Printed Molds

[Big Epp]

Anyone have experience 3D printing plastic molds?

[Jazzatomo]

Been doing it for a few months. I have a basic FDM printer, the ANET A2. 

I can print moulds and have them inject well with PLA at 0.1mm and 40% fill, but the moulds will warp from the heat over time. 

Its great for testing ideas, but you do end up with lines from the layers in the final bait. 

I know some guys who use resin printers, which can print even finer again and they say they get no lines on their baits, but i havent seen the baits close up to be sure. 

[Vodkaman]

Unfortunately, the PLA melting point is roughly the same temperature that you are pouring, and so severe distortion is unavoidable. You need to find a printing material with a higher temperature tolerance. Distortion can be mitigated by load spreading plates and plenty of clamping. But you still have the problem of pouring into an insulating material with poor cooling qualities.

I don't own a printer but class myself as a CAD expert seeing as CAD design has been my job for 35 years. Also, I am hard-baits and so not hampered by the extreme temperatures of the soft-bait pourer. The best that you can do IMO, is print a master and then cast it in POP or some other casting material that can take the heat.

As far as hard-baits is concerned, my plan was to print a PLA negative mold to cast a positive mold in another material, designing the PLA negative such that the resulting positive was symmetrical, in other words, both mold halves were identical, so only one PLA master was needed.

Unfortunately, the heat distortion from the exothermic reaction of POP or other cast materials made mating the halves impossible. With my financials being stretched and 3D prints costing $100 a time, I cannot throw money at a whim.

However, I have a lure design on the go that needs building, and the replication accuracy required means that only 3D printing can give me what I want. I will have to design a positive and print both halves for pouring polyester resin. The design will have a ridiculous number of clamping holes and load spreading wooden plates. The design will help me to determine the minimum clamping required as I try various clamp configurations.

I am trying to summon up the enthusiasm to hit the design again as lure wall thickness was a problem on my last attempt, giving incomplete pours.

I really do need my own printer as this project is costing me way too much in 3rd party services. I know it makes fiscal sense, but I want to see some success before I commit.

The beauty is that if the design is successful, I could take it straight to production injection molding on a grand scale with confidence.

Good luck with your project.

Dave

[Jazzatomo]

18 hours ago, Vodkaman said:

Unfortunately, the PLA melting point is roughly the same temperature that you are pouring, and so severe distortion is unavoidable. You need to find a printing material with a higher temperature tolerance. Distortion can be mitigated by load spreading plates and plenty of clamping. But you still have the problem of pouring into an insulating material with poor cooling qualities.

I definitely appreciate what your saying Dave. 

Making masters is definitely a viable option and there a number of approaches from just printing the bait, to printing a half injection mould with the master still in it for each side.

 Surprisingly, injecting at approx 150 deg C / 302 F produces some great baits, with only the warping of the mould to contend with. Ill get 10 - 15 runs of baits through a PLA + mould before the mould starts to bow and get flashing on the baits. There are higher heat filaments available, but my poor little printer cant get the hot bed hot enough for the halves to adhere correctly. 

For rapid prototyping I definitely prefer just injecting straight into the plastic. When I can reprint a 6 slot mould overnight, the 2 or 3 days of work to make a pop mould is a bit beyond. Especially when i am testing 1 - 4 moulds a week when I get inspired


 

[Vodkaman]

Try building more clamping holes into the mould, back drill through some plywood backing plates and clamp up the sandwich tight. This is obviously not a convenient solution involving more work in putting the mould halves together, but it may get you more pours or even solve the problem.

If you try it then give me feedback, positive or negative.

Dave

[Jazzatomo]

2 minutes ago, Vodkaman said:

Try building more clamping holes into the mould, back drill through some plywood backing plates and clamp up the sandwich tight. This is obviously not a convenient solution involving more work in putting the mould halves together, but it may get you more pours or even solve the problem.

If you try it then give me feedback, positive or negative.

Dave

Will let you know mate. Would have to work out a way to do it in such a way that all the different moulds I have made up. Or just size the smaller ones to an arbitrary dimension. But i can see where you are coming from.... Hopefully in the new year ill have a CNC and i can just do it all in aluminium.

[Vodkaman]

CNC is a BIG step, so good luck with that one.

The problem is that the mould plastic softens with the heat. With the standard 4-corner clamping, the mold will still bow in the center, even clamp plates may not solve this. Clamping needs to be close to the cavities and well distributed.

Here is a pic of the mold I was about to have printed, but I have since changed the design in my head, and so needs remodeling. You can see all the clamp bolt holes.

As a side note, you can also see that this plate is the same for both halves; flip and rotate 180 degrees.

Dave

[mark poulson]

Forgive a non-CAD fluent question, but would embedding the mold halves in support wooden boxes that you can clamp together prevent mold warping?

[Vodkaman]

Mark - Yes, basically what I want them to do; between plywood backing plates, but with a lot more clamping. I didn't mention plywood thickness, I would say at least 0.5" or thicker.

The problem with a 3D print the size of a mold is that it can take 24 hours to print, and so the overall mold thickness tends to get compromised. BUT, the mold is going to warp what ever thickness that you make it except it is going to require more effort to correct an overly thick mold, and it will take more intermediate bolt clamps to correct an overly thin mold. As always, design is a compromise.

Just a thought - If we ever get the PLA molds to work, we could consider internal cooling pipe matrix for an air flow or possibly a water flow, but we should solve the immediate problems first.

Here is an ISO view of my hard-bait mold half.

Dave

Edited November 12, 2020 by Vodkaman

[Travis]

I haven't tried printing a mold as simply takes too long for something that I know isn't going to work as needed.  PLA molds for soft plastics simply is a poor media. Much better off just printing the bait and molding it in both time, effort, and use of product.

 Maybe I will goof around over winter break with printing some masters and see about making a mold of them.  I am so proficient in Fusion 360 might be done next winter. 

 

Edited November 12, 2020 by Travis

[Vodkaman]

Travis - my hard-bait molds should fare better being a cold process with a little exothermic reaction.

It will be interesting to see if my suggestions can extract more pours directly from a 3D printed mold, it is just a prototyping method, and may produce enough for own use only applications.

I do agree that printing a positive and molding in POP or other material would be the way to go, as I posted in my first reply.

Dave

[TheHardcoreCarnivore]

Print them in PET-G. Higher temp threshold. Probably 4 walls and 40% gyroid infill. The cost difference of the filament is negligible. I print lures but can't CAD for the life of me so haven't gotten to molds yet.