A Guide to Sand Blast Cabinets

A Guide To SandBlast Cabinets.

This Guide on Sand Blast Cabinets was shared to me and I thought I would share it with you.

I cannot take the credit for such a great article, the article was compiled by John and his team and the full article can be read here 

I have added links from my shop to show our products

Sandblast Cabinet

Introduction

This article provides comprehensive information about sandblast cabinets. You will learn how these sandblast cabinets are made and their materials of construction as well as applications, advantages, and drawbacks.

Read further to answer questions like:

  • How do sandblast cabinets work?
  • Why should you select sandblast cabinets instead of other cleaning and surface preparation equipment?
  • What can sandblast cabinets do? How can you optimise your manufacturing operations with abrasive blasting equipment?
  • How are sandblasters made? What are the materials of construction?
  • How do I specify a sandblast cabinet when ordering or submitting an RFQ?
  • What types of abrasives, shot and blast media are used?
  • Can I dispose of, reuse, and recycle used abrasives, shot, and blast media?
  • Does the blast media wear out sandblast cabinet components?
  • And much more…

I. What is a Sandblast Cabinet?

Sandblast cabinets include systems or machinery and components for projecting blast media against a part‘s surface to abrade, clean, or modify the surface. Sand, abrasive, metal shot, and other blast media are driven or propelled using pressurised water, compressed air, or a blast wheel.

Sandblast cabinets are also known as abrasive blast cabinets, dry blast cabinets, wet blasting cabinets, micro-abrasive blast cabinets, micro-blasters, micro-jet machines, and shot peening cabinets.

II. Sandblast Cabinet Types and Technologies

Sandblast Cabinet Technology

If you want an answer to, "How do sandblasters work?", then you will need a better understanding of the technology empowering blast equipment. The shape and hardness properties of the media, or whether any media is used at all, is another parameter controlling the blasting process.

The technology employed to energise, propel or project the blast media is an important aspect characterising sandblast cabinet types.

The propulsion technologies blast machinery employs to clean, peen, or modify surfaces include:

Air Blast or Dry Blast Cabinets – Air abrasive blasting or dry blast equipment utilised compressed air to move the blast media. Pneumatic or compressed air blast systems can be divided into two types, suction, and direct pressure.

Suction or Syphon Blast Cabinet – Suction blasters or blast cabinets employ the venturi syphon effect to such abrasive into a pressurised stream of fluid, air, or water.

Venturi devices utilise a constriction in a moving stream of fluid to generate a pressure differential or vacuum. Blast media is sucked into the air or water stream at the constriction.

Suction Blasters Use the Venturi Principle
 

Venturi devices are found in many industries. Venturi generators are used to create a vacuum for mechanical holding applications. Ejectors and eductors move fluids, powder, or solids in chemical process industries.

Suction blast cabinets or portable syphon blasting pots cost less than pressure blast systems. Economy blasters tend to be suction sandblasters. They do not require a pressure vessel and consume only half of the pressurised air compared to pressure blast cabinets. However, suction blasters require higher air pressure levels to maintain media flow.

Siphon or Suction Blast Gun
 

Suction blast cabinets are less aggressive and take longer to impact clean.

Suction blasters are commonly used in short-run or light production, maintenance, and remote field applications.

The less aggressive nature of suction or siphon blasters increases the time to strip or clean parts. On the upside, the lower aggressiveness reduces the wear rate of the parts within a suction blaster. Suction blaster parts tend to last longer reducing blast equipment maintenance costs.

Small handheld sandblasters can have a cup above the blast gun to gravity feed into a blast gun‘s venturi point. Gravity blasters are a type of suction blaster because gravity-fed blast guns still make use of the venturi syphon effect.

Direct Pressure Blaster Machine Layout
Direct Pressure Blaster Machine Layout
from Titan Abrasive Systems
 

Direct Pressure or Pressure Blast Cabinets – Pressure or direct pressure abrasive blast equipment makes use of a pressure vessel to energise the abrasive media. A pop-up or metering valve on the pressure vessel is opened to release pressurised fluid and blast media into a blast hose. The pressurised media travels through the blast hose to the direct pressure cabinet and blast gun.

Direct pressure cabinet blast machines expel the blast media at much higher flow rates or speeds compared to suction blast equipment. Impact or kinetic energy (K) of the blast media is K = ½ mv² where m = blast media mass and v = velocity.

Doubling the flow or velocity quadruples the impact energy and blast cleaning efficiency.

The higher blast media speeds enable direct pressure systems to impact clean parts up to 4 times faster than suction blast machines. Pressure levels are more adjustable with direct pressure blast cabinets, so cleaning and surface modification can be more precisely controlled.

Direct pressure blast equipment can lift and propel heavy media such as steel shot, cut wire shot, and steel grit. Suction sandblasters struggle with heavy media. Doubling the blast media mass doubles the impact energy. Heavier blast media (denser or larger) is more efficient at cleaning and profiling compared to lighter, lower density, or smaller media.

