Melt cushion quizz

[down2die]

Hi there im new on here, some good info around. currently training in injection molding at moment and have a quizz with our course that I thought was good for anyone learning, it helped me. give it your best shot, answer away


A process is set up correctly. The melt cushion is 4mm. Some changes are to be made, in each case the process is reset to the start point before the next change is made. What will happen the melt cushion (guess what the new cushion will be in mm) if:

1. Shot size changed from 21 to 22mm
2. Injection Speed ...25 to 50mm/sec
3. Switchover... 10-11mm
4. RPM speed ...150-250RPM
5. Back Pressure ...5-10 bar
6. Decompression distance ...4-8mm
7. Injection Pressure ... 115 to 135 Bar
8. Injection Time ...3 to 5 sec.
9. Holding Time ...4-6 sec
10. Holding Pressure ...20-30 bar

[Suhas]

Interesting! I think this will be good for those who are just getting into molding. - We have a few out here right?
I think the people with more than 5 years should stay away :)

[down2die]

Everyone's welcome to answer, lets see peoples knowledge and perhaps their will be disagreements. the newbies haven't answered yet. I myself being one :o

[nemanja]

Hi,

is good question, and i will try to answer.
1. same 4mm
2. same 4mm
3. higher for around 1mm
4. lower
5. same 4mm
6. same 4mm
7. lower
8. lower
9. lower
10. lower

I use to work with cm3 but i can imagine is more less same with mm.
If you have answers, i would like to know where i make mistakes. ;)
And do you have more of this quizzes??? :D

best regards,
Nemanja.

[down2die]

Good attempt, ill reveal the correct answers when we have 5 or more attempts. ive a few more up my sleeve too.

[brentb]

Final cushion will be 4.145253967821mm

KOM
brent

[Suhas]

Captain Brent! (like Senor Capitan of the Mexican team),
Sorry, but you must check your calculations!! There is an error, and I did not expect this from you!! You are off by at least 0.00005 mm!!
Mr. Down2Die,
We do not have much junior members here and so you may not get 5 replies. I thank you for your contribution but please go ahead and post the answer (with reasons if possible) in about 2-3 days.
Thanks for being a part of the forum. Please keep posting. We all have been good friends here and make fun of each other. So don't take us seriously. We all want everyone to learn.
Regards,
Suhas

[Jendalf]

hi,

if the process is set up correctly according to yours datas.
You´ll get the unstable process by new setting. The product will be overflown bc you rise shot size and holding time and preassure.
And even if you rise the switchover also the change in 1mm isn´t enough to get the same correct set up like you´ve had at old settings.

anyway 2. 4. 5. 7. 8. will not affect the final cushion.
if you suck back only air and the melt plastics will not push the new batch out of screw after suck back the 6. hasn´t also affection on the final cushion.

all what left is the equivalent change in shot size ans switchover but holding conditions are 1/2 higher

it means that finall cushion is around 3mm.
:)

[brentb]

Error de dedo or typo in English!

KOM
brent

[pjhall]

Cushion will be:

