GB Innomech has considerable expertise in the precision cutting of materials from drilling fine holes in quartz glass to precisely cut pen nibs by using a number of techniques.
Laser Precision Cutting Systems | Water Jet Precision Cutting Systems | Mechanical Precision Cutting Systems | Hot Cutting Systems
Laser Precision Cutting Systems
GB Innomech has used lasers extensively for non contact precision cutting systems. These fall into 3 main types, Excimer, YAG and CO2 lasers, each having different characteristics and many variants which have to be matched to the specific precision cutting applications.
The most costly and most specialist is the Excimer laser which operates in the UV spectrum, where the beam is invisible and hence potentially very harmful. These lasers are typically very large for their power output and require several specialist gasses.
However being UV, the beam is easily absorbed by quite thin glass. This facilitated the development and manufacture of machines that could drill, at production rates, the precise parallel hole, in a high strength glass used as the delivery tip for a needleless drug delivery device.
Other applications for the Excimer laser include marking PTFE cable by changing the colour of the PTFE, (but not affecting its insulation properties), thereby creating an indelible mark. GB Innomech was involved in the development of this equipment which is now used extensively by most of the world’s aircraft manufacturers.
More common are YAG and CO2 lasers. These come in various forms and wide ranges of powers. GB Innomech has developed many systems, with a wealth of knowledge combined with that from specific suppliers, to mark cut and drill a wide range of materials. It is very important to match the correct type of laser to the material and process.
For instance a precision cutting application required a number of 200W CO2 lasers. Whilst a lower power could have been used and speeds reduced, this resulted in the burning of the edge that the higher speed available with the higher power prevented. The same laser however could not put a 2D matrix code on the material as it did not create a suitable contrast whereas a smaller YAG laser did provide the high contrast marking but would not cut the product adequately.
All lasers require great care with guarding to make sure they are safe in use or during preventative maintenance and the installed system is compliant with the safety standards.
Water Jet Precision Cutting Systems
Water jet systems, if properly configured, can cut soft and even absorbent materials such as paper without making them wet. The basic system uses a very high pressure pump that forces filtered water though a small orifice to produce a high speed jet, which can cut through most materials, by the water abrading the edge of the cut. Pure water is ideal for pharmaceutical and food products as the pressurisation acts to sterilise the water and there is no contamination of the product.
The precision cutting performance can be significantly improved if an abrasive is introduced to the water jet as it leaves the nozzle. This effectively produces a file of fine abrasive particles carried on the outside of the water jet promoting much more abrasion; however there is a risk of contamination of the cut surface by the abrasive particles.
There are some limitations to precision cutting using a water jet, not the least being the relatively high power consumption needed to pressurise the water. GB Innomech have undertaken several trials and investigations on water jet cutting including soft plastics and rubber sheets, both giving excellent results.
Mechanical Precision Cutting Systems
Mechanical Precision Cutting Systems fall into 2 main types; those that mechanically tear and those that saw or grind.
Mechanical Tearing
Punching with blades onto a platen, as in kiss cutting, or into a die have been extensively used on numerous of our projects. Label and lid stock is most efficiently produced using rotary dies to kiss cut through layers carried on a backing strip, which itself is not pierced. Whilst the production of the tooling is a specialist process, GB Innomech through various products fully understand the issues that may be encountered and how these affect the strip production process, and the application of the lid or label.
Guillotines are extensively used and have been successfully automated for specific applications. The efficiency of the cut for specific materials has been researched by many over the years and GB Innomech have drawn on that knowledge to provide shears or guillotines for products from paper to steel. Rigidity and close control of the blade gaps as well as sharpness are vital to achieve reliable and energy efficient cuts.
Guided knives still have uses but tend to be replaced these days by non contact systems due to the rapid blunting of blades.
Sawing or Grinding
These fall into two basic forms; cutting using teeth or grinding with an abrasive medium. The cutting edge can reciprocate as in a hand or mechanical saw or be continuous as in a band saw or circular saw. Each has specific benefits and applications and it is important to understand these when specifying what to use on a particular project.
Reciprocating saws are simple but the blade only cuts in one direction and so half of the blade motion tends to be wasted. It tends to be non-uniform in motion and so the optimum cut speed is never achieved and blades tend to wear unevenly. The advantage is that blades are usually cheap and easy to replace.
Band saws are a Continuous form of the simple saw blade. The speed, the feed rate and force applied to the product can all be optimised to give an efficient cut performance. The blades have a tendency to wear on one face and this then initiates wander and non straight cuts, this can be exacerbated by the flexibility of the blade and difficulty in accurately guiding it. Replacing blades needs good access and care has to be taken to ensure proper tension control and guide adjustment.
Circular saws come in many shapes and sizes from in excess of one metre to a few mm diameter and from hundreds of TPI (teeth per inch) to individual teeth spaced many inches apart. The blade may be very thin and utilise the centrifugal forces to hold it stiff or be thick enough to provide its own support. The speeds we have used vary from tens of thousands of RPM to a few RPM as it is the circumferential speed of the teeth that is important, matched to the tooth form and material being cut. Circular saws do not like side loads and blades will shatter or jam with even slight side loads, which a band saw would not even notice. However the circular saw by its nature produces an accurate straight cut.
The finest tooth form is the grinding or slitting disk. This can be a thin sheet of graphite with a bonding media that is only a fraction of a millimetre thick. When static it is very fragile but at high speed it becomes very rigid and capable of cutting almost any hard material. As it cuts it loosens material from the periphery exposing more grinding media and the side cheeks polish the cut edges so producing a very precise ground cut. Other forms of disk with diamond tungsten carbide bonded to the edge produce saws that can cut fast and accurately though the hardest or media with very little wear but tend to remove more material leaving a wider cut.
It is not always obvious what is the optimum solution or number of teeth required for a given job. One client required large quantities of polystyrene coving to be cut to length. Instinct suggested fine teeth on a conventional hardened steel blade but after trials and investigation to understand the precision cutting process, it was found the optimum blade had only 4TPI with alternate off-set 3mm wide tungsten carbide teeth. Similarly precision cutting an array of 1mm diameter polycarbonate fibre optics needed a saw with only 6TPI but run at very high speeds and controlled feeds with no back lash.
At the other end of the spectrum, precision cutting a pen nib utilised the same grinding disks that had been used on the customer’s manual systems, but run at a very accurate peripheral speed, continually adjusted to compensate for disk wear and the cut feeds accurately matched to the various material properties from the very hard ball on the tip, through the heat affected weld zone, into the parent metal and the break out into the ink feed hole. This resulted in much reduced disk wear, high accuracy and reliable quality.
Hot Cutting
The final group of cutting technologies is hot cutting.
These can be simple and applicable to automation but are now usually replaced by laser systems. Product is heated to the point where it melts and it is either forced to one side by a mechanical component, for example a hot wire or a blast of hot gas or plasma
