The converting process can pose many challenges for machine operators, but one issue that comes up time and time again is Angel Hair. Not as heavenly as it sounds, Angel Hair is the term given to short slivers of board inadvertently generated during the die-cutting process. These thin strands of board are classed as contamination by packaging convertors, especially by those operating in the food and drink sector. Manufacturers of this type of packaging need to eliminate the risk of Angel Hair occurrence. If Angel Hair goes unresolved, the packaging convertor runs the risk of losing a valuable contract as the food supplier cannot use packaging which poses a risk of contamination to the consumer. If any of these strands were to enter the food chain, the food supplier is open to having a law suit pursued against them.
How does Angel Hair occur?
Angel Hair contamination generally manifests itself when the paperboard substrate is trapped between the damaged tip of the cutting blade and the steel cutting plate situated on the bed of the Auto Platen.
Due to the nature of a damaged cutting rule tip, a clean cutting process cannot occur. When the tip is damaged the substrate is pinched between the damaged tip and the machine cutting plate. This causes slivers of board to attach themselves to the finished die-cut product.
It is also important to understand that there is a correlation between the width of the Angel Hair strands and the damage to the tip of the blade. The more damage inflicted on the cutting blade, the wider and longer the Angel Hair slivers will be.
When can Angel Hair occur?
Machine operators are often placed under immense pressure to reduce down time. Management are conscious that an unproductive machine costs money. In situations like this, good working practices can be overlooked on the converting machines, which unfortunately, can cause problems further down the line. Over pressuring the cutting die to speed up the set-up will damage the tool. If the cutting blade is over pressured, you effectively blunt the knife and cause the substrate pinching effect mentioned previously which generates Angel Hair.
The main factor in the reduction of Angel Hair is protecting the blade from being over pressured, it should be noted that too much weight on the machine, a bad patch up, and a poorly maintained cutting plate can all be contributing factors. Uneven, pitted or worn cutting plates will add to the pinching effect – so worn plates must be replaced – and poor rubbering processes on the cutting die also need to be eliminated.
Control of factory humidity and board moisture content is difficult, but extremely important, a dry board with short fibres is susceptible to bursting and affecting the cutting process. Recycled boards are more susceptible to Angel Hair due to them having shorter fibres in the substrate make-up. The more the board is recycled, the shorter the fibres become, this in turn will lead to difficult die-cutting conditions. It’s suggested that a recycled substrate shouldn’t include fibres that have been through recycling on more than 20 occasions, but I’m still unsure how we evaluate that.
When does the cutting rule supplier usually find out there is a problem?
Generally, the steel rule supplier’s first point of contact will come from the die-maker who, after producing a high quality, individually designed tool, telephones for assistance when the die-cut boxes have been rejected at the packaging convertors due to Angel Hair.
So how can we overcome damage to the tip of the blade?
As mentioned above, the primary cause of Angel Hair is the cutting blade tip becoming damaged – generally due to over pressure on the Auto Platen machine which either creates a flat spot on the tip or a hook at the very end of the blade cutting tip. Managing these various contributing factors will help to reduce the risk:
- Operator Training – Refresher training, resulting in a better understanding of good setup procedures, for an operator who’s under pressure to shorten down time will undoubtedly improve and eliminate overpressure issues.
- Cutting Plates – Badly scored and damaged machine cutting plates will create an uneven surface on which to die-cut effectively. Under impression, this will cause a nipping effect of the substrate and result in the creation of Angel Hair.
- Rubbering – Ineffective rubbering of the cutting tool can also cause the substrate to burst apart on ejection instead of cutting cleanly. Bursting causes fibres to break away and create dusting and Angel Hair.
- Board condition – Consistent control of humidity and board moisture content is a must have environment for clean die-cutting conversion. Die-cutting dry board with a low moisture content is not conducive to effective die-cutting. However print on the board must be dry. Similarly, control of corrugated board moisture, starch and liner thickness are a must.
Are there cutting blades that may assist with Angel Hair?
Bohler and Martin Miller have experienced R&D departments with state-of-the-art equipment and world leading production machinery at their disposal. The introduction of different bevel tip angles, profiles and coated cutting rules by these blade manufacturers has certainly helped to reduce some of the issues faced by packaging companies.
A case in point
I recently received a phone call from a Die-maker, one of their customers was producing packaging for a beverage company. The Die-maker asked if I could undertake a joint visit as the Angel Hair problem at the convertors was becoming a problem. Unresolved the packaging company was at risk of losing a contract with the drinks company, therefore, the Die-maker would have subsequently lost their tooling contract with the packaging manufacturer.
The joint visit took place to the packaging facility where I was met with a “What are you going to do about it?” situation. The manager of the packaging company was adamant that it was down to poor tooling and bad rule.
On entering the building, the machine tooling was thumping through the board which is never a good sign, but before making any suggestions, I went to look around the machine area along with the Die-maker. I must admit, I have never seen Angel Hair in such large quantities or strand widths before. I spoke with the machine operator and asked to look at the tool to assess the damage. I know the Die-maker very well and know he produces a HQ tool, but on inspection the blades in the cutting tool were flat, I then requested to view the patch sheet, the patch sheet had very little patch tape on it, everything was pointing towards excess pressure and little respect for the tool.
During the patch up process, no calibrated patch sheet or industry specific patch tapes had been used. Instead, the patch up had been performed using a mix of masking tape and brown parcel tape. It was obvious to me at this point where the problem lay. It was a case of too much initial weight on the tool and a bad patch up process. There were no signs of the patch up process that the machine manufacturer usually recommends.
While speaking with the packaging manager about improving the setup, there was a definite lack of understanding to the damage being inflicted on the cutting die. Unusually the manager had no experience in setting up and running a converting machine himself. Whilst discussing the machine practice I’d witnessed, I explained that I felt that the machine operator would probably benefit from updated training on performing a correct patch up process. The manager’s view had been that a machine standing idle costs money – “Let’s get the machine running”. Neither the operators or the Production Manager had an understanding of the damage that they were causing to the rule or tooling, they just continued to increase the weight on the platen so that they could run the machine quicker.
The recommended training to be undertaken by the Die-maker would help the Operators to understand the damage they can cause to the cutting die, and that, if they insist on over pressuring the cutting rules, they will inevitably end up with an Angel Hair problem. The subsequent training provided by the Die-maker resulted in a better understanding of the Die-cutting process, and a huge reduction in Angel Hair over the next few months.
Although using quality steel alone isn’t the answer to eliminating Angel Hair altogether – after all, one impression can kill the cutting blade – I would advise Die-makers use a HQ blade with a hardened tip. In this case a Bohler steel rule (Stabilo or Microtop) was also recommended to the Die-maker. You’ll be glad to hear the advice and training did eliminate Angel Hair at the packaging company and they have further benefited by saving money on tooling. The £200 per hour down time has been offset by the fact that they no longer require tooling to be replaced as frequently.
- Overpressure is a blade killer – if you overpressure a cutting tool, you will damage the cutting blades with a single impression.
- You only remain Angel Hair free by following good machine practices, excellent rubbering techniques and controlling your substrates.
Nick Myatt has served the packaging industry for over 40 years as an Auto Platen Operator, Die-maker and Global Technical Sales Manager. Currently a Technical Sales Manager with the Partwell Group, Nick, with his particular specialist knowledge of cutting rules and their application, has been asked to address the subject of Angel Hair on numerous occasions over the years.