You set the job up, the first two hundred sheets look right, and then the colour starts drifting light. You open the ink duct another click, then another, and by the time the mid-tones come back the solids are grainy and the next operator writes “washed out” on the job card. On a Heidelberg SM 102 that pattern almost never means “add more ink”. It means the ink train is not delivering the ink it has been asked to deliver.<\/p>\n
This guide covers the four causes behind most ink density complaints on SM 102 and CD 102 presses, in the order you should check them — fastest and cheapest first, written for the operator or technician standing at the unit.<\/p>\n
The ink train does four separate jobs. The ink duct gap decides how much ink the duct roller can pick up. The duct clutch and ductor decide how much of that ink reaches the oscillator. The roller train — oscillators, distributors, form rollers — spreads it into an even film. The Alcolor dampening system decides how much water sits on the plate when that film arrives.<\/p>\n
Weak density means one of those four links is under-delivering. Opening the duct wider hides the symptom and makes the diagnosis harder, so instead run a test sheet at your normal duct setting and watch the ink train while the press runs. It usually tells you which cause you are dealing with.<\/p>\n
On the SM 102 the ink rollers are thrown on and off the plate by pneumatic cylinders. When the seals inside those cylinders harden, air leaks past the piston and the roller engages late, engages only partly, or drops off the plate part-way through the run. The result looks exactly like a density problem, because the plate is not being inked the way the duct setting assumes.<\/p>\n
Typical clues:<\/p>\n
Check air pressure at the unit before you condemn anything, and compare the stroke of a suspect cylinder against a good one rather than against a number from memory. If the cylinder is the fault you have two options: fit a new SM102\/CD102\/72\/SORM ink roller cylinder<\/a>, or rebuild the failed one with an SM102\/72 ink roller cylinder rebuild kit<\/a>. Rebuild when the bore is clean and only the seals have gone hard; replace when the bore or rod is scored.<\/p>\n A slipping clutch does not fail all at once. It leaks a little torque, so the duct roller turns slightly less than it should on each stroke. On press that shows up as density falling away in waves or drifting light over a run, and it gets worse as the unit warms up.<\/p>\n Confirm it before you pull the unit apart. Mark the duct roller and its drive with a witness line, run a controlled number of revolutions at a known duct setting, and check that the roller returns to the same position. A slipping clutch will not repeat. Clutch wear is also why a press that ran fine last week suddenly cannot hold density on a long run when nothing in the job has changed.<\/p>\n The roller train has to transfer an even film. When form roller stripes are too light, or an oscillator stops oscillating properly, density suffers in ways that look random.<\/p>\n On a press with Alcolor dampening, too much fountain solution looks identical to not enough ink: the ink film emulsifies, transfer drops, density falls. Rule this out before chasing mechanical faults — it costs ten minutes and no parts.<\/p>\n Work down this list on the unit that is misbehaving, and stop as soon as you find the fault:<\/p>\n Cylinders and clutch assemblies are the parts where rebuild versus replace actually matters. Rebuild when the failure is seals and the wear surfaces are still within tolerance — fine housings, fine bore, only soft parts aged out. Replace when the bore is scored, the rod is bent or pitted, or the cylinder will not hold pressure after a rebuild attempt. In a busy shop a rebuild kit on the shelf is the difference between an hour of downtime and a three-day wait for a cylinder, which is why most maintenance teams keep one kit per press model on hand.<\/p>\n RelyOffset supplies OEM-compatible replacement parts for Heidelberg SM 102, CD 102, SM 72 and SM 74 presses, including ink roller cylinders, cylinder rebuild kits and Alcolor dampening components. Browse the ink roller cylinder and press parts range<\/a> or order a rebuild kit<\/a> and get the unit back into production.<\/p>\n RelyOffset parts are OEM-compatible aftermarket components. Brand names are trademarks of their respective owners.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":" Density falling off on your Heidelberg SM 102? Work through the four real causes – ink roller cylinders, duct clutch, roller stripes and Alcolor dampening – before you open the duct wider.<\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_metadesc":"Ink density dropping on your Heidelberg SM 102? Diagnose ink roller cylinders, the duct clutch, roller stripes and the Alcolor dampening system.","footnotes":""},"categories":[1241,1244],"tags":[1258,1264,1265,1263,1266],"class_list":["post-9840","post","type-post","status-publish","format-standard","hentry","category-heidelberg-parts-guide","category-troubleshooting","tag-heidelberg","tag-ink-density","tag-ink-roller-cylinder","tag-sm-102","tag-troubleshooting"],"_links":{"self":[{"href":"https:\/\/relyoffset.com\/de\/wp-json\/wp\/v2\/posts\/9840","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/relyoffset.com\/de\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/relyoffset.com\/de\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/relyoffset.com\/de\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/relyoffset.com\/de\/wp-json\/wp\/v2\/comments?post=9840"}],"version-history":[{"count":1,"href":"https:\/\/relyoffset.com\/de\/wp-json\/wp\/v2\/posts\/9840\/revisions"}],"predecessor-version":[{"id":9883,"href":"https:\/\/relyoffset.com\/de\/wp-json\/wp\/v2\/posts\/9840\/revisions\/9883"}],"wp:attachment":[{"href":"https:\/\/relyoffset.com\/de\/wp-json\/wp\/v2\/media?parent=9840"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/relyoffset.com\/de\/wp-json\/wp\/v2\/categories?post=9840"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/relyoffset.com\/de\/wp-json\/wp\/v2\/tags?post=9840"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Cause 2: The duct roller clutch is slipping<\/h2>\n
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Cause 3: Roller settings, Z roller support and oscillator wear<\/h2>\n
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Cause 4: The dampening side is stealing your density<\/h2>\n
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A ten-minute diagnostic order<\/h2>\n
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Replace or rebuild: how to decide<\/h2>\n
Keeping density stable long term<\/h2>\n
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Need the parts?<\/h2>\n