What should be paid attention to when the automatic sandblasting machine treats the surface of the workpiece?

The core points for attention of automatic sandblasting machine for surface treatment of workpieces revolve around four dimensions: equipment operation safety, accurate sandblasting process, workpiece protection reaching standard and equipment maintenance specification. The core follows the principle of * * "first protection, then startup, first trial blasting and then mass production" to avoid excessive sandblasting, workpiece damage, equipment failure and personal safety accidents, and ensure the uniformity and consistency of surface treatment of workpieces. The following are the matters needing attention in the whole process of actual production, covering the core steps such as preparation before operation, process parameter setting, field operation, workpiece protection and equipment maintenance, which can be directly implemented:

First, preparation before operation: basic control of safety and equipment to avoid risks from the source.

The automatic sandblasting machine is a high-pressure sandblasting operation. The equipment is pressurized and the sandblasting medium is sprayed at high speed, and some media (such as quartz sand) are easy to raise dust. Safety protection and equipment inspection must be done before operation. It is forbidden to start the machine until the inspection is completed:

Personal safety protection: totally enclosed protection to prevent splashing/dust injury.

Operators must wear special sandblasting protection suits: impact-resistant sandblasting mask (with goggles), wear-resistant sandblasting gloves, anti-static sandblasting clothes, and anti-smashing and anti-skid shoes. Bare skin is prohibited from touching the sandblasting area. If it is an open automatic sandblasting machine, a protective enclosure and warning signs should be set in the operation area to prevent irrelevant personnel from entering to prevent the sandblasting medium from splashing and injuring people.

Omni-directional inspection of equipment: ensure trouble-free operation under pressure.

Air pressure system: check whether the air compressor pressure reaches the standard (0.4~0.8MPa), the air pipe and sandblasting pipe are free from aging, air leakage and cracking, the joint is firmly sealed, and the pressure gauge and pressure regulating valve display normally;

Sandblasting component: check that the spray gun is free from blockage and nozzle wear (nozzle wear exceeds 1/3 and needs to be replaced in time to avoid the deviation of sandblasting flow), and the sandblasting valve and sand regulating valve are opened and closed smoothly without jamming;

Conveying/positioning system: for the belt/roller conveying and tooling positioning mechanism of the automatic sandblasting machine, check that the operation is smooth without jamming, the workpiece positioning fixture is firm, and there is no loose deviation (to prevent the workpiece from shifting and uneven treatment during sandblasting);

Dust removal system: turn on the dust removal equipment, check that the fan and filter cartridge are running normally, and the dust removal pipeline is not blocked, so as to ensure the timely collection of sand blasting dust (to avoid dust exceeding the standard and prevent medium dust from entering the equipment and causing wear);

Safety device: check whether the emergency stop button and door interlock device of the equipment (the equipment cannot be started when the sandblasting door is not closed tightly) are effective, and the sealing rubber strip of the door is not damaged to prevent the high-pressure sandblasting medium from splashing from the gap.

Sand blasting medium and workpiece pre-preparation

Media screening: Select suitable sandblasting media (such as quartz sand/steel shot for rust removal of metal parts and nylon sand/walnut sand for deburring of plastic parts) according to the material and treatment requirements of the workpiece. The media should be dry, free from caking and impurities (wet media will easily block the spray gun and the impurities will scratch the surface of the workpiece), with uniform particle size (screen according to the process requirements to avoid uneven treatment effect caused by mixed particle sizes);

Pre-treatment of workpiece: remove oil stain, water stain, viscose and thick rust/paint layer on the surface of workpiece (oil stain will cause caking of sandblasting medium, and thick impurities will affect sandblasting efficiency), which can be wiped with cleaning agent or passivated by pickling in advance, and then dried before loading;

Tool adaptation: Customize special positioning tools (such as fixtures and jigs) according to the shape and size of the workpiece, so as to ensure that the workpiece is not blocked or shaken when sandblasting, and the parts to be protected (such as threaded holes, bearing positions and precision mating surfaces) should be blocked and protected in advance.

Second, process parameter setting: accurate matching to avoid workpiece damage and substandard treatment.

