Abstract: A cylinder liner for an internal combustion engine and a method of making the same are disclosed. The cylinder liner may generally include a cylindrical body configured to receive a piston assembly. The cylindrical body may further include a main body portion configured for selective engagement with an engine bore, and an upper flange configured to support the cylindrical body within the engine bore. The cylindrical body may also define an undulating cooling gallery adjacent the upper flange. The undulating cooling gallery generally defines a single coolant flow path extending about a perimeter of the cylindrical body.

Abstract: Provided is a cylinder block which includes a liner and a water jacket having a closed-deck structure in a simple configuration and which has a structure providing high rigidity and enabling easy formation at low cost. A cylinder block of the present invention includes a liner arranged on an inner circumference surface of a bored hole and a water jacket arranged on the outside of the liner in the radial direction. By a bending process of folding back an end portion of a cylinder-shaped member, a hollow portion capable of forming the water jacket is formed integrally in one end portion or both end portions of a liner portion forming the liner, and the cylinder-shaped member is enclosed with a cylinder block forming material by casting.

Abstract: A powder metal cylinder liner with a ratio of the length to the wall thickness greater than 12 made of at least two end to end cylinder liner pieces with each piece having a ratio of the length to the wall thickness of less than 20. The powder metal composition includes approximately between 85% and 99% sponge iron powder, approximately between 0.1% and 2.0% graphite, and approximately between 0.1% and 2.0% ethylene bis-stearamide wax. The cylinder liner pieces can be made using conventional powder metal compaction and sintering processes.

Abstract: A corrosion-resistant alloy tube is formed and bonded to a pre-machined steel alloy rod to form a riser tensioner cylinder rod. During assembly, an epoxy is injected into an annular space between the tube and rod and then cured. The bonded tube is ground to a desired surface finish prior to installation and utilizes a double seal arrangement that prevents external pressure or corrosive fluids from entering the cured epoxy in the annular space.

Abstract: The invention relates to a supporting sleeve (10) for cylinder head screws, which is provided with a self-threading external thread.

Abstract: In a processing method for processing a cylinder block, a finish processing for the cylinder bore is performing, by pressing the portion of the bolt phase for fastening the cylinder head on the cylinder portion outer peripheral surface forming the inside surface of a water jacket, on the condition that the rigidity of the pressed portion on the cylinder portion toward the pressure from the side of the cylinder bore (the surface pressure from the grinding stones by honing process) is enhanced compared with the other portions.

Abstract: A method for making cylinder liners and cast engine blocks having cylinder liners having a strong mechanical bond with the engine block. The method includes providing a cast metallic cylinder liner having an outer surface of the cylinder liner. The surface of the cylinder liner is preferably machined to remove surface effects or defects present from the casting process. Grit particles are directed at the outer surface of the cylinder liner with a grit blasting device at a predetermined angle of contact at a sufficient velocity to form cavities on the outer surface. The cavities that are formed have a geometry capable of forming a mechanical bond with the casting material of the engine block.

Abstract: A cylinder liner for use in a cylinder crankcase includes a liner body having at least one end face, and a material strip. The material strip is affixed to the liner body and projects axially from the at least one end face of the liner body.

Abstract: The disclosure relates to surface roughening methods in which a cutting tool having a radial cutting blade with first and second cutting edges is fed along a longitudinal axis of an article while rotating the cutting tool about the axis. The first cutting edge forms a first machined pattern of peaks and valleys on a surface of the article, and the second cutting edge removes at least a portion of the peaks to form roughened fracture surfaces in a second machined pattern defining an arrangement of grooves, corresponding to the valleys, separated by lands, corresponding to the roughened fracture surfaces. The disclosure also provides cutting tools useful in practicing the surface roughening methods. The disclosure further describes cylindrical articles having interior or exterior surfaces roughened using the methods. The methods, cutting tools and articles have applications including fabrication of cylinder blocks for internal combustion engines.

Abstract: A cylinder liner for receipt in an internal combustion engine cylinder block having a water cooling jacket surrounding a portion of the cylinder liner and method of construction thereof. The cylinder liner has a wall with an inner surface providing a cylinder bore extending along a central axis for reciprocation of a piston against an axial portion thereof and an outer surface opposite the axial portion. The outer surface has a hardened outer layer of purely martensitic microstructure for direct exposure to fluid in the water cooling jacket.

