Injection molding machine procurement project is not a small investment projects;Buying too big an injection molding machine is wasteful, but buying too small is not appropriate.Therefore, choosing an injection molding machine that meets the needs of its own products has become the most concerned content of every buyer.Small make up the integration of multiple information, edit a relatively simple and practical matters needing attention to choose and buy, hope to give plastic injection processing plant customers and friends a little good advice and help!
One, according to the injection molding machine specifications
According to the weight of injection products in each region, the injection volume of injection molding machine should be calculated
1) When the injection molding product is made of polystyrene (PS), the injection molding machine shall have the injection volume of Wps:
Wps = (product weight + total gate system) ÷ (0.75 ~ 0.9)
That is, Wps = (1.3 ~ 1.1)× (product weight + total gate system weight)
2) If the product is other plastics (named as X plastics), following the above method, calculate the theoretical injection volume of such plastics as Wx:
Wx = (1.3 ~ 1.1) × (product weight + total gate system weight)
However, Wx cannot be simply used to determine the injection volume of the injection molding machine. Wps value must be changed. The conversion formula is as follows:
The Wps = Wx present p
Where P is the specific gravity of the plastic
3) Another relatively simple method is to determine whether the jet weight meets the following requirements:
W = 0.75 ~ 0.8 * Wmax * P
W: The maximum weight of the actual molded product (including the weight of the glue mouth)
Wmax: Maximum PS injection weight of model screw
P: The proportion of raw materials
As long as the product gram weight is less than the calculated W, that's ok.Taking HMD128M6-B screw molding PP material as an example, the maximum injection weight of PS theory is 239g, namely Wmax = 239.
PP material density is 0.9, that is, P = 0.9.
W = 0.75*239*0.9 = 161(g)
That is, as long as the product weight is less than 161g of PP material products 128M6B screw can meet the requirements.
2. Calculate the clamping force P according to the vertical projection area of the injection product on the template (head plate or two plates)
Mode-locking force = mode-locking force constant × projected area of product
So P is Kp times s
Type in the
P-clamping force (T)
S- Vertical projection area of the product on the template (Cm2)
Kp- modulus locking force constant (T /cm2),Kp values listed in the following table (Table 1)
Kp (For injection moulding of more precise products)
3. Determine the internal spacing size of the tie rod (guide column) of the injection molding machine based on the outer contour size of the mold;The latter is greater than the former.
4. The mold opening stroke of the injection molding machine is determined by the product height;The latter should be more than twice the former.
5. Other minor factors
1) The volumetric modulus of the non-molding machine should be appropriate to the height of your mold;
2) Thimble stroke, top output;
3) Process factors.
Two, according to injection screw selection
Standard screw selection
General injection molding machine has A.B.C three - gear screw, part has four - gear.The same type A screw injection pressure is the largest, generally can reach 190~210MPA or so, gram weight is the smallest.C screw injection pressure is the minimum, generally around 120~130MPA, gram weight is the maximum.B type or C type is generally chosen.Only in the production of raw materials PE,PP,ABS products thick case, can be considered to use C screw.
A screw must be selected for the following products:
The wall thickness is below 1mm.PC,ABS, nylon, steel and other engineering plastics, products complex, high precision.Some products require side gelling due to design and are over 80 times longer (the length of the gelling point to the end of the product and the thickness of the product).
2. Special screw selection
1) PC special stainless steel or electroplating screw, some models can choose standard A screw plating.
PC screw, thread gradient small, high injection pressure
2) SPVC, UPVC granular material
SPVC headless electroplating screw and UPVC headless electroplating screw are selected. In addition, for products with high requirements, a strong air cooling device should be installed on the material barrel.
3)PA6,PA66 without glass fiber
Nylon special screw, part of the nylon material can be used standard screw, but the cutting speed is not as fast as the special screw.
4) PA6, PA66 and glass fiber
Under 15%, it can be considered that ordinary double alloy screw with ordinary barrel, 15%-30% special double alloy screw with double alloy barrel, 30%-50% special full hard double alloy screw with full hard double alloy barrel.
Double alloy screw
5)PC color mixing and partial thin-wall PP color mixing
Special color mixing screw, more than 268 models equipped with color mixing mixing head
6) Small gram heavy transparent PC products
Small gram weight transparent PC product is to point to gram weight is less than standard A screw shoot glue gram weight 20%.It is suggested to select special small screw and shorten the length to diameter ratio of screw to 20-22:1 at the same time.Prevent PC material yellow, dark, insufficient whiteness.