Injection Molding Discussion


Hey All!

Setting up a thread for Inejction Molding discussions as it relates to Formlabs printers! Please jump in and drop your thoughts, opinions, expertise, questions, and anything else!


Is there a Formlabs “jumping off” page somewhere that curates all your resources and recommended guidelines for injection molding? I know I’ve gotten a few in my emails lately:

Low-Volume Rapid Injection Molding with 3D Printed Molds

How a Contract Manufacturer Uses 3D Printed Molds for Low-Volume Production

How to Quickly Fabricate Short Run Injection Molds: A Live Panel Discussion


Great question! I think a more substantial IM “hub” is in the works which should take some of the guess work out of finding those resources.


I’m looking forward to making better molds and better parts. Thank you to FormLabs people for your help making this seem possible!

My resources:
I have a table-top molding machine from LNS ( and a couple small mud-frames The press is great but it is very low-tech. I am running Solidworks - but I don’t have the plastic mold-analysis feature. Oh, and I have a Form2 printer (w/ high temp, grey pro & some others). For molding, I have some virgin PP that molds nicely with the sample (metal) mold LNS supplied.

My issues:
(1) What I think I could use help with is how to design a mold that helps me utilize these tools. What I mean is that the mold press doesn’t let me know how much material I’m pressing into the mold so I get a lot of short-shots and blow-outs. I should probably make some strategically-placed big-ish exits (1mm diameter) so that material can escape and then when I see this, I’ll know it’s filled. (This might mean I don’t get as much packing pressure, but maybe that’s a trade-off)
(2) Another thing I want to improve is the main gate I was over-complicating things and put in a funnel-shaped washer on my first runs & that was really hard to clean. I think a flat washer will be much better.
(3) The LNS press comes with a standard clamp and an extra quick-release clamp. I want to design my molds so that I can get the most out of the clamping (to hopefully get less blow-outs). I did one hybrid mold where the ballast was made from my FDM printer (much less $ to run) and it filled out the mud frame & only the important parts when on the Form2. I would do this again.
(4) Lastly - I wonder what is a good first-part to test with this setup? Anybody want to suggest a simple part to make - and share an STL of the mold? Mold making and 3d printing are lots of fun but a little overwhelming - so many possibilities…!



Does anyone have experience with the MicroMolder lineup?
I’d also like to talk to an injection molding shop about doing a run for me on tooling that I’d print here.

DW Horton


I was looking at the MicroMolder myself as well…but the shot size looks so small that I’m unsure how useful it would be realistically.


The MicroMolder is not out yet. They currently claim the early bird shipments (10 in US and 10 internationally) will start shipping at the end of June, but could be delayed again due to shortage of components.

Including this one, I know of 3 injection molding machines launched on Kickstarter over the past 7 years. I know one was called the AllForge, can’t remember the other one. All have been fully funded, but none have delivered yet. They all get into the testing stage and then you don’t hear anything about them again.

I’d be leary about pre-ordering until they actually start shipping. The people who pre-ordered the AllForge after their Kickstarter closed lost all of their money. By the time the company folded it was too late to get their money refunded by their credit card companies. It was in a similar price ranges the MicroMolder.

BabyPlast injection molding machines out of Italy are shipping, but I have no idea of cost, since you have to contact a sales person for pricing.


ProtoLabs used to have some design guides for molds and other types of manufactured parts. It might be worth browsing their web site to see what they have available.


I think BabyPlast machines are in the order of $10-20K from a quick google. I know several people who use these machines and they are legit.


That’s helpful, thanks very much.

I’ve contacted probably five injection molding businesses and nobody will attempt to use printed tooling. I’ve shared every white paper FL has on the subject, but can’t convince them.

I have a job ready that I’m currently using my 3L to fill, but I’d like to increase the qty and lower costs (don’t we all).


Thanks! I will check it out.


I felt that the 3D printed molds were for the small injection molding machines that are being discussed here, not for machines run by injection molding companies. I have clients that have their own small machines (most are the manual kind). They just need someone to make the molds.

You’ll also find that most molding companies won’t accept aluminum or steel molds made by other injection molding companies. They will only use the mold they make with their equipment. There are two main reasons -

  1. Mold making is a HUGE moneymaker for those companies. The clients try to shave pennies off the cost per part, but the cost to make the mold doesn’t ever have any wiggle room except to change the material the mold is made from. They charge thousands for the simplest mold, which is why everyone is trying to find an alternative ways to make molds.

