Offset printing device

Abstract

To provide a simply structured offset printing device that reduces the peripheral speed difference between a blanket and a cylindrical body even when the cylindrical body has a bottomed, substantially conical shape, prevents blurring and smearing of fine designs and letters, and ensures consistently good print quality.SOLUTION: An offset printing device 100 comprises: a mandrel 111 that rotatably holds a metallic cylindrical body 140 formed in a bottomed, substantially truncated conical shape; and a blanket 121 that moves while pressing on a print surface 142 of the cylindrical body held on the mandrel 111 at a transfer position P and transfers ink T. The offset printing device comprises: a drive unit for rotating the mandrel 111; and a rotation control unit 150 that controls the drive unit. When the cylindrical body 140 held by the mandrel 111 comes into contact with the blanket 121, the rotation control unit 150 can control the rotation speed of the mandrel 111 to a predetermined rotation speed via the drive unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an offset printing apparatus that performs offset printing on the surface of a metal cylindrical body that is formed into a substantially truncated cone shape with a bottom. [Background technology]

[0002] A conventional method for printing letters, pictures, etc. on the surface of a beverage container or the like is to use an offset printing device that has a mandrel that rotatably holds a cylindrical tubular body, a blanket that moves at a transfer position while pressing its transfer surface against the printing surface of the tubular body held by the mandrel, and a blanket wheel that rotates with the blanket attached to its outer peripheral surface, and the tubular body against which the blanket is pressed at the transfer position rotates together with the mandrel relative to the blanket, which moves as a result of the rotation of the blanket wheel, thereby transferring ink from the blanket to the printing surface of the tubular body.

[0003] Furthermore, the offset printing apparatus (printing apparatus 100) known from Patent Document 1, in addition to the above configuration, has a motor (500) capable of rotating the mandrel (holding mechanism 310), and before the blanket (32) and the cylindrical body (bottle 8) come into contact with each other, the motor (500) rotates the mandrel (holding mechanism 310) in the co-rotating direction faster than the peripheral speed of the blanket (32). This prevents the cylindrical body (bottle 8) from being pulled in the rotational direction due to contact or friction with the blanket (32), causing the cylindrical body (bottle 8) to become misaligned, thereby preventing a deterioration in print quality. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-72268 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is still room for improvement in the offset printing apparatuses known from the above-mentioned patent documents and the like.

[0006] In other words, in the offset printing device known from Patent Document 1, the peripheral speed of the cylindrical body is faster than the peripheral speed of the blanket, so when the blanket and cylindrical body come into contact at the transfer position, the difference in peripheral speed causes the ink to be transferred in a circumferentially rubbing manner, which could result in less good printing than in a method in which the cylindrical body rotates together. Furthermore, when the cylindrical body is approximately conical in shape with a bottom, the diameter differs in the axial direction and the circumferential speed differs in the axial direction, so there are inevitably points where a difference in circumferential speed occurs between the blanket, which has a uniform circumferential speed, and the cylindrical body. This makes it easy for the ink to be rubbed in the circumferential direction, and fine designs and characters can be crushed, or the transferred patterns and characters can be rubbed significantly in the circumferential direction of the cylindrical body and become unclear (shearing), which could result in unstable print quality. Furthermore, the difference in peripheral speed causes the blanket to wear more quickly in certain areas, which may require the blanket to be replaced more frequently, resulting in increased burden on workers and increased production costs.

[0007] The present invention aims to solve these problems and provide an offset printing device that has a simple configuration and can suppress the difference in peripheral speed between the blanket and the cylindrical body, even when offset printing on a cylindrical body with a bottomed, approximately conical shape, suppress the occurrence of crushing or shearing of fine designs and characters, and consistently maintain good print quality. [Means for solving the problem]

[0008] The offset printing apparatus of the present invention includes a mandrel that rotatably holds a metallic cylindrical body formed into a substantially bottomed truncated cone shape, a mandrel turret that rotates with the mandrel attached to its outer periphery, a blanket that transfers ink by moving while pressing its transfer surface against the printing surface of the cylindrical body held by the mandrel at a transfer position, and a blanket wheel that rotates with the blanket attached to its outer periphery, wherein the rotation axis of the mandrel and the rotation axis of the mandrel turret are substantially parallel, and the rotation axis of the blanket wheel has a predetermined inclination with respect to the rotation axis of the mandrel at the transfer position. The above problem is solved by arranging the blanket wheel and the mandrel turret so that, at a transfer position, the blanket moves while pressing the printing surface of a cylindrical body held by the mandrel in a substantially vertical direction, thereby transferring ink, and the mandrel turret has a drive unit that rotates the mandrel and a control unit provided with a rotation control unit that controls the drive unit, and the rotation control unit is configured to be able to control the rotation speed of the mandrel to a predetermined rotation speed via the drive unit when the cylindrical body held by the mandrel and the blanket come into contact with each other. Effect of the Invention