The higher speeds, ability to handle heavy steel media, more aggressive nature and better control of direct pressure sandblast cabinet make pressure blast equipment more widely employed in high volume production and automated blasting applications. The higher blast media speeds enable pressure sandblaster guns to operate at greater stand-off distances from the part.

Pressure blasters consume two to three times the volume (CFM) of compressed air compared to suction blast cabinets. Pressure vessel maintenance and safety are a concern. The failure of a pressure vessel could harm operators and damage equipment. Blast system pressure vessels need to be manufactured to American Society Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Codes.

Wet Abrasive Blast Cabinets – Water can replace air as the fluid used to propel the blast media. Wet abrasive blast or water blasting can reduce the dust generated during abrasive blasting by over 90%, which can be important when stripping or cleaning a part containing heavy metals and hazardous materials. While some suppliers refer to wet abrasive blasters as dustless blast equipment, no abrasive blasting system suppresses 100% of the dust generated.

Water blasting can keep the parts cooler compared to dry blasting, which can reduce warping or distortion of thin sections. If the dust generated during blasting is explosive such as aluminium or titanium dust, then wet blasting is advantageous because static discharges and ignition are suppressed.

Water blasting can consume up to 50% less blast media compared to dry blasting. Wet blasting provides deep cleaning with less or no imbedding of abrasive media. Wet blasting systems can employ closed-loop media can recyclers, oil separators, demisters, and filtration systems. Dust is converted to clean, disposable sludge waste.

In dry blasting, the dust must be removed with an air blow gun or washing. Wet blasting combined washing and dedusting with the blasting step. Detergents can be added to the water to loosen deposits, dissolve oils or greases and accelerate the cleaning process. Rust inhibiting agents can be added to the water to prevent rusting of wet steel after the blasting process is complete. If rust suppressors are not added to the water, then the steel should be dried, oiled, or painted after blasting to prevent rust formation. Bacteria and microbes can grow in the blast water forming slime films and releasing odours. The blast water like other metalworking fluids and grinding coolants require the addition of antimicrobial agents.

There are several types of water blasters and water abrasive blasters.

Slurry Wet Abrasive Blast Cabinets
 

Slurry Sandblast Cabinets –Dry blasting equipment can be retrofitted to provide wet blasting. Slurry blast systems are also known as air abrasive water blasters. A water injection nozzle or water ring (halo) is attached to an air blasting gun, which introduces water into the blast media stream. They suppress 50% to 85% of the dust generated. The water ring or halo nozzles provide less dust control than the water induction or injection nozzles.

Slurry blasters have a high degree of versatility because they can dry blast, wet blast, rinse, and dry parts.

One drawback of slurry blasters is cleaning up the muddy mess generated in field applications. Slurry blast equipment is tiresome for operators to carry and handle because a heavy water hose is attached.

Wet Venturi Blaster
 

Wet Venturi Sandblast Cabinets –Wet venturi blasters are like dry suction blasters except a compressed air-generated venturi vacuum sucks in an abrasive-water mixture. Some manufacturers call these systems modified sandblasters. While venturi blasters successfully suppress dust, they require high blast pressure to operate effectively resulting in high consumption rates of water and blast media. Flow control is limited.

Vapor Abrasive Blaster
 

Vapor Abrasive Sandblast Cabinets – In vapour abrasive blast machines, the abrasive and blast media are premixed in a pressurised vessel. Vapour abrasive blasters are also known as mist blasters or dustless vapor blasters, and dust-free blasters. Vapour abrasive blast systems provide the highest level of dust suppression, up to 95%.

The abrasive slurry travels through a blast hose to the slurry blasting nozzle. Additional compressed air can be added to regulate the aggressiveness of the wet blasting process. The regulating compressed air generates a mist of wet abrasive particles. The regulating air pressure and the blast media consumption rate can be controlled independently.

Vapour abrasive blasters consume much less water and media compared to venturi and slurry blasters.

Vapour sandblasters have a wide operating pressure range and finer control of the wet abrasive blasting process compared to other wet blasters. Vapour abrasive blast machines operate at very low pressures (30 psi) for paint stripping to very high pressures such as white metal blasting for corrosion control applications.

Wet Sandblast Cabinet
Wet Sandblast Cabinet
from Midwest Finishing Systems
 

Ice Blast Cabinets – Dry ice blasters and water ice blasters impact clean with a frozen media such as dry ice (solid carbon dioxide) or water ice (H2O). Dry ice and water ice are non-aggressive types of media.

Ice blasting cabinets must be designed to handle the colder media, as well as the condensation on lines, cabinet walls, pots, and vessels. The materials of construction cannot include types of plastics or metals, which become brittle at lower temperatures.