Abstract: With regard to a surface hardening method that a surface of an engine member is coated with an alloy layer having high abrasive resistance so as to improve life of the member and a production method of a piston or the like that abrasive resistance of the member is improved by the hardening method, a surface of a metal base material is coated uniformly with mixture including metal powder, a binder and solvent so as to form a coat, and the coat is dried and applied thereon with laser or electron beam so as to be sintered and dispersed for forming an alloy layer on a surface of the metal base material and for bonding the alloy layer to the metal base material.

Abstract: An internal combustion engine includes a piston adapted to reciprocate in a cylinder. The piston includes a first portion, a second portion, and a third portion. The first portion of the piston forms a crown surface of the piston, the second portion of the piston forms a piston ring groove of the piston with the piston ring groove arranged and configured to receive a piston ring, and the third portion of the piston forms a crankcase side surface of the piston with the crankcase side surface facing a crankcase of the engine. The second portion of the piston is formed of a material having a higher thermal conductivity than a material forming the first portion of the piston and a material forming a third portion of the piston.

Abstract: The disclosure relates to surface roughening methods in which a cutting tool having a radial cutting blade with first and second cutting edges is fed along a longitudinal axis of an article while rotating the cutting tool about the axis. The first cutting edge forms a first machined pattern of peaks and valleys on a surface of the article, and the second cutting edge removes at least a portion of the peaks to form roughened fracture surfaces in a second machined pattern defining an arrangement of grooves, corresponding to the valleys, separated by lands, corresponding to the roughened fracture surfaces. The first and second walls may include concave regions within the grooves. The disclosure also provides cutting tools useful in practicing the methods, and cylindrical articles having interior or exterior surfaces roughened using the methods. The methods may have applications to fabrication of cylinder blocks for internal combustion engines.

Abstract: A new method for internal combustion engine cylinder finishing is proposed. Techniques for engine bore out, cylinder finish, and metal sleeve replacement have been developed for internal combustion engines. Separately, mandrel pull-through cold-working methods for fatigue life improvement have existed for holes with cracks. However, despite the decades old technology, mandrel pull-through cold-working has not been applied as the critical step in engine cylinder finishing. The first filing for the invention was provisional patent application 60883908 for “Cold-working application in combustion engines” submitted by the inventor on 8 Jan. 2007. This invention provides multiple techniques for applying mandrel pull through technology to cylinders that experience the hot, high cycle environment found in internal combustion engine cylinders. The method of employing cold-working as a critical step in engine cylinder finishing forms the basis for all claims listed.

Abstract: A cylinder block has at least two cylinder banks each having cylinder bores arranged in at least two directions relative to an axis for a crankshaft. A rotator on which the cylinder block is securely disposed has a convex rounded surface. When the rotator rotates, the convex rounded surface moves along a concave rounded surface of a rotator-holding base. As a result of the rotation, the cylinder bores of the first bank or the cylinder bores of the second bank face upward in the vertical direction. Accordingly, with a single spray gun, sprayed coatings can be formed on inner surfaces of the cylinder bores of the first and second banks without having to change a mounting position of the cylinder block.

Abstract: A rotor body (22) having a plurality of cylindrical bores (24) each adapted to receive a piston (30) for reciprocating movement therein, each of the bores (30) being lined with a ceramic liner (42) having a first split (44), and a method of forming a rotor (16) having a ceramic bore liner (42) that includes the steps of providing a rotor body having at least one bore (140), providing a ceramic bore liner having a first end, a second end and a split having a width (142), and compressing the bore liner to decrease the width and securing the bore liner in the at least one bore (144).

Abstract: A cylinder liner for receipt in an internal combustion engine cylinder block having a water cooling jacket surrounding a portion of the cylinder liner and method of construction thereof. The cylinder liner has a wall with an inner surface providing a cylinder bore extending along a central axis for reciprocation of a piston against an axial portion thereof and an outer surface opposite the axial portion. The outer surface has a hardened outer layer of purely martensitic microstructure for direct exposure to fluid in the water cooling jacket.

Abstract: At least one transfer channel (9, 29) is formed in the cylinder wall (4, 24) of the cylinder (1, 21) for a two-stroke engine. The transfer channel (9, 29) is closed to the cylinder outer side (5, 25) by a cover (10, 30). The method for making the cylinder (1, 21) provides that the cover (10, 30) is assembled in a first step on the cylinder (1, 21) and, in a second step, the cylinder bore (3, 23) is machined.

