It’s an easy thing to slip into, and we all do it. Every single one of us.
We go about our work without questioning our assumptions—doing things the way they’ve always been done because they work well enough.
Engineers and sourcing managers will pass by a table full of people manually plucking slugs, watch someone removing slugs from the press by hand or inspecting parts for slugs, and think nothing of it. This is how it’s always been. It doesn’t occur to us to question it.
All photos courtesy of IMPACT CSS
But what if there were a better way? What if re-examining your slug removal methods with fresh eyes meant that you could become better, faster? And what if doing things differently could actually put money in your pocket?
De-slugging should be thought of differently than waste removal. If you use solid dies and are still relying on manual slug removal, the stark reality is that removing slugs offline adds cost to every job. It also causes quality control issues and extends project timelines.
Hand labor is expensive, inefficient and leaves too much room for error. Missed slugs can delay downstream processes and operations. Often, the solution is having more workers inspect parts and gather discarded slugs.
There’s a huge opportunity cost to maintaining the status quo.
Step into the Future
It’s 2022. Technological and engineering advancements abound. Converters know this. But that doesn’t necessarily mean they know how those advancements translate into practical solutions for their business, or more granularly, their projects, or even more granularly, their presses.
Modern inline slug removal and disposal can be accomplished as part of the diecutting process with specialized dies, or with customized, modular tools and equipment that eliminates slugs in a step following the cutting process. “Custom” may sound expensive, but cost/benefit analysis shows these solutions can actually save money over the long run. Why and how? You eliminate labor from the cost per part.
What’s Possible
Converters often attempt to solve common problems that stem from lack of control over rotary press parameters by modifying the cutting die. For example, improper web tension and speed may produce diecut parts that are too long (or too short) in the web travel direction. Changing dimensions of the die cavity will not solve the problem.
There are many diecutting challenges that can be addressed by adding features to the rotary die. Finding the specific solution that’s right for you depends entirely on what’s being made and the material with which it is being made. Generally speaking, the following slug removal methods will work with solid tooling and give you options to optimize your process, so you can utilize your people for higher-value work.
- Standard air eject: This method utilizes an air probe inserted through the journal of the die to deliver forced air through the die cavities with each rotation. It is a relatively low-cost solution and is simple to set up and use. It is most effective with smaller-diameter dies, and slugs that don’t require a lot of pressure or force to remove
- Example uses: Removal of chad holes in small labels or tags
- Pulse air ejection: This is a system that offers an improvement over standard air eject tools. It utilizes a special air manifold to control and direct the burst of air to each cavity as the tool rotates. This means you achieve effective slug removal while reducing the amount of air pressure required. These dies typically require no press modification, are effective at high press speeds and are very user friendly. They are most effective with larger parts
- Example uses: Blister cards, tags, hanger tabs, folding cartons with holes, and other larger products with small-to-medium slugs. This method prevents label lift by ensuring labels stay on the liner when low-tack adhesives are in use
- Vacuum transfer: Sometimes due to press constraints, it doesn’t make sense to eject a slug immediately after cutting. The vacuum-transfer with pulse air injection method allows slugs to be held in the die cavity under vacuum and transferred around the die to a preferred point of ejection into your collections system. This method also allows you to separate an inner slug from a finished (OD) part without using separate die stations. This eliminates the need for die-to-die registration between die stations
- Example uses: Similar products to pulse air ejection, but the vacuum collection component allows for optimization of your press and greater slug removal control. For instance, vacuum collection can be accomplished from the top or bottom, depending on your equipment
- Stripping pin removal: This is a system that uses a matched die and anvil configuration. Matched set tooling uses a “pin” to stab the scrap and pull it down through a removal comb. Some minor modification is required to the support/drive rolls for pin clearance and the addition of the comb for stripping the pins. Advantages include minimal operator involvement and operation at the fastest press speeds
- Example uses: This method is highly versatile and can be used for circles as small as 5/16-in., windows as large as 2-in.+, carton hanger holes that look like sombreros or scrap waste around cartons
- Feed/vacuum thru: Vacuum dies offer an effective means for removing small diecut waste from the web. A vacuum die uses suction to pull waste through the center of the die, and out the end of the journal using a vacuum assist block. Removable inserts are used to provide increased clearance for the waste slugs that must pass into the die’s core, reducing the chance of buildup that could cause blockage of the air passage. Vacuum dies are most effective on small cavities, thin materials, tag stock and materials without adhesives
- Example uses: Removal of circles, small rectangles or registration marks on non-adhesive, lightweight materials like thin mylars, paper stocks and PETs
- Ties or nicks: Some of your customers might not want or need you to complete slug removal as part of the converting process. If parts can be cut to include ties or nicks, then slugs can be removed by the customer at the time of part assembly. In this case, consideration of the material being cut will determine nick strength, dimension, and the optimum number of nicks to make the assembly process smooth and easy for the customer
- Example uses: Not all hanger holes can be removed with stripping pins, so this is a great alternative. It’s also a way to save costs for the customer who doesn’t need 100 percent slug removal
- Ejection foam: This is a simple and inexpensive method to keep slug waste from building up in die cavities. Various thicknesses of foam are available to be applied to specific cavities within the die to aid in ejection on problematic areas, or foam can be applied to the entire cutting surface of the die
- Example uses: This method is a bit of an art form and can be used to hold several labels (including ODID labels) down on a low-tack adhesive liner
- Spring plungers: A mechanical method for avoiding slug buildup in cavities, spring plungers provide more force than ejection foam. Spring plungers are threaded into machined holes in each die cavity and are typically used when die cutting stiff or rigid materials
- Example uses: This is a great option for converters with no air or no removal anvils on their presses who are working with rigid cardstock, thick mylar and rigid PETs
Right for You?
If your head is spinning at this array of options, don’t fret. Talking to an expert can help optimize your process. When you start the conversation about slug removal, expect to be asked one key question that will shape your entire discussion: “What does the part do?”
Additional questions cascade from that answer. As with any custom solution, the approach must be comprehensive and specific. While deciding what tooling and equipment best suits the needs of a specific job, several factors will come into play, though the weight and priority given to each will vary based on the project.
Press type and die type matter. But know there are a variety of dies and tools that can be applied to a variety of presses. Generally, solid tooling allows creativity with slug removal, whereas flexible dies eliminate the possibility of the modular approach.
From there, materials, dimensions, geometries, drawings and tolerances coalesce into a puzzle that the right expert can help put together.
Open your mind! Optimize your process! Inline de-slugging eliminates the pitfalls and costs associated with manual labor and offers huge gains in efficiency and speed. Saving time and money on your assembly line, while promoting quality and efficiency, can be achieved by looking at slug removal with a fresh set of eyes and a willingness to embrace technological advancements. Your competitors certainly will.
About the Author
IMPACT CSS was formed with the combination of six entities in 2021: Atlas Die, Bernal, Midway Rotary, Atlas Chem Milling, Die Craft and GC Dies. Its product lines include steel rule dies, rotary dies and modules, solid steel narrow web rotary dies, flexible and flatbed dies.