China Metal Machining Surface Finish Manufacturer

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Sinster provides cnc machining surface finish, lost wax casting surface finish, die casting surface finish, and metal stamping parts surface finish. Let’s learn the machining surface finish first.

What is the machining surface finish?

Surface finish is a process of artificially forming a surface layer on the surface of the base material that is different from the mechanical, physical and chemical properties of the base, including machining surface finish, casting surface finish, forging surface finish, and stamping surface finish.

The purpose of machining / casting / forging / stamping surface finish is to meet the product’s corrosion resistance, wear resistance, decoration or other special functional requirements. For metal castings, our more commonly used surface finish methods are mechanical polishing, chemical treatment, surface heat treatment, and spray surface. Surface finish including machining surface finish is to clean, sweep, deburr, degrease, and deoxidize the surface of the workpiece.

CNC Machining Surface Finish Introduction

Generally speaking, there are two explanations for Machining surface finish in China

One is surface finish in a broad sense. The surface finish includes pretreatment, electroplating, coating, chemical oxidation, thermal spraying and many other physical and chemical methods. The other is a narrowly-defined surface finish, that is, the pre-treatment part that only includes sandblasting, polishing, etc., which is what we often say.

What we are talking about below is mainly surface finish in a narrow sense

In the process of processing, transportation, storage, etc., the surface of the workpiece after machining surface finish is often covered with oxide scale, rust molding sand, welding slag, dust, oil and other dirt. For the coating to be firmly attached to the Machining surface of the workpiece, the machining surface of the workpiece must be cleaned before painting. Otherwise, it will not only affect the bonding force and corrosion resistance of the coating to the metal, but also make the base metal even if it is coated. It can continue to corrode under the protection of the layer, causing the coating to peel off, affecting the mechanical properties and service life of the workpiece. Therefore, the surface finish of the workpiece before painting is an important guarantee and measure to obtain a high-quality protective layer and prolong the service life of the product.

Surface Finish History

Surface finish is the oldest technology

Since there were humans on the earth, surface finish is the earliest technology that humans have mastered. The life of primitive humans is extremely hard and they live in groups. In order to survive, they make stone tools and apply grinding technology to make the stone tools have sharp edges and produce a “pointing” effect.

In the Neolithic Age

The stone tools used by primitive people were polished, the surface was delicate and smooth, and the decoration effect was emphasized, which has become the mainstream of the times. In primitive society, as important as grinding stone tools is primitive painting technology. Primitive humans have a sense of beauty.

In the late Paleolithic age

They used mineral dyes to paint and paint small personal entertainment items.

In the Neolithic period

The invention of pottery brought the original color coating technology to its peak, forming a famous painted pottery art in history, and unveiling the prelude to surface finish coating technology.

Surface Finish Method

CNC machining surface finish before painting In order to remove all kinds of foreign matter (such as oil, rust, dust, old paint film, etc.) attached to the surface of the object, provide a good substrate suitable for painting requirements to ensure that the coating film has good anti-corrosion performance, Decoration performance and some special functions, the surface of the object must be pretreated before painting. The work done by this kind of treatment is collectively referred to as pre-painting (surface) treatment or (surface) pretreatment.

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Manual processing such as scraper, wire brush or grinding wheel

The rust and oxide scale on the surface of the workpiece can be removed by hand, but the manual processing has high labor intensity, low production efficiency, poor quality, and incomplete cleaning.

Chemical treatment

Chemical treatment mainly uses acidic or alkaline solutions to react with oxides and oil stains on the surface of the workpiece to dissolve them in an acid or alkaline solution to remove rust, oxide scale and oil stains on the surface of the workpiece, and then use nylon Brush roller or 304# stainless steel wire (a steel wire brush roller made of acid and alkali resistant solution can be cleaned to achieve the goal.

Advantage and disadvantage of chemical treatment

Chemical treatment is suitable for cleaning thin plates, but the disadvantage is: if the time is not properly controlled, even if the corrosion inhibition is added It can also cause over-corrosion of steel. For more complex structural parts and porous parts, after acidic solution pickling, the residual acid immersed in the crevices or cavities is difficult to completely remove. If it is not handled properly, it will become a workpiece. Corrosion is a hidden danger, and the chemicals are volatile, and the cost is high. The chemical discharge after treatment is difficult. If not handled properly, it will cause serious pollution to the environment.

Mechanical treatment

With the improvement of people’s environmental protection awareness, this treatment method is being mechanically treated Method to replace. Mechanical treatment of nylon brush roller nylon brush roller mainly includes wire brush roller polishing method, shot blasting method and shot peening method.

