Adding vacuum to your exposure unit

Why fit vacuum to your machine?
The modification is quick and simple to do, it only takes 5 minutes 
It is reversible.
It will produce an excellent product every time, it’s far better than with just using the weight of the glass to compress the sachet.
It is much faster to make plates using imagepac, doubling your productivity and reducing labour costs.
If you don’t do it you are relying upon luck to make a perfect plate.

Why use imagepac?
Much faster – save an average of 10 mins per plate
Much easier – can delegate manufacture, plate making becomes simple.
Much cleaner – no pouring, no spills, no stickiness
More reliable – machine manufactured, accurately filled, consistent exposure times, no air bubbles and consistent quality.
More cost effective – lowest cost per sq. cm. of printing plate and labour savings.

What does the modification do?
It uses a vacuum pump to pull the upper and lower glass sheets together compressing the sachet. It brings the upper glass down onto the imagepac with greater force to ensure you have perfectly made stamps- quickly.

How do I modify my exposure unit?
Attach the hose retaining clip to the front corner of the exposure unit. Place this on the front left, it
should be on the metal edge of the machine which should be cleaned with a spirit based cleaner first to
remove any dirt or polymer.
                                                                              
How do I use imagepac?
You can use imagepac exactly the same as you use pouring polymer, but to make excellent plates you should:
• make sure the imagepac is compressed- your vacuum will do this excellently.
• make sure the imagepac is level- bearers around the edge will do this.
• make sure there isn’t any excess light around the outside of the imagepac- the black template will do this.

Lay bearers
Use the bearer strips provided to ensure correct compression of the sachet onto the negative. Place one strip in each corner directly onto the glass, this will compress a 2.3mm imagepac accurately.

Lay template
Light from the lower second exposure will bounce off the inside of the machine and come up and fill in the floor, the black template around the negative will stop this from happening and keep all your exposure times constant.

Masking off around your negative with a template is good stamp making practice in general, but it is more important with imagepac because the excess of backing sheet around the edges of a conventionally made plate acts like a light block.

You should ensure that the base of your exposure glass is entirely covered with negative or template.

Standard use

Exposure times
Start with the same exposure times that you use with pouring polymer.
After exposure press the imagepac between finger and thumb and you can tell if the times are right without cutting and washing out. If the text feels soft and isolated characters or thin lines fly off into the liquid resin, then increase the main exposure.  If the text is surrounded by very little liquid resin then reduce the back exposure. If your fingers almost meet then increase the back exposure.
Always test using warm bulbs.
The floor should be between 30 and 45% of total thickness- adjust back exposure time accordingly.
Relief should have just held the finest detail, so take it down so you lose a fine dot or a line is wavy, then add 30 secs onto this time.

Processing imagepac
Using a scalpel cut the side that was next to the negative. Cut right around the edge inside the seal. Do not remove the cut plastic, but press the sachet firmly to the washout plate.  Then peel one corner of the cut plastic away, fold it back on itself to keep clean hands and peel 

Good platemaking
Examine the plate by looking at fine text and see that the shoulders of text are formed correctly.  In profile you should see an angle of about 30% to the vertical this ensures that isolated full stops for instance are supported.  If the text looks straight or worse egg-timer in profile then the plate is underexposed.  If the fine reverses look filled in (usually this is only possible to test on a self inker) then reduce the main exposure.
 
Problem solving
Using your micrometer, measure the total plate thickness, you obviously want it to be level.  If it is wedge shaped then you can get an underexposed part where the plate is high, i.e. where you will lose fine characters.  Correspondingly where the plate is low you may get a high floor, low relief and that part may look overexposed.  Level the two glasses by checking the bearers are sitting on clean glass outside the imagepac.
Measure the floor, if it is uneven, there is only cause, the light bed is uneven.  In this case move the negative and sachet away from where the floor was low and retest. If it still not level then replace the bulbs. Remember that if you are going to lose fine text it is likely to be around the perimeter of the plate where the bulbs emit least light.

How else can we help you?
We are experts in stamp making- we make hundreds of tonnes of polymer and millions of imagepac every year. We make exposure units from the largest in the world to the lowest cost and have helped stamp makers right across the world to improve their processes. We provide our information freely and without cost to our customers, here are some topics that may be of interest:

• Negative making – direct digital printing
• Exposure times – optimisation to improve image and increase 
throughput
• Image improvement – installation of imagebright filter
• Exposure units – faster process time and replacement parts
• Dryer stamps – better post exposure procedure
• Shinier stamps – better looking sheets
• Masking – no-cutting stamps for mass replication of the same design