Full FAQ of 15 Core Shoe-Making Machines for Complete Production Line

Full FAQ of 15 Core Shoe-Making Machines for Complete Production Line

Q: Why does the swing arm rotate sluggishly with harsh friction noise?

A: Lack of grease lubrication on the vertical column or worn ball bearings. Inject grease via the oil cup on top of the column immediately, and check if the column lock nut is overly tightened.

Q: The ram does not descend after stepping on the foot pedal. Where should we inspect?

A: First check if the foot pedal micro switch has poor contact or damage; then use a multimeter to test if the hydraulic solenoid valve coil for ram

pressing is burnt or open-circuited.

Q: How to extend the service life of the plastic cutting mat?

A: Rotate and flip the mat regularly during operation, and slightly adjust the ram stroke to avoid long-term stamping on the same position and depth by cutting dies.

Q: Heavy "thudding" vibration occurs during stamping, and the pressing depth is inconsistent on both ends.

A: The four-column hydraulic balance system is out of adjustment or mechanical connecting rods are loose. Readjust the synchronous balance valve and check if the oil filling volume on both sides is balanced.

Q: The oil pump motor starts normally but cannot build enough pressure to cut materials.

A: Check if the hydraulic oil level is too low causing the oil pump to suck air; inspect if the overflow valve (pressure regulating valve) is stuck or blocked by dirt, which leads pressure oil to flow back directly to the oil tank.

Q: The machine can be started by pressing only one of the dual start buttons. What safety hazards does this bring?

A: This is a severe equipment failure. The dual-button interlock safety relay is damaged or short-circuited illegally. Starting the machine with one hand may easily crush the other hand, so shut down the machine for maintenance at once.

Q: The leather cut edge gets scorched or the material tears during cutting.

A: Scorched edges are caused by decreased vibration frequency or dull blades generating friction heat; torn material results from insufficient vacuum adsorption that shifts leather during cutting. Clean debris on the suction platform and increase the power of the exhaust fan.

Q: The cut pattern size deviates from the drawing (e.g., a square is cut into a rectangle).

A: Pulse parameters of X/Y servo motors drift, or the timing belt slips due to wear. Re-calibrate the mechanical zero point in the system and tension the timing belt.

Q: The cutting head stops vibrating suddenly while the carriage moves along the track normally.

A: The high-frequency vibration motor driver triggers overheat protection, or the flexible cable connected to the cutting head has internal wire breakage after repeated bending.

Q: Why does the band knife drift back and forth and fail to stay fixed during operation?

A: The eccentric wheel balance block controlling band knife tension and positioning is loose, or oil stains on the drive disc cause slipping. Wipe the drive disc with alcohol and retighten positioning bolts.

Q: The split leather surface shows obvious wavy lines or uneven thickness.

A: The cutting edge of the band knife is worn unevenly; feeding rollers are partially dented or wrapped with leather scraps. Grind the knife with the built-in grinding wheel, clean or replace worn feeding rollers.

Q: The grinding wheel produces heavy sparks but the knife edge remains blunt. How to adjust?

A: The grinding wheel surface is passivated by oil contamination. Dress the wheel surface with a diamond dresser to expose new sharp abrasive grains.

Q: The glue pot heats up extremely slowly, or the display still shows an error after reaching the set temperature.

A: The electric heating tube inside the glue pot is burnt and open-circuited, or the thermocouple (temperature sensor) is oxidized by carbon deposits leading to inaccurate temperature measurement.

Q: Why are folded edges uneven in width or wrinkled?

A: The clearance between the folding hammer and feeding wheel is too large; adjust mechanical clearance according to material thickness. The stroke of the pneumatic cutting knife is improperly set, failing to cut holes for loose folding at curved sections.

Q: The glue nozzle is fully clogged after restarting the machine following long shutdown.

A: Hot melt glue carbonizes and forms coke under persistent high temperature. Lower the glue pot temperature before long-term shutdown. If clogged, heat the nozzle and unclog it with fine steel wire plus special cleaning agent.

Q: Frequent skipped stitches occur during sewing. What is the inspection sequence?

