Injection molding is an economical and very efficient method of producing injection molded parts. It can produce millions of parts with exactly the same shape, dimension, and quality. Some examples of injection molded parts are the mobile phones, mouse, keyboard, and many components found inside the automobile.
Just heat the resin until it melts then force it into the cool mold. Allow it to solidify. Open the mold then take off the molded part.
As the molten resin is being injected into the mold, it enters the mold opening called the sprue. From the sprue this molten material will then be distributed to the runners then it will be fored into the gate and then into the cavity. The cavity must be filled precisely to avoid short shots but it must not be over packed (over packing is forcing more than enough pressure to the resin and it can damage the mold). The molten resin will stay in the cavity for 30 seconds to 1 minute or more until it cools down and solidify. When the resin solidify a molded part is formed. The mold will open and then the molded part will be ejected. The mold closes and its ready for another shot.
Why is an injection mold expensive?
Injection molds are made up of special, high quality steels that have a good machinability property. Some standard mold components such as springs, bolts, and limit switch are prefabricated and costs lower.
Most standard components such as ejector pins, ejector sleeves, sprue bushings, and leader components are not prefabricated which mean they will only be manufactured when you order them. They are not mass produced thus they are expensive. The cavity and core are mold components which make the mold really expensive. It involves careful design engineering and processing. Most of the tools used in making these components are very expensive.
This explains the WHY, WHAT, HOW and WHERE of mold temperature control.
Why do we need to control the mold temperature?
The mold temperature has significant impact on molding cycle, dimensional accuracy of molded part, and warping of molded part.
If the mold temperature is too cool, the runner and gate will solidify before the resin could completely fill up the cavity. However, if the mold temperature is too hot, the resin will take more time to solidify affecting the molding cycle time. If some portions of the molded part solidify a lot faster than the other portions, chances are warp or deformed molded part –the dimensional accuracy cannot be satisfied.
What are the methods of controlling the mold temperature?
There are 3 methods to control the temperature of the mold. It depends on the temperature range that the mold will be set for production.
1. Water: 40~90?
2. Oil: 80~120?
3. Heater cartridge: 120? and over.
How and where should we apply the mold temperature control?
The purpose is to control the temperature of the cavity and core so keep the cooling line (water hole) close and evenly placed around the molded part. The image below shows the ideal placement of water hole. But this is only a general rule -mold structure, manufacturability, and ease of maintenance are to be considered.
Microsoft Office 2010 Home and Business with Outlook.
Domain hosting / DNS not provided by ISP.
Not within Microsoft Exchange.
Your message did not reach some or all of the intended recipients.
Subject: Test outgoing email
Sent: 2011/03/26 12:00
The following recipient(s) cannot be reached:
Yana (firstname.lastname@example.org) on 2011/03/26 12:00
Server error: ’550 5.7.1 <email@example.com>… Relaying denied. IP name possibly forged [188.8.131.52]‘
For those of us who are not very IT minded this is how to fix it.
This happens when your DNS or mail server is not provided by your ISP. You need to authenticate your outgoing server. It took me several phone calls to Microsoft which was not helpful (paid instances! about $100 per instance) and several hours of digging before I figured the answer.
Solution: You have to dig deeper! Here’s how…
1) Go to control panel and double the icon “mail”. You will only find this if you already installed and configured your Outlook.
2) Click “E-mail Accounts…”
3) Select the email name you want to fix then click “change…”
4) Make sure all information is correct and then click “More Settings…”
5) Check the box shown in the figure below to authenticate your outgoing server then click “OK”.
Injection molder or injection molding machine is a machine for producing plastic molded parts by molding process. It has 2 main parts, an injection unit and a clamping unit.
An injection molder have 2 methods of fastening the mold -horizontal or vertical. Most injection molder are horizontally oriented because molded parts can easily be removed after ejection by leveraging gravity -the molded parts will just fall down into the container below. Vertical injection molders are used for insert molding applications because inserts are inserted into the core side of the mold before molding.
There are also manual injection molder for hobbyists. It is simple in consruction and does require manual force to inject the resin. An example of such machine is from Galomb, Inc. They make Benchtop injection molder.
Types of injection molding machines
Injection machines are classified mainly by the type of system that drives them: Hydraulic, electric, or hybrid.
Hydraulic injection machines uses ram system for its clamping mechanism. This type of machine is used by majority of molding companies.
Electric injection machines are driven by motors. Unlike the hydraulic machines, which continously pump hydraulics to the cylinder throughout the whole molding cycle, an electric machine only makes use of energy during closing and openning of the clamping unit. It uses toggle system for its clamping mechanism in order to build up tonnage. It is also faster, quieter, and have higher accuracy, but it is also known to be more expensive. The first maker of electric injection machine is Nissei Plastic Industrial Co., LTD.
As much as possible use a uniform wall thickness. If you must change the wall thickness, change it gradually to avoid warping.
If the strength is not compromised, design the part with minimal wall thickness to allow faster cooling time and cycle time.
Draft angle is necessary for easy removal of molded part from the mold. Draft angle should be applied in the direction of draw from the cavity and core.
Parts with textured surface require greater draft angle in order to avoid scratches on the textured surface as the part is being removed from the mold. 1 to 3 degrees normally applies to moderately matte or sand-blasted surfaces and 3 to 5 degrees for roucher surface.
But for smaller precision molded parts, it is sometime unnecessary to include draft angles as long as the cavity and core are highly polished.
Apply radius on corners as much as possible. A proper radius size is not less than the wall thickness of the part.
Radius reduces the stress on the corner thus reducing the warpage compared to corners without radius.
Apply rib instead of using thicker wall thickness. Uneven cooling of thick wall will lead to uneven shrinkage inside and outside the wall. This could cause warpage and sinkmark due to internal stress. Applying rib will help improve the rigidity and geometric integrity of the molded part. It also improves the cooling time.
Rapid prototyping is a technology used to rapidly construct solid objects using three-dimensional computer aided design (CAD) data. The first technique in prototyping, stereolithography, was develop in the late 1980′s to produce prototype parts and models. In todays rapid prototyping techniques, parts can be manufactured in near production-quality in relatively small numbers, sometimes eliminating the use of injection molded parts.
Among the obvious advantages of rapid prototyping are:
costly faulty designs can be reduced early in the development stage,
effective communications between marketing, engineering, manufacturing, and purchasing,
development time can be reduced,
minimize engineering changes
These advantages greatly benefits the product development process in terms of cost, quality, and lead-time.
Rapid prototyping process:
3D CAD model is converted to Stereolithography (.STL) format.
The Rapid Prototyping machine processes the STL file layer by layer.
Yesterday, while surfing the internet looking for new tools for mold design, I discovered DraftSight, a 2D CAD tool from the Dessault Systemes. DraftSight is available for free download. Is it going to be valuable tool for mold design? One way to find out…
I downloaded the installation file (about 42Mb) to give it a try. The installation was quick and easy. I have to send my email to activate the software.
The interface has a clean layout and it has a command line, much like Autocad. Unfortunately for me, I use a very different 2D CAD software at work.
Below are my observation about DraftSight.
FREE download for everyone. Professionals or students.
Performance is slower than my 2D CAD.
Very Autocad like. Therefore, difficult to use… at least for me.
LINUX version will be available later this year. This is good news.
I do not know for how long DraftSight is going to be free, so download it now.