Using ProMax-One Machine Selector™
Step 3. Calculate clamp force, shot size and select injection molding machines.
Open ProMax-One Machine Selector™. Select the Machine Selector option
from the main menu at www.injecneering.com
and run the program. ProMax-One Machine Selector calculates the required clamping force and barrel size to specify the injection molding machine. Retrieve the mould record as explained in step 2.
Create a new machine selection study.
Click on the New Calculation button
Type in a description of the analysis
Create a new machine selection study.
Assign the Material’s Generic Name by pressing the arrow button in front of the corresponding text box and selecting it from the list. Do the same to select the Trade Name.
Click on the radio buttons to select the values to be used in the calculations. Use your experience and criteria to decide on the values. When a radio button is clicked, the corresponding textbox in the Used Values row is filled up with the chosen number. Alternatively, if based on your experience and knowledge none of the values satisfy your criteria, you can enter you own values manually.
As shown in the picture above, the chosen values for this study are 1.05, 1.8, 3 and [1.3-2]
2. Enter parts and tool information.
Enter the values for part number 1. Since the tool has not been designed yet, as the project is still in an early stage, some assumptions will need to be made. It is a good exercise to lay the parts’ views in a CAD program to better visualize how the mould may be laid out. Since the study will be saved in a database, it can be revisited and reviewed when a tool design is available.
Wall Thickness: If the part has different wall thicknesses, use an average value (use your judgement). Ignore wall thickness for ribs and bosses unless you think they can substantially affect the clamp force in which case, slightly reduce the value of main wall thickness. For our study, the parts’ wall thicknesses are uniform
Flow Length: This is the maximum distance the melt will travel inside the cavity.
After the values are entered, the average pressure in the cavity is calculated
Projected area & Number of Cavities: Enter the projected area of one part and the number of “identical” cavities. The clamp force for part 1 will be displayed.
Slides projected Area & Back Angle: Sometimes the area in contact with the slide is large in proportion of the part’s projected area. The pressure of the melt on the slide is transferred to the contact surface between the slide and the heel block. By entering the slides area and the back angle, the program calculates the force component in the direction of the machine opening. This force is added to the previously calculated clamp force to calculate the total clamping force for the current part.
In this study, no slides are involved and hence no data is entered.
Runner Projected Area: this value can be entered either as a numeric number or as a percentage of the total projected area. Since the mould has not been designed yet, a percentile value will be entered. As previously mentioned, this information should be revisited when a tool design is available. A 5% of the total projected area will be assumed. The clamping force for the runner is now calculated. This value will change as new information is entered for the other parts.
Part Volume: Enter the part volume for part 1. The total volume is calculated.
Runner & Sprue Volume: As with the projected area for the runner system, the volume can also be enter either as a numeric or a percentile value. 10% will be used in this case.
To enter the information for the second part, click on the check box as shown below.
New text boxes be displayed.
Enter the information for Part 2. Notice how the values for the Runner projected area and Runner & Sprue volume are recalculated.
The required clamp force and shot weight are displayed in the results area. Two approaches to calculate the clamping force are used; the first multiplies the projected area by the calculated average pressure. The second uses the rule of thumb where the total projected area is multiplied by a constant whose value is determined by the type of material (not our favourite approach as it does not factor the wall thickness and flow length)
Using the results.
The results suggest that (Using the P•A approach) 86 Tons of clamp force are required. Applying a safety factor of 15%, 100 Tons are needed. Using the generic machines database provided, the next standard machine is a 120 Ton machine. Our smallest generic 120 ?nject?on mach?ne has a barrel capac?ty of 148 cm3; about 2.4 shots in the barrel. Since the values are obtained through theoretical methods, it must be ensure that the tool also be buit to fit in a smaller machine (in our case an 80 Ton machine). That way, once the tool is build, the 80 Ton machine can be tried and evaluated. Save your analysis. |