Etching technology and laser technology:
frequently asked questions

Do you have any questions about etching technology and laser technology?
You can find answers to the most frequently asked questions on this page.

Questions and answers on etching technology

Which materials are suitable for graining?

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
tool components (sliders, inserts, etc.) should be produced from the same
material to avoid possible risks to the grain quality and gloss level.

Suitable materials include:

Code nameMaterial no.Eschmann name
40 CrMnNiMo 8-6-41.2738 ESTES Aktuell 1000
---Special alloyES Aktuell 1200 *)
Standard for master pattern
40 CrMnMo 71.2311 ESTES Aktuell
---Special alloyES Multiform SL
X37 CrMoV 5-11.2343 ESU *)
limited
ES Maximum 500
---Special alloy *)
limited
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!

*) see “What is meant by gloss level?”


 

Can non-ferrous metals be etched?

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 do not have 100 percent graining capability.

 


 

What are segregation lines or stripes?

Segregation lines due to strain hardening!

Surface compressions, streakiness and similar problems

Surface compressions in the material to be textured often occur 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 depth
deviations, blotchiness, streakiness, etc.).


Possible causes

  • Blunt milling cutters
  • Incorrectly ground turning tools
  • Mechanical damage (e.g. careless hammering on the mould surface when changing inserts)
  • Damage due to improper handling of clamping equipment or other tools

Similar irregularities may arise with improper heat treatment or due to physically-induced segregation in the steel production.


 

Are special polishes required?

Reference image
Milling cutters
Hardened edge, grooves

Polishing

Areas to be applied with a grain structure must have a certain surface quality (polish) depending on the design and grain depth.


Requirements

  • General, 320 grain, groove-free
  • Fine textures, 400 grain, groove-free
  • Completely remove spark eroded residues, milling marks, etc.
  • Split lines must be aligned and free of burrs
  • Design and light edges must be maintained
  • Provide a test area sized 50x50 ready for graining outside the split plane

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.


 

Can textures be welded?

Hardened edge
Porous
Edge

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 same structure 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.


Welding requirements:

  • Sufficient preliminary work (including sanding cracks in U-shaped moulds, etc.)
  • Correct choice of welding electrode
  • Suitable heat treatment to avoid increased hardness and stress cracks
  • Damages caused by incorrect handling of
  • See also: page 38 of the technical catalogue of Eschmann Stahl GmbH

ATTENTION! Deviations in the gloss level and grain depth on the finished product cannot be excluded even if welding is carried out by professionals!


 

What should be taken into consideration
for draft angles?

The minimum draft angles for the ejection of the full grain depth are indicated for each structure.

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 design and contour (e.g. cooling, sprue, sliders, etc.) and production parameters in injection moulding operations can influence this value. For example, in areas with expected core shrinkage, three times the standard conicity value 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:

  • the minimum draft angle for the structure (according to information provided by the graining company)
  • material-related aspects (e.g. for PC-ABS, ABS, PP-compounds, etc.)
  • tool-related aspects (e.g. core shrinkage, wall thickness changes, gas channels, etc.)

A reduction in the grain depth is possible and must be agreed in individual cases with the end user!


 

What is meant by scuffing?

Scuffing is a deformation 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 thickness changes, 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 impression.

Note:
The occurrence of scuffing cannot generally be excluded, even with adequate draft angles as well as reduced grain depth!


 

What does “texturing over tool split” mean?

Free-form areas on the sliders and/or insert split lines 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:

  • Partitions must be aligned and free of burr before etching.
  • Inserts/sliders must be aligned when fixed on the cavity (installation aids are to be provided by the customer or the (slider) in build, e.g. with large tools, is to be supported by a tool maker).
  • All graining areas remain visible and accessible even when fixing loose parts.
  • Sharp-edge partitions ("cutter edges/top") are avoided to prevent damage caused by the removal of material during etching, otherwise this will affect the running time.

The position and distribution of partitions should generally be agreed with the end user.

If loose parts are not suitable for graining in the assembly (e.g. due to restricted access, tendency towards burring, etc.), free-form areas can be agreed.

ATTENTION! Free-form areas 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 where necessary.


 

What happens with shut off areas?