Dry Ice Snow Blast Cleaning Space Telescope Mirror
 

Dry ice is gentler and softer than plastic media. Dry ice media can be in two forms: pellet and shaved or snow-like flakes. NASA engineers have used dry ice or carbon dioxide snow-like crystals to clean particle contaminants and molecules from the surface of a space telescope mirror while generating zero scratches or profile changes.

Dry ice and water ice blasters have clean-up advantages over conventional blasters. Water ice grits will evaporate after blasting. Dry ice sublimes in gaseous carbon dioxide. The sublimation of dry ice absorbs heat from the part‘s surface, which can aid in paint removal and cleaning.

Sandblast Cabinet Types – By Size and Application

Sandblast cabinets can consist of complete blasting machines or abrasive blast packages reconfigured with the required components. Sandblast cabinets can be modular. You can configure a sandblasting system specifically for your application by selecting various parts from a supplier‘s catalogue. Parts include blast guns, wear-resistant nozzles, pressure vessels, valves, dead man handles, blast cabinets, blast rooms, and blast hoses.

Sandblast cabinets can vary greatly in size and configuration depending on the specific application, end-use or function, and setting (lab/shop, production line, or field/remote sites) where they are used.

Bench top Micro Blasters and Pencil Blasters – Micro-abrasive blasters or micro blasters have small 0.018-to-0.125-inch diameter nozzles. Some nozzles are made of sapphire or single crystal alumina. Media sizes range from 10 to 350 microns are used to blast surfaces. Micro blast cabinets are bench top or floor mounted. Handheld pencil blasters are a type of micro blaster. They usually have a small gravity-fed media cup.

Cleaning, stripping, and etching of small parts and detailed work in dental, jewellery, and electronic (PCBs) applications are common for micro-abrasive blasting systems. Stainless cannula, micro tubes, and hypodermic needles are deburred with micro blasting systems.

Manual Blast Cabinets or Cabinet Blasters – Manual blast cabinets have two holes with rubber blasting glove protruding into the cabinet, which allow an operator to manipulate parts and hold the blast nozzle at the appropriate stand-off distance to generate a hot spot and then move the hot spot across the surface to clean or etch a surface.

The blast cabinets have a window and internal lighting, so the operator can see the parts and guns without getting blasted in the face. Some blast cabinets blast air across the window to maintain visibility by preventing dust build-up.

Blast Cabinet Gloves, Grating, Window and LED Lighting
 

Spent blast media drops through the cabinets steel or fibreglass grate and into a collection hopper. The used blast media was conveyed to a media separator to recover the abrasive. Economy blast cabinets might skip the separator step and directly reuse the spent media. Without separation, dust and finer broken media are blasted, which can reduce efficiency and damage filters.

Ideally, the media and dust generated from blasting parts is contained within the cabinet and filtration system. Blast cabinets develop leaks as seals wear and tear over time. Leaking around doors is a common problem because cabinet doors are not always clamped tight around the whole periphery.

Manual Blast Cabinet
 

One leading manufacturer, Titan Abrasive Systems, has developed a patent-pending technology for "leak or warp" proof blast cabinet doors. The doors have double panels and two rigid, steel channels. The doors also have a better closing mechanism to better clamp the door shut along the edge. A knife-edge on the door forms a positive seal every time the door closes.

Blast cabinets can have front, top and side opening doors. Some cabinets have multiple doors. Double doored cabinets allow shuttling in of a dirty part, while a cleaned part is removed. Blast cabinet doors can swing open, swing up, or slide open. Pass-through cabinets are available for etching glass sheets or panes and metal plates. Pass-through blast systems come up with a narrow gap with special brush or rubber flap seals to prevent abrasive leaks. The sheet or part is pushed into the gap and passed through the cabinet on rollers.

Manual blast cabinets are ideal for machine shops, garages, body shops, light production or short runs, touch-up of production parts, prototyping, and custom wo

III. How Are Sandblast Cabinets Constructed?

Sandblast Cabinets are constructed from a wide variety of parts cabinets, pressure vessels, hoses, guns, nozzles. These individual components are made using sheet metal fabrication, casting, welding, mechanical fastening, machining, and specialised processes.

Blast cabinets are essentially fabricated metal boxes. They are typically made by cutting, bending, and forming steel sheets and plates into sides, legs, and doors needed to form a box. Blast cabinets parts can be welded or fastened together. Fastening allows the parts to be more easily removed for cleaning, repair, and replacement. Welded blast cabinets tend to be more airtight with less leakage of blast media and dust into the shop, but replacement of worn cabinet sides or bottoms is difficult. The abrasive blast stream wears the bottom and sides of the cabinet over time. The seals and windows on the cabinet will also age, wear and require replacement.

What Are Blast Cabinet Materials of Construction?

Blast cabinets for dry or air blasting are made of steel with powder coatings or industrial paint. Wet blasting cabinets are made of more corrosion-resistant materials such as stainless steel.

