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Category Archives: Letterpress

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Dies, Letterpress

Printing Plates

Letterpress printing has made a tremendous comeback and the ease of photopolymer plates is a big part of this comeback. We manufacture copper, magnesium, photopolymer and wood printing plates. Photopolymers are by far the most popular.

The two most popular photopolymer products are KF-95 and KF-152. These are filmed based products that have a transparent and flexible base. The 95 represents .95mm or .037’’ in total thickness. The 152 is deep relief and represents 1.52 mm or .060’’ in total thickness. By subtracting these numbers from type high or .918’’ and the thickness of your type, you set the height of your base plate. .881’’ for KF-95 and .58’’ for KF-152.

A base plate for deep relief or KF-152 is a very versatile plate. It not only allows you to mount KF-152 but also any 16 gauge (.063’’) metal such as copper and magnesium. Copper is by far the premium choice for printing or foil stamping. It is due to the hardness of the metal. Because it is very hard, it can be etched with virtually no shoulders on the image. This allows for clean transfer of foil or ink with no plugging, or ink pink up on the bevels. Copper can also be hit very hard to give maximum debossing of the stock. Photopolymers must have a bevel because it is not as hard and small type and strokes will not hold up.

Cost is a major consideration in choosing plate material. The most common minimum plate charge is $30. You can get up to 48 sq inches of KF-95 or 45 sq inches of KF-152. Up to 30 square inches photopolymer or copper is the exact same cost, $30. If you have the base plate, the cost is the same and the material is superior why not choose copper.

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Jan192016NOCOMMENTS

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Dies, Letterpress, Photopolymers

Scoring on a Cylinder Press

A lot of printers utilize equipment for die cutting on machines that were converted from letterpress printing presses. The most popular of these are Heidelberg but there are others such as Millers.  Recently we have seen more customers cutting on Vander Cook proofing presses. All of these presses are work horses and do a great job on die cutting registered work. One of the particularities of a cylinder is score heights. A cylinder press exerts different forces along the vertical and horizontal directions. Forces on scores that run parallel to the cylinder are less than scores that run perpendicular to the cylinder. We typically offset the score height by .005’’.

Score height is computed by taking the cut height (.918 virtually all letterpress equipment) and subtracting the caliper (in inches) of your paper. If you are using matrix you will need to subtract an additional .003’’ for plastic or fiberboard matrix and .009’’ for steel backed matrix

.918’’ cut height (type high)

-.010’’ paper caliper

-.003’’ plastic matrix

.905’’ crease Ht.  horizontal               .900’’ crease Ht.  vertical

 

We actually made a pocket folder die for an Accu-cut table press last week. We had to offset the vertical scores by 0.015’’ because the vertical scores were die-cutting the stock. You may have to experiment with your die maker to get the perfect combination on your press.

Using matrix or some sort of female channel is imperative for achieving a true letterpress crease. Crushing the paper without a channel will give you a folding line but your paper will definitely tend to crack. This may be fine on white stocks but probably not acceptable on colored or printed papers.

The unequal forces may also be a problem when cutting or kiss cutting a grid pattern. Many times operators may damage the horizontal knives by increasing pressure because the vertical knives are not cutting. It may be possible with a very long make ready but we usually suggest running it on a platen style press like a Kluge or Bobst. Another solution may be to run the vertical knives in one pass and the horizontal knives in another pass.

 

Give us a call with any of your die cutting challenges or visit us at our website, graphicdies.com 

 

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Letterpress, Photopolymers

Setting up files for letterpress or photopolymers

plateShoulder3

Adobe Illustrator- preferred art or a PDF with fonts embedded.

Before sending in illustrator file make sure that you outline all texts or else it runs the chance of being replaced when we open it. (type <outline) and save the layout as a new file name so you can go back and edit the text if necessary. Save as a PDF, AI or EPS to send to us

Rastor images are not recommended unless grayscale is avoided and use 1200 bitmap mode. By rastor we mean scanned artwork into Photoshop and then created into vector files. Please use caution with these types of files as creating vector artwork might not capture all detail of the original artwork.

Do not use a JPEG for your artwork; it will create a low quality die that neither you nor we will be happy with.

If printing in one color make sure the file is all in 100% black (K) only in CMYK mode.

When creating artwork please be aware of font and line requirements.  It depends on your plate but If your plate has a 94 or 95 in the product name, we recommend at least a 0.25 point thickness (or larger). If your plate has 145 or 152 in the product name, we recommend at least a .35 point/.007″ thickness (or larger). Watch out for typefaces with swirl curves that thin or have breaks or fonts with fine cross bars. Also, no hair lines please! Undersize dots and lines may not hold on the plate during production, or during printing or impressions.

On dots, we recommend at least a 1 pt diameter if the plate is a 94 or 95 in. Boost that to 1.25pt diameter for plates that are 145 or 152 in thickness. Each of those dots has to stand on it’s own on the plate and that thickness will provide the support at the base of the plate to hold the dot.

 

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