Mechanically scribed line (CNC)

Tool with scribed line
Up to 1 mm around the witness: protection of the shut-off area with acid-resistant paint
Undercut: etched tool with an optional shut off area

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 machine or 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 / free-form areas must be dealt with by the customer depending on the position and draft angles to prevent the grain shearing off when ejecting the item.

Examples of poorly scribed lines

Shut-off completely over-grained – reposition AS/slider
Shut off area over-grained and burring
Scribed line based on a pattern: free-form areas uneven
Free-form area too large

 

What is meant by gloss level?

*) Image source: BYK Gardner

"Gloss is a visual perception that occurs when viewing surfaces. The perception of glossiness 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: 

  • Surface roughness
  • Plastic reproduction accuracy
  • Tool wall temperature
  • Plastic and processing parameters
  • Wall thicknesses
  • Measuring angle (medium/matt gloss at 60° - 85° angle of reflection)
  • Thermal conductivity of the steel used, etc.

The gloss level can be measured reliably on flat surfaces.
A specific gloss level for the item cannot be guaranteed. 

 


 

How do tools need to be delivered?

Questions and answers relating to laser technology

Which materials are suitable for lasering?

In general, lasering suits all materials that are also recommended for conventional chemical etching. Aluminium is also good for lasering.
All other non-ferrous metals on request.

Suitable materials include:

Code nameMaterial no.Eschmann name
40 CrMnNiMo 8-6-41.2738 ESTES Aktuell 1000
---Special alloyES Aktuell 1200 *)
Standard for master pattern
40 CrMnMo 71.2311 ESTES Aktuell
---Special alloyES Multiform SL
X37 CrMoV 5-11.2343 ESU *)
limited
ES Maximum 500
---Special alloy *)
limited
ES Primus SL

  • Special consideration of the material's suitability for graining must particularly be taken into account when combining laser technology and conventional chemical etching, e.g. with heavily directionally orientated graining or the like.

The same requirements apply here as for classic graining produced in an etching process.

*) see “What is meant by gloss level?”


 

Which data must be available?

Laser technology is a purely digital process chain. In addition to the graphical information greyscale) of the respective structure, the tool data is also used as a basis for the processing. This must be provided in a .stp or .iges format and correspond to the final set of tool data. We need the data solely for the contour area to be processed, i.e. without base plates, mould frames and assemblies or the like.

The graining direction (e.g. through the crosshair or the like) and also the graining limits should be clearly defined in the data, particularly with directionally orientated textures.

An exchange of data is possible via the download portal of the Eschmann Textures Group or via the data exchange platforms of the respective customers.

The data should be made available to the processing location at least 3 weeks prior to delivery of the tool.

 


 

Are special polishes required?

Areas to be provided with a lasered structure must have a certain surface quality (polish) depending on the design.

Requirements

  • General, 320 grain, groove-free
  • Fine textures, 400 grain, groove-free
  • Completely remove spark eroded residues, milling marks, etc.
  • Split lines must be aligned and free of burrs
  • Design and light edges must be maintained

A test area sized 50x50 mm outside the split plane is recommended – as with conventional etching technology.

Lasering and high gloss! Excellent matt-gloss effects can be produced in combination with highly polished surfaces, particularly when using suitable
tool steels and plastics.


 

How are loose parts lasered?

Generally loose parts in the main visual area, such as sliders or inserts, should be lasered in the assembly with the main mould (cavity). Loose parts must be produced from the same base material.

If loose parts cannot be lasered in the assembly, e.g.in an undercut situation or if there is restricted access to the (slider) in build, a reference point system for the tool needs to be agreed with the toolmaker, which ensures perfect laser control for separate processing. Fitting holes outside the graining area, for example, which define the precise position in the X/Y/Z direction for the laser process, suffice in this respect.


 

What is meant by gloss level?

*) Bildquelle: BYK Gardner

"Gloss is a visual perception that occurs when viewing surfaces. The perception of glossiness 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: 

  • Surface roughness
  • Plastic reproduction accuracy
  • Tool wall temperature
  • Plastic and processing parameters
  • Wall thicknesses
  • Measuring angle (medium/matt gloss at 60° - 85° angle of reflection)
  • Thermal conductivity of the steel used, etc.

The gloss level can be measured reliably on flat surfaces.
A specific gloss level for the item cannot be guaranteed.

 


 

How do tools need to be delivered?