How to avoid product deformation in the process of taking parts by injection molding manipulator?

Combined with the characteristics of large plastic parts such as plastic trays, the anti-deformation practical methods are sorted out from five dimensions: grasping scheme, action logic, parameter setting, environmental back stage and mold matching, so as to solve the problems of warping, depression, indentation and distortion.

First, the optimization of grasping fixture (root cause prevention and control, the most important)

Reasonable layout of adsorption/clamping points

Give priority to multi-point distributed grabbing, avoid thin walls, suspended ribs and edge areas, and focus on the main reinforcement, thick-wall plane and load-bearing ribs of the tray to disperse the stress and prevent single-point tensile deformation.

Large-size tray adopts whole suction cup group, not only a small number of small suction cups; Special-shaped tray is matched with sucker and soft auxiliary stay, which is supported at multiple points to prevent the middle part from falling and warping.

Rubber/silica gel cushion must be added to the jaws to increase the contact area and reduce the unit pressure. Hard metal clamping is strictly prohibited to avoid pressing out dents and fracturing tendons. Adjust the clamping force to "just fixed and not loose" to prevent overpressure.

Fixture structure adapts to product form

High-temperature just-demoulded plastic parts (tray surface 80~120℃) can avoid direct bonding of large-area metal fixtures. The rapid heat conduction of metal can easily lead to local quenching, resulting in uneven cold and hot deformation and white surface.

For the flat-plate trays that are easy to warp, limit bars are added to the fixture to limit left and right twisting and prevent twisting in transit.

The sucker is made of high-temperature resistant silica gel, and the disk surface of the sucker is flat without damage or eccentric wear, so as to ensure uniform adsorption force.

Parameter matching of vacuum system

The negative pressure should not be too high, and the conventional control is -0.6 ~ -0.7MPa. If the negative pressure is too large, it will easily suck the thin-walled plastic parts. Insufficient negative pressure will slip and shift.

Each group of suction cups is independently controlled by air/zone ventilation, and local air leakage is replenished in time to avoid unilateral stress and inclined deformation.

Suction cups are blocked, accumulated materials and oil stains are cleaned in each shift to ensure balanced adsorption.

Second, the manipulator movement and trajectory control (dynamic deformation prevention)

Speed and acceleration and deceleration are strictly controlled.

Low speed in the whole process of taking parts in the mold and rising: forced deceleration within 100mm near the mold, and high-speed downward impact on the product is prohibited.

Extend the acceleration and deceleration time (0.8~1.5s), and prohibit sudden start, emergency stop and sharp turn; The inertia of the large pallet is large, and violent start and stop will pull and distort the plastic parts.

Running horizontally, the transfer speed is lowered, and the overall movement is smooth and smooth.

Action sequence reservation buffer

After the suction cup adsorption/clamping jaw is closed, delay for 50~150ms before lifting, and then perform the next action to prevent local pulling.

Thimble matching: the ejection height of the injection molding machine is moderate, only the product can be separated from the cavity, and the ejection is not too high; Stay for a short time after ejection, and then take the parts by the manipulator, so as to avoid the double stress superposition of ejector pin ejection and manipulator pulling.

Motion path planning

Linearize the trajectory to reduce the oblique pulling action; Ensure that the product is in a horizontal state all the time, and it is forbidden to tilt and hang.

Obstacles are avoided in the transfer process, and no rubbing or collision occurs; Sufficient safety clearance shall be reserved with peripheral equipment.

III. Placement and temporary storage after taking the parts (deformation prevention in cooling and setting stage)

Placement table requirements

The blanking table top must be level, flat and rigid, without bulges, burrs and depressions, so as to prevent uneven warping when landing.

High-temperature plastic parts are prohibited from dangling single-point support and unilateral lap joint.

Specification for stacking and placement

Multi-layer stacking is prohibited for high-temperature trays that have just been demoulded, and the stacking extrusion will be permanently deformed when the residual heat is not exhausted; When the surface is cooled to below 50℃, it will be palletized in order.

When palletizing, it should be aligned up and down, and the stress between layers should be uniform, without unbalanced load or skew.

Cooling environment

Avoid cold air blowing local plastic parts directly, local rapid cooling will produce internal stress, leading to warping; Just keep the air flow in the workshop uniform.

Four, the manipulator and injection molding machine linkage parameter adjustment

In-mold residence time

Don't take the parts immediately after opening the mold, and delay for a short time, so that the plastic parts can be preliminarily shaped in the mold to reduce the deformation risk under high temperature and soft state.

Linkage logic

Strictly implement the sequence of "opening the mold in place → ejecting it in place → taking the part by the manipulator → completing the part taking → closing the mold", and do not skip or grab the action, so as to avoid the product being rubbed and pulled by the mold and ejector pin.

Five, mold, raw materials and process assistance (front-end collaborative deformation reduction)

Injection molding process coordination

Optimize the cooling waterway, ensure the overall cooling uniformity of plastic parts, and reduce internal stress from the source; Mold temperature and material temperature are set according to raw material standards to avoid plastic parts from being too soft.

Reasonable use of release agent, thin spray evenly, to prevent forced pulling deformation after die sticking.

Mould state

Check whether the cavity and thimble are stuck or burr, and prevent the product from sticking to the mold; It is forbidden to drag the manipulator forcibly when sticking the mold, and immediately stop the machine for manual treatment.

Six, daily inspection and exception handling

Check the appearance of products in each shift, observe whether there are depressions, warpage and distortion, and fine-tune the suction cup position, negative pressure and clamping force in time.

Replace the fixture immediately if it is loose, the sucker is aging and the cushion is worn, so as to ensure the stress state remains unchanged.

When the manipulator shakes and moves, the accuracy and fastening mechanism should be calibrated in time to prevent abnormal stress caused by motion deviation.