Three Methods of Imposition in Printing
In offset printing, multiple pages or multiple jobs are often imposed onto a large printing sheet to improve efficiency and reduce production costs. There are three common methods of double-sided imposition: Work & Turn, Work & Tumble, and Work & Back.The main difference lies in how the sheet is handled after the first side is printed.
1. Work & Turn
Work & Turn is a widely used method that uses the same printing plate for both sides of the sheet.How it works:
- The first side is printed.
- The sheet is flipped (side-to-side), but the gripper edge remains the same.
- The sheet enters the press using the same gripper position as the first run.
- The second side is printed using the same plate.
Advantages:
- Only one plate is required, reducing plate-making costs.
- Excellent registration accuracy because the same gripper edge is used.
- Suitable for symmetrical layouts and paired page counts.
Disadvantages:
- Imposition must be symmetrical; otherwise, the flipped side will not align.
- Not suitable for jobs requiring different layouts or asymmetrical designs.
2. Work & Tumble
Work & Tumble is similar to Work & Turn in that the same plate is used for both sides, but the sheet is handled differently.How it works:
- The first side is printed.
- For the second side, the sheet is tumbled end-over-end (top-to-bottom), not flipped side-to-side.
- Because of this motion, the gripper edge changes when printing the second side.
Advantages:
- Also saves cost by using only one plate.
- Allows more flexibility for layouts that require top-to-bottom changes.
Disadvantages:
- Registration accuracy may be slightly lower since the gripper edge changes.
- Imposition is more complex and requires careful planning.
3. Work & Back
Work & Back is the standard method for double-sided printing and uses two separate plates, one for each side.How it works:
- The first side is printed using Plate A.
- The sheet is flipped and re-fed.
- The second side is printed using Plate B.
Advantages:
- Maximum flexibility—each side can have a completely different layout.
- Reliable registration and suitable for complex or multi-page jobs.
Disadvantages:
- Requires two plates, increasing plate-making costs.
- Slightly more involved in terms of operation.
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