3.141592653589793238462643383279502884197169399375 105820974944592307816406286 20899862803482534211706798214808651328230664709384 4609550582231725359408128481 11745028410270193852110555964462294895493038196442 8810975665933446128475648233 78678316527120190914564856692346034861045432664821 3393607260249141273724587006 60631558817488152092096282925409171536436789259036 0011330530548820466521384146 95194151160943305727036575959195309218611738193261 1793105118548074462379962749 56735188575272489122793818301194912983367336244065 6643086021394946395224737190 70217986094370277053921717629317675238467481846766 9405132000568127145263560827 78577134275778960917363717872146844090122495343014 6549585371050792279689258923 54201995611212902196086403441815981362977477130996 0518707211349999998372978049 95105973173281609631859502445945534690830264252230 8253344685035261931188171010 00313783875288658753320838142061717766914730359825 3490428755468731159562863882 35378759375195778185778053217122680661300192787661 1195909216420198938095257201 06548586327886593615338182796823030195203530185296 8995773622599413891249721775 28347913151557485724245415069595082953311686172785 5889075098381754637464939319 25506040092770167113900984882401285836160356370766 0104710181942955596198946767 83744944825537977472684710404753464620804668425906 9491293313677028989152104752 16205696602405803815019351125338243003558764024749 6473263914199272604269922796 78235478163600934172164121992458631503028618297455 5706749838505494588586926995 69092721079750930295532116534498720275596023648066 5499119881834797753566369807 42654252786255181841757467289097777279380008164706 0016145249192173217214772350 14144197356854816136115735255213347574184946843852 3323907394143334547762416862 51898356948556209921922218427255025425688767179049 4601653466804988627232791786 08578438382796797668145410095388378636095068006422 5125205117392984896084128488 62694560424196528502221066118630674427862203919494 5047123713786960956364371917 28746776465757396241389086583264599581339047802759 0099465764078951269468398352 59570982582262052248940772671947826848260147699090 2640136394437455305068203496 25245174939965143142980919065925093722169646151570 9858387410597885959772975498 93016175392846813826868386894277415599185592524595 3959431049972524680845987273 64469584865383673622262609912460805124388439045124 4136549762780797715691435997 70012961608944169486855584840635342207222582848864 8158456028506016842739452267 46767889525213852254995466672782398645659611635488 6230577456498035593634568174 32411251507606947945109659609402522887971089314566 9136867228748940560101503308 61792868092087476091782493858900971490967598526136 5549781893129784821682998948 72265880485756401427047755513237964145152374623436 4542858444795265867821051141 35473573952311342716610213596953623144295248493718 7110145765403590279934403742 00731057853906219838744780847848968332144571386875 1943506430218453191048481005 37061468067491927819119793995206141966342875444064 3745123718192179998391015919 56181467514269123974894090718649423196156794520809 5146550225231603881930142093 76213785595663893778708303906979207734672218256259 9661501421503068038447734549 20260541466592520149744285073251866600213243408819 0710486331734649651453905796 26856100550810665879699816357473638405257145910289 7064140110971206280439039759 51567715770042033786993600723055876317635942187312 5147120532928191826186125867 32157919841484882916447060957527069572209175671167 2291098169091528017350671274 85832228718352093539657251210835791513698820914442 1006751033467110314126711136 99086585163983150197016515116851714376576183515565 0884909989859982387345528331 63550764791853589322618548963213293308985706420467 5259070915481416549859461637 18027098199430992448895757128289059232332609729971 2084433573265489382391193259 74636673058360414281388303203824903758985243744170 2913276561809377344403070746 92112019130203303801976211011004492932151608424448 5963766983895228684783123552 65821314495768572624334418930396864262434107732269 7802807318915441101044682325 27162010526522721116603966655730925471105578537634 6682065310989652691862056476 93125705863566201855810072936065987648611791045334 8850346113657686753249441668 03962657978771855608455296541266540853061434443185 8676975145661406800700237877 65913440171274947042056223053899456131407112700040 7854733269939081454664645880 79727082668306343285878569830523580893306575740679 5457163775254202114955761581 40025012622859413021647155097925923099079654737612 5517656751357517829666454779 17450112996148903046399471329621073404375189573596 1458901938971311179042978285 64750320319869151402870808599048010941214722131794 7647772622414254854540332157 18530614228813758504306332175182979866223717215916 0771669254748738986654949450 11465406284336639379003976926567214638530673609657 1209180763832716641627488880 07869256029022847210403172118608204190004229661711 9637792133757511495950156604

[brentb]

My wife made rhubarb and strawberry (sugarless pie last night. I made it unhealthy (but delicious) with some Indian mango ice cream one of the ladies here gave me!

KOM
brent

[Josue]

excelente espanol senor Brent !

[down2die]

A process is set up correctly. The melt cushion is 4mm. Some changes are to be made, in each case the process is reset to the start point before the next change is made. What will happen the melt cushion (guess what the new cushion will be in mm) if:

1. Shot size changed from 21 to 22mm cushion = 5 mm (increase)
2. Injection Speed ...25 to 50mm cushion = 4mm (no change)
3. Switchover... 10-11mm cushion= 4mm (no change)
4. RPM speed ...150-250RPM cushion= 4.2mm (slight increase)
5. Back Pressure ...5-10 bar cushion = 4.2mm -4.8mm increase)
6. Decompression distance ...4-8mm cushion = 4.2mm- 4..5mm (0.1 for every mm moved its forward leakage)
7. Injection Pressure ... 115 to 135 Bar cushion = 4mm (no change)
8. Injection Time ...3 to 5 sec. cushion = 4mm (no change)
9. Holding Time ...4-6 sec cushion = 4mm (no change)
10. Holding Pressure ...20-30 bar cushion= 3.9mm (decreases)

all can be verified have done so several times. all correct.