(1) Polishing

Polishing method means that the brush roller is driven by the motor, and the brush roller moves in the opposite direction to the movement of the rolled piece. The upper and lower surfaces of the strip are rotated at a high speed to remove the oxide scale. The brushed iron scale is washed away by a closed-circulation cooling water washing system.

(2) Shot blasting

Shot blasting is a method of using centrifugal force to accelerate the projectile and projecting it to the workpiece for rust cleaning. But throwing The pill has poor flexibility, limited by the site, and some blindness when cleaning the workpiece.

Advantage

It is easy to produce dead spots on the inner surface of the workpiece. The structure of the equipment is complex, and there are many vulnerable parts, especially the blades and other parts. , One-time investment is large. Using shot blasting for surface finish, the impact force is large, and the cleaning effect is obvious.

Disadvantage

However, the treatment of thin plate workpieces by shot blasting can easily deform the workpiece, and the steel shot hits the surface of the workpiece (whether shot blasting or shot blasting) The metal substrate is deformed. Because ferroferric oxide and ferric oxide have no plasticity, they peel off after being broken, and the oil film deforms together with the material. Therefore, shot blasting and shot blasting can not completely remove the oil stains on the work piece with oil stains.

(3) Sandblasting

Among the existing surface finish methods for workpieces, the best cleaning effect is sandblasting.

Advantage

Sandblasting is suitable for cleaning the surface of workpieces with higher requirements.

Disadvantage

However, the current general sandblasting equipment in China is mostly composed of hinged dragons, scrapers and top-quality It is composed of primitive heavy sand conveying machinery such as hoist. The user needs to construct a deep pit and make a waterproof layer to install the machinery. The construction cost is high, the maintenance workload and the maintenance cost are huge, and a large amount of silica dust is generated during the sandblasting process and cannot be removed. Which seriously affects the health of the operators and pollutes the environment.

Sandblasting spraying equipment

The sand suction machine is used as a machine for conveying sand. The sand suction machine is actually a super large vacuum cleaner. A thicker conveying pipe connects the hopper with the suction. The sand machine is connected to suck the sand into the storage tank.

The characteristic of the sand suction machine

The characteristic of the sand suction machine is that the construction difficulty and process are simpler than the bucket elevator, and it is convenient and easy to control, and requires less maintenance, but it consumes a lot of power.

Choose the suitable equipments

The sand suction machine is currently available in China Several manufacturers specialize in sand suction machines, but the technology is relatively immature, so most surface finish companies mainly use bucket elevators. Plants that need to do blasting are choosing sand conveying equipment.

Choose the suitable dust removal equipment

When working with dust removal equipment, you must fully consider the actual production situation, and try to choose equipment with a larger power than the production needs. Since the equipment used for shot blasting generally wears out quickly, such or other problems will have a lot of impact after long-term use.

The advantage of insufficient power of dust removal equipment

For production, the selection of equipment with higher power will greatly reduce the time and expense wasted in future maintenance. Insufficient power of dust removal equipment not only harms the health of workers, but also seriously affects the visibility of the sandblasting room. The inability of dust to be discharged also affects the quality of the sand itself and the surface roughness of the workpiece.

Manual sandblasting room designed

The manual sandblasting room should be designed according to the actual situation to be more spacious than the accommodating workpiece. It should not be too restrictive or it will affect the manual work of the workers. At the same time, the lighting conditions must be good. For drier areas, sand throwing can be carried out outdoors.

Technology Classification

According to the different methods used, the surface finish technology can be divided into the following categories.

Electrochemical method

This method uses electrode reaction to form a coating on the cnc machining surface finish of the workpiece. The main methods are:

(1) Electroplating

The process of forming a coating on the surface of the workpiece in the electrolyte solution as the cathode under the action of external current is called electroplating. The plating layer can be metal, alloy, semiconductor or containing various solid particles, such as copper plating, nickel plating, etc.

(2) Oxidation

In the electrolyte solution, the workpiece is the anode, and under the action of external current, the process of forming an oxide film on the surface is called anodization, such as the anodization of aluminum alloy. The oxidation treatment of steel can be done by chemical or electrochemical methods. The chemical method is to put the workpiece in an oxidizing solution, and rely on chemical action to form an oxide film on the surface of the workpiece, such as bluing of steel.

