Scrap Reduction

When the plastic sits idle in the barrel during an interuption in the cycle, the plastic will absorb more heat and will flow easier into the mold.

So you will have to reduce the injection pressure or injection speed or transfer position as you did to stop the flash. This is normal. Other ways to counter it is to purge the barrel before restarting.

Better still, stop the interuptions.

All the best

Paul.

Approach the issue systematically. First, you need data. Pareto the defects to identify the defects that are causing the most problems so that you can prioritize your focus. Then pull together a cross functional team (processing, quality and tooling) to analyze the data and brainstorm potential root causes. Eliminate potential root causes with data from existing sources or create experiments to confirm or refute each potential root cause until you have identified the root cause(s). Some problems will be obvious, most will not be (otherwise you would have fixed them already). And remember that complex issues seldom have a single root cause. They are usually a confluence of several things coming together at the same time (aka The Perfect Storm).

It could be that everyone is trying too hard.

Check how many production interrupts there are per shift.

Usually the night shift has less as no one is breathing down their necks.

Then pick a shift and slow down the problem machines slightly until the machines run with out any hiccups.

This usually leads to more production and everyone is relaxed and happy.

Worth a try.

Bob Burns

What is the nature of the scrap?

If the raw material and the process have not changed, then it's almost certainly the mold that's the root cause.
A good tool maker will be able to zero in on the problem.

Paul Mulville
Tooling Transfers

I recommend using a commercial purge compound to clean the hot runner system. Most purging compound companies offer grades that are hot runner safe.

Ultra Purge is safe and effective at purging hot runners and it is recommended by one of the largest manufacturers of hot runners in the world.

Feel free to contact Moulds Plus International for a free sample of Ultra Purge.

Andrew Reeder
Moulds Plus Intl - Ultra Purge
877-884-3129
www.ultrapurge.com

You did say MOLD,correct?
Then fix it!
Or is it the Machine?
Then find the problem and fix it!
Or is it the Material?
Replace it?
Or is it the Method?
The do it right!
Or is it the Manpower (Molder)?
Train or replace!
1st find the problem, it is one or more of the 5 M's listed.

If you have trouble with the above, hire a consultant such as Bill.

Keep on Molding!

brent

Thanks for the information. I will try the suggested 80 / 20 rule and look @ optimizing the process.

Steps:

Optimize the cycle - see what you get see what's holding you hostage.

As Brent says: FIX THE MOLD

Look for plugged waterlines, lack of setup documentation, blah blah.

You can make any piece of junk a good mold. The real question is who will pay for it and what do you get out of making it work?

Bill

Start with the 80-20 rule.

80% of the scrap comes from where?

Restarts? Why? What is causing cycle interuptions?
Fix that.

What causes the next 80%?

Balance of flow? flashes on restart - correct runner imbalance as best as possible

Shut-offs on tool are weak and need tightened - do it.

Color changes....are you cleaning the screw or purging with a compound - which? Determine which cost less and is the most effective.

The 80-20 rule has never failed me.

Most of it is from restarts or color changes. We have to usually scrap 3-5 shots after interruption because the mold will flash if you don't raise the transfer position up and gradually bring it back down.

What is actually wrong with the product produced from the mold?

Is it flash?

Is it short?

Does it have sink marks?

Please explain.

Paul.

Fix or replace the mold!

Keep on Molding!