December 12, 2014 admin

Get the polish level you need

Getting to the desired surface quality takes time patience and know how.

It should be noted that the surface finish of the end product is
not only determined by the tool steel and the applied surface preparation
process, but also the application process itself has a big impact on the
result. Polymers have different material characteristics at plastic moulding
and this will definitely influence the final surface finish

surface-quality

Steel Choice
To produce highly reflective and glossy surfaces ESR-remelted or PM
steels are to be used. However, conventional ingot cast steels can
give a very good surface finish, if both steel manufacturing and
polishing are performed according to a good practice.
Analyses of different micro structures and
steel manufacturing processes clearly prove that the amount
of carbides and non-metallic inclusions have a decisive effect
on the quality of the polished surface.
Therefore steel should only be sourced from sources that are known to take this in to consideration.

Total number of particles per mm2
(oxides + sulphides + carbides + nitrides)
particles-in-steel

Conventional ingot casting (IC) (Conventional),
Continuous casting (CC) (Conventional),
Electro slag remelting (ESR), and
Powder metallurgy (PM)

The oxides quantity does not vary much between the 4 production methods however the carbides and sulphides are more common in IC and CC (the oxide size is normally smaller in ESR and PM).
This is what makes the ESR and PM steels more suitable for mirror finish polishing.

We can strongly recommend these 2 steels as good value high polish-ability steels:
DAIDO NAK80 – Ni-Cu-Al – ESR Steel – (37 – 43HRC)
DAIDO S-Star – SUS420J2 Modified – ESR Steel – (53HRC)

Polishing Technique
At The Tool Hub we recommend to use an 11 or 12 step polishing method to minimize surface defects.

STEP TECHNIQUE TYPE OF TOOL LUBRICATION
1 Hand-held unit Stone 320 Dielectric oil
2 Hand-held unit Stone 400 Dielectric oil
3 Hand-held unit Stone 600 Dielectric oil
4 Hand-held unit Paper 400 Dry
5 Hand-held unit Paper 600 Dry
6 Hand-held unit Paper 800 Dielectric oil
7 Hand-held unit (linear) Brass 5 x 5 mm DP 9 µm Dielectric oil
8 Hand-held unit (linear) Wood 5 x 5 mm DP 9 µm Dielectric oil
9 Hand-held unit (linear) Wood 5 x 5 mm DP 6 µm Polishing oil
10 Hand-held unit (rotational) Hard felt 10 mm DP 3 µm Polishing oil
11 Hand-held unit Piece of cotton wool DP 1 µm Polishing oil

Example of possible steps
polishing-steps

Abrasives
Selecting the right abrasive is an important factor.
It should be selected based on the type of material to polish, the required finish, and lastly on the current polishing step.

Today, the following main groups
of abrasives are normally used:
1. Diamond designation
2. Aluminium oxide designation
3. Silicon carbide designation
4. Boron carbide designation
5. Cubic boron nitride designation

ABRASIVE HARDNESS KNOOP
Diamond 7 000
Aluminium oxide 2 100
Silicon carbide 2 500
Boron carbide 2 900
CBN 4 700

At The Tool Hub we recommend using Diamond or Aluminium Oxide in most cases

A comprehensive guide on polish defects has been released by Assab Uddeholm.
It can be downloaded here:
Download

Feedback
Please contact us and tell us how we can support.

Email: info@thetoolhub.com
Phone UK: +44 1865 922 550
Phone SE: +46 31 30 88 200

We are always happy to hear from you!