by James D. Banister, BS, MBA, AMPM, LSS BB, Bobst North America Inc.

The trouble operators face nowadays is the procedure of efficaciously removing the home or external ( trim ) waste fabric from the diecut tabloid at high speeds. Data validates that the undress department is a critical reason why machines period ( see Diagram 1 ). Sheets break apart – leaving cartons, trim consume or rubbish pieces lying on or sliding across the cardinal stripping board, tripping off the machine photocells that are located between the denude and blank sections ( see Diagram 2 ) .
The early problem is that management focuses, in my opinion, more on the price of a finished tool, or the materials ( pins, claws, etc. ) than the actual money hemorrhaging from the bed channel when the machines are down, waiting while personnel are creating, adjusting, fabricating or setting lower pins to get a strip fructify of tools to perform. The truth is that the operator has fiddling or no dominance over how well the stripping tool is going to perform. Why ?

Critical requirements outside the operator’s control:

  • Machine condition: This is the most important and includes gripper bars, chains, Bernoulli, etc. Proper annual maintenance and the amount of chain stretch are critical to successful stripping. The smaller the waste, the more important it is – regardless of the stripping technology.
  • Structural design: Waste areas in designs and layouts smaller than 4.5 to 5 mm (0.177″ to 0.197″) in width.
  • Layouts: Not turning flute/grain direction of layouts based on what is required to strip. Thin and small pieces should be perpendicular to the gripper edge.
  • Natural nicks (knife joints) and nicks not in correct locations.
  • CAD: Not properly placing carrier rule to help guide the blanks over large stripped areas and not placing numbers in scrap areas to print.
  • The lower board skiving and foam placement on the upper tool.
  • The lack of properly supporting the central stripping board with steel rails under the tool – for the larger format machines, especially.
  • Stripping or removing too much waste, thus creating an unstable sheet at high speeds.
  • Inferior quality pins utilized in the upper tool that are not sharp or hardened.
  • Non-perpendicular or skewed upper tool components manually pounded into the upper, causing the tool pins and blades to be non-perpendicular in various directions, thus creating problems in tight areas and compounded with gripper bar and chain variation.
  • The material: Curl, moisture or printing not centering the sheet or not planning enough side or back trims to effectively remove the trim in the stripping process.
  • Not utilizing quick locking technology to avoid frame-to-frame variation.

Critical stripping functions inside the operator’s control:

  • Validate the tool alignment during the makeready process.
  • Don’t tap upper tool components to avoid marks on the cartons. This usually creates more issues and weakens the tool.
  • Don’t add nicks to scrap areas in incorrect areas: The die should match the dynamic stripping requirements to balance and hold the scrap. Only make existing nicks slightly larger.
  • Properly handle the tooling during every step between the assembly, makeready and storage of the tools.

The history of stripping tools

As cutter technology and speeds advanced, so have the tool fabrication and operation requirements. Stripping tool is no different. The follow four core historical strip technologies represent the drift post-clamshell diecutting to the fastest diecutter running at 12,000 sheets per hour. Each of these effect stripping systems has its pros and cons, but when weighed on the balance of price and productivity, they are not adequate .
Universal (see Diagram 3)

Pros

  • Reusable upper pins
  • Tools can be manually made or remade on site

Cons

  • Labor intensive off press and on press
  • Weight of the pin rack requires two people to lift, even for 3B format
  • Machine downtime for adjustments
  • Requires lower pins set-up

Conventional (see Diagram 4)
Pros

  • Generally sold at a lower price vs. dynamic
  • Tools can be fabricated on-site
  • Generic CAD programming offsets

Cons

  • Labor off press and on press
  • Machine downtime for adjustments
  • Requires lower pins labor each run
  • Actual cost of materials is not less than dynamic

Dynamic – made conventionally using hammer for assembly (see Diagram 5)
Pros

  • Generally effective and reduces most lower pins
  • Tools can be manually fabricated on-site
  • Customized CAD solutions can be manually created for upper/central components/interferences
  • Can adapt several components in the upper tool, such as pins, claws and wood blocks

Cons

  • Cost is higher than dynamic made digitally
  • Requires the use of a router or laser to precut the slots and holes into upper stripping board
  • Manual insertion of components into upper board can bend components, causing them to be non-perpendicular across the tool, resulting in considerable problems on small scrap pieces
  • A poor laser or router preparation can cause loose pins, blades and claws, causing production problems or failure

Dynamic hybrid – totally digital with automated assembly (see Diagram 6)
Pros

  • The lowest cost solution since the first universal stripping systems were introduced
  • Generally effective and reduces most lower pins and machine adjustments
  • Only system capable of creating a 3D upper tool
  • At a previous drupa, a digital hybrid machine was released that can place crown pins and claws into the upper tool without the need to precut the upper stripping board
  • Another option to the digital stripping portfolio is a pin-setting digital machine to automatically set all pins, but if claws are needed, they can be manually inserted into a precut slot
  • Customized CAD solution exists to create tools quickly
  • All of the components placed into the upper board are perpendicular to eliminate most sheet breakups at high speeds and provide the safest elimination of damage to the brand owner’s product in tight areas

con

  • To eliminate the assembly labor and quality variation, the immediate con is the investment for the acquisition of this new hybrid (digital) automated pin and claw manufacturing machine.

