1、 Limited material adaptability

1. Challenges in processing high filling materials
   • problemHalogen free flame retardant materials often require the addition of a high proportion (such as 40% -60%) of glass fiber, mineral fillers, or metal hydroxides to enhance flame retardancy. These high filling materials require high wear resistance of the screw, and traditional halogen-free screws may have a shortened lifespan due to coating wear or substrate fatigue.
2. The bottleneck in processing low melting point materials
   • problemSome halogen-free materials (such as TPE and EVA) have low melting points (<150 ℃), but require high temperatures (180-220 ℃) during processing to promote the dispersion of flame retardants. Low temperature materials are prone to degradation at high temperatures, and if the screw is not optimized for low-temperature fluidity, it may lead to material burning or uneven discharge.
3. Insufficient compatibility with special flame retardant systems
   • problemPhosphorus based, nitrogen based and other halogen-free flame retardants may cause chemical corrosion to the surface of the screw, while the decomposition products of certain new flame retardants (such as ammonium polyphosphate) may accelerate coating aging. If the screw is not surface treated for a specific flame retardant system, it may cause early failure.

2、 High cost

1. Material and process costs
   • Base material costHalogen free screws require the use of corrosion-resistant alloys (such as SACM-645, 316 stainless steel) or high-temperature alloys (such as H13 steel), which are 3-5 times more expensive than ordinary carbon steel.
   • Coating costTungsten carbide, ceramic or nano coating processes are complex, and the cost of coating a single screw can reach hundreds to thousands of yuan, accounting for 30% -50% of the overall cost.
   • caseA halogen-free screw with a diameter of 80mm and a length to diameter ratio of 32:1 may have a material and coating cost that is 2000-5000 yuan higher than ordinary screws.
2. Maintenance and replacement costs
   • frequent replacementIn high filling or corrosive environments, the lifespan of screws may be shortened to 1/3-1/2 of that of ordinary screws, resulting in an increase in replacement frequency.
   • Repair costIf the screw needs to be repaired after wear (such as spraying or welding), the single repair cost may reach 40% -60% of the price of the new screw, and the performance may decrease after repair.

3、 High maintenance complexity

1. Difficult to clean
   • problemZero halogen materials (especially high filling types) are prone to residue on the surface of the screw, forming a stubborn adhesion layer. Ordinary cleaning methods such as high-pressure water guns and chemical solvents may damage the coating, requiring the use of specialized cleaning agents or ultrasonic cleaning, which increases maintenance time and cost.
2. Strict lubrication management
   • problemHalogen free screws require the use of special lubricating grease that is wear-resistant and heat-resistant, and should be replaced regularly (usually every 500-800 hours). Improper lubrication may lead to accelerated wear of bearings or screws.
3. High requirements for wear monitoring
   • problemScrew wear needs to be regularly detected by professional equipment (such as laser calipers), and if the wear is greater than 0.2mm, it needs to be repaired or replaced immediately. If monitoring is insufficient, it may lead to equipment failure or product quality issues.

4、 Challenges in machining accuracy and stability

1. High precision requirements for temperature control
   • problemZero halogen materials are temperature sensitive and require precise control of the barrel temperature (within ± 5 ℃) during processing. If the temperature fluctuates too much, it may cause material degradation or flame retardant decomposition, affecting product performance.
2. Difficulty in cutting thermal management
   • problemWhen high filling materials flow in the screw, shear heat is easily generated. If the screw design is not optimized (such as the angle of the screw edge and the depth of the screw groove), it may cause local overheating, leading to material decomposition or burning.
3. Difficulty in controlling the uniformity of discharge
   • problemThe flowability of halogen-free materials varies greatly (such as high filling and low filling formulas). If the screw mixing ability is insufficient, it may lead to uneven discharge and affect the dimensional stability of the product.

5、 Environmental and compliance risks

1. Controversy over the Environmental Protection of Coating Materials
   • problemSome screw coatings (such as metal coatings containing chromium and nickel) may not comply with the restrictions on heavy metals in RoHS or REACH regulations, and environmentally friendly coatings without chromium and nickel (such as ceramic and nanocomposite coatings) need to be selected, but the cost is higher.
2. Cost of waste disposal
   • problemWorn or scrapped halogen-free screws need to be treated as hazardous waste (as they may contain heavy metals or corrosive substances), and the treatment cost can reach 3-5 times that of ordinary scrap steel.