Injection Molding FAQ

 Injection Molding is the standard manufacturing process for mass-producing plastic parts with high consistency and tight tolerances. At Boona, we specialize in Rapid Tooling (Bridge Production) and Low-Volume Production. We use aluminum or steel molds to inject molten plastic into a cavity, creating parts identical to final mass-produced products but with a much faster turnaround time than traditional mold makers.

• Rapid Tooling (Soft Tooling): Uses Aluminum (7075) or soft Steel (P20). It is cheaper and faster to build (10-15 days) but has a shorter life (10k-50k shots). Ideal for market testing.

• Production Tooling (Hard Tooling): Uses hardened Steel (NAK80, H13). It costs more and takes longer (4-6 weeks) but lasts for millions of cycles. Boona helps you choose the right strategy based on your volume.

No. Unlike traditional factories that demand 10,000+ units, Boona supports Low-Volume Manufacturing. We can mold as few as 50 to 1,000 parts for your pilot run. If you only need 1-10 parts, we recommend 3D Printing or Vacuum Casting.

 For simple molds, we can ship T1 samples (first shots) in as little as 10-15 days. Complex molds with side actions or sliders usually take 20-30 days.

You do. Once you pay for the tooling, the mold is 100% your property. We store it in our facility for free for your future production runs, or we can ship it to you (shipping costs apply).

Tooling cost is driven by:

1. Part Size & Complexity: Larger parts require larger mold bases. Undercuts require expensive sliders/lifters.

2. Cavity Count: More cavities = higher tooling cost but lower unit price.

3. Mold Material: Steel is more expensive than Aluminum. Tip: To get an accurate price, upload your STEP file to our Online Quote Form.

•  Remove Undercuts: Simplify the design to open/shut without side actions.
• Use MUD Inserts: We use shared standard mold bases (Master Unit Die) and only machine the core/cavity inserts for your part. This saves 30-50% cost.
• Relax Tolerances: Tighter tolerances require EDM machining, which increases cost.

 A Family Mold creates multiple different parts (e.g., Top Case + Bottom Case) in the same mold base during one shot.

• Pro: Saves tooling cost (1 mold instead of 2).
• Con: Hard to balance flow if parts have different sizes. Boona engineers will advise if your parts are suitable for a family mold.

While the initial tooling cost is high, the material cost (plastic pellets) is very low, and the cycle time is fast (seconds). Once you produce over 100-300 units, Injection Molding becomes cheaper per unit than 3D Printing or CNC Machining.

Yes, absolutely. A draft angle (usually 1° to 3°) allows the part to eject smoothly from the mold without dragging or scratching.

• Smooth surfaces: 1° is minimal.
• Textured surfaces: Require 3° or more. Our DFM engineers will help you analyze draft angles before cutting steel.

 Uniform wall thickness is key. Variations cause cooling issues.

• Recommended: 1.5mm to 3.0mm.
• Issue: Thick sections cool slowly, causing Sink Marks. Thin sections may cause Short Shots (incomplete filling).
• Solution: If you need a thick section, core it out and use ribs for strength.

Yes. We use Sliders (Side Actions) or Lifters to mold undercuts. Note that these mechanisms increase the tooling cost. For low-volume parts, we can also use “Hand-Loaded Inserts” to save money.

Edge Gate: Most common, located on the parting line. Easy to trim.

• Sub Gate (Tunnel): Automatically trimmed upon ejection.
• Sprue Gate: Direct flow for large parts, but leaves a large mark.
• Hot Runner: For mass production, zero waste, but expensive setup.

Yes.

• Overmolding: We can mold soft rubber (TPE/TPU) over a hard plastic substrate (e.g., Tool handles).
• Insert Molding: We can place metal inserts (threaded brass nuts) into the mold before injection. This is stronger than heat-staking post-process.

We process hundreds of thermoplastic resins. Common choices include:

• Commodity: PP (Polypropylene), PE (Polyethylene).
• Engineering: ABS (Standard), PC (Polycarbonate – High impact), Nylon (PA6/PA66 – Wear resistance).
• High Performance: PEEK, ULTEM (Aerospace grade). Check our full Material List.

Yes. Adding glass fiber (e.g., PA66+30%GF) significantly increases strength and stiffness. However, it increases mold wear and may affect the surface finish (fiber exposure).

Yes. We use Pantone or RAL color codes. We mix masterbatch pigments with the base resin to achieve the exact color you need.