In certain dry blasting applications such as surgical instruments and medical implants, stainless steel construction materials might be used to avoid iron contamination of a surface.

A system for blasting stainless steel parts would typically use stainless steel shot or grit or non metal abrasive media as well. Steel components or steel shot impacting stainless steel parts can transfer metal to the stainless surface, which can alter passivation and lead to rust on the surface.

Wear-resistant steel liners are strategically placed within blast chambers to reduce wear of the blast machine. Wear-resistant alloys include manganese steels such as Manganal and nickel and chromium white cast irons such as Ni-Hard alloys.

What Are The Parts and Consumables In a Sandblaster?

Sandblast cabinets tend to be self-destructive due to the aggressive blast media. Blaster parts are consumable and will wear out over time as abrasive or media flow over or through these parts.

Of course, the blast media or abrasive grits are consumable as well. Some types of blast media like steel shot, ceramics, and aluminium oxide can be recycled through the blaster a hundred times or more. Soda, dry ice, sand, and coal slag are only used once.

The parts in abrasive blasters, wheel blasters, and shot peeners need to be regularly inspected for wear. When the nozzle's inner diameter changes or the throwing blades change geometry, the efficiency of the blasting process can be compromised.

Sandblaster parts include:

  • Sandblasting Guns / Blast Guns
  • Sandblasting Nozzles / Blast Nozzles
  • Blast Wheel Parts - Blast Wheel Blades, Cages, and Impellers
  • Wear Plates
  • Pressure Regulators
  • Sandblaster Valves – Air inlet valves, abrasive metering valves, shut-off valves, media mixing valves, and pop-up valves
  • Blast Cabinet Windows
  • Blast Cabinet Floor Grating
  • Blast Hose
  • Blast Room Floor Grating
  • Deadman Controls, Handle, and Valves
  • Foot pedals
  • Dust Collectors Filters
  • Media Separator Screen and Parts
Nozzle Material Life (x Ceramic Nozzle Life)
 

Blast nozzles are made of extremely wear-resistant materials including:

  • Ceramic, aluminium oxide, or alumina (Al2O3)
  • Binderless tungsten carbide, Pure WC (ROCTEC®, Cerbide™)
  • Boron carbide (B4C) (Norbide®)
  • Cemented tungsten carbide, WC with cobalt binder
  • Ceramic SiAlON or silicon aluminium oxynitride
  • Silicon Nitride
  • Steel
  • Zirconium oxide or zirconia, (Zr02) or zirconia-alumina

Boron carbide, alumina, pure WC, and silicon carbide ceramic are the most wear-resistant materials.

Depending on the blast media, cemented tungsten carbide and SiAlON nozzles will last 10 to 20 times longer than ceramic or alumina nozzles. Boron carbide is the hardness and the most wear-resistant of the nozzle materials. Boron carbide typically costs 3 times as much as cemented WC, but boron carbide lasts 3 to 25 times longer than cemented WC or sialon. They do not have the toughness and impact resistance of cemented tungsten carbide. Binderless tungsten carbide (WC) nozzles have double the life boron carbide nozzles.

Steel nozzles are acceptable for air blow guns, washout guns, and blasting of exceptionally soft media such as soda, dry ice, walnut shells, and plastic media. Steel nozzles will not break when dropped. Economy and non-industrial sandblasters for home or DIY use often come with low-cost steel nozzles.

Based solely on wear resistance boron carbide and binderless WC last up to seven-time longer than cemented WC. If you bang a boron carbide or silicon nitride nozzle into a part, grate, or cabinet wall, then the nozzle is more likely to crack compared to a cement tungsten carbide nozzle.

Nozzle service life will depend on the media blasted through the nozzle as well. Sharper angular steel grit will wear nozzles faster than spherical cast shot. Aluminium oxide and silicon carbide will wear out nozzles more quickly compared to garnet or coal slag. Cleaning equipment blasting plastic media, soda, corn cobs, or walnut shell media could last indefinitely.

In addition to consumable wear components, a variety of sandblasting accessories and ancillary equipment can improve the blasting process:

  • Sandblast masking tapes, films, and materials
  • Masking caps and shields
  • Dust Suppressants
  • Media Separators reclaimers and Recyclers
  • Industrial vacuums
  • Moisture traps, water separators, air dryers
  • Air Blowguns
  • Vibrators
  • Material handling equipment
  • Blasting Water Additives - Passivates, Rust Inhibitors, and Antimicrobial agents
  • Blast hose back pressure tester
     
    Blast Hose Back Pressure Tester
  • Blast nozzle wear gage
     
    Blast nozzle wear gage

Sandblasting and shot peening processes require abrasive blasting personal protective equipment (PPE):

  • Sandblasting Masks
  • Sandblasting Hoods
  • Blasting Suits
  • Sandblast Respirators
  • Sandblasting Gloves
  • Blast Cabinet Gloves
  • Hearing Protection

IV. What Can Sandblast Cabinets Do? How is Sandblasting Used?

Sandblast cabinets modify surfaces of parts or structures in a variety of ways depending on the media type and blasting parameters. Softer media at lower pressure can gently remove coatings. Extremely hard abrasives projected at high pressures can aggressively etch and pattern or carve surfaces.

