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| Author | Topic: Lightweight Polypropylene |
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mademan5284 Senior Member Posts: 18 |
posted September 25, 2005 01:02 PM
   
Melt flow 4g/10min. name: profax 6523 homopolymer for general use but FDA approved. This material just pours out with little pressure. Extuder output is erratic. Using screen pack and barrier screw with 4" mixing section. I think I should be using a compression screw but the one I have is incompatable with the extruder in use. what is the most common screw type associated with lower density polypropylene's or polypro. in general. IP: Logged |
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Tom C Moderator Posts: 618 |
posted September 25, 2005 08:27 PM
This material is one of the standards we use for twin screw simulation work. Runs well on a twin, so it should handle any abuse from a single. What barrel temperatures are you using? Can you measure the melt temperature? Typical temperatures are around 450F. As stated before, I am local to you and could shoot it with an IR gun to get a reading. ------------------
Tom Cunningham
Extrusion Technical Services www.ExtrusionTechnicalServices.com IP: Logged |
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mademan5284 Senior Member Posts: 18 |
posted September 26, 2005 12:13 AM
using a 1 1/4" extruder almost at full rpm to create pressure to try and get stable output. Melt temp is 313F, what size machine do you run it on. Assuming I crank up the heats to get a melt temp reading of 450F, would this discolor.Slowing the machine down is not an option to my boss. I'm worried because its white and a smooth surface is needed.Ok so by this I'm assuming that it will be more stable at a higher melt temp. The use of a compression screw is still in my thoughts. IP: Logged |
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Tom C Moderator Posts: 618 |
posted September 26, 2005 08:05 AM
Everything you are telling me is out of wack. The melting point of this PP is 334F. Are you sure your temps are in F? C would make more sense from the observations. IP: Logged |
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louis33 Senior Member Posts: 137 |
posted September 26, 2005 08:17 AM
What is "Full RPM" on that machine? Sounds like a lot of mechanical energy going into that melt. IP: Logged |
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mademan5284 Senior Member Posts: 18 |
posted September 26, 2005 02:36 PM
The readout on the melt temp gauge was 174C is my conversion wrong 174c x 1.8= 313.2f Ok here goes the RPM readout varies for example 12.17 - 12.39 this is a four digit read out.When turned past 19.80 it goes blank but you can turn it up even higher until the dial stops. My job is to make it run, so i'm keeping it within the "readout zone"and going by lowest rpm visible. I can get 500- 800 psi but after 48 hrs screen pack is full and I'm looking at 2500- 2900 psi and I lose my surface. So the suggestion of higher temps sounds right,less pressure longer,and screen pack life. So is 334f my target melt temp for my 1 1/4 fixer upper. I have to make do with what I have until maitainance can get to it, which will be after the run. IP: Logged |
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Tom C Moderator Posts: 618 |
posted September 26, 2005 03:02 PM
quote:
Are you sure nobody wants to discuss outside technical support? ------------------
Tom Cunningham
Extrusion Technical Services www.ExtrusionTechnicalServices.com IP: Logged |
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mademan5284 Senior Member Posts: 18 |
posted September 27, 2005 02:30 AM
OH man I forgot to add 32! Ok the job got put on hold a higher priority FEP job just came up customer needs 500,000 pieces by Monday. Ill find out when this polypro job is scheduled to run again and let you guys know of my findings. I need more free time, all my superiors do is rush ,rush, rush, with out stopping to solve the problem. IP: Logged |
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louis33 Senior Member Posts: 137 |
posted September 27, 2005 08:36 AM
You should meet Brian at the plastics.com site. You share the same problem with management  IP: Logged |
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mademan5284 Senior Member Posts: 18 |
posted October 06, 2005 02:11 AM
Ok the job is back Let me give more detail it is a solid rod. They won't listen to me when I recomended raising the temps, they are afraid of change. So I'm going to wait until they have had enough then I will run it right. By correctly converting Celsius to farenheit I got the melt temp to 375F and noticed the material got stickier and it got more stable. Before I could get into the 400's the next shift took over, and had their way with it. I can run this but keeping the ovality down is a challenge. If there is any more details you would like to know let me know. Is it possible to run a solid round profile of profax through a vacuum tank? Do you think my ovalty problem is related to the colder heats, and would it improve with hotter heats? I think I know the answer to these questions, but I have to ask. [This message has been edited by mademan5284 (edited October 06, 2005).] [This message has been edited by mademan5284 (edited October 06, 2005).] IP: Logged |
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louis33 Senior Member Posts: 137 |
posted October 06, 2005 09:13 AM
Vacuum sizing will not work! Cooling the OD too fast will result in very round rod filled with voids. Keep the OD hot and the ID as cold as you can possibly run it to avoid voids. What is the diamiter? IP: Logged |
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Tom C Moderator Posts: 618 |
posted October 06, 2005 09:24 PM
The lack of roundness is likely caused by the very low temperatures being used. Some of the material will be much hotter because of viscous heating in the screw, while other areas of the extrudate will be cold. Flow will be inconsistent out the die. This must be another one of those companies that thinks it is saving money by not employing engineers. Being your own lawyer, self surgery, process engineering without any technical resource; not recommended. While plant operators often dismiss engineers as being clueless, sometimes it helps to have someone who can spend time thinking about resolving process issues rather than just stuggling with the line. I, for one, am very dispointed with this trend in the USA. ------------------
Tom Cunningham
Extrusion Technical Services www.ExtrusionTechnicalServices.com IP: Logged |
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mademan5284 Senior Member Posts: 18 |
posted October 07, 2005 01:11 AM
To Louis33 We were experiencing some voids but how would I keep the center of the rod colder. Any info on getting rid of the voids would be great. My O.D. is .095 + or - .005. To Tom Your right on the money with my companies description. The big wigs are losing patience with the supervisors. I have asked for some uninterupted time as I will be stepping up to the plate soon. My success will extinguish some of the stubborness. It will be a victory of which they will neverunderstand. I already know of two co-workers who will frown upon my success, because I'm always happy and smileing. I'm super confident and positive and they hate it. I just don't understand???????? IP: Logged |
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mademan5284 Senior Member Posts: 18 |
posted October 08, 2005 04:53 PM
As stated before the machine Rpm gauge varies. Along with the fact that whoever setup the head used too much antiseize, the tip was loose, and the screw was not inserted fully. The mixing section of the screw barely fits in the barrel. When I cleaned it out the tip of the screw was almost touching the screens. We are wasting our time using the present extruder. The pevious shift was using 45F water in first tank and they wonder why they couldn't maitain ovality. Ill get back to you guys when we have our things together. IP: Logged |
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mademan5284 Senior Member Posts: 18 |
posted October 11, 2005 01:11 PM
Ok I got it last night using hotter heats and a shorter plug and smaller die. They had a longer plug and it was too close to the land length. They switched it on me and didn't document it. And by heating the water a bit I reduced the ovality to a max of .0005 Thanks guys !!!!!!!!!!!!!!!!!!!! IP: Logged |
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