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Unformatted text preview: ME 419 - Fundamentals of Injection Molding Spring 2004, Assignment #5
Due Monday, April 5 2004, in class Please use regular letter-size (8.5x11) paper Problem 1
This homework assignment is intended to help you understand the factors and procedures involved in estimating the part cost. During the process development stage, part cost
estimate is important in evaluating the process economics and proﬁts. It is also used for
bidding the request for quote (RFQ) from your potential customers. In general, part cost ($/part) consists of (1) material cost, (2) mold cost, (3) processing
cost (machine rate), and (4) post-molding cost (e.g., secondary operations, packaging,
shipping, overhead, etc.). In addition, you want to add proﬁt margin before you send the
quote to your potential customers. ' Suppose today you are an injection molder and you are going to mold the housing of a
cell phone. The following is the information either you received from your potential
customers or you already know based on your own experiences or estimate. Information about material cost (based on the part and mold designs)
Part volume: 6.2 cm3 /part
Sprue/Runner volume: 3.6 cm3 / shot (note that it is not per part)
Scrap/reject rate: 2% (i.’e., you reject 2 bad parts out of every 100 parts)
No regrind allowed (i.e., you cannot recycle the plastic from sprues and runners)
Targeted product production: 150,000 parts
Density of resin: 1.32 g/ cm3
Material cost: $4.8/kg (purchased from resin supplier) Information about mold cost:
Mold cost: $25,000 (for this batch of production only)
Mold maintenance: $120/ 12,500 molding cycles Information about machine rate
Cycle time: 12 seconds
Cavities per mold: 2 (Le, you mold two parts per molding cycle)
Machine rate per hour: $48.00/hr
Set up cost: $200/per 7,500 molding cycles (to mount the mold, to set up the
processing conditions, try-out,,etc.)
Downtime: 2% (i.e., for every 100 hour operation, the machine is idled for 2
hours for maintenance or troubleshooting) Information about post-molding cost:
Packaging: $60/1,000 parts
Shipping: $20/ 1,000 parts
Overhead: $100/1,000 parts Please calculate the followings: SP‘P‘PP’NE‘ 9° Problem 2 Total material required Material cost per part Mold cost per part Processing cost (machine rate) per part, and Post-molding cost per part Total part cost ($/part) Cost breakdown (i.e., % material cost, % mold cost, % processing, % post-
molding cost) If your proﬁt margin is 10%, how much will you quote for a total production
of 150,000 parts? In this homework assignment, you are going to determine the number of cavities in the
mold based on the following information: 0. Machine speciﬁcation (see attached, use information under injection unit “A”
column. Namely, the Inj. Capacity, Max GPPS is 8.90 oz. or 252 grams)
Machine plasticating capacity: 300' gm/minute The available production time is 40 working days (3 -shift 24 hour per day)
The required production volume is 150,000 parts The rejection rate is 5 %, machine down time 2% Cycle time: 60 seconds, part weight (including runner & sprue per part): 52
grams Material: general purpose PS (GPPS) Estimated max. injection/packing pressure: 40 MPa (i.e., 4x107 N/mz) Part projection area (including runner & sprue per part): 100 cm2 Unit conversion factors: 1 ton (metric) = 9810 N Please determine the number of cavities based on the criteria of (1) production quantity,
(2) machine shot capacity, (3) machine plasticating capacity, and (4) clamp force, and
suggest the most appropriate number of cavities. " _ g: No. of Pyrameters . - VI '3 :IEiectorStrake . '
s .. ._I.Mu;_gEiector‘Forc_e‘f-’ ' 5 .Width .' t, ﬂUEUEIIUTz' j INJECTION Umf “sf ciﬁandust lni. (opacity, Max GPPS
- Max. Ini. Press. Note 1
Max.. Innate-Note l5 .
Max. Pack Press
Max. Ini, Press; Hates 1,2 '
- laikatetiotes 1,2 .
Max. Pack Press Notes 1,2
Screw Strolre " ‘ ‘
Screw Dia. . 3
Screw L/D Ratio
Screw Speed, Max.
Screw Speed; Max. Note 2
Nozzle Touch Force
Barrel Heat Control 2 :(Barrel/Noz'zle)
Total Heat Capacity CLAMP SPECIFICATIONS . Tonnage
MEX/Min Mold Height
Mair (lamp Stroke
“Dry: Cycle limeNote 3 ‘
» _‘ Platen: Size“ ‘ '
TreBar Spacing lie ltoclE Diameter . iii Dimensions Overall ‘ " Er: Length ’
‘ Length (note 4) "Height ' ,
Power MEI-chine. ' ' ‘
Z'Suppty; External Outlets ». _
Main Breaker Size
water It , ' mars
Feeclthroat Only _ Mecume.IS.PEcI:F!cAII6us, English A B C D E E Metric A B C D
“10.59" 14.69 mm m 7 634
“IE i943 26-95 , 57-61 313-5 , V .
mmm 47.1 mm 425 74%?
mm 311334" 21596421752 17,064 m 537371177 ‘
m 22-27 26-50 "31-19 '
m 34.128" 28.440 255%" '? WA M/A ' " 6-93‘ 6-93 WWW 203 260-160 ~
, n 1-39 s 113 mmmn
-mm_ -‘ 1- ‘ ‘i ' W m
Iii-mm er -
—lnzlmmmml 23-5 - English n“
n ' n
' a 3.30 _ tent English Metric
m—ra—mal w "—r .V .,73.4 m
“In. ' —— .
— 200 VAC or 220 VAC +/-w% 3Ph 50Hz or 60H: - r
m . .- 35.0 , 350 ‘Note2,4_ , _—
. Connect 3/ 8" Hose Barb HDTES: t) Limitations may apply in certain conditions '2) High Speed/High Pressure Option. Other combinations Psi/ Rates are possible. 3) Hall stroke w/o eject 4) Large capacity barrel E, F 27 ...
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- Spring '04
- Moldmaker, Injection molding, Cycle Time, Max GPPS, mold cost