Abstract: A piston-cylinder unit, in particular gas spring, has a cylindrical pressure tube which has a surface protection on its outer surface. The piston-cylinder unit further has a piston, which is axially displaceable within the pressure tube and has a piston rod. The piston rod is led out of the pressure tube in a sealed manner through an end side opening at a piston-rod-exit end side of the pressure tube. To improve the corrosion prevention properties and the durability of the surface protection, an end region of the pressure tube which starts from the piston-rod-exit end side is excluded from the surface protection. A process for producing such a piston-cylinder unit is also disclosed.

Abstract: The disclosure relates to surface roughening methods in which a cutting tool having a radial cutting blade with first and second cutting edges is fed along a longitudinal axis of an article while rotating the cutting tool about the axis. The first cutting edge forms a first machined pattern of peaks and valleys on a surface of the article, and the second cutting edge removes at least a portion of the peaks to form roughened fracture surfaces in a second machined pattern defining an arrangement of grooves, corresponding to the valleys, separated by lands, corresponding to the roughened fracture surfaces. The cross section of the grooves is substantially asymmetrical, and each groove may further include a notch. The disclosure also provides cutting tools useful in practicing the surface roughening methods. The disclosure further describes cylindrical articles having interior or exterior surfaces roughened using the methods.

Abstract: A production method of a water jacket spacer for use in a cylinder block with a water jacket formed around plural cylinder bores. The method comprises the fist step of integrally forming a tubular spacer body with a peripheral wall and a connecting bridge by way of synthetic resin molding so that corresponding regions of the peripheral wall are connected to each other via the connecting bridge, and the second step of cooling the tubular spacer body, with the connecting bridge fixed thereto, to prevent deformation of the tubular spacer body during the cooling process, and the third step of removing the connecting bridge from the tubular spacer body.

Abstract: A cylinder sleeve for being inserted in a cylinder bore defined in a block body of a cylinder block for an internal combustion engine. The cylinder bore includes a first annular recess and a second annular recess, and projecting walls. The cylinder sleeve comprises a hollow cylindrical body that is inserted into the cylinder block with at least part of an outer circumferential wall thereof adjacent to an inner circumferential wall of the projecting walls of the cylinder block, a larger-diameter portion projecting diametrally outwardly from an upper end of the outer circumferential wall of the hollow cylindrical body, a step disposed on an outer circumferential wall of said larger-diameter portion, by which the larger-diameter portions of adjacent cylinder sleeves are stacked, and a reduced-diameter portion provided by reducing a diameter of an inner circumferential wall of said hollow cylindrical body.

Abstract: A cooling jacket casting core according to the invention for the production of a cylinder head of an internal combustion engine comprises at least one impression of a cooling jacket. The cooling jacket casting core itself has a slot running at least in part substantially in the direction of a crankshaft longitudinal axis and separating the cooling jacket casting core in at least one section. In accordance with a further development, the slot runs at least in part in the impression of the cooling jacket. The slot preferably has at least approximately one elevation arranged perpendicular to the longitudinal axis of the cooling jacket casting core. This longitudinal extension of the slot runs parallel to a crankshaft associated with the cylinder head in an internal combustion engine.

Abstract: A coolant groove-type internal combustion engine has a cylinder block that includes a frame having at least one longitudinal surface and a lateral member transverse to the longitudinal surface, the lateral member defining a coolant passage therethrough, wherein the lateral member also defines at least one cylinder opening and a groove coolant port extending from the coolant passage to the cylinder opening. A cylinder liner includes a cylindrical member, defining an elongated cylinder bore. The cylinder member has an outer surface that has a diameter that allows the cylindrical member to be fitted into the cylinder opening so as to form a coolant jacket between the outer surface of the cylindrical member and the longitudinal surface. The outer surface of the cylindrical member includes an upper portion that plugs the groove coolant port.

