide:

Thanks Alan – I’m going to take your advice and print a funnel into the next attempt.  Its already on the printer.  The syringe is a very kind offer – I’ll shout if I cant get the funnel to work.  I’m going to make sure that everything is nice and warm so it flows easily (so long as it doesn’t set too quickly).

I’m also going to have a go at over-molding a part to see what happens.  Probably end up a mess, and I know your friend didn’t like his results, but it’s fun trying.

I’ll post when I’ve finished the attempts.

[Neil WyattModerator @neilwyatt]

I’ve not had issues with printing TPU, big, robust items print OK.

The secret is many extruders benefit if you print and install (or machine) a little guide to bridge the gap between the extruder gears and the nozzle entry. Works a treat.

Neil

[Dave SParticipant @daves59043]

Long flat sections are going to be a problem to fill. I’d attempt to have multiple sprue entrances to each flat piece.

[FatgadgiParticipant @fatgadgi]

Well, tried the over-moulded part …. success (almost).

The part is good and very usable, very happy.  But the mold looked a bit bedraggled after I opened it (because of sticking).  I need 4 in total, so I need to improve this.

Photos below show the printed mold and the finished part.  I warmed everything up this time and filled it in a vertical orientation, which with the funnels and large fill-holes, filled really easily.  I included a few interlocks on the printed shell, plus roughed it up with coarse sandpaper.

Going to modify the mold for the next attempt, plus I’ll try the solid rubber part as well.

Cheers – Peter

[renardiere7Participant @renardiere7]

Looks like a creditable result.

[Author]

Posts