What do you need to know and which questions should you be asking before you buy your next conveyor dryer? Read on to find the answers and make a truly informed dryer choice
Show me the cost
It may seem sensible to look for a dryer that fits in a set price range, but by looking only at the cost of the dryer and not at the running costs, you could end up paying more than you bargained for. “Make sure you ask for detailed running costs of the dryer and any possible savings you can make,” advises John Potter, managing director of MHM Direct, distributors of the Tesoma range of German-made dryers. “Check the validity of these figures with customers who actually have that particular dryer – and speak to more than one customer!”
Mark Smith, sales director for Adelco Screen Process, adds: “Request operating cost charts from the manufacturer to ensure you are buying an efficient dryer.”
John also points out that no manufacturers will supply pipework or ducting, so remember to get quotes for exhaust ducting and gas supply pipework from a reputable supplier to work out the total investment cost.
Gas vs electric
If properly designed, both types of dryer can work well, says David Zimmer, textile products manager for M&R Print. “In our experience though, gas-fired convection dryers, which use forced air to do the heating/drying/curing, can be less expensive to operate, and work well on a variety of ink types, including the latest plastisol-alternative inks (such as high-solids acrylics, water-based, discharge, and so on) that are becoming a more and more important consideration in many markets.”
Mark Smith Concurs, adding: “Adelco manufactures dryers in both electric and gas fired versions, which enables us to provide an unbiased decision according to the throughput, ink types and products to be printed. The more airflow in a dryer, the better the curing ability, if the airflow, and therefore temperature consistency, is accurate. Pushing more air through an electric dryer will require more heating elements, which will increase kilowatt consumption and running costs. Gas fired dryers that use an efficient burner will use less gas, reducing running costs significantly and lowering your carbon footprint. The larger the dryer, the greater the savings in energy costs. For example, an average sized gas dryer for a single automatic screen printing press will save sufficient energy over an electric version to pay for the complete dryer investment over a three-year period. This is why over 90% of Adelco dryer sales are gas-fired versions.”
Pete Buffham, director of Wicked Printing Stuff, says “Not all inks cure the same, therefore when looking for a dryer it’s important to think about what your requirements are and note what is essential and what would be a nice to have, otherwise you can end up spending money on a solution which may not meet your needs.”
“The type of ink being cured is a key criteria when choosing a tunnel dryer,” agrees Andrew Stocking, partner at Dalesway Print Technology. In his opinion “the industry standard range of plastisol-based inks and hybrid PVC-free inks cure best with infra-red heat and, where large production throughput is required, an element of forced air inside the drying chamber to move heat around. It is also possible to cure water-based ink and direct-to-garment ink with an infra-red dryer, but it should be noted that the production capacity from the dryer will be around 30% of plastisol capacity.”
Mark Smith disagrees. He states that, “Infra-red dryers do not cure water-based or discharge ink systems as efficiently, but they are less expensive to buy and a more cost effective option when buying a small dryer for manual print production. A hot air dryer is a more efficient curing method for water-based and discharge inks, particularly with medium to high production output from automatic screen print or higher production digital machines. It is also kinder to fabrics than radiated IR and it is for these reasons that hot air dryers are by far the most popular option for most printers.”
Before you get carried away and sign on the dotted line, check the dryer will actually fit through the door. Yes, really. “If there is any doubt, ask the manufacturer for a site visit to ensure the product will get into your factory and fit within your production space, and allow for working area and maintenance access,” says Mark Smith.
Think about where the dryer will be in the room, warns Pete Buffham: “Positioning is important for an optimal printing area: having to walk across the room to put a garment on the belt is not a good use of time.”
Next, think about what you’ll be using it for and discuss this with the manufacturer. The manufacturer should be able to help you calculate the optimum size dryer for your printshop, explains David Zimmer: “It’s a simple mathematical equation – we have a spreadsheet that we use to estimate production needs, which allows us to recommend the proper dryer.”
For those looking to save money, Mark says it’s usually less expensive to buy a wider belt width than a longer oven, space permitting, adding: “Ensure the dryer is modular so it can be expanded at a later date to future proof your purchase should your print or production requirements change.”
Split belt options will let you run two different ink systems down the same dryer at the same time, irrespective of differing curing times, says John Potter.
When judging gas dryers, John Potter advises looking for a strong build quality, adding: “Look at existing dryers that the manufacturer has installed to check for burn marks around the oven joints. This indicates leaking hot air, which is inefficient, as are burn marks on the inlet or outlet of the dryer, which is easily evident. Is the exterior of the dryer cool to touch? Lost heat energy is particularly uncomfortable for the workforce, making the environment unbearable during the summer months.”
Cleaning and maintenance
“Can you lift the hoods to enable quick and easy cleaning of the dryer interior?” asks John Potter. “Don’t forget that lint is a fire hazard so it’s a good idea to keep everything as clean as possible. Also are the main filters accessible and what provision has the manufacturer made for easy cleaning or replacement?”
A good dryer will have minimum maintenance requirements and should be simple to maintain, says Mark Smith: “Ask for a copy of the site preparation guide, operator manual and maintenance manual.”
“Gas-fired dryers must be vented appropriately to ensure proper operation and safety,” says David Zimmer. “Electric dryers (presuming that infrared energy is doing the curing) generally also require venting, but the type and style required can vary quite a bit.”
“When curing water-based or direct-to-garment inks, always remember that the dryer must be fitted with an exhaust and make-up forced air system to effectively and efficiently remove all moisture from within the drying chamber,” says Andrew Stocking. “Fumes can be ducted to the outside via flexible plastic tubing or galvanised steel. However, clients should always bear in mind that the standard exhaust systems fitted to most dryers will have a limit on how long the venting pipes can be, and additional fans will be needed when the total length exceeds around 4 metres.”
Mark Smith adds that there are two types of exhaust system to consider. The first is internal exhaust of materials created from the curing of ink and residuals created from heating various fabric types and dye content. “A good dryer will have its own extraction and have variable air recycle to minimise running costs,” he notes. The second is feed and exit exhausts that remove fumes created by hot prints/fabrics, “particularly when they exit the oven and remain hot.”
It’s good to talk
“Make sure you take the time to visit a number of existing customers to see the dryer in action; don’t just listen to the manufacturer and don’t let them take you to their one favourite customer,” John Potter adds. He advises visiting or, if that’s not possible, speaking to at least three or four companies.
Don’t get caught out: it’s good business practice to check the history of any supplier. “Run a credit check on the company,” suggests Mark Smith. “It is easy to get a free credit check of any business online.”
“Do you have single or three phase power?” asks Pete Buffham. “Most industrial units have three phase power which gives you more options and cost effectiveness when choosing a dryer. The on-going running costs of a three phase unit are typically cheaper than a single phase power machine. Three phase gives you more options especially when considering purchasing a longer or wider tunnel. Find out from the manufacturer how many amps per phase/Kw hours the dryer is designed for.”
Digital vs analogue
David Zimmer believes digital control of the dryer operating temperature is critical to ensuring consistent results. Andrew Stocking disagrees, pointing out that traditional analogue controls are cost-effective and – he believes – probably more reliable in terms of length of service and reliability. It’s an argument you’re going to have to decide for yourself.
“Support is possibly the single most important consideration when purchasing equipment for a production environment, yet one that buyers often neglect to really consider,” warns David Zimmer. “Having access to timely, professional, responsive service can literally mean the difference between success and failure in a shop.”
Try before you buy
As a potential customer you can request curing tests from the manufacturer. “It may mean a journey to do so but it is always better to try before you buy, especially if you are using any special ink systems or materials,” says Mark Smith.