Definition: 1: a state of equilibrium as among forces 2: a state of stability 3: within a mold, uniformly filling each impression equally in all stages of fill.

When discussing balance it must be stated that it is meant to be about cavities as in multicavity tools and or family tools. The basic definition of the two is a multicavity is one similar part with many impressions, 2 to 96 or more, and a family tool is a group of parts not the same in size and shape.

Balance in the respect of how they are filling. There are many discussions out there on filling and uniformity of the fill. The Melt FlipperŪ is a solution and has many benefits even to a single cavity tool. The 5-Step Process™ is a tool to use in examining the balance of a tool / mould and allows you to separate filling issues between the tool (steel size) and shear of materials, an excellent tool.

This discussion is on calculating balance if the above tools are not employed. Balance is important from the fact that uniformity in fill gives uniformity of part performance. In days gone by the issue was that if we had a naturally balanced runner system the parts were thought to fill uniformly, (not necessarily true) but a lot better than a non natural balanced system. While this was how tools were perceived and built in actual practice it was found that naturally balanced tools were not always balanced.

From a standpoint of running production parts it is critical to have uniformity of fill. The issue being that the tool is already created and parts have been worried out of it for many months or years or maybe it is brand new. If we run a short shot, (always done by limiting the volume of material injected) do all the cavities fill to the same percentage?

What is meant is that if it is a multicavity tool, hopefully all parts weigh the same, but in most they may not so slight weight variation may be acceptable. In a family mold the parts do not weigh the same so percentage of fill by weight is the only way to see what the balance is.  Thus to be accurate the full part weight should be established. Further, the cavities should be marked / numbered so as to be checked.

The procedure

1-     weigh full complete parts and document

a.       this may require multiple shots if weight is small

b.      this should be multiple shots to confirm and possibly average

2-     eliminate the pack and hold off the machine setting

a.       This should produce part/parts that are without pack and hold, and short.

b.      On some machines this may require to eliminate the time function

3-     Produce enough shots at this setting to get a good sample.

4-     Reduce the shot size to achieve a 75% full part on average

a.       Run enough parts to get a good sampling

5-     Reduce shot size to 50%

a.       Run enough parts to get a good sampling

6-     Document the results in spread sheet and or data table

7-     Run the following calculation

a.       Divide the actual weight (short shots) by the full part weight and multiply by 100

b.      The result is now in percentage of fill

Example:

4 cavity tool of all the same parts (multicavity)

Full part	50 grams / 100%	51grams /100%	49.5 grams / 100%	50 grams /100%
No pack and hold	48 / 96%	47 / 92%	48 / 97%	49 / 98%
75%	40 / 80%	38 /  74%	38 /  77%	42 / 84%
50%	25 / 50%	22 / 43%	27  / 54%	24  /  48%

 The first number is grams of weight and the second is % of fullness as compared to the full part. Thus on no pack or hold the variation is between 92% and 98% full.  A 6% variation while at 50% full we have 43% to 54% or an 11% variation.

The issue is that we do have variation, and it is through out the short shot test and if the test were to go to 25% full we might well find a pattern or issue. The issue here is how close is close. Ideally 5% would be nice, is 10% variation okay? It cannot be said as what is the part, what are its functions and what are its issues. If to get 100% full on all we start to over pack / fill others resulting in flash, than it would be an issue. If it was that on occasion there is a short, but the process is such that we have minimized pack to eliminate flash than it is an issue.

These tests can be used on a multi gated part to see if the part has a uniformity of fill. In some parts it is too often found that warpage or un-fill was caused by non-uniform fill of gates. In one recent project it was found that 50% of a part was filled prior to the gate opening on the other side of the part and the part had 4 gates.

The next step is to determine why the imbalance, from which steel and runner diameters should be measured, and or to investigate using the 5 Step Process™.  This tool and others mentioned are great, and show what is going on within our factory which is called the mould.

Within the molding of parts it is too often the processor whom has to bend to allow for worrying out parts, typically narrowing the window with which the process is allowed to function. This than adds to part cost due to rejects, increased inspection, and skill required for the molders dance. Understanding the balance of the mold and using what ever tools or system to define and than to improve is worth the investment in the long run.

Melt Flipper is a registered trade mark of Beaumont Technologies, Inc.

5-Step Process is Trade Marked by Beaumont Technologies, Inc.

