For those new to the injection molding industry, choosing the right injection molding machine can be overwhelming. Even experienced professionals sometimes need a refresher. Whether you only have product samples, a basic understanding, or require special features like a hopper, this guide will simplify the process and help you find the injection molding machine that perfectly suits your needs.
Gather These 4 Key Pieces of Information First
Before researching machines, collect these details—they’ll be your core checklist for every decision:
- Mold details: Width, height, thickness, weight, and special designs (e.g., complex cavities).
- Plastic type: Single material (e.g., PP, ABS) or multiple materials (for 2-color parts).
- Product specifications: Length, width, height, thickness, and weight of the part.
- Production requirements: High-quality parts, fast speeds, or a balance of both.
Narrow Down Your Machine Selection
With the above info in hand, follow these steps to find your match:
1. Choose the Right Machine Type
Start by matching the machine to your product and plastic:
- Plastic compatibility: Standard thermoplastics (e.g., PE) work with regular machines; PET or Bakelite need specialized models.
- Color needs: Single-color, dual-color, or multicolor parts require different machine series.
- Extra features: For high precision (closed-loop control) or ultra-fast injection, pick a series that includes these functions.
2. Ensure Mold Compatibility
The machine must have enough space for your mold. Check these 4 points:
- Mold width/height ≤ machine’s tie-bar spacing (gap between main pillars).
- Mold fits within the machine’s platen size (flat surface holding the mold).
- Mold thickness is between the machine’s minimum and maximum mold thickness limits.
- Avoid molds smaller than the machine’s recommended minimum size.
3. Ensure Easy Part Removal
After molding, you need to take the part out smoothly. Focus on two factors:
- Opening stroke: Machine opening distance ≥ twice the part’s height + length of the gate (plastic flow path for the mold).
- Ejector stroke: The part-ejecting mechanism has enough range to fully release the part.
4. Securely Lock the Mold (Clamping Force)
High-pressure plastic injection tries to push the mold open—clamping force (in tons) must resist this. Estimate your needs:
- Calculate the part’s projected area (area viewed from the mold opening direction, in cm²).
- Multiply by cavity number (e.g., 4 cavities = ×4) and mold internal pressure (350–400 kg/cm² for most plastics) to get the "mold-opening force".
- Choose a machine with clamping force 1.17x higher than this force (for safety).
5. Inject Enough Plastic (Injection Capacity)
The machine must inject enough plastic to fill the mold. Follow this rule:
- Calculate total plastic weight needed (part weight × cavity number).
- Machine’s injection capacity (max plastic it can inject) ≥ 1.35x the total weight (ensures stable production).
- Match screw diameter to this capacity: smaller screws = less capacity; larger screws = more capacity.
6. Achieve High-Quality Injection (Pressure & Screw Design)
Some plastics (e.g., engineering plastics like PC) need specific settings for good molding:
- Injection pressure: Smaller screws usually provide higher pressure—ideal for tough plastics.
- Screw compression ratio: Affects plastic melting. Ask the manufacturer for the right ratio for your material.
7. Inject at the Right Speed
Fast injection is critical for thin products (e.g., phone cases). Check these:
- Does the machine’s injection speed meet your needs?
- For ultra-fast speeds, ask about add-ons like accumulators or closed-loop control.
- Note: High-pressure screws often have slower speeds (and vice versa)—balance speed and pressure for your product.
Special Cases to Consider
Standard machines don’t always fit. Here’s how to handle common exceptions:
Mold & Capacity Mismatches
- Large mold, small shot volume: Use a "big clamp + small shot" setup (standard large clamping unit + smaller screw).
- Small mold, large shot volume: Use a "small clamp + large shot" setup (standard small clamping unit + larger screw).
High-Speed or Fast-Cycle Machines
Many buyers want faster production to cut costs. Machines achieve this in 4 ways:
- Faster injection: Larger motors/pumps or accumulators (closed-loop control improves performance).
- Faster feeding: Larger motors or smaller hydraulic motors (speed up screw rotation).
- Multi-circuit systems: Perform 2–3 actions at once (e.g., cooling + feeding) to save time.
- Better cooling: More water channels in the mold to speed up plastic solidification.
Note: Faster machines have higher upfront costs and energy use. Calculate if the speed boost will bring long-term savings.
Ready to Find Your Machine?
Whether you need a brand-new injection molding machine for high-volume production or a reliable used one for smaller projects, Elite Mold Tech has you covered. We’ll help you match the right machine to your product and budget.
- WhatsApp us: +86 19860504405
Let’s find the perfect machine to bring your products to life.
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