- Many fixture failures come fromSuction cups, pneumatic tubing, joints, seals, spacersaging, wear or leakage of wearing parts, rather than damage to the main structure.
- The performance of wearing parts decreases, ranging from weak vacuum gripping, unstable clamping, slow rhythm, to severeWorkpiece slips, bumps, scratches。
- There is no unified replacement cycle and should be combined withFrequency of use, environment and workpiece characteristicsJudgment and perform "regular inspection, status replacement, and immediate replacement if abnormal".
- It is recommended to create according to the fixture numberList of wearing parts and keep appropriate quantities in stock, only by maintaining the small parts in place can the fixture be safe and stable for a long time.
The clamp is responsible for the tasks of transporting, turning, positioning, and clamping workpieces. Once the performance of wearing parts decreases, the vacuum gripping may not be strong, the clamping may be unstable, and the rhythm may slow down. In severe cases, the workpiece may slip, bump, or be scratched, which may even affect the safety of personnel and equipment. Therefore, the maintenance of custom tooling should not only check whether the cylinder, guide rails and structural parts are intact, but also pay attention to the consumable parts that are in direct contact with the workpiece and related to the pneumatic line seal.
01Why do fixture wearing parts affect handling safety?
Common clamping methods for Pneumatic Industrial Manipulator tooling units include vacuum gripping, pneumatic clamping, mechanical lifting, sponge vacuum gripping, inner support and outer clamping, etc. Either way, it ultimately relies on sufficiently stable vacuum gripping, clamping force, friction and sealing properties.
For example: after the vacuum suction cup becomes hardened, it cannot fit the surface of the workpiece, and the vacuum degree decreases; air leakage in the pneumatic tubing causes unstable system pressure and slow movement; wear of the sealing ring causes insufficient thrust of the cylinder; after the rubber pad of the clamping jaw is polished, the workpiece may slide down during transportation. Many on-site problems may appear to be caused by "hard-to-use fixtures", but the actual root cause is often that wearing parts are not inspected and replaced in a timely manner according to working conditions. Maintenance personnel should establish a regular inspection system and incorporate the inspection of wearing parts into the daily maintenance of equipment, rather than waiting until the workpiece falls or the line is stopped.
02Common fixture wearing parts and replacement judgment
1. Vacuum suction cup
Vacuum suction cups are commonly used for handling workpieces such as sheets, glass, metal parts, plastic parts, and packaging boxes. Under long-term pressure and tension, and affected by oil pollution and temperature changes, it will gradually age, harden, crack or deform. Replacement should be considered when the following conditions occur: there are cracks on the edge of the suction cup, and the lip is curled or chipped; the surface is hard and the rebound after pressing is poor; the vacuum establishment time is significantly longer when adsorbing the same workpiece; the value of the vacuum gauge decreases; the workpiece slightly slides or shakes during handling. For rough surfaces, oil stains or high-frequency handling conditions, the suction cups will wear out faster and the inspection cycle should be shortened.
2. Sponge suction cup
Sponge suction cups are often used on workpieces with uneven surfaces, slight roughness, strong air permeability, or large changes in size. They have strong adaptability, but are more susceptible to dust, debris, oil stains, and compression fatigue. Common problems include blocked pores, surface wear, localized tears, insufficient rebound, lax sealing, etc. During the inspection, you can observe whether the surface of the sponge collapses, whether a large amount of dust adheres to it, and whether there is any obvious air leakage sound after vacuum gripping. If the vacuum-gripping performance cannot be restored after cleaning, it should be replaced in time.
3. air line
The pneumatic tubing is responsible for transporting compressed air or taking on the vacuum line. Common problems include aging and hardening, bending and flattening, skin wear, air leakage at joints, and insufficient temperature resistance leading to softening or cracking. You can listen for air leakage during inspection, and you can also use soapy water to check whether the joints and bends are bubbling. The pneumatic tubing should avoid being pinched, dragged, close to high-temperature parts or rubbed against sharp edges for a long time. If you find surface cracks, bulges, obvious creases, wear or hardening, you should replace it immediately. It is not recommended to wrap it with tape for long-term use.
4. Quick connector
Quick-plug joints are easy to install, but after long-term plugging and unplugging, vibration or external force pulling, problems such as loosening, air leakage, locking failure, and damage to the internal sealing ring are prone to occur. Air leakage usually occurs at the air-line insertion port, threaded connection or sealing ring. During maintenance, you should check whether the air hose is inserted to the bottom, whether the end face is cut flat, whether the joint is loose, and whether the thread seal fails. If air leakage persists after replacing the air hose, in most cases the joints should be replaced at the same time.
5. Seals
Seals include O-rings, gaskets, cylinder seals, vacuum generator seals, valve block seals, suction cup seat seals, etc., which directly affect vacuum degree, air pressure stability and cylinder output force. After aging, problems such as hardening, compression permanent deformation, cracks, expansion, and damage will occur. On-site manifestations include weak cylinder movement, shortened pressure holding time, reduced vacuum, and air leakage around the valve body. When replacing, attention should be paid to whether the material, specifications, temperature resistance, and oil resistance match. It is not advisable to replace it with a seal ring of similar size.
6. Clamp pad, polyurethane pad, rubber pad
This type of pad is used to increase friction, protect the workpiece surface, buffer clamping impact, and directly contacts the workpiece. It is a typical mechanical consumable part. After the surface is ground flat, cracked, degummed, hardened or embedded with metal chips, the clamp may become unstable and slippery, and may also scratch the surface of the workpiece. When handling spray-painted parts, aluminum profiles, stainless steel parts and exterior parts, the status of the pads must be carefully checked.