Standard production uses 100% virgin material for best properties. If you require cost savings or sustainability, we can discuss using specific regrind percentages.

 Sink marks are depressions on the surface caused by uneven cooling in thick areas.

• Prevention: Ensure ribs are no more than 60% of the main wall thickness.

Flash is excess plastic leaking from the parting line. It usually means the clamp pressure is too low or the mold is worn. Boona maintains strict mold maintenance to prevent flash.

Our standard tolerance is ±0.1mm (DIN 16742 / ISO 20457). High-precision molds can achieve ±0.05mm. Note that some materials (like PP) shrink more than others (like ABS), affecting tolerance.

If the parts do not meet your drawing specifications due to our error, we will modify the mold (mold tuning) at our cost and re-sample until approved.

We follow the SPI (Society of the Plastics Industry) standards:

• SPI A-1 to A-3: High Gloss (Diamond Polish). Requires hardened steel.
• SPI B-1 to B-3: Semi-Gloss (Paper Polish). Good for hiding marks. •
• SPI C-1 to C-3: Matte (Stone Polish).
• SPI D-1 to D-3: Textured (Sandblast). Best for consumer electronics. Learn more at our Surface Finishing Options.

Yes. We can apply EDM textures (VDI) or chemical etching (Mold-Tech) to the mold cavity to give your part a specific grain (e.g., leather look, matte finish).

Yes. We offer post-molding services including:

• Spray Painting: Soft touch paint, UV coating.
• Electroplating: Chrome plating on ABS.
• Laser Etching: For backlit buttons.

• Choose Vacuum Casting: For 10-50 parts. Low tooling cost (Silicone mold), but high unit price. Good for marketing models.
• Choose Injection Molding: For 100+ parts. Higher tooling cost, but very low unit price. Real production material.

Yes. “Rapid Injection Molding” is increasingly popular for prototyping because it provides the exact material properties (which 3D printing often mimics but doesn’t replicate 100%).

Yes. We provide a One-Stop Service Solution. We can mold the parts, install inserts, paint, print logos, and assemble the final product with packaging.

Absolutely. We work with many international clients and strictly adhere to NDAs. Your mold designs and part files are kept confidential on our secure servers.

• Export your design as a STEP/STP file.

• Visit our Get a Quote page.

• Specify material, quantity, and finish. We will provide a DFM report and quotation within 24 hours.

Yes. For complex parts, we perform Mold Flow Analysis before cutting steel. This simulation predicts filling patterns, air traps, weld lines, and potential warpage, allowing us to optimize the gate location and design in advance.

Ejector pins are necessary to push the part out of the mold. They leave small circular marks. 

• Solution: We will discuss the pin locations with you during the DFM phase, ensuring they are placed on the non-cosmetic side (B-side) or hidden under features.

Warpage is caused by uneven shrinkage.

• Design: We recommend uniform wall thickness.
• Process: We adjust cooling time and packing pressure.
• Fixturing: If necessary, we use “Cooling Fixtures” to hold the part in shape immediately after ejection until it fully solidifies.

We have injection machines ranging from 50 Tons to 800 Tons. This means we can mold tiny gears (0.5g) up to large automotive covers (approx 1000mm length).

We perform Mold Maintenance (cleaning, greasing, and rust prevention) after every run. We store your mold in our climate-controlled warehouse for free for up to 2 years of inactivity, ensuring it is ready for your next order anytime.

Yes. While we offer free storage at our facility, you can export your mold anytime. If you plan to move production to the USA or Europe in the future, please inform Boona Prototypes during the RFQ stage. We will purposely build your mold using internationally recognized standard components, such as DME (Imperial/USA standard) or HASCO (Metric/European standard), ensuring it mounts seamlessly onto your local injection machines without costly retrofitting.

To minimize your financial risk, the industry standard for custom injection molds is split into milestones:

• 50% Deposit: To initiate DFM engineering, order the steel, and begin CNC machining the mold.

• 50% Balance: Only payable after you have received, tested, and officially approved the T1 (First Article) samples.

If you leave the mold at Boona’s facility for production, we provide a Lifetime Maintenance Guarantee for the agreed-upon lifespan of the tool. For example, if you purchase a Class 103 mold (guaranteed for 500,000 shots) and a slider breaks or a core pin snaps at 200,000 shots, we will repair or replace the damaged steel components entirely at our own cost.