The process parameters of the automatic sandblasting machine directly determine the surface treatment effect of the workpiece, and the core parameters should be accurately set according to the material, thickness and treatment requirements of the workpiece, following the principle of * * "from light to heavy, trial blasting before mass production", and it is forbidden to blindly adjust the parameters:

Control of core parameters: accurate matching of four elements

Parameter Setting Principles & Precautions

Sand blasting pressure metal parts (carbon steel/stainless steel) 0.5~0.8MPa, thin-walled metal parts/plastic parts/aluminum alloy parts 0.2 ~ 0.4 MPa; If the pressure is too high, the thin-walled parts will be punctured/deformed, and if it is too low, the treatment will not be thorough.

The distance between sandblasting and the surface of the workpiece is 10~30cm. If the distance is too far, it will lead to the attenuation of sandblasting strength and uneven treatment, and if it is too close, it will easily lead to excessive local sandblasting and surface scratches.

The angle of sandblasting is 45 ~ 75 between the spray gun and the workpiece surface. Vertical sandblasting will easily lead to medium rebound, too large pitting on the workpiece surface, and too small an angle will lead to low treatment efficiency.

The sandblasting time shall be set according to the treatment requirements (such as derusting for 10~30s, deburring for 5~15s, and matte surface for 3 ~ 8s); Automatic sandblasting machine needs to accurately set the conveying speed/spray gun swing frequency to avoid local sandblasting time being too long.

Test spray confirmation: it must be done before mass production.

When treating or replacing workpieces/parameters for the first time, take 1-2 samples for trial spraying. After trial spraying, check the surface of workpieces: no scratches, no deformation, no excessive sandblasting, and the surface roughness (Ra) and cleanliness meet the design requirements; After confirmation, lock the equipment parameters (non-professionals are forbidden to adjust them at will) before mass production.

Automatic operation parameters: adapt to workpiece conveying and spray gun action.

Conveying speed: according to the setting of sandblasting time, ensure that the residence time of the workpiece in the sandblasting area meets the processing requirements. If the speed is too fast, the processing will not be thorough, and if it is too slow, the sandblasting will be excessive;

Swing/rotation of spray gun: for special-shaped workpieces (such as pipe fittings, valve bodies and special-shaped metal parts), turn on the swing or rotation function of spray gun, with the swing frequency of 10~30 times/minute, so as to ensure that all the surfaces to be processed of the workpiece can be covered by sand blasting without dead ends;

Sand blasting medium flow: controlled accurately by sand regulating valve, if the flow is too large, the spray gun will be blocked and the surface area of the workpiece will be sand; if it is too small, the treatment efficiency will be low, so it is necessary to ensure that the medium is sprayed in a uniform mist.

Iii. On-site operation: standardize operation to ensure consistency of treatment and safety of equipment.

During the operation of automatic sandblasting machine, it is necessary to do real-time monitoring, deal with abnormal situations in time, avoid batch scrapping caused by equipment failure and workpiece displacement, and strictly abide by the equipment operation specifications:

Start-up and operation specification

Follow the * * startup sequence of "dust removal first → air compressor last → sandblasting system last"; When the equipment is running, it is forbidden for operators to put their hands and tools into the sandblasting cabin and open the sandblasting cabin door. When the workpiece is found to be displaced and the fixture is loose, stop immediately and deal with it after pressure relief. It is forbidden to operate under pressure.

Real-time monitoring and inspection

Regular inspection in the production process: check whether the spray gun spray is uniform and without deviation, whether the sandblasting medium is sufficient, and whether the dust removal system is normal (no dust overflow); Observe the surface treatment effect of the workpiece. If there are problems such as local spray leakage, excessive sandblasting and scratches, stop the machine immediately for investigation (such as spray gun blockage, parameter deviation and workpiece positioning deviation).

Specification for loading and unloading

When loading, handle it with care, and accurately put the workpiece into the positioning fixture to ensure no skew or occlusion; Wear gloves when blanking to avoid direct contact with the surface of the workpiece after sandblasting (grease and sweat on your hands will pollute the workpiece, which will lead to the decrease of adhesion of subsequent painting/coating); Follow-up treatment (such as sand blasting, cleaning, rust prevention) should be done to the sandblasted workpiece in time to avoid secondary corrosion caused by long standing.

Abnormal situation handling

Blockage of spray gun: immediately stop and turn off the air compressor, remove the spray gun to clean up the caking/impurities in the internal medium, check the dryness of the medium, and replace the drying medium if necessary;

Sudden pressure drop: check the air leakage of the air pipe, the failure of the air compressor and the blockage of the sandblasting pipe, and then start the machine after repair;

Dust overflow: check whether the dust removal filter cartridge is blocked or not, and clean/replace the filter cartridge in time to ensure the dust removal effect.

