Injection machine problems and my solutions - OSR - Forum

Author: Clarissa

Sep. 01, 2025

Injection machine problems and my solutions - OSR - Forum

Problems:
1. Plunger sticking in the top of the tube.
2. Plastic running out of the nozzle between injections.
3. Very rough finish and excessive sinking/shrinking in finished parts.

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Solutions:
1. Moved one of the heaters to the top of the tube and moved the temp sensor under the hopper.
2. installed ball valve on nozzle end.
3. Changed the the geometry of the handle to double the injection pressure, added a stirrup to stand in to apply pressure for 1 minute after injection.

My parts now have a smooth, shiny finish and the accuracy and strength is greatly improved.  Attached are pictures of my hacks.

Hi, @tathata, thank you for the kind words. The plastic is HDPE and I’m using a Precious Plastic injection machine built exactly to the plans and then modifying it slightly as my previous posts show. The nozzle temp is 210C and the barrel is 190C.

I also love cnc machines. I’m now building a cnc router with the parts I’ve made. I think it will be rigid enough to cut aluminum using a 1.5 KW spindle. I’ll post my results under “Share you creations” here in the forums.

I hope this helps.

Hi, guys! This desing of CNC runner is of interest to me too.
I have been thinking along similar lines for some time. My variant on the idea has been to cast the bearing-holder bracket (looking much the same as your drawing) from molten scrap aluminium. If plastic is stiff enough do the job, that’s even easier! The rest of my plan is to make a large, level table in the garden – with straight *scaffolding poles* (about 9 feet long) running along the table top on each side. These brackets & bearings would then be suitably-sized to run on the scaffolding poles. The moving bridge 90 degrees across would carry a small table with a universal fittings for interchangeable tools. Even without CNC control to begin with, I could mount a swivelling circular saw, and cut up full sheets of ply in both the x & y direction… or change the tool to a router, and mill a rough piece of wood flat by moving the router about. Maybe larger versions of this fitting *would* be sturdier, if cast in aluminium. The process is not really harder: Plenty of youtube videos show people melting scrap aluminium in steel cans in their back garden. I apologise for not contributing much to the *main* issues in this thread. I’ll do better next time! I guess this CNC table idea excites me more, on this occasion, because I really miss not having one.

Hi, I have changed the design a little to add a little more rigidity, I’ll upload my current dxf file. The bearings are 625 (5mm bore, 5mm wide, 16mm diameter. I’m going to machine a new mold tomorrow. Allowing for some shrinking is a little tricky.
To get all the holes in the right place I milled grooves in each half of the mold and drilled the holes for the aluminum framing. I placed threaded rods in the grooves and bolts in the holes and removed them after injecting the part. I then drilled the holes to size. I’m going to try 5mm rods in my new mold and try to press them out with a small arbor press. If that doesn’t work well I’ll go back to threaded rods, they are easy to unscrew.

Yes, I drew some inspiration from MPCNC. I’ve built some machines using maker slide with the plastic rollers and I think this is more rigid, that was my intent. I designed the slides around larger tubing, 1.5″(38mm) tubing for more rigidity as well. Do you know if 38mm is a common size in Europe? 1.5″ tubing is easy to get and pretty cheap here in the US. I’ll share my results here when I finish a machine with these parts. An inexpensive machine to make molds is my intent.

What Are Mini Injection Molding Machines Used For and How Do ...

In the world of plastic manufacturing, mini injection molding machines are gaining popularity due to their versatility, cost-effectiveness, and efficiency. These compact systems are increasingly being used by businesses aiming to produce small to medium-sized parts. But what exactly are mini injection molding machines used for, and how do they meet the diverse needs of their users? This article explores various aspects such as product materials, usage scenarios, sourcing tips, and how to choose the right machine, providing a comprehensive overview of this essential equipment in the plastic industry.

