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Plastic Injection Molding Machine: Injection Speed Considerations

When you’re looking for a plastic injection molding machine, one of the most important factors to consider is the injection speed. The faster the injection speed, the more quickly your machine can produce parts. However, if the speed is too fast, it can cause defects in your parts.

The injection speed is one of the most important factors when it comes to plastic injection molding machines. It determines how quickly the machine can inject molten plastic into the mold and how fast the part will cool down. Injection Molding Machines come with both high and low injection speeds to meet your needs. We can also find some machines with adjustable speeds so that you can find the perfect setting for each job.

If you’re not sure what the best injection speed is for your machine, you could be wasting time and money. Choosing the right injection speed is critical to achieving the desired results from your plastic injection molding machine. There are a few things you need to consider when choosing the right injection speed for your needs.


How Fast a Plastic Injection Molding Machine Should Work?

You don’t need to be a mechanical engineer or technician to understand injection molding. Injection molding process isn’t difficult and you can learn everything about it with the following content of this article.

Here is some necessary information on how fast a Plastic injection molding machine should work:

The speed of the injection molding machine is indicated by the capacity in ton/h. You can choose a suitable speed for your injection machines according to your product’s specifications. Injection speeds are related to output per hour based on a single cavity machine running one shot at a time, and thus will vary with the size of the product.

Plastic products that are large and simple in design can be made at speeds of up to 90 cm/min. On the other hand, smaller or more detailed pieces should be run no faster than 30-45 cm/min. The optimum injection speed for a given machine is determined by many factors which include the screw design, the machine’s horsepower, and the melt mass of the plastic.

In order to determine the optimum injection speed, you need to know your product’s specifications first. Then you can set up a test shot by changing your screw design or investing in a new machine with a larger power supply.

The size of your product, as well as its design and complexity, will determine the optimum speed for your injection molding machine. The rule of thumb is that the larger and more complex a product, the lower its injection speed should be.


How long does it take to injection mold a part? 

The answer to that question is it depends. It literally depends upon many different factors, which are outlined below. There are also many other variables that affect the time an injection molding project will take. This article will be focusing on just the major factors that have effects on the production cycle time of an injection molded part. How long it takes to make an injection mold is often dependent upon the size and type of part being produced. Also, it depends on the specific plastic material chosen for production, or even how many parts will be produced within each cycle.

For larger parts with longer cycle times, it may not be possible to hold a complete mold in one machine for the entire cycle. Instead, the mold may be removed and placed into another machine with different settings for producing more parts. This is referred to as multi-cavity tooling. Some factors that influence the production time are below:

1. Lead Time

Lead time is the duration between when a customer places an order with their molder, and when they receive it in their warehouse. Generally speaking, lead times are composed of 3 major variables:

● Planning time (including design changes)

● Production time

● Delivery time   

2. Planning Time (Including Design Changes)

When designing a product, it would be foolish to assume no design changes will happen.   Thus, it is vital that the time spent designing a product is factored into one’s lead time estimate.

3. Production Time (Including Post-Mold Processing)

The actual manufacturing time that it takes to produce a product will vary depending on the complexity of the part.   Factors such as draft angles, cores, slides, inserts, and any other secondary operations will contribute to production time. Some manufacturers offer additional services such as sand blasting, painting, and plating to customers.

4. Delivery Time

As the old adage goes: time is money!   In short, a business should try to avoid paying extra for unnecessary delivery time as it only increases the cost of one’s part.     To that end, it is advisable that the product designer choose a reputable injection molding company with a plant near to them.


Calculation of Plastic Injection Molding Machine Speed

We should determine Plastic injection molding machine speed by the product design. However, overall processing time can be divided into three different processes: first is plastic filling time, second is clamping force holding time, third is cooling time.

It takes two cycles for melting plastic to be injected into a molding machine and finally for the product to be ejected out. That is to say, injection time includes both the plastic filling process and cooling period of time.


Plastic Filling Time

Attention should be paid to how much material will terminate at the front end of the barrel. Because it affects plastic filling speed. Thus, the positioning accuracy of the barrel is very crucial. Generally, material which terminates at the front end of the barrel is called gate position offset. Product design and parameters should be taken into consideration in order to reduce or even avoid this gate position offset.


Clamping Force Holding Time

After the filled plastic material gets through the gate, it will enter into the cavity molding machine and then begin the solidification process. As a result, clamping force holding time is introduced. In order to shorten clamping time, equipment and design of clamping devices should be considered.


Cooling Time

The plastic material which has already been filled in the cavity machine will enter into the cooling process stage after getting through the gate. During this period, heat exits from plastic to the cavity machine, so as to solidify the material at a certain temperature range and reduce production cost. However, cooling time is never up to elimination. That is largely affected by the following factors:

● Molding machine configuration

● Product design

● Type of material


Overall Processing Time

After the injection molding cycle ends, product will come out from the cavity machine. That is to say, the overall injection cycle finishes there. The length of this time depends on the cooling time.

For example, if the plastic filling process needs 20 seconds, clamping force holding time needs 10 seconds and cooling time takes 25 seconds. So, total processing time will be 65 seconds (20+10+25=65) for one cycle.


Consider speed of injection before buying a Plastic Injection Molding Machine

Here are some guidelines to help you decide which injection molding machine is right for your manufacturing plant. I use the information provided in this article when determining which machines to recommend to my clients if their application requires higher than usual speeds or throughput.

The speed of an injection molding machine is based on how fast the screw rotates. Most screw rotation speeds are measured in RPM (revolutions per minute). An rpm of 100 is like the tip of your index finger rotating at one revolution per second.

Typical injection molding machines speed ranges from 10 to 250 rpm. The following list shows you what each number equals in terms of output per hour:


Fast Injection Molders (75 – 250 rpm)

This speed range is good for higher production requirements and plastic injection molding machines that require shorter cycle times and higher output rates per hour than Standard Injection Molding Machines. It will also produce parts with more narrow detailed features and tighter tolerances, compared to Standard Machines.


Very Fast Injection Molders (180 – 400 rpm)

This is a superior speed range and will produce even higher output rates per hour than Fast Injection Molding Machines. It will also produce parts with finer detailed features and tighter tolerances, compared to Standard/Fast Injection Molders. These molders are mainly for high production requirements.


Final Words

Injection speed is an important consideration for plastic injection molding machines. You can achieve the best results by selecting a machine that has the correct injection speed for your product. We hope this article has helped you understand how to select the right machine for your needs.


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