Abstract: A cylinder head (10) for an internal combustion engine has hydroformed port liners (18) positioned within selected ports, either exhaust and/or intake ports (14, 16). The hydroformed port liner (18) includes an air gap (24) for an insulation layer within the selected port (14, 16) between an outer surface (19) of the hydroformed port liner (18) and the wall of the port (14, 16). A cylinder head (12) with a predetermined port configuration has selected ports (14, 16) cast with protrusions (22). The selected ports (14,16) have a larger diameter than a standard size port diameter for that cylinder head to provide a predetermined port configuration by a preset amount based on the thickness of the hydroformed port liner (18) and a desired air gap (22). Protrusions (22) in the wall of the selected ports (14, 16) or on the insert sleeves (17) facilitate formation of the air gap during the hydroforming process.

Abstract: A cylinder liner (2) for a cylinder block has a contouring (6) at one end. The contouring (6) serves to support the liner (2) on a sleeve (4) inside a die-casting tool. When the liner (2) is cast in, recesses (10) of the liner (2) are filled by the material of the cylinder crankcase whereby preventing the liner (2) from seating toward an oil chamber (14). The invention also relates to a method for producing a cylinder liner of the aforementioned type.

Abstract: A cylinder liner has an outer circumferential surface around which another metal is to be cast. The cylinder liner also has a plurality of protrusions disposed on the outer circumferential surface and having respective substantially conical undercuts or necks which are progressively spread outwardly from the outer circumferential surface. The protrusions have respective flat faces on the distal ends of the undercuts.

Abstract: Electrochemical machining is used to generate the helical lobe profiles of the stator of a progressive cavity pump or motor. A thin, elastomeric liner, of uniform thickness is bonded either to the interior of the stator, or to the exterior of the rotor. Where the elastomeric liner is to be bonded to the interior of the stator, bonding is improved by electrically etching the interior of the stator during the electrochemical machining process to produce a roughened surface.

Abstract: A resin cylinder head cover includes an attaching portion and a sleeve. The attaching portion is formed of resin, and is a portion of the cylinder head cover to which the oil control valve is to be attached. The sleeve is embedded in the attaching portion. The sleeve has an interior space that permits the oil control valve to be accommodated therein and oil holes. Each oil hole is selectively connected to one of ports of the oil control valve accommodated in the interior space of the sleeve. The sleeve is formed of material having higher rigidity than the resin forming the attaching portion. Therefore, the cylinder head cover maintains highly reliable attachment of an oil control valve without a large number of high precision machining steps and prevents deformation of the attaching portion.

Abstract: A cylinder liner for insert casting used in a cylinder block is provided. The cylinder liner includes an outer circumferential surface having a plurality of projections. Each projection has a constricted shape. A film of a metal material is formed on the outer circumferential surface and the surfaces of the projections. As a result, the cylinder liner ensures sufficient bond strength with the casting material of a cylinder block, and sufficient thermal conductivity with the cylinder block.

Abstract: A cylinder liner has an upper portion and a lower portion with respect to an axial direction of the cylinder liner. A high thermal conductive film is provided on an outer circumferential surface of the upper portion. A low thermal conductive film is provided on an outer circumferential surface of the lower portion. The cylinder liner reduces temperature difference of a cylinder along its axial direction.

Abstract: A cylinder liner 2 is enveloped in a cylinder block through insert casting. The cylinder liner 2 includes a cylinder liner body 2a and a metal coating layer 8 formed on the body 2a through a cold spraying method. Since the metal coating layer 8 is formed in a non-molten and oxygen free state, few oxygen films or oxygen layers are formed on the surface of or in the interior of the metal coating layer 8. Thus, the thermal conductivity of the metal coating layer 8 is sufficiently high. As a result, the thermal conductivity from the metal coating layer 8 to the cylinder block is sufficiently high.

Abstract: A cylinder liner for an engine cylinder block. A roughening process is performed only on an upper region of the outer surface of the cylinder liner. This increases adhesiveness with a sprayed layer at the upper region compared to a lower region of the liner outer surface. Therefore, difference in thermal conductance is produced in the axial direction of the cylinder liner. This maintains the wall temperature of the cylinder bore in an appropriate temperature range. Even if adhesiveness at the lower region of the liner outer surface is low, bottleneck-shaped projections are distributed on the liner outer surface. Thus, the bonding strength between the cylinder liner and the sprayed layer and the cylinder liner and the cylinder block via the sprayed layer is sufficient. This maintains the roundness of the cylinder bore and prevents fuel efficiency from being lowered by exhaust gas loss and mechanical loss.

