How to Replace Heidelberg GTO 52 Delivery Grippers

If your Heidelberg GTO 52 is dropping sheets, marking the gripper margin, or jamming at the delivery
pile, the delivery grippers are the first place to look. On a GTO 52 the gripper bar carries the sheet
from the last printing unit around the delivery drum and releases it onto the pile. That single job
depends on gripper springs, pads, the opening cam and the slow-down system all working together. When
one of them wears, the symptom shows up downstream — as a pile jam, a torn leading edge or a printed
sheet with gripper bite marks. This guide covers how to diagnose worn delivery grippers and how to
replace them properly.

How the GTO 52 Delivery Gripper System Works

The delivery gripper bar rides on two delivery chains and is driven around the delivery drum. Each bar
holds a row of individual grippers that clamp the sheet by its leading edge as it leaves the last printing
unit. As the bar approaches the pile, an opening cam and pin lifts the gripper fingers so
the sheet is released. At the same moment, the slow-down ring or slow-down band decelerates
the sheet so it lands square and flat on the pile instead of slamming into the stops.

Everything in that sequence is mechanical and time-based. Gripper clamping force comes from springs;
release timing comes from the cam; landing quality comes from the slow-down system and the pile height
setting. Wear in any one of them throws the others out of balance, which is why “the delivery is
misfeeding” is rarely a single-part fault.

Symptoms of Worn GTO 52 Delivery Grippers

• Gripper bite marks on the leading edge — the most common sign. Worn or flattened
  gripper pads and weak springs let the sheet shift under the gripper during transfer.
• Sheets not released cleanly at the pile — a worn opening cam or a bent cam pin
  delays release, so sheets are pulled out of the pile or drag back into the delivery.
• Sheets arriving curled, skewed or out of register on the pile — usually a
  slow-down ring or slow-down band problem rather than the grippers themselves.
• Torn or nicked gripper margin — excessive clamping force from over-tightened springs,
  a damaged gripper finger, or a worn gripper pad that no longer spreads the load.
• Rattling or a rhythmic knock from the delivery — loose gripper bar bolts, worn
  gripper bushings, or excessive delivery chain slack.
• Gripper bars that vary sheet to sheet — some bars hold the sheet, others do not.
  On a multi-bar chain this usually means the bars have been serviced at different times and now differ
  in spring preload and pad wear.

Parts Worth Having on the Bench

A GTO 52 delivery gripper bar is a small assembly, not a single part. Before you pull the bar out, have
the consumables ready:

• A complete replacement gripper set — for many shops the fastest route is a
  GTO52 delivery gripper complete
  assembly, which lets you build up a spare bar off the press and swap it in during a changeover rather
  than during a run.
• Gripper springs (compression or torsion depending on gripper type) — springs are the parts that take
  the fatigue, and they are cheap compared with a press stoppage.
• A new GTO delivery
  gripper opening cam and pin if release timing is inconsistent or the pin shows a flat spot.
• Slow-down rings or bands, if the sheets land hard. For GTO and MO presses the
  GTO/MO slow-down ring is the standard
  consumable.
• Gripper pads or backing plates if the bar surface or the pad faces are grooved.

Step-by-Step Replacement

1. Isolate the press

Stop the press, switch off the main drive, and lock out the power. The delivery chain is heavy and
under tension — never work on a bar position that the main drive can index while you have hands in the
delivery.

2. Index the chain to a comfortable working position

Bring the bar you intend to service to the lower front of the delivery, where you can reach both ends
of the bar. Mark the bar and its chain position before removal so it goes back on the same links.

3. Release the chain tension and unbolt the bar

Slacken the delivery chain tensioner, then undo the gripper bar mounting bolts at both ends. Support
the bar as the last bolt comes out — do not let it hang on one end. Lay it on a clean bench, gripper side
up.

4. Inspect before you replace

On the bench, check each gripper for spring preload (all fingers should feel the same), pad wear, and
free movement on its pivot. Check the bar for straightness, the backing plate for grooving, and the
opening cam and pin for flat spots. Replace the whole set if more than a couple of grippers are worn —
mixed old and new grippers on one bar guarantee uneven sheet hold.

5. Fit the new grippers

Build the bar up on the bench: grippers, springs and pads first, then check that every finger closes
and opens smoothly with no binding. Keep the assembly clean and dry — oil on gripper pads causes sheet
slip and marking.

6. Refit the bar and set the chain tension

Reinstall on the marked chain links, tighten the mounting bolts evenly, then restore chain tension to
the value given in the GTO 52 service manual. A delivery chain that is too tight loads the sprockets; too
loose, and the gripper opening timing drifts.

7. Check gripper opening timing

Turn the press over by hand and watch a gripper bar release a sheet at the pile. Release should be
progressive and identical on every bar. If one bar releases late, the cam or pin is worn; if the whole
delivery releases late, the opening station setting has drifted. Use the timing figures from the press
manual — do not set this by eye.

8. Test run

Run a few hundred waste sheets at production speed with the pile at working height. Check for bite
marks on the leading edge, sheets dragged back out of the pile, and square landing. Then re-check chain
tension and gripper bar bolt torque after the first run, since a new bar seats itself into the chain
run.

Adjust or Replace?

Not every gripper fault needs new parts. Weak spring preload, a slightly late cam and a low pile can
all be adjusted. But when gripper pads are flattened, springs have taken a permanent set, or the opening
cam pin is worn through its hardening, adjustment only buys time — the press will drift back out of
spec within a few shifts. In a production shop the economical answer is usually a spare bar: build one
up with new grippers, keep it on the shelf, and swap it in so the press is down for minutes instead of
hours.

RelyOffset supplies GTO 52 delivery gripper assemblies, gripper springs, opening cams and slow-down
rings as OEM-compatible aftermarket parts, with more GTO and SM series delivery parts listed in our
delivery and gripper parts range.

RelyOffset parts are OEM-compatible aftermarket components. Brand names are trademarks of their
respective owners.