[0009] The offset printing apparatus of claim 1 has a mandrel turret, a drive unit that rotates the mandrel, and a control unit provided with a rotation control unit that controls the drive unit. The rotation control unit is configured to be able to control the rotation speed of the mandrel to a predetermined rotation speed via the drive unit when the cylindrical body held by the mandrel comes into contact with the blanket. Therefore, if the rotation control unit controls the rotation speed of the mandrel via the drive unit so that the peripheral speeds of the printing surface of the cylindrical body and the blanket match, it is possible to prevent a decrease in print quality due to differences in peripheral speed such as ink rubbing, such as crushing or shearing of fine designs and characters, when ink is transferred from the blanket to the printing surface of the cylindrical body at the transfer position. In addition, when offset printing on a cylindrical body with a bottom that is approximately a truncated cone shape, the circumferential speed varies depending on the diameter of the printing surface, which can result in bias in print quality depending on the position on the printing surface. However, by matching the circumferential speed of the printing surface at points where print quality is likely to deteriorate to the circumferential speed of the blanket, extreme deterioration in print quality can be suppressed.

[0010] According to the configuration described in claim 2, the rotation control unit is configured to be able to control the rotation speed of the mandrel via the drive unit when the cylindrical body held by the mandrel comes into contact with the blanket so that the circumferential speed at any position on the printing surface of the cylindrical body is the same as the circumferential speed of the blanket.Therefore, for example, the circumferential speed at a printing position that is prone to be affected by ink rubbing, such as fine designs or crushing or shearing of letters, can be selectively matched to the circumferential speed of the blanket, and good offset printing can be performed without crushing letters, fine designs, etc. According to the configuration described in claim 3, the rotation control unit is configured to control the rotation speed of the mandrel via the drive unit so that the peripheral speed of the large diameter side or small diameter side of the printing surface of the cylindrical body held by the mandrel is the same as the peripheral speed of the blanket.This makes it possible to suppress localized wear of the blanket abutting the large diameter side or small diameter side of the printing surface, which is a location where blanket wear is likely to occur significantly depending on the settings of the offset printing device, and prevents localized deterioration of printing quality and increased frequency of blanket replacement.

[0011] According to the configuration described in claim 4, the rotation control unit is configured to control the rotation speed of the mandrel via the drive unit so that the difference between the circumferential speed of the printing surface of the cylindrical body held by the mandrel and the circumferential speed of the transfer surface is within a range of 4.5% or less.This makes it possible to minimize the circumferential speed difference between the entire printing surface and the transfer surface, and suppresses localized wear of the blanket caused by a large circumferential speed difference. According to the configuration described in claim 5, the information acquisition unit is configured to be able to instruct the rotation control unit on the rotation speed of the mandrel when the cylindrical body held by the mandrel comes into contact with the blanket based on information on the rotation speed of the blanket wheel.This makes it possible to more accurately match the circumferential speed of the cylindrical body to the circumferential speed of the blanket, further preventing a decrease in the printing quality of the cylindrical body. [Brief description of the drawings]

[0012] [Figure 1] 1 is an overall schematic diagram of an offset printing apparatus 100 according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a front view showing a mandrel 111 of the offset printing apparatus 100 according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a front view of a cylindrical body 140 to be offset printed by the offset printing apparatus 100 according to an embodiment of the present invention. [Figure 4] FIG. 2 is a front view of the mandrel 111 on which the cylindrical body 140 is attached, of the offset printing apparatus 100 according to one embodiment of the present invention. [Diagram 5] 1 is a schematic top view showing the positional relationship between a blanket 121 and a cylindrical body 140 at a transfer position P in an offset printing apparatus 100 according to an embodiment of the present invention. [Figure 6] 3 is an enlarged view of a portion A showing the positional relationship between a blanket 121 and a cylindrical body 140 at a transfer position P in the offset printing apparatus 100 according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An offset printing apparatus 100 according to an embodiment of the present invention will be described below with reference to FIGS.

