Does anyone knows how to inject blow grade HDPE

Ladies,Gentlemen,

Here is a problem that involves mechanical, chemical,and Heat exchange technologies combined.

I have a 750 ton injection machine and a supply of low MFI 0.7 HDPE blow grade, that i want to inject into a wash basin injection mold of 64 cm of diameter and 17 cm high. The mold was conceived for a mif 5 to 10.

Why? because I have a readily supply of cheap natural blow grade material, and have only injection molding machines.

To inject blow grade material with an MIF 0.7 one needs first to melt the material by heat and friction inside the barrel much above normal required temperature for injection grade materials and inject it as fast as possible into the mold before the material starts to cure before filling the mold.

As you know, the higher the L/D ratio of the screw the more pressure and the less material is available. High L/D ratios are used for thin walls molds using high MFI 15 to 35 because there is no need for injection speed but rather for pressure to force the material into the very small wall thickness of the mold.

In my case, I had to open the core of the mold so the material could flow easily. However, using a high pressure screw gave me one problem and a sub-sequent one.

First, the material would start to cure before filling the mold and thus obliging the screw to force the rest of the material to finish the filling. The result is that the toggle of the machine would give in and the mold would open giving me flashes or shorts alternatively."one shot long than one shot short"

Should I use Low L/D ratios , I would have a fast filling of the mold while the materials is still molten requiring less injection pressure, thus less pressure on the toggle. BUT to do that I must apply more heat to the material and use a chiller to transfer the heat from the surface of the mold to the cooling circuitry. By the time the plastic is cured the mold is ready for the next shot. But then again the 2 minutes cycle time I obtain due to the high temperature and the thickness of the mold, gases start to produce in the barrel and start an unwanted ejection process of materials at the nozzle level of the barrel giving a short supply of material on the next shot

Any one knows How to inject blow grade into injection molds?n How do I calculate the pressure needed for a specific melt index v/s the wall thickness. Is speed more appropriate than injection force in his case?

Thanks,

Issa