Frequently asked questions

What materials are suitable for photoengraving?
All types of steel, alloys and other, aluminium, kirksite, nickel, brass, copper, titanium, zinc, bronze, graphite, and even glass.

Is it possible to weld moulds?
Welds always involve a certain degree of risk, as they can cause variations to the structure, composition and hardness of the material, inducing a different reaction during the engraving bath.
In principle, therefore, it is always best not to weld moulds. If, however, there is no other option, we recommend that you contact specialised companies.
If this is not possible, it is essential to follow some basic criteria:
1) heat the workpiece before welding;
2) use the same material of the mould for the welds, so as to ensure the finished product’s uniformity;
3) reheat the welded mould and allow it cool down in a furnace.
In any case, make sure to always inform Pel Plastic technicians of any welds, so that they can adopt all the measures and precautions necessary to reduce any problems.

Is it necessary to follow certain special precautions for mobile carriages?
Just as with welds, using the same material of the mould also is essential with mobile carriages. Moreover, in the case of induction tempering and tenifer, be sure to perform the treatment after photoengraving.

What should I do in the case of removable elements?
If the moulds include parts that do not need to be engraved, it is best to remove them. This applies both to plugs and columns and, more generally, to all removable elements. However, if the task is too complex, we recommend that you contact a Pel Plastic technician for advice.

Do photoengraved moulds need to have a special surface finish?
That depends on the type of texture you have chosen. For example, with a “fine” texture type K5, you will have to finish the mould with canvas 320, since the grain cannot hide any flaws, on the other hand, if the grain is “coarse”, you can also leave the finished mould with EMD or high speed. Whichever the case, though, it is advisable that you contact Pel Plastic.

Can I photoengrave mirror-polished moulds?
Of course; but keep in mind that a mirror finish may be ruined during the photoengraving process. Lapping, in fact, is carried out with special pastes, which, because they are particularly greasy, leave a film on the surface that you necessarily have to remove before photoengraving. This cleaning operation is performed with chemicals that could compromise the gloss of the mirror polish. Chemical treatments, moreover, which by nature are aggressive, if applied to a lapped mould, inevitably will cause superficial oxidation, which, however, is easy to get rid of.

Are their limitations in the size or weight of photoengraved moulds?
No, there are no such limits. At Pel Plastic, we have equipment that can lift moulds weighing up to 12 tonnes. If the cranes in the manufacturing plant are inappropriate, you can contact specialised companies, which can provide all the machinery you may need to solve the problem at hand.

What options do I have, if the deforming grades are limited?
Unfortunately there is no universally correct formula. The best we can do is offer some suggestions on how to limit the problem of extracting the moulded pieces.
For example, we recommend that: 1) you use shallow directional designs; 2) you arrange them perpendicular to the deforming line; 3) you splash them lightly in critical areas.

Roughness comparative table
The table and values shown below are purely indicative. In fact, the values are subject to change, due to the chemical composition of steel, as well as its overall hardness.

Ra is the arithmetic average value of the deviation from the profile of the average line.
Rz is the average distance between the ridge and furrow, obtained from five “L”-shaped sections.

Roughness table

PP Draft
K20 1,5°
K40 2,5°
C4 2,5°
C7 3,5°
C9 3,5°
C12/1 3,5°

The values listed in the table correspond to the average of three measurements taken at different points on moulded samples in polypropylene.