Axis Of Rotation Box In Lost Foam Casting Process Design

Abstract: This thesis discuss the 300—axis of rotation in the lost foam casting process. When the box of thin wall adopts the lost foam casting to production, the model should obey a principle of “vertical superior to horizontal”, the set of inner gate should obey “give priority to top gating, multi-point to cut.” The density of foam model is better to keep low, the pour temperature better to high.

Key words: Lost Foam, thin wall box, give priority to top gating, multi-point cut

1. The technical parameters of axis of rotation box

Geometric dimensioning: 700mm×320mm×320mm

Material quality: HT250

Monomer weight: 78kg

Wall thickness: 7mm

2. Technology characteristics 

The axis of rotation box is featured with thin wall, porous, no tiepiece, deform easily. The inner quality requirements of casting are serious, and the pressure test are required to prevent the phenomenon of oil spilling after combination. The requirements for multi-axis coordination are also strict with physical dimension.

3. The technical design principle of LFC.

3.1 The foam model craftsmanship

1) The axis of rotation box belongs to iron casting, which adopt EPS to make foam model.

2) Transmission case: Length: 700mm, wall thickness7mm, belong to long thin wall parts. To assure the strength and preferable surface roughness of foam piece, it’s better to adopt small beads with a certain density.

3.2 The placing of model

Lost foam casting foam models placed in the sand box position to follow the "can not stand lying" principle. But there are workpiece with length of 700mm, wall and thin, if you want placed upright in the sand filling and vibration compaction process prone to distortion and overall sidewall deformation. So with box placed upward Celi way. Easy to operate only sand, sand thickness is small (tension is small), the possibility of occurrence of deformation model is also relatively small.

3.3 Inner sprue pitching-in position

Axis of rotation is thin wall casting. The design principle of thin wall castings’ inner sprue is based the three theories of “give priority to top gating, multi-point to cut, heat balance”. Top pour in multi-sprue is determined. 

3.4 Pour temperature 

As thin wall and high density of model, the pour temperature should be above the normal temperature.

4. LFC casting technology process for Axis of rotation  

4.1 The production of foam model

4.1.1 Luo Yang Liu Shi mould provides aluminium alloy mould. One machine with two-mode piece constitutes one piece of axis of rotation mould.

4.1.2 Pre-foaming 

Bead pre-foaming adopts "Ji Ning lost foam" provide semi-automatic positive pressure intermittent pretest machine. Use the dragon king card P4S expandable polystyrene beads, pretest probability density: 21 g/L, ripening time 10 hours.

4.1.3 Molding

Hydraulic semi-automatic molding machine, steam pipe pressure 4.5Kg/cm, air pressure 7.0Kg/cm, cooling water temperature 35 ℃, mold clamping gap 2mm, PLC program control.

4.1.4 Bonding model

Foam piece after 12 hours of drying at room temperature into the drying room drying 36 hours, using cold glue adhesive, die gap between rough papered with a thin paste Yan Ping. In order to prevent deformation of the model to operate on a glass plate bonded to the flat, the adhesive on the glass after drying continues.

4.2 Pour system technical parameters

4.2.1 Top pour

Double wall at the top were set four ingates, ingates sectional area 70mm × 30mm, the gate cross-sectional area 70mm × 6mm, excessive slope, in order to facilitate removal, leaving no residual roots. The two inner gates are connected  through the "工" shaped horizontal pouring gates.

4.2.2 Set up buffer packet (energy storage packet) under the junction of horizontal pour gate and vertical pour gate (see photo1)

                  Photo1

4.2.3 The chamber of the drive shaft and septa without stretching, casting cooling process does not shrink tension cabinet catchy, catchy size to prevent shrinkage is not in place, will advance with a wooden craft catchy fixed after pulling to the rated dimensions, taking anti-deformation measures (see photo 2).

                           Photo2

4.3 Coating  

4.3.1 Suizhou Hongsheng Industry and Trade production cast iron water-based paint, the amount of water added to the neutral high-speed stirring two hours after use. Coating two times, coating thickness 0.8~0mm.  

4.3.2 Foam models brushing paint thoroughly before drying, the drying process drying curve to be drawn.

4.3.3 Oven temperature: temperature 45 ℃, fan stir, bake mold clamp timing rotational direction to prevent the model deformation.

4.4 Sand filling and bury the models 

4.4.1 Bilateral air chamber vacuum suction and angular sand box.

4.4.2 30 ~ 50 # paddock natural sand, sphere, after removal of the phase transition 870 ℃ water of crystallization.

4.4.3 Bottom sand thickness 150mm, Calibrating real shock after placing foam models (photo 4), each containing 3 (photo 5), first with a bag of sand Fixed foam model (photo 6). Add sand to level model catchy conducted after the first shock tight, tight manner and timing of the PLC control (photo 7).

4.4.4 To prevent the casting process, the iron cup water damage, can be used as protective resin sand (photos 10-14)

4.5 Pouring molten iron

4.5.1 Teapot ladle, drying, packing, to dark red (about 800 ℃).

4.5.2 Hot metal tapping temperature, 1530 ℃, rapid slag, the slag agent covered with polyethylene polyethylene slag and insulation of hot metal surfaces.

4.5.3 First box pouring temperature> 1480 ℃, pouring temperature not lower than last packet 1420 ℃. At the same time, casting a variety of castings, first pouring thin-walled parts, after pouring thick pieces; casting with the same cast, the first pieces of heavy weight pouring model, the model after pouring lightweight pieces (photo 15).

4.5.4 Vacuum 0.06mpa.

4.6 The box clean

After pouring time of 5 minutes to maintain the negative pressure, for 4 hours, after unpacking the pieces (photos 16-19).

5. Discussion

5.1

Case Casting Lost Foam Casting should be adopted, not only do core making, the next core, co-boxes and other areas to reduce many processes, but also fundamentally overcome the partial core, floating core cause uneven thickness defects, especially thin-walled , will lead to uneven thickness leakage occurs, serious consequences.

5.2

Lost foam casting process described is simple, but in practice management must pay attention to the details of any one part of the small oversights can lead to rejection occurred. LFC waste occurs, for reasons beyond the craft, often lax in management.

About the author

Shenzhen Zong (1986) Yanshan University after graduation has been in the solid An Jining Foundry Equipment Co., lost foam production process for the study, participated in Han China Yan and other projects, is now solid An Jining Foundry Equipment Company Limited. Tel: 18631619137.

Reference

LFC gating system design and defect analysis, internal data, Liu Lizhong.