7. Mechanical wearing parts such as springs, pins, bushings, and limit blocks
Springs, pins, sleeves, limit blocks, buffer blocks, positioning blocks, etc. are also common in custom tooling, which bear the functions of reset, guide, rotation, limit and buffer. Spring fatigue will cause the reset to not be in place; wear of the pin shaft and bushing will create a gap, causing the fixture to shake; wear of the limit block will affect repeat positioning accuracy; damage to the buffer block will increase the impact of the mechanism. During inspection, attention should be paid to abnormal noise, gaps, looseness, slow reset and positioning deviation.
03Suggestions for inspection and replacement of fixture wearing parts
| Consumable parts | Frequently Asked Questions | On-site inspection methods | Replacement suggestions |
|---|---|---|---|
| Vacuum suction cup | Aging, hardening, cracking, decreased vacuum holding capacity | Observe the lips, press the rebound, and check the vacuum gauge | Replace when cracked, deformed or unstable vacuum gripping |
| Sponge suction cup | Clogging, wear, insufficient rebound, loose sealing | Check the pores, listen to the sound of air leakage, and measure the vacuum gripping time | Replace when cleaning is ineffective or collapse is obvious |
| Air Tubing | Aging, bending, wear and tear, air leakage | Listen for air leaks and check for bends and wear spots | Replace the entire section when cracked, hardened or worn out |
| Quick connector | Looseness, air leakage, damaged sealing ring | Check insertion depth, leak detection with soapy water | If air leakage persists after plugging in tightly, replace it. |
| O-ring/gasket | harden, flatten, break, swell | Disassemble and inspect the sealing surface and observe for indentations and cracks. | When repairing the cylinder, valve body and suction cup seat, replace them simultaneously |
| Cylinder seal | Internal leakage, weakness of movement, crawling | Observe the action speed, thrust, and exhaust | Replace the sealing component when it becomes weak or leaks internally. |
| Gripper pad/rubber pad | Wear, degumming, hardening, chipping | Check contact surfaces and workpiece clamp marks | Replace when worn, cracked or seriously contaminated |
| spring | Fatigue, fracture, insufficient reduction | Check free length and return action | Replace when reset is slow and elasticity is insufficient. |
| Pin / Bushing | Wear, gap increase, abnormal noise | Shake the mechanism and check for shaking and wear marks | Replace when the gap is obvious or there is abnormal noise. |
| Limit block/buffer block | Wear, deformation, cracking | Check the limit surface and impact marks | Replace when positioning deviation or buffer failure |
04How to judge the replacement cycle under different working conditions
There is no completely unified replacement cycle for fixture wearing parts, which should be judged based on the frequency of use, environment and workpiece characteristics.
- High frequency handling: The suction cups, air hoses, joints and jaw pads should be inspected more frequently. It is recommended to inspect them on a shift or weekly basis.
- Dust environment: Sponge suction cups, vacuum filters, and joint seals are more likely to be clogged and worn. You should focus on checking the vacuum gripping time and vacuum degree.
- High temperature environment: pneumatic tubing, suction cups and seals are prone to softening, hardening or cracking. Please confirm the temperature resistance level of the material.
- Oily environment: Ordinary rubber parts may swell, slip or lose elasticity. Oil-resistant materials should be selected and the replacement cycle should be shortened.
- Rough surface workpiece: The lip of the suction cup, the sponge layer and the jaw pad wear quickly, and should be determined based on the actual wear status, not just the calendar time.
05What phenomena indicate that the fixture needs maintenance?
- Vacuum gripping time becomes longer: It may be that the suction cup is aging, the sponge suction cup is clogged, the air line is leaking or the filter is clogged.
- The workpiece slides or shakes during transportation: Focus on checking the suction cup vacuum holding force, gripper pad wear, clamping force and mechanical clearance.
- Insufficient clamping force: It may be related to insufficient air pressure, internal leakage of the cylinder seal, abnormal pressure regulating valve, air leakage in the air hoses or wear of the clamping mechanism.
- Air pressure or vacuum fluctuates significantly: Push-in fittings, pneumatic tubing, valve blocks, vacuum generators and seals should be inspected.
- The operation feels heavier: In addition to the balancing system, it is also necessary to check whether the fixture shaft, pins, sleeves, and limiters are worn or lack of oil.
- The cycle time of the action slows down or the release is not clean: It may be caused by blockage of the air path, poor response of the valve, adhesion of the suction cup, bending of the pipeline or blockage of the silencer.
06Spare parts management suggestions
In order to reduce downtime, the workshop can stock an appropriate amount of commonly used fixture wearing parts. It is recommended to give priority to stocking commonly used specifications of vacuum suction cups, sponge suction cups, pneumatic tubing, quick-in connectors, O-rings, sealing gaskets, clamping claw rubber pads, polyurethane pads, springs, pins, sleeves and limit blocks.
Three points should be paid attention to in spare parts management: first, establish a list of wearing parts according to the fixture number, and record the specifications, materials, brands or drawing numbers; second, distinguish between general parts and customized parts, customized suction cup seats, special pads, and special-shaped seals should be stocked in advance; third, record the replacement time and cause of failure, so as to judge whether certain types of wearing parts are improperly selected or mismatched in working conditions. For standard parts shared by multiple fixtures, the inventory can be appropriately increased; for non-standard parts that are not frequently damaged but have a long procurement cycle, safety stock should be retained. A standardized list of wearing parts and inspection records can often reduce long-term maintenance costs more than a single emergency repair.