[0014] An offset printing apparatus 100 according to an embodiment of the present invention performs offset printing on the surface of a metallic cylindrical body 140 formed into a substantially bottomed truncated cone shape, and as shown in FIGS. 1 and 2, includes a mandrel 111 that rotatably holds the cylindrical body 140, a mandrel turret 110 that rotates with a plurality of mandrels 111 attached to its outer periphery, a blanket 121 that moves while pressing a transfer surface 122 against the cylindrical body 140 held by the mandrel 111 at a transfer position P to transfer ink T that forms a printing layer 143, and a blanket turret 110 that rotates with the blanket 121 attached to its outer periphery. The blanket wheel 120 includes a plate cylinder 130 having a printing plate 131 mounted thereon for transferring ink T to the blanket 121 mounted on the blanket wheel 120, a drive unit (not shown) for rotating the mandrel 111 at the transfer position P, and a control unit 150. The control unit 150 includes a rotation control unit 151 capable of rotating the mandrel 111 at a predetermined rotational speed via the drive unit (not shown), and an information acquisition unit 152 capable of acquiring information on the rotational speed of the blanket wheel 120 and instructing the rotation control unit 151 on the rotational speed of the mandrel 111.

[0015] The mandrel 111 has a connecting rod 112 rotatably connected to the mandrel turret 110, and a support surface 113 that supports the back side of a post-molding printable surface 142, which is the printing surface of a cylindrical body 140 described later. The support surface 113 is configured as an inclined surface that can come into close contact with the inner surface side of the printing surface 142 of the cylindrical body 140 after molding.

[0016] The mandrel turret 110 is configured to temporarily suspend rotation after moving the mandrel 111 holding the cylindrical body 140 to the transfer position P, and to resume rotation after the transfer of the ink T at the transfer position P is completed, so as to move the next mandrel 111 to the transfer position P. The rotation axis of the mandrel turret 110 and the rotation axis of the mandrel 111 are approximately parallel to each other.

[0017] Further, the blanket wheel 120 is disposed such that the rotation axis Cb of the blanket wheel 120 is inclined at a predetermined angle with respect to the rotation axis Cm of the mandrel 111 in the horizontal direction. Moreover, the blanket 121 has a uniform thickness, and the width of the blanket 121 in the direction of the rotation axis Cb of the blanket wheel 120 is longer than the width of the printed surface 142 after forming.

[0018] As shown in FIG. 3 , the cylindrical body 140 is formed in a generally truncated cone shape with a bottom, and has a tapered cylindrical body portion 141, an opening portion 146 which is the large diameter end portion of the cylindrical body portion 141, and a bottom portion 147 which is connected to the small diameter end portion of the cylindrical body portion 141. The surface of the cylindrical body 141 is provided with a molded printable surface 142 formed at a taper angle r, an opening side body 144 formed on the opening 146 side of the molded printable surface 142, and a bottom side body 145 formed on the bottom 147 side of the molded printable surface 142. The taper angle r of the printing surface 142 after molding is equal to or greater than 2.6 degrees and equal to or less than 5.6 degrees.

[0019] The molded printed surface 142 is composed of a smooth surface and has an upper printing surface 142a on the larger diameter side, a lower printing surface 142c on the smaller diameter side, and a middle printing surface 142b which is continuously connected to the upper printing surface 142a and the lower printing surface 142c. In addition, the upper printing surface 142a is a portion of the molded printed surface 142 that has an outer diameter that is 3% or more larger than the outer diameter at the center of the molded printed surface 142, and the lower printing surface 142c is a portion of the molded printed surface 142 that has an outer diameter that is 3% or more smaller than the outer diameter at the center of the molded printed surface 142. Examples of materials for the metallic cylindrical body include steel, stainless steel, aluminum or an aluminum alloy, copper, iron, or an alloy containing these metals. Furthermore, the inner or outer surface of the cylindrical body may be laminated with an organic resin coating. Examples of organic resin coatings include coatings derived from paints such as acrylic paints, urethane paints, silicon paints, and fluorine paints, as well as thermoplastic resins such as polyethylene terephthalate (PET).

