You are in:
Welding the world of print
A steady business with satisfied clients and a growing order book is something to be proud of in today's economic climate. One company with a healthy order book is Stevensons Advertising Plastics, a supplier of screen printing services for ultrasonic welded plastic products.
The company's success lies in the diversity of the product range it can tackle as well as its concentration on providing the customer with excellent service, making it easy for them to do business. Managing director, Andrew Stevenson, makes a point of knowing the progress of every job through production. Most have a short lead time, some within the day. All this adds up to a total service that in difficult times will enable the company not just to survive, but to prosper.
One of the challenges for the production of binders and office products is the use of PVC. There are conflicting schools of thought on the environmental probity of PVC, but suffice to say that its use is widespread and will be for a long time. Users of PVC in this industry aim to use as much recycled material as possible. Polypropylene is used wherever it is suitable.
Much of the fabrication of binders, place mats and plastic goods is done by ultrasonic welding. This uses the vibrations set up in the process to weld two similar plastics together. For best results, the two plastics will be identical. Sound is generated that cannot be heard by the human ear and this is concentrated through a device known as a horn. The vibrating horn is brought into contact with two pieces of plastic, one on top of the other, and the vibrations created between the two surfaces cause them to melt and fuse together. This fusing process will only work when the plastic is amorphous rather than crystalline. ABS, acrylic, polycarbonate and PVC are amorphous, whereas polypropylene and polyethylene are partially crystalline. Where ultrasonic welding is not suitable heat, in the form of hot air or conduction using contact, can be extremely effective. Polyethylene is ideally suited to hot air welding.
Get the message
No matter what process is used for joining, staking or forming, manufacturers are still faced with the task of printing the message onto the substrate. Screen printing continues to cover most if not all of the applications. Of course if images are four colour process then the line ruling of a print that is viewed within arms length should ideally be better than 80 lines per inch, preferably over 100 lines per inch. This is where the marriage of digital and screen technologies can be perfect. If, however, the volume is large and fine resolution is required, lithographic printing can take over.
Producing the product after the substrate is finished and formed is where the skill and added value lies. If the application is simply line colour and particular Pantone matches, then screen printing still remains the most cost effective solution. For short runs digital printing has to be the best bet. Print and cut increases the viability of digital printing as an additional finishing process is removed. Hot foil blocking and even heat applied transfers are also used extensively.
It seems that the market is becoming less pro or anti digital and screen and the combination of various processes can provide very attractive effects. Innovative design will entice purchasers into buying added value products to everyone's benefit. Those practitioners who can select the most suitable printing method for the particular application are the ones who succeed. Sometimes it can be rather like trying to put a nail in with a screwdriver or a screw with a mallet. Using the wrong process is the way to burn money fast.
Working in harmony
With this sector of the market the printing processes used are just part of the overall product offering. They have to work in combination with other operations. Normally the plastic substrate, be it PVC, polyethylene or polypropylene, is printed before it is assembled into the finished product. On occasions however, items that have already been produced are printed in their finished form.
This is where pad printing comes to the fore. The item may be too uneven to screen print, too delicate to foil block or too awkward to print on a flat bed digital printing machine. Pad printing requires limited capital investment but has the capability to print a wide range of substrates and designs.
Visiting some of the UK's sub-contract printing companies demonstrates the versatility of the various processes in the hands of experts. Much of the equipment may be twenty years old but still earning good money for the company. That's because there is no substitute for experience and the ability to adapt equipment and methods to suit a particular application. Practical skills like this, namely the ability to design, build and operate solutions to practical problems, are the backbone of industrial development.
