Unformatted text preview: Dt :0 ar . ie= 2 1 5 Solutions to Injection Mold Homework 1a. Width and height of the trapezoidal cross-section of tertiary runner: Total runner length from sprue to gate is 9.25in. From table on page 17 of handout, the effective diameter for high density polyethylene with runner length of 9.25 equals 0.125in. h= 7 e . t 0 r 1 aa i r : 2Dt tr s () = 0 Di e e (+ ) wt :: = ( ) i 1 ht e = n c o s r 2 1 0 8 e r c o s () 2 Dp . nDd it s= = Dd at 1 i o io a w n0 . 2 wu 0 i: + a m s t r e a m n s t r e a m re3 n er 5 a w a= 2 e i e i : = Dt D a . i a 2 nDs : t +n0 De =r r a . ic 0 1 5 7 s c e
1b. WidthD i and the trapezoidal cross-section of secondary runner: a s height of e c s () For : ( n ws upstream runner with n branches: = + ) 1 i e c 2 c o s () n i e 1 s . c 5 n :h 2 0 == e s c Dp : s +n0 a r = Ds i i De i e i c ac . a 2 Dp i ai 0 ir n w == 0. 24 .2 5 15 De a i c s Since two hs : branchesooff( )secondary runner: of c s e = 2 c n i D r i i a p height hp1c. Width and of the trapezoidal cross of primary runner. : = ( ) c o s i r 2
Since two branches off of primary runner: h 0 1 i 2 r . p= n i Solutions Con't 1d. Gate dimensions: Determined by part thickness Depth - Width - Land lgate~ 0.5*dgate 1e. Vent dimensions and spacing: From table on page 21 of handout drunnervent= 0.002in and drunnercavity=0.001in Spacing of runner vents: Spacing cavities :=0.2*[2* pi* r + 2*(6-2*r)] Spacing cavities :=2.97in 2. Clamping Force: From page 27of handout: t: 0 =. 5 i8 p a r wr 0 0.215) + 8 (1 0.153) =D .5 .301 + 4 (4 i + ) ( in wp : 1 s () r Wr=7.214 in2 i =2 c o s () Amc=Area of cavity projected onto parting surface/plane n i Amc = r 2 + (6 - 2r ) (2 r )
mc 2 =13.67in F = 0.75 P1 7.214 8 + 0.5 P1 7.792
F=7.56 x10 lbs 3. If the parting surface/plane is oriented in the vertical as shown on page 1, the polymer will enter the mold and start filling the cavity from the lowest point. As the polymer fills the mold air will be pushed toward the top of the cavity. If a vent is not in this location air will be trapped here. Two solutions to this would be make sure a vent is located there and/or make the surface of the parting surface/plane rough enough to allow air to escape through the parting surface. The drawback of just using venting through the parting surface is the cycle time will have to be increased to allow the air to escape through the parting surface/plane. A "better" location for the gate would be the center of the flat surface on the part.
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- Spring '08
- Cycle Time, Trigraph, runner, trapezoidal cross-section, Total runner length, secondary runner