We engineer molds according to Plastics Industry Association classifications to match your volume:

• Class 105 (Up to 500 cycles): Extremely low volume. Often achieved via CNC Machining of aluminum cores.

• Class 103 (Under 500k cycles): Standard production molds made of P20 or NAK80 steel. Highly cost-effective.

• Class 101 (1 Million+ cycles): Extremely high volume. Requires hardened H13/S136 steel (HRC 48-52) and expensive wear plates.

“Steel Safe” is a critical risk-management strategy. It means we purposefully machine the mold cavity slightly smaller (leaving extra steel on the tool) in areas with extremely tight tolerances. When we test the T1 sample, if a plastic feature is too small, we can easily machine away more steel to enlarge it. If we cut too much steel initially, adding metal back (via laser welding) is costly and leaves cosmetic marks.

Yes, for high-precision components. Scientific molding separates the injection process into three distinct stages: Fill, Pack, and Hold. By installing cavity pressure sensors inside the mold, we rely on exact data (rather than machine settings) to control the plastic flow. This guarantees that part weight and dimensions remain identical from shot #1 to shot #100,000, regardless of ambient temperature or resin batch variations.

To ensure the soft rubber (TPE/TPU) doesn’t peel off the rigid plastic substrate, we must consider compatibility.

• Chemical Bonding: Certain plastics naturally fuse together under heat. For example, TPU chemically bonds perfectly to ABS and PC.

• Mechanical Interlocks: If the materials are incompatible (e.g., trying to mold TPE over POM/Delrin), they will not stick. In this case, Boona engineers design physical “under-cuts” or holes in the rigid part, allowing the rubber to flow through and physically lock itself in place.

For low volumes, we use hand-loaded threaded cores (which are manually unscrewed by the operator). However, for mass production, we engineer molds with Automatic Unscrewing Cores. These use hydraulic racks and pinion gears built directly into the mold base to automatically rotate and extract the threaded pins during ejection, drastically reducing cycle time and labor costs.

Traditional cooling channels are drilled in straight lines, which can’t reach deep corners. Conformal Cooling uses channels that perfectly follow the 3D contour of the part. Boona utilizes Metal 3D Printing (DMLS) to manufacture custom mold inserts with complex internal cooling channels. This reduces cooling times by up to 40% and completely eliminates warpage on difficult geometric parts.

Under massive injection pressure (often exceeding 10,000 psi), the core and cavity halves of the mold can slightly shift, causing wall mismatch. For absolute precision (e.g., optical lenses), we machine tapered Interlocks into the mold base. These precisely guide and lock the two steel halves together just before the plastic is injected, guaranteeing zero shift.

 For standard molding, an L/T ratio of 100:1 to 150:1 is typical. For Thin-Wall Injection Molding (e.g., drone shells or laptop covers under 1.0mm thick), we use high-flow resins and high-speed injection machines to achieve ratios up to 250:1 without the plastic freezing off prematurely.

Yes. We can source resins that comply with stringent global standards, including FDA food contact compliance, RoHS/REACH environmental directives, and USP Class VI biocompatibility for medical devices. Please specify your certification requirements in your RFQ, and we will provide the corresponding Material Certificate of Analysis (COA) with your shipment.

For electronic housings and battery cases, passing fire safety standards is mandatory. We mold materials engineered to meet specific UL94 ratings (HB, V-2, V-1, and V-0). We can supply high-performance FR (Flame Retardant) PC/ABS blends or halogen-free plastics that achieve a UL94 V-0 rating (self-extinguishing within 10 seconds).

* TPE/TPU: Molded via standard thermoplastic injection machines. Highly cost-effective for tool handles and consumer goods.

• LSR (Liquid Silicone Rubber): A thermoset process requiring specialized cold-runner pumping equipment. LSR offers superior biocompatibility, extreme temperature resistance (up to 200°C), and chemical inertness. It is the premium choice for medical wearables and automotive seals.

Gas-assist molding involves injecting molten plastic into the mold, followed immediately by high-pressure nitrogen gas. The gas hollows out the thick sections, pushing the plastic tightly against the mold walls. This process is essential for manufacturing large, thick, tubular structures (like appliance fascias or thick handles) without sink marks, reducing part weight by up to 30%. For hollow metal tubular structures, consider our Sheet Metal Fabrication capabilities.