Definition: 1: a state of equilibrium as among forces 2: a state of stability 3: within a mold, uniformly filling each impression equally in all stages of fill.

When discussing balance it must be stated that it is meant to be about cavities as in multicavity tools and or family tools. The basic definition of the two is a multicavity is one similar part with many impressions, 2 to 96 or more, and a family tool is a group of parts not the same in size and shape.

Balance in the respect of how they are filling. There are many discussions out there on filling and uniformity of the fill. The Melt FlipperŪ is a solution and has many benefits even to a single cavity tool. The 5-Step Process™ is a tool to use in examining the balance of a tool / mould and allows you to separate filling issues between the tool (steel size) and shear of materials, an excellent tool.

This discussion is on calculating balance if the above tools are not employed. Balance is important from the fact that uniformity in fill gives uniformity of part performance. In days gone by the issue was that if we had a naturally balanced runner system the parts were thought to fill uniformly, (not necessarily true) but a lot better than a non natural balanced system. While this was how tools were perceived and built in actual practice it was found that naturally balanced tools were not always balanced.

From a standpoint of running production parts it is critical to have uniformity of fill. The issue being that the tool is already created and parts have been worried out of it for many months or years or maybe it is brand new. If we run a short shot, (always done by limiting the volume of material injected) do all the cavities fill to the same percentage?

What is meant is that if it is a multicavity tool, hopefully all parts weigh the same, but in most they may not so slight weight variation may be acceptable. In a family mold the parts do not weigh the same so percentage of fill by weight is the only way to see what the balance is.  Thus to be accurate the full part weight should be established. Further, the cavities should be marked / numbered so as to be checked.

The procedure

1-     weigh full complete parts and document

a.       this may require multiple shots if weight is small

b.      this should be multiple shots to confirm and possibly average

2-     eliminate the pack and hold off the machine setting

a.       This should produce part/parts that are without pack and hold, and short.

b.      On some machines this may require to eliminate the time function

3-     Produce enough shots at this setting to get a good sample.

4-     Reduce the shot size to achieve a 75% full part on average

a.       Run enough parts to get a good sampling

5-     Reduce shot size to 50%

a.       Run enough parts to get a good sampling

6-     Document the results in spread sheet and or data table

7-     Run the following calculation

a.       Divide the actual weight (short shots) by the full part weight and multiply by 100

b.      The result is now in percentage of fill

Example:

4 cavity tool of all the same parts (multicavity)

Full part	50 grams / 100%	51grams /100%	49.5 grams / 100%	50 grams /100%
No pack and hold	48 / 96%	47 / 92%	48 / 97%	49 / 98%
75%	40 / 80%	38 /  74%	38 /  77%	42 / 84%
50%	25 / 50%	22 / 43%	27  / 54%	24  /  48%

 The first number is grams of weight and the second is % of fullness as compared to the full part. Thus on no pack or hold the variation is between 92% and 98% full.  A 6% variation while at 50% full we have 43% to 54% or an 11% variation.

The issue is that we do have variation, and it is through out the short shot test and if the test were to go to 25% full we might well find a pattern or issue. The issue here is how close is close. Ideally 5% would be nice, is 10% variation okay? It cannot be said as what is the part, what are its functions and what are its issues. If to get 100% full on all we start to over pack / fill others resulting in flash, than it would be an issue. If it was that on occasion there is a short, but the process is such that we have minimized pack to eliminate flash than it is an issue.

These tests can be used on a multi gated part to see if the part has a uniformity of fill. In some parts it is too often found that warpage or un-fill was caused by non-uniform fill of gates. In one recent project it was found that 50% of a part was filled prior to the gate opening on the other side of the part and the part had 4 gates.

The next step is to determine why the imbalance, from which steel and runner diameters should be measured, and or to investigate using the 5 Step Process™.  This tool and others mentioned are great, and show what is going on within our factory which is called the mould.

Within the molding of parts it is too often the processor whom has to bend to allow for worrying out parts, typically narrowing the window with which the process is allowed to function. This than adds to part cost due to rejects, increased inspection, and skill required for the molders dance. Understanding the balance of the mold and using what ever tools or system to define and than to improve is worth the investment in the long run.

Melt Flipper is a registered trade mark of Beaumont Technologies, Inc.

5-Step Process is Trade Marked by Beaumont Technologies, Inc.