A: 1. Check if the needle is bent or installed reversely (the needle groove must face the shuttle hook); 2. Verify shuttle hook timing: when the needle bar rises 2mm from the lowest point, the shuttle tip should be 0.8–1.1mm above the needle center line.

Q: Floating stitches appear (tight bottom thread, loose top thread). How to adjust?

A: The tension of the top thread is too low or the bottom thread tension is excessive. Slightly turn the thread tension nut to increase top thread pressure, or adjust the shuttle spring screw to loosen bottom thread tension.

Q: The upper and lower feeding rollers fail to convey material, and leather slips in place.

A: Anti-slip teeth on rollers are worn flat, or air pressure of the presser foot cylinder is insufficient. Increase cylinder air pressure or replace worn rollers.

Q: A loud bang occurs during high-speed operation, the machine locks up and the screen shows "Spindle Locked".

A: Needle collision happens; broken needle fragments jam the shuttle hook, or the shuttle hook seizes due to instantaneous high-speed impact. Disassemble the shuttle hook and clear metal debris.

Q: The sewn pattern is tilted or shrunk after importing a new shoe design file.

A: The format/resolution of the pattern file exported by design software mismatches the machine system; X/Y guide rails lack lubrication causing excessive resistance and servo motor lost steps. Unify file output standards, lubricate guide rails and re-calibrate zero position.

Q: Automatic thread trimming fails, leaving overly long thread ends or complete thread detachment.

A: Cutting edges of moving and fixed trimming knives are dull and cannot cut thick threads; the stroke speed of the trimming cylinder is mismatched with spindle stop timing. Replace trimming knives and adjust cylinder throttle valves for synchronous action.

Q: The pulling claws often tear upper leather during lasting.

A: Air pressure for primary pulling force of claws is set too high; temperature of heating tiles inside claws is over-high and scorches leather. Reduce air pressure and lower the temperature controller value.

Q: After the sweeping arms close, bulges (cat ears) form on both sides of the toe lasting edge.

A: The stroke matching of primary and secondary pressing arms is improper. Adjust the primary pressing to close sweeping arms first, then increase secondary pressing force to flatten leather fully against the insole edge.

Q: Which key positions need adjustment when switching lasts of different sizes?

A: 1. Height of midsole support platform to align with sweeping arm surface; 2. Forward and backward distance of positioning stoppers; 3. Opening range of left and right pulling claws.

Q: The rubber tightening band shifts left and right when wrapping the heel.

A: The heel positioning support platform is skewed, or air pressure of tightening cylinders on both sides is unbalanced. Re-calibrate the central line and balance cylinder pressure on both sides.

Q: The glue area on upper leather turns white and loses adhesion after heel lasting.

A: The built-in heating sheet of the tightening band is burnt out, failing to activate hot melt glue instantly. Inspect and replace heating components.

Q: The manipulator frequently drops shoe lasts during gripping.

A: Anti-slip rubber pads on clamping jaws are worn and slippery; magnetic proximity switches of clamping cylinders shift position, triggering the next action before full clamping. Replace rubber pads and readjust sensor positions.

Q: Glue remains sticky and bubbles form on shoe surfaces after passing through the oven.

A: Oven temperature is excessively high with poor exhaust and dehumidification. Solvents inside glue boil instantly and form bubbles. Reduce heating tube power and boost exhaust fan airflow on top of the oven.

Q: The drive motor buzzes, while the conveyor belt slips and moves intermittently.

A: The belt stretches loose after long service; key grooves of drive rollers wear and slip. Adjust the tension screw at the tail to re-tighten the conveyor belt and repair worn rollers.

Q: Infrared heating tubes burn out frequently with short service life.

A: Unstable factory voltage generates surge voltage; poor circulation of oven fans leads to local heat accumulation and over-temperature operation of heating tubes. Install voltage stabilizers and overhaul circulating fans.

Q: Air bag pressure drops gradually during pressure holding and cannot maintain the set value.