[0020] Next, a procedure for offset printing onto the cylindrical body 140 by the offset printing apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS. First, as shown in FIG. 1, a blanket 121 attached to a blanket wheel 120 transfers ink T arranged in the shape of a pattern or letters to be offset printed from a printing plate 131 attached to a plate cylinder 130 arranged around the blanket wheel 120 to a transfer surface 122.

[0021] Next, the mandrel 111 attached to the mandrel turret 110 moves to the transfer position P while holding the cylindrical body 140 . At this time, as shown in FIG. 4, the mandrel 111 holds the cylindrical body 140 in a position where the support surface 113 is in close contact with the inner surface side of the formed printable surface 142 of the cylindrical body 140 . As a result, the central axis Cc of the cylindrical body 140 and the rotation axis Cm of the mandrel 111 coincide with each other.

[0022] The blanket 121 moves to the transfer position P by the rotation of the blanket wheel 120 . As shown in FIG. 5, the rotation axis Cb of the blanket wheel 120 is inclined horizontally at a predetermined angle to the rotation axis Cm of the mandrel 111, so that the transfer surface 122 of the blanket 121 attached to the outer peripheral surface of the blanket wheel 120 also presses against the cylindrical body 140 held by the mandrel 111 at the transfer position P in an orientation inclined horizontally at a predetermined angle to the rotation axis Cm of the mandrel 111.

[0023] In this case, when offset printing is performed only on the molded printable surface 142 of the cylindrical body 140, the transfer pressure can be stabilized from the large diameter side (opening side) to the small diameter side (bottom side) of the molded printable surface 142 by tilting the rotation axis Cb of the blanket wheel 120 so that the transfer surface 122 is approximately parallel to the molded printable surface 142. That is, as shown in FIG. 6, the balance of transfer pressure between the upper transfer surface 122a and the upper printing surface 142a, the middle transfer surface 122b and the middle printing surface 142b, and the lower printing surface 122c and the lower printing surface 142c can be stabilized.

[0024] However, in the cylindrical body 140, the post-molding printed surface 142 is formed in a tapered shape with a taper angle r, so that the upper printing surface 142a, the middle printing surface 142b, and the lower printing surface 142c each have a different circumferential length. In other words, when ink T is transferred from the transfer surface 122 of the blanket 121 to the molded printable surface 142 at the transfer position P, if the cylindrical body 140 is rotated by the blanket, only one point on the molded printable surface 142 will have a circumferential speed that matches the circumferential speed of the transfer surface 122, and the points on the molded printable surface 142 that do not have a circumferential speed that matches the circumferential speed of the transfer surface 122 will have a circumferential speed that is faster or slower than the circumferential speed of the transfer surface 122.

[0025] Here, in the case of a printing method in which the cylindrical body 140 rotates along with the blanket, for example, when printing fine patterns or letters on the upper printing surface 142a, if the peripheral speed Sc of the lower printing surface 142c matches the peripheral speed of the transfer surface 122, the peripheral speed Sa of the upper printing surface 142a on the large diameter side will be excessively faster than the peripheral speed of the transfer surface 122, which may cause the pattern or letters transferred from the blanket to the upper printing surface 142a to be distorted or cause the ink T to be rubbed significantly in the circumferential direction of the cylindrical body 140, resulting in a decrease in print quality. It is also difficult to control the parts of the molded printing surface 142 that match the peripheral speed of the transfer surface 122, and the parts of the molded printing surface 142 where the print quality deteriorates change with each offset printing, which may result in unstable print quality. Furthermore, for example, if a design is set so that the start and end of offset printing overlap by a specified width, if the point at which the circumferential speed of the transfer surface 122 of the printed surface 142 after molding coincides changes, there is a risk that the overlap width between the start and end of the offset printing will also change.

[0026] The offset printing apparatus 100 according to one embodiment of the present invention has a drive unit (not shown) that rotates the mandrel 111, and a rotation control unit 151 that can control the rotational speed of the mandrel 111 via the drive unit (not shown). Therefore, by controlling the rotational speed of the mandrel 111 by the rotation control unit 151 so that the peripheral speed Sa of the upper printing surface 142a matches the peripheral speed of the transfer surface 122, distortion or misalignment of patterns or characters transferred from the transfer surface 122 to the upper printing surface 142a can be suppressed, and good print quality can be maintained. Furthermore, if the peripheral speed Sa of the upper printing surface 142a is made to match the peripheral speed of the transfer surface 122, the peripheral speed Sc of the lower printing surface 142c will naturally be excessively slower than the peripheral speed of the transfer surface 122. However, by designing the pattern to be transferred to the lower printing surface 142c to be a band that extends continuously in the circumferential direction, or otherwise, which is less affected by the circumferential rubbing of the ink T, it is possible to suppress deterioration in the printing quality of the lower printing surface 142c and maintain good printing quality over the entire printed surface 142 after molding.

