Material selection and heat treatment play a key role with regard to the later graining
result. Even at the material procurement stage it is important to ensure that only
steels are used that are suitable for graining. All relevant toolcomponents (sliders,
inserts, etc.) should be produced from the same material to avoid possible risks to
the grain quality and gloss level.
Suitable materials include:
|Short name||Material no.||Eschmann name|
|40 CrMnNiMo 8-6-4||1.2738 EST||ES Aktuell 1000|
|---||Special alloy||ES Aktuell 1200 *) Standard for master pattern|
|40 CrMnMo 7||1.2311 EST||ES Aktuell|
|---||Special alloy||ES Multiform SL|
|X37 CrMoV 5-1||1.2343 ESU *) Limited as shown below||ES Maximum 500|
|----||Special alloy *) Limited as shown below||ES Primus SL|
Use ESR (electroslag remelting) quality material in hot work steels. There may be a difference
in the grain quality and/or gloss level (depending on the thermal conductivity, amongst other
things) in comparison to conventionally hardened and tempered plastic mould steels due to
case hardening and the alloy!
Apart from alloyed steels, the most common non-ferrous metals (e.g. copper, aluminium,
brass or zinc) and non-alloyed steel can also be etched. However, it is generally recommended
to test the desired etching result in advance on a trial plate. For some of these materials a
rougher etching base and/or a completely deviating grain quality, amongst other things, may
be produced as a result of the chemical reaction of the acid with the base material.
Non-ferrous metals have good graining capability!
Surface compressions, streakiness and similar Surface compressions in the material
to be textured often occurs when machining the workpiece. The steel microstructure
can be substantially compressed through mechanical processing, which results in a
tendency to higher surface hardness. When graining the workpiece, this then leads
to an uneven block diagram in the microstructure (e.g. grain depthdeviations, blotchiness,
Similar irregularities may arise with improper heat treatment or due to physically-
induced segregation in the steel production.
Areas to be provided with a grain structure must have acertain surface quality (polish)
depending on the design and grain depth.
Graining and high gloss? Highly polished surfaces already suffer minor damage
(fine scratches) through cleaning, paint application and processing of the grain structure.
Highly polished surfaces should usually be polished up by the customer after graining.
Welding should generally be carried out by a specialist company and the graining capability
of the welded areas needs to be guaranteed. A key factor in determining a structure's
suitability for welding is that the weld metal has the samestructure as the base material
in terms of composition, hardness and strength. Accordingly, the welding method, material
and necessary heat treatment must be selected on the basis of their later graining capability.
ATTENTION! Deviations in the gloss level and grain depth on the finished product cannot
be excluded even if welding is carried out by professionals!
The minimum draft angles for the ejection of the full grain depth areindicated for
The following rule of thumb applies:
A maximum grain depth of 0.02 mm can be ejected for each 1° of conicity.
Plastic properties (e.g. flame-retardant design, glass-fibre reinforced, etc.);material
shrinkage, wall thicknesses and tool structure (e.g.cooling,sprue, sliders, etc.) and
production parameters in injection moulding operations caninfluence this value.
For example, in areas with expected core shrinkage, three times the standard
conicityvalue for the ejection of the full grain depth may be necessary.
The following should be taken into consideration for a tool design compatible
with a moulded part:
A reduction in the grain depth is possible and must be agreedin individual cases with the
Scuffing is deformations of the plastic in the direction the item is ejected and is frequently
referred to as "stress whitening". The causes for this may be wall thicknesschanges, high
graining pressure, insufficient shrinkage of the item, material properties of the plastic used,
etc. Although it is possible to optimise the scuffing over the grained surface by reducing the
grain depth, this must be agreed in detail with the end user as this will change the grain
The occurrence of scuffing cannot generally be excluded, even with adequate draft angles!
Witnesses on the sliders and/or insert splitlines are often not permitted for items in which
the graining is in the main visual area. Loose tool parts are grained in the assembly in such
cases, i.e. over partitions.
It is important to ensure the following:
The position and distribution of partitions should generally be agreed with the
If loose parts are not suitable for graining in the assembly (e.g. due to restricted access,
tendency towards burring, etc.), witnesses can be agreed.
ATTENTION! Witnesses should also be completely etched to avoid ejection problems and
are not intended as split line protection. Partial etching is possible and should be agreed
Mechanical scribed line (CNC)
All non-visible shut off areas must be scribed by the customer before delivering the item
for graining. Scribed lines must be made using a CNC or a die-spotting press. Scribed lines
based on the patterned part are inaccurate due to material shrinkage, manual handling,
amongst other things, and can lead to burr formation and/or unacceptable clear areas in
the "worst case scenario".
Shut off areas (not split lines) are generally provided with up to 1 mm unetched clear areas.
clear areas / witnesses must be dealt with by the customer depending on the position and
draft angles to prevent the grain shearing off when ejecting the item.
"Gloss is a visual perception that occurs when viewing surfaces. The gloss perception is
more pronounced, the more directionally the light is reflected". The light is not only
reflected in the main direction of reflection but also reflected diffusely in other directions
with rough – and thus etched – surfaces. This reduces the reproduction accuracy of the
surface: a reflected object is no longer depicted as a brilliant image, but as a blurred image.
The more uniform the diffusion of light into the room, the lower the intensity of the
directional component and the more matt the surface.
The gloss level is determined by:
The gloss level can be measured reliably on flat surfaces. A specific gloss level for the
item cannot be guaranteed.