Abstract: A cylinder liner for insert casting used in a cylinder block is disclosed. The cylinder liner has an outer circumferential surface, and upper, middle, and lower portions with respect to an axial direction of the cylinder liner. A high thermal conductive film is formed in a section of the outer circumferential surface that corresponds to the upper portion, and a low thermal conductive film is formed in a section of the outer circumferential surface that corresponds to the lower portion. The high thermal conductive film and the low thermal conductive film are laminated in a section of the outer circumferential surface that corresponds to the middle portion, thereby forming a laminated film portion. As a result, temperature difference along the axial direction of the cylinder is reduced.

Abstract: A cylinder liner has an outer circumferential surface on which a film is formed. The film functions to form gaps between the cylinder block and the cylinder liner. Alternatively, the film functions to reduce adhesion of the cylinder liner to the cylinder block. The cylinder liner suppresses excessive decreases in the temperature of a cylinder.

Abstract: Selective laser and induction hardening are applied to areas of a water jacketed engine cylinder liner to provide improved resistance to scuffing resulting from the rubbing contact of the walls and piston rings of an associated piston. An upper bore portion and port relief areas of the liner are fully induction hardened to improve wear resistance. The port area is then fully laser hardened to improve wear resistance. If desired, the laser hardening process may continue beyond the intake port area to the port relief areas to ensure full hardening of the port relief areas and continuous hardening between the intake ports and the port relief areas to improve wear resistance.

Abstract: The present invention relates to a cylinder liner made from gray cast iron, an aluminum material or a ceramic material for an engine block for an internal combustion engine. According to the invention, it is provided that the cylinder liner has a thermally sprayed layer of a low-alloy iron alloy or a bonding layer, which consists of a nickel-aluminum alloy made up of 80 to 95% by weight of nickel and 5 to 20% by weight of aluminum, on its worn running surface, and has a layer serving as a tribological running surface on top of the bonding layer. The present invention also relates to a method for producing a cylinder liner of this type and to a composite part made up of an engine block for an internal combustion engine and at least one cylinder liner of this type. The invention allows the inexpensive repair of worn cylinder liners without the need to adapt new pistons.

Abstract: A valve case includes an attaching portion and a sleeve. The valve case is attached to a cylinder head cover main body formed of resin. The attaching portion is formed of resin and is a portion of the valve case to which an oil control valve is to be attached. The sleeve is embedded in the attaching portion, and has an interior space that permits the oil control valve to be accommodated therein and oil holes. Each oil hole is selectively connected to one of ports of the oil control valve accommodated in the interior space of the sleeve. The sleeve is formed of material having higher rigidity than the resin forming the attaching portion. Therefore, the valve case prevents deformation of the attaching portion.

Abstract: A reduced-diameter portion (44) with a taper portion (46), a portion whose diameter is reduced in a tapered form, is provided on an inner peripheral wall of a cylinder sleeve (20a, 20b, 20c). On the outer peripheral wall of the top end of the cylinder sleeve (20a, 20b, 20c) is provided a large diameter portion (36a, 36b, 36c) projected outward along the diameter direction. Under the action of a friction stir welding tool (50), the cylinder sleeve (20a, 20b, 20c) inserted in a communication hole (16) of a block body (18) is joined to the block body (18) with the reduced-diameter portion (44) and the large-diameter portion (36a, 36b, 36c) in between. A closed deck-type cylinder block (10) is constructed with the process above. In the cylinder block (10), the gasket face (12) side of a water jacket (22) is closed by the large-diameter portion (36a, 36b, 36c).

Abstract: A method of providing an iron cylinder liner (1) for incorporation in a cast aluminium block for an internal combustion engine, including the steps of placing the liner (1) in a heated fluidised bed so as to simultaneously clean and heat the liner, and then positioning the cleaned and heated liner on the sand barrel core (2). The barrel core having been sized to accept the heated and thus expanded liner, which will subsequently cool and retract locking the liner onto the sand core in the correct position, in readiness for casting of the aluminium cylinder block.

Abstract: An internal combustion engine includes at least one cylinder block having at least one combustion cylinder. A number of cylinder liners are respectively associated with each combustion cylinder. Each cylinder liner defines a corresponding cylinder inside surface. Each cylinder liner includes a plurality of discrete oil retaining indentations in a predefined pattern on the cylinder inside surface. The plurality of oil retaining indentations are bounded in both peripheral and longitudinal directions of the corresponding cylinder liner.