[0027] Furthermore, in locations where there is a large difference in peripheral speed between the transfer surface 122 and the post-molding print surface 142, wear of the blanket 121 is likely to progress locally, and there is a risk that the frequency of replacing the blanket 121 will increase. In particular, wear of the blanket 121 is likely to progress in a portion (upper transfer surface 122a) where the peripheral speed of the shaped printable surface 142 is faster than the peripheral speed of the transfer surface 122. Therefore, it is desirable to rotate the mandrel 111 via a drive unit (not shown) using the rotation control unit 151 so that the peripheral speed of the position of the post-molding printing surface 142 that is closer to the upper printing surface 142a matches the peripheral speed of the transfer surface 122. Depending on the offset printing settings, the blanket 121 may also be subject to significant wear on the lower printing surface 142c side due to the large difference in peripheral speed between the lower printing surface 142c and the transfer surface 122. In this case, it is desirable to rotate the mandrel 111 via a drive unit (not shown) using the rotation control unit 151 so that the peripheral speed of the position of the post-molding printing surface 142 that is closer to the lower printing surface 142c matches the peripheral speed of the transfer surface 122.

[0028] In addition, the control unit 150 is configured to acquire information on the rotational speed of the rotating blanket wheel 120 using the information acquisition unit 152, and to be able to instruct the rotational speed of the mandrel 111 from the information acquisition unit 152 to the rotation control unit 151. This makes it possible to more accurately match the circumferential speed of the transfer surface 122 to the circumferential speed of the printed surface 142 after molding each time, further preventing a deterioration in print quality.

[0029] As described above, when offset printing is performed on the tapered molded printable surface 142 formed on the outer peripheral surface of the bottomed, approximately conical cylindrical body 140, the circumferential speed at a predetermined position on the molded printable surface 142 at transfer position P is matched to the circumferential speed of the transfer surface 122 to transfer ink T, thereby preventing extreme differences in circumferential speed between the transfer surface 122 and the molded printable surface 142.This prevents distortion and shearing of fine patterns and characters, allowing for clear printing, and suppresses localized wear of the blanket 121. Specifically, for example, if there is no particular bias in the printing position of patterns or letters, controlling the rotation speed of the mandrel 111 so that the peripheral speed of the center of the printed surface 142 after molding matches the peripheral speed of the transfer surface 122 is suitable for maintaining good printing quality and suppressing localized wear of the blanket 121. Furthermore, for example, when the patterns or letters to be printed are small and fine, and particularly when printing cut-out letters in which ink T is transferred to areas other than the letter portion to reproduce the letters, it is preferable to adjust the contact pressure between the blanket 121 and the cylindrical body 140, as well as to control the rotation speed of the mandrel 111 so that the peripheral speed at a position a predetermined distance closer to the lower printing surface 142c than the center of the printed surface 142 after molding is matched to the peripheral speed of the transfer surface 122, in order to maintain good print quality. In this context, small, fine characters refer to characters of 5 pt or less. In addition, when offset printing is performed on the molded printable surface 142 of the cylindrical body 140, the circumferential speed within the molded printable surface 142 can be adjusted so that the maximum difference between the circumferential speed of the transfer surface 122 is within the range of 3% to 4.5%, thereby adjusting the wear at the upper and lower ends of the blanket 121 so that it is uniform, thereby maintaining good print quality and sufficiently suppressing localized wear of the blanket 121.

[0030] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various design modifications can be made without departing from the present invention described in the claims.

[0031] In the above-described embodiment, the mandrel has a support surface that supports the inner surface of the printed surface after molding, and is described as holding the tubular body by bringing the support surface into close contact with the inner surface of the printed surface after molding. However, the method of holding the tubular body is not limited to this. For example, in addition to the support surface, a pressing member that presses the bottom from the outside may be provided to hold the tubular body by sandwiching it between the mandrel. In addition, in the above-described embodiment, the information acquisition unit is described as being configured to acquire information on the rotational speed of the blanket wheel and to instruct the rotation control unit on the rotational speed of the mandrel, but the configuration of the information acquisition unit is not limited to this, and for example, it may acquire information on the circumferential speed of the transfer surface directly, or there may be no information acquisition unit.