Different Processes of Grit, Bead and Wetblasting
 

For example:

  • Spherical or round blast media can smooth and harden surfaces.
  • Crushed, angular shaped abrasive etch or rough surfaces
  • Soft plastic and organic media can remove paint and coating layers while leaving underlying aluminium, fibreglass, or composite surfaces untouched.
  • Water blasting without media with ultra-high pressure can remove heavy scale from boiler tubes or even demolish concrete.
  • Soda blasting can remove paint while leaving behind a corrosion protective film on a steel surface.

Some of the end-use or surface modification functions sandblaster can provide to optimise your production operations are:

Cleaning / Stripping – Impact cleaning or mechanical cleaning is the most widespread end-use of Sandblast Cabinet. Abrasive blasting is highly effective at cleaning surfaces and stripping or removal of rust, oxide scale, mineral deposits, corrosion grease, dirt, coatings, sealants, carbon deposits, and varnish.

Wire brush wheels, abrasive belts, abrasive discs, and other coated abrasives tend to load quickly when removing paints, coatings, grease, and contaminants. The abrasive blasting process removes the surface contamination and converts it into dust. The dust and media are handled using dust collectors, industrial vacuums, and separators.

The level of cleaning aggressiveness can be broadly adjusted through the selection of blast media, pressure, flow rates, and blast machine type.

Abrasive blasters can gently remove graffiti, paints, and coatings without the removal of the base material. The abrasive blaster can also deeply blast a steel surface to completely remove any rust, scale, or adherents to a NACE/SSPC "white metal" cleanliness grade.

Blending, Smoothing, and Surface Finishing – Removing marks or way lines from machining and grinding processes. Spherical media such as steel shot and glass beads are especially good at blending and refining surface finishes.

The round edges hammer down higher points on the surface producing a brighter, matte finish. Blasting with sharp, angular abrasive produces a duller, satin finish, which has excellent bonding characteristics.

Spherical & Angular Blast Media Surface Profiles
 

Refining the surface finish or reducing the surface profile can increase fretting fatigue strength from 20% to 200%. A larger diameter or heavier cast shot can be used first to impart a deep residual stress layer. Next, the surface is peened with small spheres or microbeads to refine the surface finish.

If the part has a rough (high roughness average, Ra) surface finish like an as-cast or as-forged surface, then peening can modestly refine the surface finish. If the part has been ground or machined to a smooth or low Ra finish, then shot peening will result in a rougher surface finish.

De flashing – Flash or excess material forms where the two halves of a mold meet in plastic molding, rubber molding, sand casting, or die casting. The flash on the molded metal, plastic, or rubber parts needs to be removed and then the remaining parting line blended in. Plastic and rubber parts are cryogenically frozen with liquid nitrogen at -300°F (-184°C). The plastic and rubber flash becomes friable and is easily blasted away.

Deburring – Slivers, attached swarf or metal chips, and sharp overhanging edges can form on parts during sawing, machining, drilling, cutting, shearing, grinding, and other metal removal operations. Burrs and slivers can easily cut worker‘s or customer‘s hands and represent a handling hazard. Sandblasting can quickly remove burrs from edges even in recesses where mechanical deburring blades and chamfering tools cannot reach.

Drilling / Carving – Micro abrasive blasters can drill small holes in printed circuit boards. The abrasive blaster can carve glass, wood, stone, and other materials to create 3D shapes and 2D patterns.

Patterning / Marking – Abrasive blasting can create patterns or mark surfaces with images, part numbers, and text. Blasting masking tapes, masking films, and masking compounds are used to create the patterns. The mask materials are typically soft or rubbery, which protects the masked areas from the abrasive blast. Micro-abrasive blasters have a very narrow blast pattern, so they can pattern or mark without masking in some applications.

Peening / Surface Engineering Surface engineering entails modifications to the surface of a part to provide unique characteristics enabling or enhancing performance in specific applications.

Spherical Cast Stainless Steel Shot for Peening and Blasting
Spherical Cast Stainless Steel Shot for Peening and Blasting
from Great Lake Finishing Equipment
 

Peening impacts the surface with spherical steel, stainless steel, glass, or ceramic media. It is also used to strain harden and impart compressive residual surface stresses on a part. The common media used is ‘cast steel shot‘ with a Rockwell C hardness of 40 to 55.