A: Internal air circuit leakage. Check if sealing gaskets at the joint between air bag and metal base are aging; inspect if the one-way sealing of intake/exhaust solenoid valves fails. Replace aged seals and repair solenoid valves.

Q: The heel part of high heels or special grooved outsoles is dented with uneven stress during pressing.

A: Install special heel supporting ejectors to balance upward supporting force of the air bag and ensure uniform stress distribution.

Q: Daily protection tips to prevent air bags from being pierced by sharp edges of soles.

A: Cover the air bag surface with high-elastic wear-resistant rubber protective film during operation; clear nails and hard burrs on soles before feeding.

Q: The internal temperature of the freezer cannot drop below minus 10°C.

A: Refrigerant leaks – perform leak detection and refill refrigerant; excessive frost blocks air ducts on the evaporator. Start the forced defrost program manually.

Q: Heavy condensation dew covers uppers and lasts after taking shoes out of the freezer, dampening leather.

A: Damaged or missing thermal insulation wind curtains at freezer inlets and outlets allow hot humid external air to enter and condense instantly. Replace airtight wind curtains.

Q: Drive chains jam or skip teeth frequently.

A: Ordinary lubricating grease solidifies under ultra-low temperature and increases friction resistance. Remove old grease completely and fill with special low-temperature aviation lubricant.

Q: Harsh metal friction noise occurs during screw feeding, and black scorch spots form on molded outsoles.

A: Noise: Heating tubes of certain temperature zones burn out, plastic fails to melt fully and the screw grinds hard material dryly. Scorch spots: Over-temperature of partial zones carbonizes plastic. Inspect heating tubes of each zone and lower temperature of overheated sections.

Q: Large flash overflow occurs at mold closing surfaces and causes waste soles.

A: Insufficient mold clamping force or internal leakage of clamping hydraulic cylinders; excessive injection metering stroke exceeding mold cavity volume. Reduce injection volume and overhaul mold clamping hydraulic system.

Q: EVA/rubber outsoles shrink severely and become undersized after demolding.

A: Insufficient mold cooling time, too short pressure holding time and pressure. Internal thermal stress of outsoles cannot be fully released before mold opening. Optimize molding parameters by extending cooling and pressure holding duration.

Q: The 3D camera scans outsoles normally, but the overall glue spraying track shifts 2–3 mm.

A: Hand-Eye Calibration data between the vision system and industrial robot is lost or slightly shifted (caused by minor collision of the robot head). Re-run the calibration program with a calibration block.

Q: The glue line sprayed by the gun diverges, splits or flows intermittently.

A: Residual glue semi-clogs the nozzle. Remove and soak the nozzle in gun cleaning solvent; check solvent liquid level of the automatic cleaning station and refill timely.

Q: The robot emergency stops suddenly and the teach pendant reports "Axis Limit / Hardware Limit Exception".

A: The programmed spraying track exceeds the physical motion limit of robot joints. Readjust the placement angle of outsoles on assembly line fixtures and re-plan spraying paths.

Q: Gripping jaws often pinch and tear heel leather during last stripping.

A: Excessive clamping pressure of jaws; polyurethane soft protective pads on jaws wear off and expose hard metal edges. Replace protective pads and lower the proportional valve pressure.

Q: The machine frequently reports "Last Stripping Torque Over Limit" and fails to pull out shoe lasts.

A: Insufficient drying and freezing setting in previous processes; unhardened glue sticks uppers tightly to lasts. Optimize parameters of the freezing setting machine, and spray proper release agent before lasting.

Q: The vision camera repeatedly fails to recognize positioning holes/gripping points on shoe lasts and shuts down frequently.

A: Fluctuating workshop lighting (strong direct sunlight or dim night light) leads to overexposure or underexposure of the camera. Install industrial light shielding hoods and constant LED strip light sources.

This complete FAQ covers mechanical, hydraulic, pneumatic, thermal control, servo automation and machine vision faults of all 15 full-production-line shoe machines. It can be compiled into workshop Standard Operating Procedures (SOP) and used for mechanic training and daily equipment inspection, greatly improving Overall Equipment Efficiency (OEE) and reducing production defect rates.