The core requirements of dynamic stripping

To effectively remove thriftlessness at high speeds without the use of lower pins requires perfect CAD planning and controlled nick of the die. The watch functions must be addressed when designing a functional active stripping cock .
Nicking
Nick placement in the dieboard is completely subject on the relationship between the upper component and the lower interference. This is an authoritative necessity for stripping success, but only one CAD software today has automated the dent placement in the dieboard to control accuracy during the stripping tool programming process. When the drug user is placing the lower interferences and the upper joyride components, a notch besides can be placed simultaneously in the dieboard file, making the process more secure and providing the operator the best opportunity for success .
Unlike conventional strip, most consume broadly needs to be nicked in at least four areas to guarantee the elimination of lower pins ( see Diagram 7 ). This is at odds to what operators and diemakers think and have been taught, as most have constantly been taught to nick only the lead edge of scrap areas .
Balance
The waste must be balanced on both the upper tool components and in the resistance during the stripping extrusion process. successful stripping without lower pins is achieved when the waste material is balanced on as many planes as potential. Tight slots force the diemaker to use a straight upper part ( hook, steel rule, etc. ), and this alone controls the quarrel on a one plane – causing the most baffling issues in stripping.

Diagram 8 demonstrates the balance of the scrap on a crown pin vs. the unstable scenario presented with a individual claw or sword sword. As for the balance of the resistance, if a neutralize area is large adequate to support four restriction plus pin combinations, the bit piece can not twist, and the resistance from the combination of the nicks and restrictions is balanced so the military unit of the upper tool can explode the waste below the restrictions embedded in the lower instrument circuit board, never to come back out the top of the dining table. For very small quarrel slots, it is only recommend to nick identical modest and offset on one slope of the time slot from the early side. Reverse nicks on sword counters besides can be helpful .
Quality of components
In our analysis, we have looked at many crown pins and other male stripping components sold cosmopolitan and reviewed the operation and quality. We found that merely one personal identification number is sincerely fabricate sharply and hardened. Reviewing customers ’ tooling, these choice hard pins have outlasted the life anticipation of the tool. Substitute engineering may save a few cents per bowling pin, but they are balmy steel or administration, and they do not effectively “ prickle and control condition ” the scrap like the original hard acuate pins. Look how the trash pieces are stabbed by the master bowling pin – this is a must to have true success in moral force strip. By spreading those few pennies of savings over the average amount of pins utilized a stripping tool set, this deviation is less than a few percentage, and when the manufacturer has to add or adjust lower pins, the cost savings on soft pins can be eroded with lone three to five minutes of machine downtime or pre-makeready time spent setting lower pins .
3D
Another crucial factor is to understand the stress of the diecut sheet during the denude action. When the sheet is in contact with the upper berth tool components, it is stressed in many directions. across-the-board foam must be placed to control the sheet from breaking apart at gamey speeds. Digital 3D capabilities allow the stripping tool to be programmed in zones where the components are placed at unlike heights, so each zone contacts the tabloid at different times – frankincense reducing the effect and stress on the sheet
( see Diagram 9 ). The spare areas need to be removed first ( level 1 in light blasphemous ) and the kernel of the layout should be removed last ( level 3 in dark grey ) ( see Diagram 10 ). Do the dynamic denudation technology and the CAD system your organization use support the 3D capabilities ?
Restrictions
Restrictions have many shapes and forms. The most common and least expensive is to use the lower board wood specially cut to extend past the diecut tongue and under the scrap consume on the lower board. other stripping systems require objects to be manually inserted into the lower tool display panel to create the interference. These by and large can work over a time period of time before these insert components wear or collapse and besides add monetary value to the tools .
Offsets
The last core technical requirement of effective active stripping without lower pins is the offsets programmed between the male component and the lower restriction and die knife. Another crucial consideration is the fabric being processed. The outgrowth dimensions ( ten, yttrium in Diagram 11 ) should change when processing certain types of materials such as flute, paper, etc. It ’ mho tied better if the CAD system can dynamically adjust these offsets based on the substantial selected in the problem project. Without going into much contingent, as each system basically uses different offsets, a good rule of ovolo is 2 millimeter ( 0.079″ ) for both the ten and yttrium dimensions. This means the lower control panel limitation is 2 millimeter ( 0.079″ ) under the scrap and the upper interference is 2 millimeter ( 0.079″ ) away from the edge of the restriction. The lower board opening is approximately 1.5 mm or 3 millimeter ( 0.059″ or 0.118″ ) overall larger than the cut area .

The final analysis

Zone of influence
The evaluation process is based on performance and cost. Diagram 12 demonstrates the influence of a crown trap vs. a single claw. In it, sharply, pointed and hardened crown pins balance “ A ” ( the scrap on all planes ) equally well as manipulate “ B ” ( more sphere ). I like to call this the “ partition of influence. ”
“1 vs. 3” dynamic
Upon evaluation, many scrap pieces generally would need three claws or blades rotated at unlike angles to do the function of what one crown pin can provide to control the scrap sphere from the exceed down .
Cost
Although Bobst does not sell or manufacture stripping tooling, we have purchased many tools from many organizations worldwide for raw machine operation testing. Productivity and performance always will outweigh the cost of a tool, and should, if the benefits of car productivity ( overall equipment effectiveness or OEE ) are greater than the cost of the tool or the monetary value of the labor to create the tool and the pin racks set up, even if the instrument was a erstwhile run.

Conclusion

On average, with the combination of refer CAD automation and proper educate, the new hybrid moral force digital strip system ( pin and claw mechanically inserted ) or the existing automated peg setting system utilizing license components, are the best do technologies angstrom well as the lowest cost solutions on the market .
James D. Banister is the continuous improvement technical manager at Bobst North America Inc. He may be reached by email at [ electronic mail protected ] . For more information, visit www.bobst.com .
Reprinted with license from The Cutting Edge.

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