The compressive residual stress from shot peening can increase the fatigue strength of parts by 30% to 500%. Increasing fatigue strength and resistance to stress-corrosion cracking is important for fastened components, gears, axles, dies, molds, shafts, springs, aircraft landing gear, and other rotating and structural parts.

The residual stress generated during shot peening can be used to peen form and peen straighten shafts back into tolerance. Shot peening also hardens the surface of parts, which increases hardness and wear resistance. Shot peening can also close surface porosity. Shot peening is used to find and remove a spot of hidden sub-surface corrosion in parts and around fasteners.

Surface Engineering with Shot Peening
 

Shot peening can texturize a surface or produce specific patterns of dimpling or depressions. A dimpled texture can better retain lubricants, grease, inks, or other fluids. Peened textures can also alter the gripping and frictional characteristics of surfaces.

Etching / Surface Profiling - This includes surface texturing, roughening, and generating a specific surface profile. Coating, paints, and adhesives adhere better to a rough surface compared to a smooth surface. An abrasive blasted surface creates an anchor profile with undercuts and more surface area for coatings and adhesives to grab onto.

A sandblast roughened surface on a stainless handrail helps people get a better grip too. Etching alters the frictional characteristics of a surface, which can be useful in mechanical power transmission applications.

Surface Preparation – Surface preparation requires a combination of surface cleaning and anchor profile generation or roughness modification. Surfaces are prepared before coating, painting, galvanising, oiling, welding, brazing, sealing, soldering, adhesive bonding, and rubber-to-metal-bonding.

Paints, coatings, and adhesives will not bond well to greasy, oily, dusty, or dirty surfaces. Surface contamination can act like a mold release agent or non-stick coating. Cleaning is required to promote chemical bonding and assure adhesion.

Rust and corrosion layers need to be removed as well, especially for protective coatings meeting the National Association of Corrosion Engineers (NACE) and Society of Surface Protective Coating (SSPC) standards. Three reasons to remove rust or corrosion with abrasive blasting are:

  1. Rust and corrosion layers are weak and softer compared to the underlying metal. The bond strength of the coating will be limited by the weakness of the corroded layer. Coating failure can occur through de lamination of the rust layer.
  2. Contact or bearing stress on the coating over rust will likely result in cracking of the coating. Once the coating is cracked, the surface is no longer protected from additional corrosion.
  3. A surface with underlying rust or corrosion can continue to corrode because the rusty or corroded layer may still contain moisture as well as salt or acidic elements.

Paints and coatings will not bond well to a low roughness or smooth surface because there are few anchor points to hold the coating. A blast roughened surface provides mechanical interlocking between the coating and substrate.

Should you surface prep for coating with the coarsest and sharpest blast media available?

No, because if a surface is too rough, then thinner protective coatings might not fully cover the surface resulting in pinholes and corrosion of the underlying surface. Shot, bead, and abrasive blasting can reduce some of the high peaks in a surface profile to improve corrosion protective coating performance.

Aggressive coarse grit abrasive blasting is best for bonding thermal spray deposits, high build coatings, and polymeric lining systems. Thinner coatings and paint perform better with a less aggressive profile (fewer high peaks), which can be produced using round steel shot, glass beads, or other spherical media.

Optimum Profile Generation with Sandblasting
 

V. Industrial Applications of Sandblast Cabinet

Industry-Specific Applications

Aerospace – Plastic media is used to remove old paint from aluminium aircraft parts without damaging or removing any of the underlying composite or soft aluminium metal. Blasting is also used during the refurbishment of jet engine parts and NDT inspection aircraft structural components.

Additive Manufacturing / 3D Printing – Abrasive blasting is used to remove support material from 3D prints. Blasting can also smooth surfaces and blend in striation lines generated during 3D printing.

Automotive Aftermarket –Sandblasters are important tools in auto body shops and automobile repair garages. They are used for auto body rust removal, body and engine repairs, and antique auto restoration.

Adhesive Bonding / Sealant Application – The surface cleaning and anchor profile generation increase the bond strength of adhesives and sealants.

Coating and Paint Application – The surface cleaning and anchor profile generation increase the bond strength of paints and protective coatings. Sandblasters are indispensable for preparing or keying surfaces to accept coatings.

Corrosion Control Industry – Stripping off damaged coatings and paint layers, rust, corrosion, grease, dirt, adhesives, sealants for recoating or repair. NDT inspection or assessment of corrosion requires precleaning of the surface. The International Standard Organisation (ISO), National Association of Corrosion Engineers (NACE) and Society of Surface Protective Coating (SSPC), and American Society of Testing and Materials (ASTM) have surface preparation standards and cleanliness grades to properly prepare surfaces before protective coatings are applied.