Iv. workpiece protection: key parts are blocked to avoid damage to non-treated surfaces.

The abrasive blasting medium is high-speed hard particles, which are easy to scratch and wear the non-treated parts of the workpiece, such as the precision mating surface, threaded hole, bearing position, mirror surface, electroplating layer, etc. Before treatment, targeted protection must be done, and the principle of * * "plugging is required whenever protection is needed" must be followed:

Sealing protection: special material, firm and without falling off.

Threaded hole/through hole: plug it with silica gel plug and rubber plug, and select suitable specifications according to the aperture to ensure firm plugging and prevent the sand blasting medium from entering the interior to cause thread damage and sand accumulation;

Precision mating surface/mirror surface/electroplating layer: tightly stick it with high-temperature adhesive tape and silicone protective film, and the edge is stuck without warping to prevent the medium from entering the scratched surface from the gap;

Central holes at both ends of shaft/rod workpieces: rubber caps and plastic plugs are used to prevent the central holes from being worn due to the entry of media;

Groove/blind hole of special-shaped workpiece: fill and plug with refractory mud and silica gel mud to ensure dense filling and easy cleaning after sandblasting.

Tooling protection: avoid tooling blocking and scratching.

The contact part between the positioning fixture and the workpiece is wrapped with soft materials (rubber, nylon) to prevent the fixture from scratching the workpiece by hard contact; The tooling design should ensure that the surface of the workpiece to be processed is fully exposed without blind corners, and at the same time prevent uneven processing caused by workpiece shaking during sandblasting.

Material adaptation: avoid the reaction between medium and workpiece.

It is forbidden to treat soft workpieces (plastic, aluminum alloy and copper) with hard media (such as steel shot and quartz sand) to prevent surface pits and scratches; Flexible media such as nylon sand, walnut sand and glass beads are preferred for soft workpieces; Stainless steel parts should avoid using ordinary quartz sand (easy to produce iron ion pollution, leading to later rust), and stainless steel balls and glass beads are preferred.

V. Sand blasting medium management: dry, clean and recycle to ensure the treatment effect.

The state of sandblasting media directly affects the treatment effect and the service life of equipment, so it is necessary to manage the storage, screening and recycling, and it is forbidden to use unqualified media:

Storage: dry and seal to prevent moisture and caking.

The sandblasting medium shall be stored in a dry and ventilated sealed silo to avoid moisture and rain; Moisture-absorbing media (such as walnut sand and nylon sand) should be dried before use (temperature 40~60℃) to ensure that the water content is ≤0.5%.

Screening: remove impurities and broken materials to ensure uniform particle size.

The recycled medium needs to be screened by screen to remove impurities, broken materials and caking (such as quartz sand broken particles and nylon sand powder) to avoid impurities from scratching the workpiece; Screen aperture shall be selected according to the particle size of medium, and screen blockage shall be cleaned regularly.

Recycling: control the loss and replenish it in time.

The medium recovery system of automatic sandblasting machine should ensure the normal operation and recover the scattered medium in time; In the process of recycling, the medium will be lost, so it is necessary to replenish new medium regularly to ensure that the medium in the silo is sufficient, and at the same time ensure that the old and new media are evenly mixed to avoid the deviation of treatment effect.

Media replacement: different workpieces/requirements shall be replaced in time.

When changing the workpiece material or processing requirements, thoroughly clean up the old media (including silos, sandblasting pipes and spray guns) left in the equipment to prevent the mixing of different media (such as steel shot mixed with nylon sand, which will cause scratches on the soft workpiece), and then add new media after cleaning.

VI. Equipment Maintenance: Regular maintenance to prolong the service life of equipment and avoid failure.

The spray gun, sandblasting pipe, dust removal system and conveying mechanism of automatic sandblasting machine are vulnerable parts, so routine spot inspection and regular maintenance are needed to avoid equipment failure caused by parts wear/blockage and affect production efficiency;

Daily maintenance (after each shift)

Turn off the power supply and air compressor of the equipment, drain the residual pressure in the sandblasting pipe, clean the medium residue in the spray gun and check the wear of the nozzle;

Clean the sand and impurities in the sandblasting cabin, and wipe the surface of the equipment to ensure that the cabin is clean and free of residues;

Clean the dust box of the dust removal system, dump the dust, check whether there is medium adhesion on the surface of the filter cartridge, and blow back the filter cartridge with compressed air (low pressure of 0.2~0.3MPa) to ensure the dust removal effect.

