The T-block of the injection mold slide is a key guiding and load-bearing component in the mold’s lateral core-pulling mechanism. Its structural design directly impacts the smoothness of the slide’s movement and the accuracy of core-pulling. The T-block typically mates with the T-slot at the bottom of the mold slide to form a sliding guide. During core-pulling, it guides the slide in the desired direction while also withstanding the lateral forces generated by injection pressure. The T-block has a T-shaped cross-section, with the horizontal portion nestling within the slide’s T-slot and the vertical portion securely attached to the mold. This structure effectively prevents the slide from dislodging from the guide rail during movement, ensuring reliable core-pulling. The T-block must be made of high-strength alloy steel, such as quenched 45# steel (HRC 40-45) or Cr12MoV (HRC 50-55), to ensure adequate wear resistance and strength. Especially for applications with high core-pulling forces (e.g., exceeding 50kN), Cr12MoV should be cryogenically treated to minimize wear and deformation during use.
The dimensional parameters of the T-block in the injection mold slide must be designed based on the slide’s size and core-pulling force to ensure load-bearing capacity and guiding accuracy. The T-block’s width is typically 1/3-1/2 the slide’s width. For example, if the slide is 120mm wide, the T-block should be 40-60mm wide. This ensures sufficient contact area without increasing machining complexity due to excessive size. The thickness of the T-block should be determined based on the core-pulling force. The calculation formula is: Thickness (mm) = Core-pulling Force (N) × Safety Factor / (Width (mm) × Allowable Material Stress (MPa)). A safety factor of 1.5-2.0 is used. The allowable stress of 45# steel is 150MPa. For example, for a T-block with a core-pulling force of 30kN and a width of 50mm, the thickness is 30000 × 1.5 / (50 × 150) = 6mm. The clearance between the T-block and the T-slot needs to be strictly controlled, generally 0.02-0.05mm. Too small a clearance will cause movement jamming, while too large a clearance will affect the guiding accuracy. The fitting accuracy can be ensured by grinding, and grease (such as molybdenum disulfide lithium-based grease) can be applied to the surface of the T-block to reduce movement friction.
The T-block on the fixed mold slide must be securely mounted to prevent loosening or displacement during core pulling. Common mounting methods include screw mounting and dovetail mounting. Screw mounting is suitable for small and medium-sized T-blocks. M6-M10 hexagon socket bolts are used, with bolt spacing 1/3-1/2 of the T-block length. For example, a 150mm long T-block requires three M8 bolts spaced 50mm apart. The bolt heads should be sunken at least 2mm into the T-block surface to prevent interference with the slide. Dovetail mounting is suitable for large T-blocks. A dovetail groove is machined into the fixed mold plate, and the T-block is secured within the groove with a wedge. This method can withstand greater lateral forces and offers high installation precision, making it suitable for applications with core pulling forces exceeding 100kN. After installation, the T-block must be inspected for parallelism and perpendicularity, ensuring a parallelism error of no more than 0.02mm/m and a perpendicularity error of no more than 0.03mm/m to ensure smooth, unobstructed slide movement.
Lubrication and maintenance of the T-block on the injection mold slide are crucial to ensuring long-term, stable operation. Regular lubrication and wear inspection are essential. Every 5,000 molds, the T-block and T-slot should be cleaned to remove residual plastic debris and oil. Then, apply a high-temperature grease with excellent adhesion and wear resistance, maintaining stable performance at temperatures above 150°C. The T-block should be regularly measured for wear during use. If wear exceeds 0.1mm, it should be repaired or replaced. Repair can be performed by surfacing welding followed by grinding to restore dimensional accuracy. For frequently used molds, the T-block surface can be nitrided. The nitrided layer has a thickness of 0.1-0.2mm and a hardness of HV800-1000. This significantly improves wear resistance and extends service life by 3-5 times. Furthermore, if the clearance between the T-block and the T-slot is excessive, it should be adjusted or replaced promptly to avoid compromising core pulling accuracy and causing dimensional deviations in the molded part.
on the fixed mold slide must consider its coordination with other core-pulling components to ensure coordinated operation of the entire core-pulling mechanism. The T-block’s length should be greater than the slide’s core-pulling distance, typically 20-30mm longer. For example, if the core-pulling distance is 80mm, the T-block should be 100-110mm long to ensure sufficient guide length when the slide is in its maximum core-pulling position. The T-block’s placement must align with the position of power components such as the inclined guide pins and hydraulic cylinder. Its centerline should align with the core-pulling direction and coincide with the force lines of the power components to avoid additional torque that could cause uneven force on the T-block. For example, for a slide driven by an inclined guide pin, the T-block’s centerline must be coplanar with the guide pin’s axis, with a deviation of no more than 0.5mm, to ensure smooth force transmission. By properly designing the T-block’s coordination with other components, the core-pulling accuracy of the fixed mold slide can be controlled within ±0.05mm, meeting the molding requirements of high-precision plastic parts.
