A Nucleating Agent Can Reduce Cycle Time And Improve Part Quality

A nucleating agent is an additive to your raw material  that will effectively improve productivity. It will reduce cooling time and help with warpage issues as demonstrated in the real life case study below.


Case Study


Material specifications:

PART MATERIALPolypropylene
MATERIAL MANUFACTURERLyondellbasell
MATERIAL GRADERandom Copolymer
MATERIAL CODERP241-R
PART NAMESteri Brush Stand
PART WEIGHT76.2gram
NOMINAL WALL SECTION mm2.0

Equipment used

  • 260 ton Sumitomo hydraulic injection moulding machine
  • chiller set at 25 degree celsius
  • single cavity mould
MOULD TYPESingle cavity
MOULD MATERIALP20
GATE TYPEHot tip
EJECTION TYPEEjector pins
NO. WATER CIRCUITS9

Step 1.

Using raw PP material, minimized cycle time until part was just within quality limits (size and warpage limits).

RESULTSRaw PP
CYCLE TIME seconds14.4
COOLING TIME seconds7.0

Step 2.

Added 2% nucleating agent (nanosil)and increased back pressure to aid in mixing during the plasticizing stage. See table below for changes in back pressure:

PROCESSING PARAMETERSStep 1Step 2
BARREL TEMPERTURES ⁰C235 230 210 205235 230 210 205
BACK PRESSURE bar4 stages 224 224 224 564 stages 392 392 392 56
INJECTION TIME seconds1.01.0
HOLD TIME seconds2 stages 0.8 0.22 stages 0.8 0.2
HOLD PRESSURE bar2 stages 504 4202 stages 504 420

Step 3.

Reduced cooling time until part was just within quality limits (size and warpage limits).

RESULTSPP with 2% nucleating agent
CYCLE TIME seconds12.5
COOLING TIME seconds5.1

Results


 The following table shows the difference in cycle time between the raw PP and with 2% addition of the agent:

RESULTSRaw PPPP with 2% nucleating agent
CYCLE TIME seconds14.412.5
COOLING TIME seconds7.05.1
CYCLE TIME DIFFERENCE seconds01.9
CYCLE TIME DIFFERENCE % 013% reduction

The cycle time was reduced by 13% while maintaining quality. This makes this particular machine 13% more productive which means an extra 912 parts per day(24hr) could be produced.

The following photo of the part shows how the quality was maintained even with a shorter cycle time. In fact, even though both parts are within quality limits, the part produced from the shorter cycle time has less distortion than the other part across the top face. The 12.5 secs part is flatter on the top face.

Conclusion.


A 13% reduction in cycle time translates into a large increase in productivity. It is a very easy way to immediately increase productivity but it does come at a cost – the price of the agent.

There are many companies selling nucleating agents for use in injection molding so by shopping around and experimenting with mixing ratios and processing parameters cost can be kept to a minimum.  





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