Electronics – Micro abrasive blasters, or micro blasters, are a powerful tool for electronics repair. Micro blasters can selectively remove solder in applications where reflow desoldering on a printed circuit board (PCB) is not a feasible option. Conformal coatings, which cannot be removed with heat or chemicals, can be stripped away with micro-blasters. Holes or vias can be drilled in PCBs using micro-sandblasters. Electrical Connections

Foundries and Forges – Abrasive blasters such as centrifugal wheel blasters and pressure blasting equipment are essential elements in foundry and forge cleaning rooms. After a shakeout operation, castings are blasted with metal shot or metal grit to remove any remaining mold sand, ceramic investment material, and then cleaned to remove any surface oxide scale on the surface. Forged parts require blasting to remove die lubricant and descale oxide layers.

Glass Fabricators – Glass panes or windows, glass bowls, glass cups, and other decorative glass objects can be frosted or patterned using stencils or masks. Micro blasting is another method used to etch or engrave words and graphics onto a glass object. Sand carving uses abrasives to deeply etch away glass and create 3D relief patterns or images. Glassware is typically blasted with 180 grit silicon carbide.

Machine Shops / Manufacturing – Most machine shops, fabricators, and manufacturers have at least one blast cabinet to perform cleaning, decreasing, deburring, and surface preparation of machined or fabricated parts. Dies, molds, drills, end mills, saw blades, and other tools are other blasted to remove burrs and embedded debris stuck on cutting edges or between teeth. Shot peening can increase the fatigue strength and life of machined or ground shafts, tools, and structural parts.

Medical / Dental – Cleaning, coating preparation, etching, and polishing of medical devices and dental restorations. For example, the investment or mold material on cast crowns or bridges can be gently removed with a small benchtop sandblaster or micro-blaster. Hip, shoulder, dental and other bone, and joint implants are blast cleaned to meet stringent FDA cleanliness requirements.

Blasting Cleaning Medical Implants
Blasting Cleaning Medical Implants
from Empire Abrasive Equipment
 

Non destructive Testing (NDT) – Coating, rust, corrosion, grease, and other surface contamination must be removed before structural components can be inspected for surface and subsurface cracks and defects. Ultrasonic, eddy current, penetrate testing, magnetic particle, and visual test methods need a clean surface for evaluations.

Plastic / Rubber Molding – Deflashing molded parts, cleaning excess resin from molds or forms. Dry ice blasting is widely used to clean plastic and rubber molds. Rubber becomes brittle at low temperatures and can be abraded away. Cryogenic blasting is used to deflash rubber and plastic parts chilled to cryogenic temperatures.

Remanufacturing – Used or damaged engines, blocks, heads, brakes, transmissions are repaired or refurbished by remanufacturers. The engine or automotive components are cleaned using a sandblast cabinet to remove any rust, grease, gaskets, and coatings on the surfaces. Mating surfaces are ground to remove any warpage. Cylinders are reground or relined. The re manufactured engine is reassembled and returned to service or resold.

Thermal Spray Coating – The formation of an anchoring surface profile using abrasive blasting of surfaces on jet engine blades and other critical components is essential attaining thermal spray deposit bond strength. Thermal spray coating will de laminate from smooth, unblasted surfaces.

Welding, Brazing & Soldering – Abrasive blasting is applied before welding, brazing, and soldering to clean surfaces and assure solid joint formation. After joining, slag, rosins, oxide patinas, weld spatter, or splatter is removed using additional blasting before protective coatings are applied.

Woodworking / Cabinetry – Removing paint or wood sap before painting wooden cabinets, furniture, and trim. Wood carving and wood sign etching are also accomplished with Sandblast Cabinet.

VI. Benefits and Drawbacks of Sandblast Cabinet

Sand Blasting Advantages

  1. Sandblasting excels at the complete removal of coatings, paint, adhesives, dirt, mill scale, welding tarnish, slag, and oxidation over the entire surface areas of a part. Areas or spots on a part can be hard to reach when using an abrasive disc, flap wheel, or wire wheels. Resulting in regions remaining dirty and unstripped.
  2. Sandblasting is exceptional at the critical step of cleaning and surface preparation before the application of coatings, adhesives, and sealants. Sandblasting creates undercuts on the surface of a part, which improves adhesion by allowing coatings and adhesives to mechanically grip onto the surface.
  3. The finer sizes of blasting media can be used to blast clean and prep inside holes, crevices, and the intricate details of a part.
  4. Sandblasting can handle round or concave as well as convex curved surfaces, which is often required for special machines and backup plates when using fixed abrasives or coated abrasives.
  5. Sandblasting is highly versatile because blast machines are available for cleaning and preparing extremely large surfaces on ships and process tanks to exceedingly small parts such as electronics and medical devices.
  6. Sandblasting does not impart any surface damage or burning of a metal part, which can be a problem when surfacing with grinding wheels and abrasive belts or discs.
  7. A wide variety of abrasive, shot, and blast media are available with different hardness values, shapes, and media or grit sizes, which allows the sandblasting process to be precisely tuned and optimized for different materials and applications.
  8. Sandblasting does not use any volatile organic compounds such as the solvents used in chemical cleaning methods.
  9. With the proper blast media, surface changes can material properties and part performance. Certain blast media like soda or sodium bicarbonate can leave a protective film on a surface after blasting to enhance corrosion resistance. Steel shot peening with a blasting machine can increase fatigue strength and longevity of parts.
  10. Depending on the abrasive or blast media used, sandblasting can be environmentally friendly and non-toxic. For instance, no harmful spent media are released when blasting with dry ice, water ice, walnut shells, corn cobs, and soda.
  11. Typically, blast media can be reclaimed, separated and reused several times, and then recycled.
  12. Sandblasting can be automated or robotically operated to increase efficiency and quality. Sandblasting can be easier to automate compared to part cleaning and finishing with grinding wheels, rotary files, and abrasive flap wheels.
  13. Sandblasting can be more cost-effective when compared to other methods because:
    1. Larger surfaces can be rapidly blasted.
    2. Blasting is less labour-intensive than alternative abrasive finishing methods such as abrasives discs, flap wheels, and wire brushes.
    3. The process can be automated.
    4. Blast equipment, blast media, and consumables are relatively inexpensive.
    5. Certain blast media types can be reused multiple times.