[Suhas]

Helo Down2Die,
Thanks for the info here. As you can see we also like to have fun and so do not take all this seriously. We are here to help also. Here are my thoughts:
1. Shot size changed from 21 to 22mm cushion = 5 mm (increase) AGREED
2. Injection Speed ...25 to 50mm cushion = 4mm (no change) NOT SURE HERE, SINCE NOW YOU ARE GETTING THE PLASTIC MUCH FASTER, SO LESS VISCOSITY AND SO POSSIBLE TO PACK MORE....THERE MAY BE SOME MINUTE CHANGES IN THE CUSHION
3. Switchover... 10-11mm cushion= 4mm (no change) IF THIS IS A THIN WALL PART, THEN THE CUSHION WILL CHANGE. SINCE IN THIN WALL PARTS THERE IS USUALLY VERY LESS PACK AND HOLD.
4. RPM speed ...150-250RPM cushion= 4.2mm (slight increase) AGREED
5. Back Pressure ...5-10 bar cushion = 4.2mm -4.8mm increase) AGREED
6. Decompression distance ...4-8mm cushion = 4.2mm- 4..5mm (0.1 for every mm moved its forward leakage) WILL DEPEND ON A FEW THINGS, BUT OK
7. Injection Pressure ... 115 to 135 Bar cushion = 4mm (no change) AGREED AS LONG AS YOU ARE NOT PRESSURE LIMITED
8. Injection Time ...3 to 5 sec. cushion = 4mm (no change) ARE YOU TRANSFERING ON TIME? OR SOMETHINGS ELSE?
9. Holding Time ...4-6 sec cushion = 4mm (no change) AGREED IF YOU HAVE DONE A GATE SEAL STUDY AND THE GATE SEALS BEFORE 4 SECONDS
10. Holding Pressure ...20-30 bar cushion= 3.9mm (decreases) AGREED.

[brentb]

íSe escribe, señor, y español Josue! You must have a gringo keyboard?

KOM

brent

[brentb]

What other assumptions are we to make with this problem?


KOM

brent

[down2die]

Thanks for input Suhas


Helo Down2Die,
Thanks for the info here. As you can see we also like to have fun and so do not take all this seriously. We are here to help also. Here are my thoughts:
1. Shot size changed from 21 to 22mm cushion = 5 mm (increase) AGREED
2. Injection Speed ...25 to 50mm cushion = 4mm (no change) NOT SURE HERE, SINCE NOW YOU ARE GETTING THE PLASTIC MUCH FASTER, SO LESS VISCOSITY AND SO POSSIBLE TO PACK MORE....THERE MAY BE SOME MINUTE CHANGES IN THE CUSHION, good info
3. Switchover... 10-11mm cushion= 4mm (no change) IF THIS IS A THIN WALL PART, THEN THE CUSHION WILL CHANGE. SINCE IN THIN WALL PARTS THERE IS USUALLY VERY LESS PACK AND HOLD. Good info
4. RPM speed ...150-250RPM cushion= 4.2mm (slight increase) AGREED
5. Back Pressure ...5-10 bar cushion = 4.2mm -4.8mm increase) AGREED
6. Decompression distance ...4-8mm cushion = 4.2mm- 4..5mm (0.1 for every mm moved its forward leakage) WILL DEPEND ON A FEW THINGS, BUT OK
7. Injection Pressure ... 115 to 135 Bar cushion = 4mm (no change) AGREED AS LONG AS YOU ARE NOT PRESSURE LIMITED Good info
8. Injection Time ...3 to 5 sec. cushion = 4mm (no change) ARE YOU TRANSFERING ON TIME? OR SOMETHINGS ELSE? transferring on stroke/distance
9. Holding Time ...4-6 sec cushion = 4mm (no change) AGREED IF YOU HAVE DONE A GATE SEAL STUDY AND THE GATE SEALS BEFORE 4 SECONDS Good info
10. Holding Pressure ...20-30 bar cushion= 3.9mm (decreases) AGREED.