sir len, sir tom, sir dwightdixon,
Thank you so much for the inputs. There are so much technical terms here that i have never encountered before. Luckily, the head of our maintenance department expained them all to me.
the melt pressures of the two extruders are not the same because they have diffent specifications running in them (meaning the product specs in Extruder 1 is not ran in Extruder 2). Same is true with amperage and melt pressure. With regards to amperage draw, I will ask our maintenance department to make an hourly check on amperage draw to check the consistency of RPM of the screw...
In our control panel (we are on a manual control not computerized), there is a BA(Blowing Agent) Pressure Controller and BA Flow controller. For example, if you have to change product specs from a density of 55 to 100, we need to lower the BA Flow from 24 lbs/hr to 16 lbs/hr....we set the BA flow and the BA pressure. the % in the set point of the erratic/non-consistent change (+/-2 lbs/hr) is 8-15%.
About the talc, we use talc in powder form (we are still proposing to management to use talc in masterbatch). We havent change suppliers for a couple of years now. Visually, its dry. This is how we prepare the materials...the talc and cooking oil (yes, we use cooking oil in very small percentage to prevent early corrosion degredation of the screw) is weighed manually using an ordinaly weighing scale (not the digital one, i think its called a dial scale) which is calibrated once a year. Last january we changed our formulation and increase our talc to 1.2%(to decrease roughness of our rolls, giving a smooth surface) on all our product specs...the feedback coming from the thermoforming department was, they had difficulty in thermoforming the rolls,the product is soft eventhough parameters were adjusted. Also, there is rampant ID/OD (inside damage/outside Damage) in the products.So by 3rd week of february, we returned to 0.7% talc.since then, we havent heard a problem from the thermoforming dept except for off-specs rolls. Back to preparation of raw materials, after weighing talc and oil, it is mixed with bags of GPPS, HIPS and scrap (GPPS, HIPS and Scrap (all are pellets) are by bags so the proportions are per bag, we do not weigh them).They are mixed in the mixer for around 5 mins. then it is transported to the feeder by screw conveyor.
Sir, what factors greatly contributes to GSM and thickness?
Here are my initial findings: For GSM - amount of blowing agent, RPM of Primary and Secondary, Thickness- the Speed of Take-up rollers, die opening..
We are using weigh feeders (gravemetric). Right now, we are on manual weighing ( we use dial scale). However, we have a colortronic system which will be operational soon (they have fixed the motor and we will just have to calibrate it first before using). As for our LPG (BA Agent), we have BA Flow controller (lbs/hr) and BA Pressure controller. We will check the effect of the ambient temp (ambient temp here is 35 C) to the Blowing Agent (thanks for the tip). Maintenance department will see if the BA feed is slaved to the extruder output (we don't know yet, i'll give you an update later).Here's how we control/set BA feed.
Method 1(before the old regulator was replaced) - We set a value to the BA flow controller. The BA pressure is a fixed value (no matter what the product specs are, while the BA flow differs for every product specs). After setting a value to BA flow we adjust the metering pump (stroke/min) until set BA flow is achieved. The play in the flow of BA with this method is +/-8-15 % (BA flow is going up and down throughout the run)
Method 2 (after installing the regulator)-Prior to run we fully open the metering pump, and then we set the regulator to certain BA flow..then, when we need to change to another product specs, we just set a value to the BA flow regulator and then we adjust the BA pressure (you can set a value) until the set BA flow is achieved. (BA flow and BA Pressure can be set to a value, and also reads the actual value)
With regards to the type of screw, we are using a flood fill single. About melt temp, i will monitor it hourly to check if its changing (will give you an update) thank you so much for the insights!