Drawbacks of Sandblasting

  1. Shot peening and sandblast cabinets generate high decibel noise and dust.
  2. Certain blast media can be harmful to the environment. Blasting abrasives containing crystalline silica should not be used because they can cause silicosis. Silicosis is a pulmonary disease caused by the inhalation of fine silica (0.5 to 5 microns).

    Certain materials such as lead-based paints and heavy metals generate harmful or toxic dust when blasted. In these applications, specialised systems are required to prevent the release of harmful materials. Proper collection, handling, and disposal of the media are required as well. Wet or water blasting systems reduce the dust problem.

  3. The abrasive blasting process puts a lot of wear on the internal components of sandblast cabinets. Media and consumable wear parts must be gaged to maintain consistency and then repaired or replaced at appropriate intervals to assure quality and safety. The cost of media and consumables should be factored into your sandblast cabinet selection process.
  4. Sandblasters or sandblasting operators can be injured during abrasive blasting. The high-pressure abrasive stream can harm skin and eyes. Abrasive media and abraded dust can be inhaled or ingested. Inhalation can cause lung disease, breathing disorders, and other health problems. Dust collectors and filters must be used and maintained to prevent operators and other workers from dust hazards. In blast rooms and remote field locations, blasting operators should wear sandblasting suits, sandblasting hoods or sandblasting helmets, respirators, blast cabinet gloves, and other personal protective equipment (PPE).
  5. Sand or abrasive blasting can generate heat during the abrasion process, which can warp thin parts. Soda, dry ice, and wet blasting keep parts cool during blasting.
  6. Abrasives and blast media can get lodged into crevices on a part and can be difficult to remove.

VII. Selecting and Ordering Sandblast Cabinet

Answering these questions will help you in selecting the right blasting system for your surface treatment application.

Start with the size, shape, and annual production volumes when considering the type of blasting equipment to select. What‘s your production volume (parts per year), the size of the parts, or the surface area being blasted?

Next, understand your cleaning and surface treatment requirements. What standards apply ISO/NACE/ SSPC?

What are the media choice options to generate the required cleanliness, profile, or surface engineering (residual stress)?
Examine the different blast media options choices

If possible, request a trial at a supplier‘s facility to evaluate different blasting processes and blast media.

Verify the blasting process parameters with an additional test or trial.

What are the operating costs of the Sandblast Cabinet?

Estimate the annual operating and consumable costs such as compressed air, water, and electrical power consumption.

What are the consumable costs such as blast media, wear part replacements, and system maintenance costs?

What are the labour costs and training requirements? How many operators are required to run the blast system? Is special safety and automation system training required?

Submit a quote for the sandblast cabinets along with any additional questions to clarify training as well as annual estimated operating, maintenance, and consumable costs.

VIII. Conclusion

  • Today‘s sandblast cabinet suppliers provide a vast range of product variations manufactured with high-quality materials and methods.
  • Blasting equipment suppliers are constantly upgrading equipment with new technology innovations.
  • Novel blast media types such as dry ice, soda, and high durability media are available to further reduce environmental impact.
  • Sandblasting experts at the leading suppliers know how to select the specific blasting and peening systems, media types, media recovery equipment, and material handlers for a broad range of industry applications.
  • Sandblasting manufacturing experts are willing to work with customers on the development of new applications that would benefit from abrasive blasting and peening technology.
  • The outlook for increased use of abrasive blasting and shot peening equipment is extremely promising considering the broad range of capabilities that modern equipment OEMs can provide to their customers as well as the benefits to the environment.
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A Guide to Sand Blast Cabinets