A 50 mm bottom-seal tape leg suits a machine designed for 2-inch tape, while a 70 mm leg adds 20 mm of panel coverage but requires verified application clearance [S2][S5].
Case erectors seal the bottom opening of formed corrugated cases with tape or hot-melt adhesive, so the tape leg must match the machine head, board geometry, case load, and line conditions [S1][S3].
What Tape Leg Length Changes at the Bottom Closure
Bottom-seal tape is commonly specified as 2-inch or 3-inch wide, and the tape head determines which width the machine can apply [S5]. A 50 mm roll corresponds to 2-inch tape, while 70 mm falls between the two common stocked widths and cannot be assumed compatible with a standard 2-inch head.
The extra width may improve contact with the side panel, but the research does not establish a universal minimum leg length, so the case dimensions, board grade, closure geometry, and downstream stacking loads must be checked before specifying it [S1][S4].
Case erectors form the blank, square the case, and close the bottom flaps mechanically. Tape is generally less expensive than glue, while glue is described as stronger, and tape heads are easier to maintain [S1].
Machine Compatibility Comes Before Panel Coverage
One available heavy-duty case erector uses an OK 55 taping head with an open tape-feed path, 50 mm maximum tape width, and 350 mm maximum roll diameter [S2]. That specification directly supports 50 mm tape, but it does not establish that the same head can feed 70 mm tape.
The OK 55 head is offered as standard equipment on that model, while an OK 75 head is listed as an option for 75 mm tape [S2]. The practical comparison is therefore between a confirmed 50 mm configuration and a separately engineered wide-tape configuration, not between two roll widths that can be substituted on the same machine.
Before ordering 70 mm material, confirm the head model, maximum tape width, roller and blade geometry, tape path, and applied length. A tape head designed for 2-inch material can track incorrectly if the roll is too wide, and insufficient sealing surface can allow cases to open under stacking weight [S5].
50 mm and 70 mm Compared by Operating Criterion
For machine compatibility, 50 mm has the clearer factory-supported route because a listed OK 55 head accepts 50 mm tape at maximum, whereas 70 mm requires verification against a wider head or another documented tape path [S2].
For panel coverage, 70 mm provides 20 mm more contact with each side of the bottom closure than 50 mm, but no source establishes that this extra coverage compensates for added roll width, positioning complexity, or machine clearance [S1][S5].
For consumable handling, standard 50 mm tape is more readily matched to the common 2-inch head format, while 70 mm can introduce a nonstandard roll diameter and width combination. The OK 55 configuration accepts rolls up to 350 mm in diameter, but the source does not say that every 70 mm roll will fit that envelope [S2].
For closure strength, tape gauge and adhesive performance can matter as much as nominal width. Most carton-sealing tape falls between 1.5 mil and 3 mil, with thinner tape generally less expensive but more prone to breakage on automated lines [S5].
Use Cases That Favor Each Tape Width
Use 50 mm tape when the case erector has a 2-inch head, the existing process uses 2-inch rolls, and the board, case dimensions, and downstream loads meet the package supplier’s closure requirements [S2][S5]. This is the lower-integration choice when the machine configuration is already documented.
Use 70 mm tape only when the 20 mm additional sidewall coverage has a defined packaging purpose, such as a validated case-design requirement, and the erector’s head and tape path are approved for that width. A packaging engineer should document the reason for the nonstandard width instead of treating it as a generic strength upgrade.
Case erector selection should also include the target rate, run length, board quality, recycled content, storage conditions, closure method, floor space, power, air, guarding, and downstream equipment [S4]. A larger tape leg cannot compensate for a poorly matched case blank or an undersized machine range.
Speed, Climate, and Adhesive Can Defeat a Wider Tape
Line speed is a hard compatibility variable because every tape has a maximum safe peel rate, and thinner tape generally breaks first at higher speeds [S5]. A 70 mm selection should therefore be tested at the intended cases-per-minute rate, not only at reduced trial speed.
Cold conditions reduce tape tack, while humid conditions can allow corrugated board to absorb moisture. Climate-specific adhesive formulations may be required outside ordinary operating environments [S5]. A 70 mm leg does not remove these adhesion risks, and 50 mm tape does not eliminate them either.
Adhesive failure can present as an open case or as residue transferred to blades and rollers, where it dulls the blade over time [S5]. The machine’s tape-monitoring package can support consistency on an automatic line, but monitoring does not compensate for the wrong width, unsuitable gauge, or weak adhesive [S2].
Validation Checklist for a 70 mm Conversion
Run a controlled trial with the intended board grade and case dimensions, comparing 50 mm and 70 mm tape on the same machine configuration where the head permits both widths. Record applied leg length, roll tracking, peel behavior, seam closure, sidewall adhesion, and downstream performance [S4][S5].
Confirm that a 70 mm roll fits the reel, feeds without folding or skew, and does not create excessive side tension. Verify the machine can apply the selected gauge without breakage at the specified speed and that roll diameter remains within the head’s limits [S2][S5].
Test completed cases under the actual closure and handling conditions, including any relevant stacking or transport load. A qualified 70 mm specification should identify the exact head, maximum tape width, tape gauge, adhesive formulation, roll diameter, case board, and validated line speed.
The next trackable signal is the erector’s installed head and tape specification: if it lists 50 mm maximum, retain 50 mm tape; if a 70 mm application is required, obtain a documented wide-head approval before procurement.