Chemical method

This method is no current action, using the interaction of chemical substances to form a coating on the surface of the workpiece. The main methods are:

(1) Chemical conversion coating treatment

Chemical conversion coating treatment is the process in which the metal workpiece is in the electrolyte solution without external current, and the chemical substance in the solution interacts with the workpiece to form a coating on its surface, which is called chemical conversion coating treatment. Such as bluing, phosphating, passivation, and chromium salt treatment on the metal surface.

(2) Electroless plating

Electroless plating is in the electrolyte solution, the surface of the workpiece is catalytically treated, and there is no external current effect. In the solution, due to the reduction of chemical substances, the process of depositing certain substances on the surface of the workpiece to form a coating is called electroless plating. Such as electroless nickel plating, electroless copper plating and so on.

Thermal processing method

This method is to melt or thermally diffuse the material under high temperature conditions to form a coating on the surface of the workpiece. The main methods are:

(1) Hot-dip plating

The process of putting a metal workpiece into molten metal to form a coating on its surface is called hot-dip plating, such as hot-dip galvanizing and hot-dip aluminum.

(2) Thermal spraying

The process of atomizing molten metal and spraying it on the surface of the workpiece to form a coating is called thermal spraying, such as thermal spraying zinc and thermal spraying aluminum.

(3) Hot stamping

The process of heating and pressing the metal foil to cover the surface of the workpiece to form a coating layer is called hot stamping, such as hot stamping aluminum foil.

(3) Chemical heat treatment

The process in which the workpiece is in contact with chemical substances and heated, and a certain element enters the surface of the workpiece at a high temperature is called chemical heat treatment, such as nitriding and carburizing.

(4) Surfacing welding

The process in which deposited metal is piled up on the surface of the workpiece to form a welding layer by welding is called surfacing, such as surfacing welding with wear-resistant alloys.

Vacuum method

This method is a process in which materials are vaporized or ionized and deposited on the surface of the workpiece in a high vacuum state to form a coating. The main method is.

(1) Physical vapor deposition (PVD)

The process of vaporizing metals into atoms or molecules or ionizing them into ions under vacuum conditions and directly depositing them on the surface of the workpiece to form a coating is called physical vapor deposition. The particles are deposited The beam comes from non-chemical factors, such as evaporative plating, sputtering plating, ion plating, etc.

(2) Ion implantation

The process of implanting different ions into the surface of the workpiece under high voltage to modify its surface is called ion implantation, such as boron injection.

(3) Chemical Vapor Deposition (CVD)

The process in which gaseous substances form a solid deposition layer on the surface of the workpiece due to chemical reactions under low pressure (and sometimes normal pressure) is called chemical vapor deposition, such as vapor deposition of silicon oxide and silicon nitride. Wait.

Other methods

Other methods are mainly mechanical, chemical, electrochemical, and physical methods. The main methods are:

(1) Painting

Idle spraying or brushing method, the process of applying paint (organic or inorganic) on the surface of the workpiece to form a coating, called painting, such as spraying or brushing.

(2) Impact plating

The process of forming a coating layer on the surface of the workpiece by mechanical impact is called impact plating, such as impact galvanizing.

(3) Laser surface finish

The process of irradiating the surface of the workpiece with laser to change its structure is called laser surface finish, such as laser quenching and laser remelting.

(4) Super-hard film technology

The technology of preparing super-hard film on the surface of the workpiece by physical or chemical methods is called super-hard film technology. Such as diamond film, cubic boron nitride film and so on.

(5) Electrophoresis and electrostatic spraying

1. Electrophoresis

The workpiece is put into the conductive water-soluble or water-emulsified paint as an electrode, and forms a circuit with the other electrode in the paint. Under the action of the electric field, the coating solution has been dissociated into charged resin ions, the cations move to the cathode, and the anions move to the anode. These charged resin ions, together with the adsorbed pigment particles, are electrophoresed to the surface of the workpiece to form a coating. This process is called electrophoresis.

2. Electrostatic spraying

The process in which the atomized negatively charged paint particles are directed to the positively-charged workpiece under the action of a DC high-voltage electric field to obtain a paint film is called static spraying.

Sinster Machining Surface Finish Services

For CNC metal parts, cast metal parts, die-cast metal parts and stamped metal parts, Sinster will provide the following machining surface finish, casting surface finish, forging surface finish, and metal stamping surface finish.

