Molding Machine & Molding

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    ONE – Basic of Injection Molding

    Plastic injection molding, by definition, is the process of injecting plastic into a mold (or mould in European circles), cooling the plastic, ejecting it from the mold, and packing the finished product for sale to the customer.

    This sounds simple and in its basic form it is, but the process involved with making all this happen is actually quite complicated. lastic can be injected into the mold with low pressure, but typically is done under high pressure upwards of !",""" #$ cavity pressure.

    There are many diverse types of injection molding and as many different types of plastic injection molding machines to go with it. #ome of the more common types of plastic molding are standard mold injection, insert molding, plastic extrusion, blow molding,  multi-color or material molding, stac molding, and rotar! molding  just to name a few. There

    are custom plastics as well, from common every day plastic resins to the more e%otic engineering grade resins used in most automobiles today. There is even injection molding grade &metals& being e%perimented with and used these days.   There are many types of injection molding machines all made for specific purposes. There are the standard hori"ontal injection molding machines which range in si'e from a few tons all the way up to """ tons and more. ou could drive car between the platens of a press that large. #ertical injection molding machines  are often used for insert molding (although this can also be done hori'ontally) and share a common cover with two ejection halves of the mold. This allows for de*molding and loading of  inserts in one half, while the other half is producing the ne%t shot of parts. There are also two and three shot injection molding machines  for producing multi*color or multi*material parts such as lenses for tail lights and gear shift knobs with hard plastic inner core and a soft vinyl out covering. The newest machines are &all electric versions& which stray from the standard hydraulic injection machines used now for years. These injection molding machines are much more efficient and repeatable then their hydraulic cousins are. +ommon injection molding machine manufacturers are $oshiba% &us!% 'incinnati% (eMaag% Engel% Nissei%

    )BE% *rburg and Bo!, just to name a few.   The basic steps to producing a plastic injection molded part on a stand injection molding machine are

    • -eating the plastic resin to the required range of the product being

    used.

    http://www.wm8c.com/custom_injection_molding.htm http://www.wm8c.com/custom_injection_molding.htm

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    • eveloping the shot si'e through use of a reciprocating screw which

    conveys the melted plastic to the front of the screw.

    • $njecting the plastic into the mold under pressure to fill the cavity of 

    the mold.

    • acking the plastic to create a full part inside the mold.

    • +ooling the plastic in the mold through the use of cooling channels most commonly with water.

    • Ejecting the cooled part from the mold.

    • /epeating the process over and over again.

    $+O – 'hoosing a Machine

    +ommon injection molding machine manufacturers are &us!% $oshiba%

    Nissei% Mitsubishi% Engel% #an (orn% (emaag% 'incinnati% &PM% )BE %

    Nigata% ,andretto% eed% *rburg% and Bo!. There are also others, but these listed cover of the most common injection molding machine

    manufacturers. Each of these manufacturers supply the standard hori'ontal

    hydraulic or toggle clamp injection molding machines, and may also supply

    co-injection% multi shot, and the more recently desired all electric

    injection molding machines.

     

    0hat type of machine is best for you1 This depends entirely on what you are planning to do with it. 2irst you need to decide what your 3iche market

    is going to be. ou then should research what types of products these

    markets will require and what types of injection molding processes will

    be required to create them. ou can do this yourself or have it done by a

    consulting or research service. 4ased on what the research tells you, you

    will then need to decide what type of machine you will need to perform those

    services for your customers. 2or e%ample, if you decided to get into the

    3iche market of automobile lenses, you will likely need a machine capable of 

    multi shot or co*injection molding. $f you are going to produce simple oneshot type molding products, or products that do not require any special

    needs, you will be looking for standard toggle  or h!draulic clamp

    machines. $f your market will require some type of insert molding, you

    could be looking for .ertical shuttle presses.

     

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    ou will also need to decide if you will need new or used injection

    molding e/uipment. This depends entirely on the level of consistency and

    comple%ity of the products you are molding. There are pros and cons to

    both avenues. 5lder used injection machines can fill a service if less

    comple%ity and repeatability are required. 3ewer used machines oftenbecome available do to someone going out of business or simply changing

    directions within the company, and these machines will be more current and

    have more current technology. They will also typically be more reliable from

    a maintenance point of view. 6sed equipment will be less e%pensive than

    new and often fill the needs of the molder.

     

    $f your business is cutting edge, or may be on the larger si'e, keeping up

    with your competition becomes more of an issue. $n this case, purchasing

    new equipment is probably the most common way to go. This will keep you

    competitive with your competition and also maintain the average age of your

    machines to something more desirable. 7gain this just depends on your

    niche and business requirements. 8any businesses try to maintain around a

    9" year average machine age to remain competitive in their fields.

    :astly, if you want the latest technology for your plant, the &all electric& injection molding machines employing electric servo controls are the latest

    to hit the market. $n the earlier years of their development, only small si'e

    electric machines (up to around ;"" ton) were available, but now you can

    easily find machines in the 9""" ton class and above that are &all electric&.

    There are also -ybrid versions with electric injection units and hydraulic

    clamp ends. The consistency and &shot to shot& repeatability of these

    machines is currently unmatched in this area.

    T-/EE * -ow to /educe #etup Times 6sing

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    companies are not at full utili'ation of their equipment, management would

    love and often pushes for the achievement of one minute changeo.ers on

    all molds so they do not loose any machine time. 0hat management does

    not always do is to support the idea with money saving devices or studies to

    help the process technician and set*up people to achieve quicker moldchange o.er0s. This often produces frustration in with the technicians and

    die setters who are trying to do a faster change over without some of the

    fancy tools to do it with.

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    personnel is paramount to the success of the mold change team and

    reducing your setup times.

    #ometimes when you=re not busy (ha*ha), get your video camera and film

    the guys (or gals) doing a mold change. 0atch them go back and forth,

    down the aisles, into the corners, on top of work benches, into the

    maintenance area do'ens of times just to get parts, tools etc to do the mold

    change. The first step is to separate your die set into two areas and those

    are &internal and &e%ternal& components. $nternal components are things

    that have to be done &during& the die set. E%ternal components are your pre

    preparation and post cleanup operations. 7 very simple way to get started is

    to do &before and after& video tapes. Tape a setup as you would normally do

    them and then review these with your die setup team. 3ote each time that

    someone leaves the frame of the picture and where they went at the time or

    what they got, and how long they were gone. 0atch for any repetitive or

    wasted steps and note them down. 4rainstorm ideas as a team on how to

    eliminate these time losses. reparation and practice is the key to success,

     just like in the 37#+7/ pits.

     

    5ne of the easiest and most cost effective things you can do to aide quick mold change is to manifold your dies. Then all your set*up people need to

    do is run the larger water feed lines to the manifolds, one in and out for

    each half, and then the mold is ready to run. This can also be done for valve

    gate hoses if you have them as well. This removes minutes, and in some

    severe cases, hours of set*up time depending on your particular set up and

    mold si'es. #tore your molds at the machine when practical. $nstall mold

    racks right at the machine to reduce fork lift travel in the plant and to keep

    handy the mold