Pad printing machine, the principle of transfer printing, is a good complement to screen printing machines, silk screen printing, also has is silk screen printing office does not have a lot of advantages, is now moving printing machine and the application of the pad printing technology is very wide.Pad printing is the most distinguished feature of indirect printing, the biggest advantage of indirect printing is made independently of the position plate and substrates, the upper plate, printing ink to the surface of the substrates of the change of the rubber pad printing head shape and make the pad printing technology greatly enhance the adaptability of shape of substrates.
        Now we will pad printing technology printed at the top of glasses involves introduce some process problems, facilitate everybody understand the pad printing technology in an overview about the glasses industry application.
1, ink selection
       Ink selection in pad printing technology occupies a very important position, in the pad printing technology and widely on substrates.Because of the frame is made of metal, require ink on the surface of the metal, better adhesion, are now widely used two-component ink, drying way to dry.Lens requires the glass printing ink, glass printing ink is usually two-component ink, drying way to dry.Two-component ink after curing ink layer has high hardness, good adhesion characteristic, but a little trouble some operation.
The use of two-component ink method briefly as follows:
      (1) according to the first add hardener to the ink with the ink of mix, for printing to pour into the oil pan.For two components will be slow to curing ink, so to control the dosage.
      (2) printed should be placed in the drying oven drying process to speed up the drying speed.Two-component ink generally at room temperature under the condition of dry up to 10 hours, it will affect the production efficiency, the drying method is ideal, often drying temperature between 150 ℃ ~ 180 ℃, 5 ~ 10 minutes.

2.Rubber pad printing head
       Pad printing technology in the choice of rubber pad printing head is crucial.
First consider the glue head size and the shape of the plastic head of pad printing effect.The shape of the rubber pad printing head to be able to print to the specified location, and ensure the deformation is small.Due to the printing area is very small frame, pad printing rubber head should be slightly pointed, through the experiment, cross-sectional area is 38 mm A7 glue head is suitable.A3 rubber head of the printing effect also is very good, but because of section a little bit small, little older printing deformation.
        Secondly the hardness of rubber pad printing head is another indicator of should consider when the choice, soft rubber head wide adaptability, but printed by large deformation.Especially like frames so small print products, graphic font is very small, large deformation is easy to give the graphic images and adhesion between lines, become blurred, so choose a bit more hard glue head is better, our test result is shaw hardness is 32 degrees of rubber head can achieve the best printing quality.
Nose head part print selected glue considering the limits of the location, should choose cross-sectional area smaller plastic head, our test result is cross-sectional area under 15 mm rubber head suit, hardness should be above 32 degrees.
3.Pad printing plate
       Pad printing machine plate steel is the edition, make a steel plate is corrosion method, frame and lenses printing graphic is very small, so the size of the steel plate does not need too big.In accordance with the standards of pad printing industries, using 75 mm x l00mm and 100 mm x 100 mm both the size of the steel plate can be, and the spectacle frame printing graphic edge also however 20 mm, the length of the longest so graphic can use 75 mm x 100 mm steel plate.
       Corrosion of steel plate produced by traditional method.Because the font is very small, on a short exposure time, can obtain the uniform depth of the steel plate.
      Steel plate, control is a key indicator of depth.Deep depth, it's easy to paste version, transfer of ink is affected, and font strokes easily uneven thickness, spacing between strokes decrescent, clarity.Depth of shallow defects is also obvious, this is the font color saturation is not high, the color is difficult to achieve striking effect.Our test result is the most ideal depth control in 19 microns.

4.Pad printing machine
Frames of the printing area is small, only printing company logo and so on, so does not involve complex graphic, also does not involve the use of color, choose a small area of the machine should be in monochrome printing machine as well.Words are mostly small frame, pad printing machine of high accuracy is higher, the better.
5.jig
In special printing industry, make fixture is a basic work.In general, production fixture function mainly, ensure that the printing area of the substrates and rubber head has a relatively fixed position, ensure product uniformity of printing.Involving multi-color overprint at the same time easy to implement overprint accurate, so the fixture position in pad printing process is indispensable.Frames is printed by the medial margin area, and the position must be through the fixture clamping can ensure parallel with rubber pad printing head.Printing process, the frames can not loose, require binding effect is good, use crystal gel casting fixture should be preferred.
Crystal gel casting method is the use of unsaturated polyester resin in under the action of hardener of solidification theory, very easy to according to the shape of the product curing.No matter how complex the spectacle frame structure, the use of this method make the fixture can well fixed frames, conform to the requirements of the printing.Production method is: first mix resin composition A and composition B, stir evenly into the prepared paper, until the resin gel state, remove frames.
          Frame and lenses pad printing although is a very simple process, but it shows that the characteristics of the pad printing process:
         Pad printing is very suitable for printing area is very small, irregular products;Is glasses to the part of the products need to be printed is special to wonderful application of pad printing process.
From the point of view of printing process, to achieve the fine printing effect, choose high quality printing ink and high hardness rubber pad printing head is must attach importance to two factors.
The stand or fall of pad printing effect and the precision of the pad printing machine and the quality of the fixture are inseparable.