Choosing an Exposure Unit?
We are often asked “what is the best exposure unit for my screen printing business?”
Like always what seems a simple question does not have a simple answer. So we thought we would put this guide together to help work through your requirements and to come up with the right answer for you.
Let us first look at what YOU for YOUR Screen Printing business. Think about these considerations and questions?
- How many screens do you plan to produce on a daily basis (a couple here and there or up to hundreds per day)
- What is the maximum screen size you use?
- Do you have any space limitations?
- Are you a hobbyist printer, commercial or educator?
- What is the size of your budget?
- What kind of artwork are you producing? E.g. Complex design with very detailed half tones / 4 Colour Process CMYK or typical T Shirt artwork (medium resolution / block style artwork)
We are going to do our best to avoid baffling techy jargon so if this is all new to you we suggest that to take a look ‘Is screen printing for me article’ and our video tutorial which will help you understand the basics.
Now let us look at the Exposure Unit solutions from simple to heavy duty.
Very simple solution, there are thousands out there, which are used every day. Good for hobbyists / home printers who make a handful of screens per day. Comes as part of our Essential and Mid range screen printing kits.
Pro: Very Cost Effective, can create excellent stencils and you can expose large screens. Note that the lamp does not have a vacuum therefore you need to ensure that the positive is tight and intimate with the screen. To do this you use sheet of glass (the heavier the better) which ensures that the film positive and screen are very tight. This Exposure Unit uses halogen bulbs (1000W) which are powerful and cheap to replace.
Cons: Very Slow (10 – 20 minutes depending on screen size), requires space (large cupboards are ideal), the printer has to time the stencil exposure – there is nothing ‘hi tech’ about the lamp solution but it works.
The WPS Mini Exposure Unit uses proven “Actinic” tubes in a tight array. This exposure unit comes with a yellow pilot light which you use to position the film positive with the screen. The unit comes with an integrated timer (you can set multiple programs) and vacuum which is extremely easy to use. We have used these units for a number of years and have been pleasantly surprised at the quality of stencil produced even with very difficult artwork. Typical exposure times from 140 – 300 seconds depending on what kind of emulsion and the number of coats you are using.
Ideal for small print shops, schools and colleges. You can also purchase the unit with a drying cabinet which really does improve production with a relatively small footprint.
Pros: Very easy to use, very tight vacuum, and uses proven technology giving high quality stencils. Different sizes of exposure unit available to accommodate different frame sizes.
Cons: Potentially tube units do not produce stencils as sharp as from a single light source. With tube units, light comes from multiple angles, potentially undercutting the positive during exposure which can result in the loss of fine detail. However we have not experienced many issues at all with this kind of unit.
These units can be used in a high production environment e.g. 50 – 70 screens per days. However do budget to replace the bulbs on a regular basis as they will gradually degrade.
The WPS LED Mini Exposure Unit, consist of UV LED technology positioned in a tight array, similar format to the “Actinic” version. It comes with a yellow pilot light which you use to position the film positive with the screen. The unit comes with an integrated timer (you can set multiple programs) and vacuum which is extremely easy to use. LED technology has started to make inroads into the screen printing industry, so the technology is relatively new and is continuing to be developed. Like the standard unit it also available with a built in drying cabinet which is great for increasing production and reducing mess.
Pros: Very quick (30 – 300 seconds depending on emulsion / number of coats etc.), Very easy to use, very tight vacuum, LED technology using low power, does not generate heat, is long lasting (stated to be very long life) and produces high quality stencils. Different sizes of exposure unit available to accommodate different frame sizes.
Cons: Initial purchase price higher than Actinic units. The LED array emits light from multiple angles undercutting the positive during exposure which can result in the loss of fine detail. However with LED technology this seems less of a problem than tube units and is commonly not considered a problem for the vast numbers of printers (99.9%). LED technology is new and is continuing be developed.
Ideal for small / mid, large screen printing shops and educational establishments who need to produce lots of screens quickly. These units are designed for high production environments. We tend sell this units to printers who have invested in direct to screen technology.
The Heavy Duty Unit uses a single point Metal Halide bulb, they come in lots of different configurations with different bulb ratings and features such as integrators (measures the quantity of light reaching the screen and adjusts the exposure if there are any voltage fluctuations or to compensate for deteriorating bulbs) and rapid start-up – it can take time for a metal halide bulb to get to the correct operating temperature. These units are fast and give very accurate stencils. Metal Halide is still probably the most popular light source used for mid and large screen printers.
Pros: Very fast (depending on the power options you choose) and can come with advanced features so you can produce large numbers of stencils quickly, consistently and accurately. Often used in heavy industry environments and for used for multi applications e.g. exposing print plates. Different sizes of exposure unit available to accommodate different frame sizes.
Cons: Metal Halide bulbs are expensive (£200 – £400 common prices), generate heat and consume much more energy than LED units (LED exposure units typically use 1/5 of the energy of a metal halide unit). Many screen printers are moving over to LED technology.
When choosing an exposure unit take some time and think about your current and future screen printing requirements. There are lots of exposure units to choose from all giving different levels of production capability and quality. The exposure units with combined drying cabinets are very cost effective and increase productivity. If you are looking to replace an older unit e.g. metal halide unit then we would highly recommend that you consider LED units.
Please feel free to contact us to discuss your requirements and we can help you to find the right exposure solution for your needs.