How to success in lost foam casting is a topic concerned with most of the lost foam casting foundries. Today, let me listen to our expert from Castchem Inc to study her experience in LFC process

1. The key to success in the lost foam casting
Author: Han Xiaohong, Deputy GM/one of the inventors of STMMA at Castchem
Translator: Wu Jong, Sales manager at Castchem Inc
With the development of lost foam casting, customers are also requiring higher product quality.
To the LFC companies, it is still the important work to improve the quality and qualified rate in
production, and of course reducing the production cost at the same time. Bad quality in white
side = Bad quality in black side, this is an equation acknowledged by all lost foam foundries.
The pattern making in the white side is an important factor restricting the benign development
of lost foam casting.
When I went to LFC foundries in China, I was always asked that what the most important thing
should be in the lost foam casting. In my opinion, the one thing is how to work out the qualified
foam-pattern, then the another is how to burn out foam-pattern quickly and completely. In that
case, we will see how an important role the pattern acted in the lost foam casting.
Then a question is arisen, how to produce qualified foam-patterns voluminously and steadily?
During the process of pattern making, including the raw material,equipments,moulds and
quality of water vapor, process control and human factor, all of these will be involved:
1.Quality raw material is the precondition for the production of quality products
2.Good equipment and mould makes the good product
3.Saturated and slightly-overheated vapour with low pressure and high flow is the ideal source
of energy
4.Effective process control is the guarantee of product stability
5.Achieve the effective control of human factor is an effective guarantee for the sustainable
production.
Foam-pattern raw materials:
Across the world, it could be separated into two sections of the pattern raw material. Section A:
EPS in China mainland, and specialized EPS for aluminum alloy in Taiwan and other countries.
Section B: Co-polymer including STMMA from Castchem China and CL300-CL600 from JSP
Japan.
All of the Chinese LFC foundries are using the expandable polystyrene(EPS) or STMMA for
pattern making. Something needs to clarify, there is no specialized EPS for lost foam casting in
China. The EPS used by Chinese foundries are mainly from the polystyrene for application of
packing and building. The source of these polystyrene raw materials are very complicated.
Most of them are containing the other materials such as fire retardant because of the flame
resistance requirement for packing and building, using this kind of EPS to make pattern results
in more defects in casting and will increase the industrial costs.
In other countries beyond China, lost foam casting foundries are used to choose the

2. specialized EPS for non-ferrous metals and co-polymer for ferrous metals. That is why the lost
foam casting in Europe, American and Japan is much better than in China.
Compare with the EPS, what is the advantage of STMMA?
1. Casting with less or eliminated carbon defect, EPS contains 92% of carbon structure while
STMMA contains 60%.
2. The pouring temperature for foam-pattern made of STMMA is about 50℃ less than EPS
pattern.
3. The decomposition of gasification way of STMMA pattern is different with EPS, it makes
less residues.
4. The dimensional stability of STMMA pattern is much better than EPS pattern because of
the molecular weight.
5. You will get quality guarantee from us, because we have sold STMMA to 13 countries all
over the world and 600 industries in China such as Lonking Holdings China, Dongfeng
Automobile, Xugong Group Machinery, FAW Group.
6. With completed after-sales service and comprehensive technology, plus 20+ years
experience in producing the raw material for lost foam casting, we will assure you 8% or
more quality increase after using our STMMA instead of using the EPS. This is proved by
our 600 of users in China, additionally with production cost reduction.
Equipments and moulds:
As same as the packing and building EPS block/mould making, the lost foam casting process
foams the pattern with white side equipments too. But they are completely different in the
technical system, the lost foam casting has many technical requirements in foaming the
pattern. So, please change your mind from packing/building EPS mould foaming if you want to
do the best in lost foam.
As a lost foam casting foundry, make sure your white side equipments are bought from
professional equipment supplier. A professional equipment supplier will not only sell you the
equipments, but also sell you whole lost foam system and comprehensive technology.
As a friendly advice to lost foam foundries, don’t bring your moulding program into ’mould
follow shape, technology undefined, repeatedly modify, finally do it again’ in order to save a
few thousand dollars. A good moulding program shall follow the rule of ‘ technology is the
biggest thing, technology decides the moulding, moulding serves technology, technologize
sprue’.
The source of ideal power - vapour
We mentioned saturated and slightly-overheated, low and steady pressure but high flow as the
necessary status of vapour during expanding the raw material beads and foaming the pattern.
Why do we need this kind of status?

3. 1. The effect of saturated and slightly-overheated vapour is to reduce the moisture content in
the vapor and improve the utilization of thermal (moist vapor: 1500KJ-360%, saturated
vapor: 2675KJ-650%, overheated vapor: 2762KJ-670%).
2. The effect of steady pressure vapor is to keep the uniformity during long time expanding of
beads, and keep uniformity of foam-patterns.
The three SAME during the foam-pattern making:
1. The SAME of the raw material beads expanding, the things affect the same of the beads
expanding include (A)The equipment performance,mainly the stand or fall of the stability,
sealing, scraper blade of equipments, air inlet and heat even or not. (B)The moisture
content, saturability and steady pressure of vapor. (C) The proper feeding quantity of raw
material beads and keeping same every time. (D) The parameters set of expander right or
not.
2. The SAME of ageing the raw material beads, the things affect the same of ageing beads
include (A)The dimension of the ageing cabin, we suggest L1.0m*W0.8m*H0.8m movable
cabin. (B) To turn over the expanded beads as far as possible from inside to outside.
(C)Ageing environment: temp≥23℃,moisture≤30%,time≥20hours in keeping ventilation.
(D)Keep the expanded beads in fluidized bed for 5 to 10 minutes.
3. The SAME of the foam-patterns, in comply with same dimension and density. The below
reasons will influence the same of the patterns: (A)The pre-expanding density and density
stairs. (B) The way of filling the raw materials, including material absorbing filling,
compressed air filling, permanent mold lifting filling. (C) The control of foam molding,
including the technique of molding the foam, vapor quality, water cooling etc. (D)To
complete the shrinkage of foam-pattern in storage aging or heat oven.
Technique process control
The technique process control is very important in the lost foam casting.
1. Make a reasonable technique process, it is allowed to have different formulations
according to different products in each of foundry. There is no unified standard of
technique process in order to achieve quality products in lost foam casting.
2. The process should be simple enough to be understood by the workers.
3. Make a permanent mold for the sprue and gating system of the foam-pattern, this will
reduce the difference between manual operations.
4. Carry out the process strictly, do not to revise it frequently .
Castchem Inc, www.china-castchem.com
Zhejiang Castchem New Material Co.,Ltd, www.zj-castchem.com
Enquiry: info@zj-castchem.com
Tel/WhatsApp:+86 15068719527