1. Electroplating

Electroplating is the process of plating a thin layer of other metals or alloys on the machining surface finish surface of certain metals using the principle of electrolysis. It is the process of using electrolysis to attach a metal film to the surface of a metal or other material to prevent metal oxidation ( Such as rust), improve wear resistance, electrical conductivity, reflectivity, corrosion resistance (copper sulfate, etc.) and enhance aesthetics, etc. For example chromate plating， zinc plasting, nickel plating, brass plating, tin plating, gold plating, titanium gold plating.

2. Anodizing

Anodizing is the electrochemical oxidation of metals or alloys. Aluminum and its alloys form a layer of oxide film on aluminum products (anode) under the action of applied current under corresponding electrolyte and specific process conditions. If anodizing is not specified, it usually refers to sulfuric acid anodizing. The workpiece can be oxidized into different colors, such as red, white, silver, green, black, gold, yellow, army green.

3. Powder coating

Powder coating refers to a treatment process for industrial metal surfaces. The plastic powder is a powder coating, which is a new type of solvent-free 100% solid powder coating.

4. Grained Finish

Part is deburred and scratched using a brush/sander to create a specific grain. This is ideal for parts where a uniform bare finish is required, but powder coating is not desired. Due to geometry, grained finish can only be applied to the outside surfaces of CNC machined and sheet metal fabrication parts, NOT on the inside of the parts.

5. Non-textured paints

Non-textured paints (Smooth Polyester, Smooth Epoxy and Smooth Polyester-Epoxy Blend Hybrid) will not cover tool marks on their own. As a result, an additional finishing operation such as grained finish will need to be performed as well.

6. Digital Printing

This is ideal for branding (such as your logo), labelling connectors and switches and for decorative purposes. (Silkscreening is also available, as an alternative to digital printing).

7. Machined Engraving

This is a form of permanent marking, ideal for labelling, branding or schematics. Also known as etching, machined engraving is available with powder coat painting, grained finish, anodising and chem film chromate coating, depending on the material.

Machining Surface Finish Sample

See below samples of manufactured products with machinig surface finish, casting surface finish, forging surface finish, and stamping surface finish.

Machining Surface Finish Chart

Aluminum Series

Aluminum 6061, 7075, 5052, 6063, 7001, 5752

Surface

Find the correct surface for your metal parts

Machined

Ra 3.2 Minor tool marks are visible on the surface

Shot blasting

Shot blasting is to change the roughness of the outer surface to improve the fatigue fracture resistance of materials/parts, prevent fatigue failure, plastic deformation and brittle fracture, and improve fatigue life.

Different colors anodizing according to MIL-A-8625F

Anodic oxidation, the electrochemical oxidation of metals or alloys. Aluminum and its alloys form a layer of oxide film on aluminum products (anode) under the action of applied current under corresponding electrolyte and specific process conditions. Improve the surface hardness and wear resistance of aluminum alloy

Hard anodizing according to MIL-A-8625F

The full name of hard anodizing is hard anodizing. The main purpose of hard anodizing of aluminum alloy is to improve various properties of aluminum and aluminum alloy, including corrosion resistance, wear resistance, weather resistance, insulation and adsorption. It is not only suitable for deformed aluminum alloy, but also for die casting aluminum alloy parts.

Powder coated

Powder coated is a surface finish method for spraying plastic powder on parts. Sprayed products are mostly used in boxes used indoors, and the paint film presents a flat or matte effect.

Brushing or mirror polishing

Polishing refers to the use of mechanical, chemical or electrochemical effects to reduce the surface roughness of the workpiece to obtain a brushing, bright, and smooth surface. It is the use of polishing tools and abrasive particles or other polishing media to modify the surface of the workpiece.

Painting

Painting is a coating method in which spray guns or disc atomizers are used to disperse into uniform and fine droplets by means of pressure or centrifugal force and apply to the surface of the object to be coated.

Stainless Steel Series

201, 202, 301, 302, 303, 304, 305, 304L, 316, 316L, 420, 430, 430F

Surface

Find the correct surface for your metal parts

Machined

Ra 3.2 Minor tool marks are visible on the surface

Brushing or mirror polishing

Electrophoresis

Electrophoresis (Electrophoresis, EP) is the abbreviation of electrophoresis phenomenon, which refers to the phenomenon that charged particles move towards the opposite electrode under the action of electric field. The technique that uses different moving speeds of charged particles in an electric field to achieve separation is called electrophoresis.

Passivated

Passivation refers to the process in which metal is oxidized by strong oxidant or electrochemical methods to make the surface inactive, that is, passivation. It is a method to transform the metal surface into a state that is not easy to be oxidized and delay the corrosion rate of the metal. In addition, the phenomenon that an active metal or alloy becomes a noble metal with its chemical activity greatly reduced is also called passivation.