[0032] In addition, in the above-described embodiment, the rotation control unit has been described as rotating the mandrel via the drive unit at transfer position P to match the circumferential speed of a predetermined position on the molded printed surface to the circumferential speed of the transfer surface, but the configuration of the rotation control unit is not limited to this, and for example, the mandrel may be rotated before reaching transfer position P to match the circumferential speed of the molded printed surface to the circumferential speed of the transfer surface, or all of the mandrels in the mandrel turret may be configured to rotate at all times, or in addition to the support surface of the mandrel, a pressing member may be provided that presses the bottom of the cylindrical body from the outside, and the pressing member may be rotated directly via the drive unit to match the circumferential speed of the molded printed surface to the circumferential speed of the transfer surface. [Explanation of symbols]

[0033] 100 Offset printing equipment 110 ··· Mandrel turret 111 ··· Mandrel 112 Connecting rod 113... Support surface 120 ··· Blanket Wheel 121 ··· Blanket 122 Transfer surface 122a Upper transfer surface 122b: Middle transfer surface 122c Lower transfer surface 130 Plate cylinder 131... printing plate 140 Cylindrical body 141 Cylindrical body 142... Printing surface after molding 142a...Top printing surface 142b ··· Central printing side 142c... Lower printing surface 143...Printing layer 144...opening side body 145 ... bottom side body 146 Opening 147 ... bottom 150 Control unit 151 Rotation control section 152... Information acquisition department P Transfer position Cc: Central axis of the cylindrical body Cm: Mandrel rotation axis Cb: Blanket wheel rotation axis r: Taper angle of the printing surface after molding T··· Ink Sa: Peripheral speed of the upper printing surface Sc: Peripheral speed of the lower printing surface

Claims

1. An offset printing apparatus comprising: a mandrel for rotatably holding a metallic cylindrical body formed into a substantially truncated cone shape with a bottom; a mandrel turret for rotating with the mandrel attached to its outer periphery; a blanket for transferring ink by moving at a transfer position while pressing a transfer surface against a printing surface of the cylindrical body held by the mandrel; and a blanket wheel for rotating with the blanket attached to its outer periphery, a rotation axis of the mandrel and a rotation axis of the mandrel turret are substantially parallel to each other; The rotation axis of the blanket wheel is arranged to have a predetermined inclination with respect to the rotation axis of the mandrel at the transfer position; the blanket wheel and the mandrel turret are configured to be capable of transferring ink by moving the blanket while pressing the printing surface of a cylindrical body held by the mandrel in a substantially vertical direction at a transfer position; The mandrel turret has a drive unit that rotates the mandrel, and a control unit provided with a rotation control unit that controls the drive unit, An offset printing apparatus characterized in that the rotation control unit is configured to control the rotation speed of the mandrel to a predetermined rotation speed via the drive unit when the cylindrical body held by the mandrel comes into contact with the blanket.

2. The offset printing apparatus according to claim 1, characterized in that the rotation control unit is configured to control the rotation speed of the mandrel via the drive unit when the cylindrical body held by the mandrel comes into contact with the blanket so that the peripheral speed at any position on the printing surface of the cylindrical body becomes the same as the peripheral speed of the blanket.

3. The offset printing apparatus according to claim 2, characterized in that the rotation control unit is configured to control the rotation speed of the mandrel via the drive unit so that the peripheral speed of the larger diameter side or the smaller diameter side of the printing surface of the cylindrical body held by the mandrel becomes the same as the peripheral speed of the blanket.

4. The offset printing apparatus according to claim 2, characterized in that the rotation control unit is configured to control the rotation speed of the mandrel via the drive unit so that the difference between the peripheral speed of the printing surface of the cylindrical body held by the mandrel and the peripheral speed of the transfer surface is within a range of 4.5% or less.

5. The control unit has an information acquisition unit capable of acquiring information on the rotation speed of the blanket wheel, The offset printing apparatus according to claim 1, characterized in that the information acquisition unit is configured to be able to instruct the rotation control unit on the rotation speed of the mandrel when the cylindrical body held by the mandrel comes into contact with the blanket based on information on the rotation speed of the blanket wheel.

Images