  2. A badly made mold provided by a customer could damage their equipment and take weeks to fix if they have to order parts or bring a technician out. Would you let a client provide their own resin that comes in an unlabeled bottle for your Form 3L when you print their job? You’d tell them no, because it could damage your 3L or create a huge mess that you’ll spend a half day cleaning up.

It could also be argued that experimentation for a client cuts into your profit margin and slows down the flow of work through your business. When I get an odd material request for one of my FDM printers, I know I’ll have to spend time to dial in the settings and might have 2 or 3 restarts on a print job to get the print as perfect as can be. This means what should be a 60 hour print job could become a 180 hour print job (or longer), so I have to give the client an estimate for 180 hours (which will be crazy expensive) or an estimate for 60 hours and eat the cost of wasted filament, electricity, wear and tear, and the money lost from other jobs being delayed. It also adds a lot of unknowns to the production schedule for clients in the queue behind the oddball request. If I tell a client that their print job will be done sometime between 2.5 days to 7.5 days, they will look for someone else to print their project.


Thanks again - I can understand the injection shop’s point of view, but I guess I didn’t consider that the large machines couldn’t be ‘dialled down’ to work with smaller tooling.
Maybe I should shift my focus towards finding someone with a BabyPlast machine who is willing to work with my tooling. Or save up and buy my own :slight_smile:

You’ve been very helpful.


I’m in the process of setting up an injection molding shop right now, and I just thought I’d drop in and explain some of the non-financial reasons companies are hesitant to use molds designed by clients. As someone else already mentioned, there are of course financial incentives, but there actually are some functional reasons as well.

Mold design is very technical. Depending on the resin used, the geometry of the part, and the gate location, something as minor as a 0.5mm difference in gate size, or even just the shape of the gate, could as much as double the injection pressure needed to fill a part. Beyond that, it might be impossible to fill a part with any amount of pressure, or you might get poor quality fills, or ugly artifacts, if the gate is in the wrong location. For all these reasons, it is very common that a mold will have to be reworked and tweaked several times before you get a good part fill. If this is being done by a customer, who doesn’t know your process, equipment, or the capabilities of your machine, getting all these factors right, at the very least would take an insanely long amount of time to keep trading molds back and forth, if it wouldn’t be flat out impossible.

For all these same reasons, quite often shops use very expensive simulation software to get an idea how a particular resin will work in a particular mold, and this software gives them a good idea where to start on their settings, to get a good fill. If you are just handed a mold with no simulation, not reports, and no starting numbers, then there is a lot of trial and error, trying to guestimate the right values, chewing up both machine time and manpower. This could very quickly end up with the “cheap” customer provided mold, actually being a more expensive job than if they had just designed the mold themselves.

There’s also the fact that you have literally no way to know how good a mold designer your customer is. It’s easy to design a mold that is just never going to produce quality parts. Sink marks, weld lines, burning, poor surface quality, these are all artifacts that can happen no matter what you do, if the mold is poorly designed. Customers don’t have good things to say about your business if the parts you make for them look like garbage, and sometimes even refuse to pay if you can’t deliver the quality they expect. If they are providing the mold, you have no control over the final quality of the part, and that presents not just a huge reputational risk, but a very high chance of a bad customer interaction, that will leave both parties wishing they had never even tried this. No one actively wants to go seeking hard feelings.

The last thing is just straight up production process issues. There is basically no decent way to cool a 3D printed plastic mold insert. In a normal aluminum or steel mold, you’re going to have plumbing running through the mold to a temperature control unit, which will keep the mold in a certain temperature range. This way, you have some control of plastic flow, crystallization, shrinkage, and demold times. With a plastic insert, it’s probably going to be too cold when you first inject plastic, giving you a short shot that doesn’t fill the part, and then after some number of shots it’s going to get too hot, and either damage the insert, or causing warping on demold, because the part hasn’t cooled enough. This means it is both time and material consuming to trial and error how many shots you have before you get a good one, and then how many good ones you get before they go bad again. That’s just not something a production job shop wants to deal with for a small order.

I hope that cleared up some of the issues, and explained some of why it can be so hard to find a company willing to deal with it.


Thanks, that’s very helpful. My main business is hot rod chassis parts which includes bars used in suspension systems. We refused to work with customer supplied tubing due to experiences with material that wouldn’t drill and tap nicely, ultimately resulting in unhappiness all around. All that to say; “I get it” :slight_smile:

I’m learning more about the process through this thread… seems like the best way is to buck up and pay the experts!

Thanks to everyone for patiently helping me through this - this is a great online community!