Chromate Plated

PVD

PVD is the abbreviation of Physical Vapor Deposition in English, which means “physical vapor deposition” in Chinese. It refers to a thin film preparation technology that uses a physical method to deposit materials on the workpiece to be plated under vacuum conditions. PVD has the characteristics of high hardness, high wear resistance (low friction coefficient), good corrosion resistance and chemical stability, and the film has a longer life; at the same time, the film can greatly improve the appearance and decoration performance of the workpiece.

Alloy Steel Series

Q345, Q235, ST37, AISI 1020, AISI 1045, AISI 1008, AISI 1035, AISI 1016, AISI 1019, AISI 1039, AISI 12L14, AISI 1144, AISI 5115, AISI 5120, AISI 5140, AISI 4140, AISI 5115, AISI 8720CR-MO, CR-V, AISI 4141

Surface

Find the correct surface for your metal parts

Machined

Ra 3.2 Minor tool marks are visible on the surface

Zinc Plating

Electro-galvanizing, also known as cold galvanizing in the industry, is the process of using electrolysis to form a uniform, dense and well-bonded metal or alloy deposition layer on the surface of the part. Compared with other metals, zinc is a relatively cheap and easily plated metal. It is a low-value anti-corrosion electroplating layer and is widely used to protect steel parts, especially to prevent atmospheric corrosion, and for decoration.

Nickel Plated

The method of plating a layer of nickel on metals or certain non-metals by electrolysis or chemical methods is called nickel plating. Nickel plating is divided into electroplating nickel and electroless nickel plating. Nickel electroplating is in an electrolyte composed of nickel salt (called main salt), conductive salt, pH buffer, and wetting agent. The anode uses metallic nickel, and the cathode is a plated part. Direct current is applied to the cathode (plated part). A uniform and dense nickel plating layer is deposited.

Chromate Plated

Chrome plating refers to the plating of chromium on other metals as a plating layer. The chrome-plated layer has high hardness and good wear resistance. The chromium plating layer has good chemical stability. It has no effect in alkali, sulfide, nitric acid and most organic acids, but it can be dissolved in hydrochloric acid (such as hydrochloric acid) and hot sulfuric acid. The stability of the electroplated nickel layer in the air is very high. Due to the strong passivation ability of metallic nickel, a very thin passivation layer can be quickly formed on the surface The membrane is resistant to corrosion by the atmosphere, alkali and certain acids.

Heat Treated

Heat treatment refers to a metal thermal processing technology in which the material is in a solid state, through heating, heat preservation and cooling, to obtain the expected structure and performance. Improve the hardness of the workpiece.

Black Oxided

Blackening, also known as boiling black or blue, is a method of surface finish of steel. The coating is formed through the reaction between the chemical liquid and the material of the workpiece itself. The thickness of the film after oxidation treatment is 0.5-1.5 microns, which has no significant effect on the size and accuracy of the parts. The oxidation treatment of steel parts is widely used in mechanical parts, precision instruments, cylinders, springs, General protection and decoration of weapons and daily necessities. The film has good abrasion resistance, dark and shiny black, and extremely beautiful.

Phosphate

Phosphating (phosphorization) is a process of forming a phosphate chemical conversion film by chemical and electrochemical reactions. The phosphate conversion film formed is called a phosphate film. The purpose of phosphating is mainly to provide protection to the base metal and prevent the metal from being corroded to a certain extent.

Power Coated

Powder coated is a surface finish method for spraying plastic powder on parts. Sprayed products are mostly used in boxes used indoors, and the paint film presents a flat or matte effect.

Real Gold Plating

The electroplated gold coating has strong corrosion resistance, good electrical conductivity, easy to weld, high temperature resistance, and has a certain wear resistance (such as hard gold mixed with a small amount of other elements), and has good discoloration resistance. At the same time, there are many gold alloy coatings. A variety of shades, gold-plated on the silver can prevent discoloration. In addition, the coating has good ductility and is easy to polish.

Titanium Gold Plating

Titanium gold plating is to use chemical methods to make titanium metal adhere to the surface of other objects. The formed titanium gold coating has excellent corrosion resistance, which can be used to protect the plated object and improve the surface wear resistance.

Brass / Copper Plating

Copper plating is one of the most widely used pre-plating layers in the electroplating industry, including soldering parts, lead-tin alloys, and zinc die-casting parts that must be plated with copper before nickel, gold, and silver are plated to improve the bonding force of the plating.