OF APPLYING ISF TECHNOLOGY ON PVC PLASTIC SHEET TO MANUFACTURING SOME NORMAL PRODUCTS

S: Market demand is always changing over time especially for plastic products. Therefore it is necessary to create sample models in the meaning of single or small-batch production which is expected with short processing time, lower cost and operating simply but also meet the technical requirement. This paper presents a research of applying ISF process on PVC plastic sheet to manufacturing sample models and small-batch products. There is also a comparison of economic efficiency between ISF technology and traditional plastic forming methods. Keyword: Appling ISF technology, ISF process, manufacturing PVC civil products.


INTRODUTION
Polymer is a popular material in social life since the fact that there are many products made from plastic material.Tranditional technology to manufacture polymer products almost follows the three steps: heatingforming -cooling in which polymer material is operated on yield or plastic status.This method is only suitable for mass production because of high cost for energy and equipment.Therefore it is necessary to have some new flexible technologies which not only applies the requirement of economic efficiency but is also suitable for small batch production and rapid prototyping.4/ Finishing: the product is considered to be qualified if its geometry is similar with that of the design model.Therefore it is necessary to check the product dimension when the process has finished.If large difference exists, the design model will be adjusted.

Part features:
-Part is in the industrial-product group.
-There are many contour transitions but it has simple boundary overall.
-High value of slope, little changing in forming area.

Trang 18
Product requirement: -Since being the industrial product, the demand on aesthetic is not strictly.
Surface is not necessary to be in very good quality and so is the accuracy.
-The final product is not damaged or twisted.
-There is not the over-deformities effect at the radius transition contour.
CAD model of the product   There are two steps for this process: -Milling the plastic supporter, fig.7 -Insert PVC sheet between the upper and lower clamping plate.Set z origin again at top surface of PVC sheet.
-Then forming PVC sheet by ISF technology  -There is no damaged surface.
-The geometry of transition contours is clear and not distorted.

Part features
-Part is in the industrial-product group.
-High value of slope, deep and wide forming area.-Shape of the product is clear and not over-deformation

EVALUATING ECONOMIC EFFICIENCY
Evaluation of economic efficiency is to provide an understanding the application of the ISF technology in specific cases.It is consider that if ISF technology can be used in rapid prototyping, single production, small batch or mass production.To answer this question, it is necessary to compare ISF process with another processing -the plastic injection method.
There does not include the cost of investment in machinery, energy, machine rental, profit.-PVC plastic seeds: 30,000 VND -Cycle of product injection: depend on each product, presented in the follow table.

Cost calculation for motorcycle box cover product
Form the demands of dimension and geometry of the part, the table of cost prediction can be calculated (table 1) for two method : Table 1.

Cost calculation for headlight product
Form the demand of dimension and geometry of the part, the table of cost prediction can be calculated (table 3) for two methods: Table .3.Trang 24 Figure14 presents the chart of manufacturing cost per headlight product in comparison between two technologies.If the more products is manufactering, this process does not bring high economic efficiency.

CONCLUSION
For ISF process the original cost is lower because of simple fixture while the other method has higher cost at the first step since high cost for die and it also takes times to manufacturing the die.
ISF technology is suitable only for rapid prototype, single batch prodution, small and medium batch production (below 550 products).In mass production, ISF technology does not have fully economic efficiency in comparison with the other plastic forming method.
ISF Plastic Injection

Fig. 1 .
Fig.1.Fixture and other equipments in ISF process -SPIF type.Market demand is always changing over time especially for plastic products.Therefore it is necessary to create sample models in the meaning of single or small-batch production which is expected with short processing time, lower cost and operating simply but also meet the technical requirement.This paper presents a research of applying ISF process on PVC plastic sheet to manufacturing sample models and small-batch products.There is also a comparison of economic efficiency between ISF technology and traditional plastic forming methods.

Fig. 2 .
Fig.2.CAD model and tool path of ISF process

Fig. 4 .
Fig.4.2D drawing of the box cover product 3D model part made by Inventor software, fig.5.

Fig. 6 .-
Fig.6.CAM model of the cover box Milling the supporter for TPIF process: a) Rough milling -Feed rate f = 1500 mm/min -Step depth ∆z = 2 mm -Cutting tool: End mill tool Ø16 -Spindle speed n =1000 rpm b) Finish Milling -Feed rate f = 1500 mm/min -Step depth ∆z = 0.3 mm -Cutting tool : finish end mill tool Ø6 -Spindle speed n =1000 rpm Product forming This model has the forming angle α from 44 o to 56 o .With the dimension shown on 2D drawing and base on the result of experiment research on maximum forming angle, these parameters of TPIF process on PVC plastic sheet is set as follow: -Feed rate f = 2500 mm/min -Tool step depth ∆z = 1.2 mm -Forming tool: tool with spheral tip, diameter d = 6 -Spindle speed: n = 1000 rpm

Fig. 7 .
Fig.7.Plastic supporter is milled on CNC machine Product review: Motorcycle cover box product after finishing the TPIF process, fig.8.

Fig. 9 .
Fig.9.2D model of the headlight -3D model of the headlight is created on Inventor software, fig.10.

Fig. 10 .
Fig.10.3D model of the headlight CAM model: is used for simulating the toothpath of headlight part on ProEngineer software, Fig.11.

Fig. 11 .- 21 Fig. 12 .
Fig.11.CAM model of the headlight On this product, there is only one step to deform the sheet blank by SPIF process using simple SPIF fixture.Headlight model has the maximum forming angle α max is about 60 degrees and has sheet: 30,000 VND -Forming time: depended on each product, presented in the follow table.

-
depends on each product.

Fig. 13 .
Fig.13.Chart of manufacturing cost in comparison between ISF and plastic injection method

Fig. 14 .
Fig.14.Chart of manufacturing cost of headlight product in comparison between ISF and plastic injection method Observing the cost curve in comparison between ISF technology and plastic injection method, we can find that the two curves intersect at around 550 products.This shows that the application of the ISF process is effective in cases processing under 550 products.If the more products is

Table . 4
Table of cost prediction for one headlight product .Table of cost per headlight product when processing with many products