Injection moulding success

Just thought I would share this.
Printed a mould using Standard Grey Resin at 50microns.
Injected with LDP using my desktop injector.
Been going now for approx 60 squirts with no visible sign of wear or damage.
The part is approx 75mm x 30mm x 5mm with some of the detail well below 0.5mm.

A UK K2 telephone box if anyone asks!
I reached the dizzying volume of 15 per hour.


And here i was thinking you were making a TARDIS… :wink:


Adding the metal bar on top between the injector and spru is a really good way to keep the printed mold from degrading.

I think this type of low pressure part is perfect for printed molds.

15 parts per hour is actually really fast for a manual machine. Any faster and the mold would probably overheat.

Looks great. I’ve wondered about doing injection molding but until now. Might actually look into it deeper.

This looks great! Getting a sense for the lifetime of printed molds is a bit challenging and your results are pretty exciting especially as you’re using Grey which has a low HDT as compared to High Temp Resin.

The metal bar is essential - the heated nozzle just burns through otherwise.
You might see two inserts eitherside of the injection point, I have two m3 bolts going thru the metal bar into the two inserts. Lines things up for me.
I have this set up quite close to my freezer. So my routine for this has been: inject, leave for 1 minute in insitu, remove to the freezer for 1 minute then crack open.
I have had the injector and been trying things for the past few months. Each project has slightly different routines and needs different nursing strategies! Leaving the mould in-situ for this one gives me a better surface finish.
I did start off trying to use HT resin in the hope I would be able to inject Nylon, but I found HT resin is quite delicate. Even showing it the vice on the injector cracked it.
To use HT would definitely require an outer metal frame.
My injector is from Travin (here in the UK). Good solid 1950’s style British engineering for approx £1500…

Well, the Dr was sighted at the Saturday march for Science;))

That looks Really Promising… When You printed that… Did you Print it flat on the Build plate or use supports

Here is the preform.

Thanks… Looks great… I am starting to play with the Injection idea and was working on a variable clamp/holder to compensate for print inconsistency when printing flat on the build platform. I really like that you got 60 Squirts so far as that was one of my real hesitations of using the printer for the tooling if a person was only going to get 10-15 uses before failure the cost of material is not enough to offset any savings by injecting. I figured my Break even point is 30 and I am not in business to break Even :slight_smile:

I have also used Standard white with similiar success

This mould produces 6 “wedges” approx 20mmx14mmx10mm.
Its still going strong.
Any new mould I make will have at least a 10mm border around the edges. I tried economising by reducing it down to 5mm but I get problems with leakage/flashing
These needed 5mins in the freezer before I could crack the mould due to the thickness of the plastic.
It might be worth considering your ( billiejean ) tank tread example in another post as a moulding candidate??

You should get better results with a high temp resin. The standard resins become too soft under heat and probably explains the flash I saw on one of the castings.
I know when I make a hot mold from my clear parts I have to be careful when de-molding the masters because they are soft and somewhat fragile.
A good post uv curing does help. If your using standard resins then the clear will probably be a little more durable than the gray. Also look cool when filling up :slight_smile:

High temp will probably break without a frame around the entire part and that’s what most of us are trying to avoid. A full frame needs to fit snug on all sides and has to be adjustable to control flashing.

I’ve switched to alumilite for my molds. You just print a negative of your mold and cast the working mold into that. Pull the printed mold off (heat as needed) and you’re good to go. It’s much cheaper to print a 1.5mm thick shell instead of a 50 x 100 x 20 block of resin. Also, you can clamp it down hard as long as the clamp covers the entire mold (no frame is needed as long as the mold is thick enough on the sides.

Smooth On also has an aluminum filled material but they’re on the West coast instead of here in Michigan. Either place has really good support.

Ahh… The tracks couldn’t be Injected just due to the design. To make them snap together there is a larger hole in the middle of the track pad that the end connector snaps into… But I have a million other ideas I would love to use injection molding on… It is a delicate balance… In the world of model building/conversions cast resin kits are usually very short runs. 100 is considered a huge success due to pricing and subject matter. But if the kits could be made in plastic you are starting to tap into a larger market so a good run could be 200-300.
That is where I am walking a fine line, trying to decide which way to go… When I start doing the math of time vs production… I love the idea of Injection molding (Just like the rest of the world) But unless I drop another $5000 on the low end to $10k or more for a entry level Semi Automatic desktop Injection Unit. But now I am limiting myself to the detail one can achieve just due to the process. (No Under cuts)
Plus I don’t want to have to sit in front of a Manual Plunger to make injected parts. That’s as bad as pouring resin for hours on end. Reminds me too much of reloading bullets as a kid for my dad for days on end.
Like Fred said… Using poured resin for the molds is a good alternative… I use to mill epoxy for mold patterns the same way.
So I have started playing with my own formulas of Mixing resin (Tough and Grey) and have had some good success with that as to keeping the detail the grey gives you and the strength the tough provides. So I am thinking of buying a second F2 and just start a small production line of printing… It is just the resin solution that is slowing me down. I have tried to talk to the guys at FL but I can never seem to get an answer. I sent in some sample files to ask their opinion but never got a reply.(Good thing I paid for the pro support) (that is also one of the reasons I am holding off on a second machine at the moment.)

Here are a few screenshots of some other parts/kits I am developing and would never be able to inject or even cast them in resin (Without some serious clean up.)

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Some parts just aren’t suitable for molding. The cylinder head would be cast in real life because of the port shapes.

You 100% can have under cuts with printed molds they just get a little more complex. Doubt they would last all that long either.

I have used dowel pins for holes in molded parts and they work fine. Fun to figure out how to remove but doable.

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I would expect the High Temperature Resin to be best for this. Both Grey and Tough Resins have relatively low heat deflection temperatures and would become soft when used with most thermoplastics. High Temp has an HDT of 289C @ 0.45MPa which is going to be compatible with most thermoplastics and also has comparable stiffness to Standard Resins.

Yes, Formlabs High Temp resin is the best for Injection molding but you need to be careful not to over cure it or it becomes to brittle to work with. It woks best to 3D print the core and cavity and used a pocketed out mold base. The prototype mold base can can have water cooling, ejection and gates and runners built in…The next step we are working on are 3D metal printed core and cavities for full production…

Thanks B

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