Regular maintenance (weekly/monthly)

Weekly: check the abrasion of sandblasting pipe and trachea, check whether the sealing strip at the joint is aging, and replace the damaged parts in time; Check the bearings and chains of the conveying mechanism and add lubricating oil to ensure smooth operation;

Monthly: Dismantle the spray gun and sand regulating valve, thoroughly clean the internal impurities, and check whether the internal bushing of the spray gun is worn; Check the oil-water separator of the air compressor, drain and discharge the sewage in time, and ensure that the compressed air is dry and oil-free (oil in the compressed air will lead to caking of the medium and oil contamination on the surface of the workpiece); Check the electrical circuit and sensor of the equipment to ensure that the connection is firm and there is no short circuit or open circuit.

Wearable parts replacement: replace in time to avoid affecting the effect.

The wearing parts such as nozzle, sandblasting tube, filter cartridge and sealing rubber strip shall be replaced periodically. When the nozzle is worn by more than 1/3, the sandblasting tube is cracked and the filter cartridge is blocked and cannot be cleaned, it shall be replaced immediately. It is forbidden to use wearing parts with injuries, so as to avoid reducing the sandblasting effect and equipment failure.

VII. Environment and occupational health: dustproof and noise-reducing, in line with production specifications.

Automatic sandblasting machine will produce dust and noise during operation, so environmental control is needed to protect the occupational health of operators and meet the environmental protection requirements of the factory:

Dust control: ensure the normal operation of the dust removal system for 24 hours, and ensure that the sandblasting cabin is fully sealed without dust overflow; Laying anti-skid mats on the ground in the operation area, cleaning up the scattered media and dust in time to avoid dust; Operators should have regular occupational health checks and wear dust masks (for open sandblasting machines).

Noise reduction control: the equipment is equipped with noise reduction devices (such as air compressor silencer and sound insulation cotton in sandblasting cabin), and sound insulation enclosures are set up in the operation area; Operators should wear anti-noise earmuffs to avoid hearing damage caused by long-term noise.

Media treatment: waste sandblasting media (such as quartz sand and steel shot that cannot be recycled) should be treated according to the industrial solid waste standard, and it is forbidden to throw them away at will; The medium easy to raise dust (such as quartz sand) is transported in a sealed way to avoid dust pollution in the factory.

Eight, the core taboo: absolutely forbidden operation, put an end to accidents and batch scrap.

It is forbidden for operators to start operation without wearing a full set of sand blasting protection equipment, and irrelevant personnel are prohibited from entering the sand blasting operation area;

It is forbidden to start the equipment without spot inspection, dust removal system, and sand blasting door, and it is forbidden to open the sand blasting door with pressure;

It is forbidden to blindly increase the sandblasting pressure and time, and it is forbidden to treat soft and thin-walled workpieces with hard media to avoid damage and deformation of workpieces;

It is forbidden to carry out sandblasting on the workpiece without pretreatment and sealing the protective parts, and it is forbidden to directly touch the surface of the workpiece to be sandblasted/sandblasted by hand;

It is forbidden to use wet, caked and impurity-containing sandblasting media, and it is forbidden to mix different kinds of media with different particle sizes;

It is forbidden to put hands and tools into the sandblasting cabin when the equipment is running, and it is forbidden to continue running with faults (such as gun blockage and sudden pressure drop);

It is forbidden to clean the equipment and replace the wearing parts without stopping the machine and relieving the pressure, and it is forbidden to directly purge the human body and the electrical components of the equipment with high-pressure air;

It is forbidden to place the sandblasted workpiece for a long time without subsequent treatment, and it is forbidden to mix the sandblasted workpiece with the non-sandblasted workpiece to avoid secondary pollution.

summary

The core logic of workpiece surface treatment of automatic sandblasting machine is * * "safety-based, accurate parameters, proper protection, standardized operation and regular maintenance" * *, and all operations are centered on "ensuring uniform surface treatment effect of workpiece, and preventing equipment failure and personal safety accidents". From safety protection and equipment spot inspection before operation, to accurate setting of process parameters and confirmation of trial spraying, to real-time monitoring of field operation, workpiece protection, and later equipment maintenance and environmental control, each link directly determines the treatment effect and production safety, and illegal operation and simplified working procedures are strictly prohibited.