Understanding Product Materials for Mini Injection Molding Machines

Mini injection molding machines are compatible with a wide variety of materials, making them incredibly versatile. Common options include thermoplastics like polypropylene, polyethylene, polystyrene, and more specialized materials like elastomers and certain biodegradable plastics. The choice of material depends heavily on the end-use of the molded part.

For instance, a small business producing custom keychains might opt for a colorful thermoplastic like acrylonitrile butadiene styrene (ABS) due to its durability and vibrant finish. In contrast, a medical device company might select a biocompatible thermoplastic such as polycarbonate-resin blends due to their strength and safety for medical applications.

An anecdotal example includes a local startup that used a mini injection molding machine to test a new biodegradable plastic for producing eco-friendly cutlery. This experimentation helped them refine their material mix before scaling up production.

Exploring Usage Scenarios: Where Do Mini Injection Molding Machines Fit?

Mini injection molding machines are ideal for a variety of applications, particularly those involving smaller parts or lower volume production. Due to their compact size, they are also perfect for settings with limited space, such as educational workshops or small-scale manufacturing facilities.

One common usage scenario is in the prototyping process. Companies often rely on these machines to produce prototypes before committing to large-scale production runs. This capability allows for ample design testing and iteration without significant financial commitment.

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Additionally, industries such as electronics, automotive, and toys often use these machines to manufacture custom-small parts or intricate components with precision. A hobbyist might use a mini injection molding machine to craft custom items such as model parts or unique artistic pieces, which can be sold online or shared in craft fairs.

Sourcing Tips: Finding the Right Supplier

When sourcing a mini injection molding machine, buyers should consider several key factors to ensure they're selecting the optimal equipment for their needs. First, it's important to assess the machine's capacity and compatibility with the materials you'll be using most frequently. Machines typically specify the type of plastic they can process, so verify this information carefully.

It's also advantageous to explore the reputation and customer service quality of suppliers. Opting for a well-known manufacturer with a strong track record in the industry is often wise. Check online reviews and ask for testimonials from other clients to gauge reliability and post-purchase support.

An effective tip is to attend industry trade shows and networking events. These platforms provide firsthand exposure to the machines' capabilities and a chance to engage with experts who can offer insights tailored to your specific queries.

How to Choose the Right Mini Injection Molding Machine

Choosing the right mini injection molding machine involves evaluating your production requirements and understanding the technical specifications that align with your needs. Start by assessing the mold size and shot capacity, these specifications dictate the maximum part dimensions and volume you can produce per shot.

An additional consideration is the machine's automation level. Fully automated machines may increase efficiency but come with higher initial costs. For startups, a manual or semi-automated machine might be a suitable initial investment, offering a balance between functionality and budget constraints.

One example of strategic decision-making comes from a small educational institute that aimed to integrate practical manufacturing lessons into its curriculum. They selected a user-friendly, semi-automated machine that facilitated hands-on learning without the complexity of a fully automated system, proving to be an ideal entry point for novice users.

Conclusion

Mini injection molding machines represent a valuable tool for producers requiring flexibility, precision, and cost-effective production of plastic parts. Whether used in a small business setting, educational environment, or by individual hobbyists, these machines can meet various needs. By comprehending the materials suited for these machines, understanding the potential usage scenarios, and carefully selecting a reliable supplier, businesses can effectively integrate mini injection molding machines into their operations.

Frequently Asked Questions

What types of products can be made with mini injection molding machines?

Mini injection molding machines can produce a wide array of products ranging from intricate electronic components to custom art pieces and small functional parts for various applications such as automotive and medical sectors.

Are mini injection molding machines suitable for beginners?

Yes, many mini injection molding machines are designed with user-friendly interfaces suitable for beginners. There are models specifically tailored for educational purposes and hobbyists, featuring straightforward operation and safety mechanisms.

How do I maintain a mini injection molding machine?

Regular maintenance involves cleaning the machine, ensuring all moving parts are lubricated, and checking for wear and damage. Following the manufacturer's maintenance guidelines is vital to preserve efficiency and extend the machine's lifespan.

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