Abstract: A method for surface treatment of the interiors of hollow bodies, especially cylinder bores, in preparation for the application of a thermally sprayed layer. The method comprises dry cutting without a lubricant or with a shortage of lubricant using a tool having a defined and/or undefined surface profile. In this method with a portion of the material forming the interior is removed and produces a surface that has a defined structure and/or quality. This eliminates the need for costly degreasing of the surface following machining.

Abstract: The invention relates to a cylinder liner (2) for a cylinder block. Said cylinder liner has a contouring (6) at one end. The contouring (6) serves to support the liner (2) on a sleeve (4) inside a die-casting tool. When the liner (2) is cast in, recesses (10) of the liner (2) are filled by the material of the cylinder crankcase whereby preventing the liner (2) from seating toward an oil chamber (14). The invention also relates to a method for producing a cylinder liner of the aforementioned type.

Abstract: A roller rocker mounting mechanism for an internal combustion engine valve actuating mechanism includes a first rocker stand having a first locating boss and a second rocker stand having a second locating boss. An indexing link has a first portion separably attachable to the first locating boss and a second portion separably attachable to the second locating boss to connect the first rocker stand and the second rocker stand in a manner that prevents rotation of either rocker stand when the rocker stands are attached to the cylinder head.

Abstract: A novel apparatus and method to engage a liner in an cylinder of an engine is provided. A wedge and rod are utilized as part of a liner remover assembly to move at least one collet axially to engage the liner. In a preferred embodiment, a novel eyehook is provided at an end of the rod to assist in the pulling of the liner from the cylinder.

Abstract: In a process for processing cylinder crankcases having sprayed cylinder barrels, in which process a cylinder crankcase is cast, those surfaces of the subsequent cylinder barrels which are to be thermally coated are roughened, the cylinder barrels are coated by a thermal spraying process, and the cylinder barrels are remachined to final dimensions. After the thermal spraying process, coating material is at least partially removed from the crankshaft-side part of the cylinder crankcase.

Abstract: In a process for thermal spraying of cylinder bearing surfaces of multi-line engines, a cylinder crankcase having at least two lines of cylinders is cast, those surfaces of subsequent cylinder barrels which are to be thermally coated are roughened, the cylinder barrels are coated by a thermal spraying process, and the cylinder barrels are remachined to their final dimensions. During thermal spraying, a shielding template is introduced in the region of the crankshaft space at least between a cylinder which is currently being thermally coated and an opposite cylinder of an adjacent line of cylinders.

Abstract: In a process for producing a thermally coated cylinder bearing surface having an insertion bevel, a cylinder crankcase is cast, those surfaces of the subsequent cylinder barrels which are to be thermally coated are roughened, the cylinder barrels are coated by a thermal spraying process, the cylinder bore is bevelled, and the cylinder barrels are remachined to their final dimensions. The cylinder crankcase is prefabricated with an oversized dimension in the region of the cylinder head sealing surface, and the insertion bevel for the cylinder bore is introduced into the cylinder head sealing surface which has the oversized dimension.

Abstract: In a process for chip-forming machining of thermally sprayed cylinder barrels of a cylinder crankcase, a cylinder crankcase is cast, those surfaces of the subsequent cylinder barrels which are to be thermally coated are roughened, the cylinder barrels are coated by a thermal spraying process, and the cylinder barrels are remachined to final dimensions. Machining of an insertion bevel and/or an end bevel and/or the cylinder head sealing surface and/or the crankshaft space and/or a cylinder bore is carried out in a chip-forming manner, and a respective chip-forming tool is guided so that the respective cutting edges penetrate into the material which is to be removed from the outside.

Abstract: In a process for preparing a cast cylinder bore for thermal coating, a cylinder crankcase is cast, those surfaces of the subsequent cylinder barrels which are to be thermally coated are roughened, the cylinder barrels are coated by a thermal spraying process, and the cylinder barrels are remachined to their final dimensions. The surface of the cylinder bore is roughened by a jet, preferably a water jet and/or liquid jet mixed with solid particles, and material of the cylinder bore is simultaneously removed. A material thickness, which may be between 0.020-0.140 mm but preferably is between 0.004 mm-0.006 mm, is removed during the roughening operation.