Skippy: Hey Buzz - happy almost Thanksgiving - we saw an interesting question in another plastics forum -
"Can a worn extruder screw cause surging? I've heard this for years but can't see how a linear variation with a period of a minute or two can be caused by a slow radial change over many weeks or months or even years. If anyone can come up with a reasonable and technically sound explanation, I would like to see it. ALG"
Buzz: - Well Skippy, I tend to agree with most that the slow evolution of “wear” is not likely to create a situation where we have good melt pumping on Tuesday, only to have it fall apart on Wednesday. Screw melt pumping conditions DO change over time with wear, and particularly when aggressive screw and screw tip cooling are employed to “throw material around” in profile tools.
Skippy: To be fair, don't we have to acknowledge here that there are a number of critical process areas that contribute perhaps as much to "surging" based on material delivery (aspect ratio of material components, mix of materials, conveying method/stability, existence of fines, drying temperature, air flow, residence time in the dryer, feed throat temperature control, zone 1 and or 2 temperature control, etc etc etc) to the feed section of a screw that are ignored or not very well understood in too many shops?
Buzz: Of course, although that conversation is way beyond the scope of this particular discussion and will be investigated more fully in the future. On the other hand, in custom plant environments where screw and barrel wear were faithfully measured by quarter on extrusion lines that ran a variety of materials from week to week (aka not just one material from beginning to end of each screw/barrel rebuild life) we observed the following –
The most amount of wear from quarter to quarter occurred at the END of the screw and or barrel life measurement period, not at the beginning. (by production hours)
R&D staff tend to prefer to “run in new items on new screws and barrels” and in short order, the “process” is/was not as "stable" to established run conditions in future runs and required “tweaking”
Many US firms have gotten caught in the trap of increasing rates to “increase contributions per hour” (false economy of course if no new sales fill the new empty machine time) at the expense of significantly closing the ‘window of process ability’ with any particular brand of elements
Skippy: I'm wondering whether the economic climate we're experiencing contributes in any way as well -
Buzz: well, we have observed that batch to batch variation in raw materials from manufacturers quite frankly (despite their “certifications” on lab materials) DO exist, sometimes in great measure and
Business conditions (and perhaps lack of cash flow?) in custom extrusion in poorly run shops affects the run to run use of varying raw material virgins and regrinds –
Skippy: How does that affect running an extrusion line?
Buzz: Well sometimes, rather than running a standard mix of regrinds back into product from the beginning of the run until the end, some houses accumulate and “rev the meter” from nearly 0 to nearly 100% which further requires "tweaking" in general to re-achieve proper melt thixotropy with varying amounts of regrind.
This can result in some rather aggressive approaches to achieving a stable melt pumping mechanism at the correct melt temperature and pressure to have the material “be one” with the intended tooling flow paths –
Skippy: So all that translates to what?
Buzz: In the case(s) above, we find that the requirements for process adjustment in a process where we KNOW that all else (listed in the opening above) is in good working order and under “control” end up being “justified” due to “changing outputs”. The bottom line is that although a good deal of data can be accumulated in “screw and barrel wear” verus "surging" it is meaningless, unless the contribution to wear can some how be tied back to the requirements for any number of the destabilizing run approach problems above in the plant as well.
Your question is an excellent one, because many shops quite frankly do not do a very good job of monitoring, mixing, drying etc the input of raw materials and then “change the process and blame the extruder” aka worn barrel and screw.
Skippy: is this likely to be a standard answer for extrusion in general?
Buzz: Quite frankly, we would guess that the pipe folks who will routinely rebuild screws and change out barrels on an “X” pounds schedule on lines running the same product 24/7 for months on end would have a totally different answer than the “custom gang” but that's just our two cents
Thursday, November 12, 2009
Friday, August 7, 2009
More on Vacuum Tank help -
Skippy: Say, we thought a bit more about the response in the last post, and hadn't realized we didn't ask a couple more 'broad brush stroke" questions -
a) are you using a color concentrate with the PE and PP that is being exuded out from the melt and being deposited/captured/coating the calibration unit or plugging vacuum holes and slots? This could be insulating the calibration unit and preventing efficient heat transfer - may need to be checked on a regular basis if the colorant system and or process can't be modified to eliminating this "plate out" effect. A rubberbanding or thinning/stretching effect in the calibration unit due to this insulating of the calibration could intermittently look like folding at the front of the calibration unit - rather than a constant haul off down the line -
b) we didn't really discuss the travel method, and assumed that the take off unit was capable of overcoming the normal calibration drag and pulling the part at a constant rate of speed - without belt/cleat slippage or obvious motor speed problems. Depending on the drive makeup, one thing to check is that the take off is operating at approximately 70-80 percent of it's rated motor speed in the correct gear reduction range if applicable at the correct haul off rate.
c) is the output of the extruder constant? as we had assumed; - if not could be a host of issues - check by cutting off 10 to 60 second pieces of hot melt at the die -several in a row, cool the mass and weigh on an accurate (gram?) scale to see what if any variation is occuring at the extruder. It is important that the sample size be large enough to overcome the inherent error in your "by hand" cut off of the samples -
Buzz: and d) we were also assuming that the calibration unit had previously been checked for obvious damage, nicks, blocked ports, correct coolant and vacuum hook ups etc. and that the Vacuum tank itself was in correct running order with adequate coolant into and out of the system - sorry for not thinking of those items as well earlier -
Good luck -
a) are you using a color concentrate with the PE and PP that is being exuded out from the melt and being deposited/captured/coating the calibration unit or plugging vacuum holes and slots? This could be insulating the calibration unit and preventing efficient heat transfer - may need to be checked on a regular basis if the colorant system and or process can't be modified to eliminating this "plate out" effect. A rubberbanding or thinning/stretching effect in the calibration unit due to this insulating of the calibration could intermittently look like folding at the front of the calibration unit - rather than a constant haul off down the line -
b) we didn't really discuss the travel method, and assumed that the take off unit was capable of overcoming the normal calibration drag and pulling the part at a constant rate of speed - without belt/cleat slippage or obvious motor speed problems. Depending on the drive makeup, one thing to check is that the take off is operating at approximately 70-80 percent of it's rated motor speed in the correct gear reduction range if applicable at the correct haul off rate.
c) is the output of the extruder constant? as we had assumed; - if not could be a host of issues - check by cutting off 10 to 60 second pieces of hot melt at the die -several in a row, cool the mass and weigh on an accurate (gram?) scale to see what if any variation is occuring at the extruder. It is important that the sample size be large enough to overcome the inherent error in your "by hand" cut off of the samples -
Buzz: and d) we were also assuming that the calibration unit had previously been checked for obvious damage, nicks, blocked ports, correct coolant and vacuum hook ups etc. and that the Vacuum tank itself was in correct running order with adequate coolant into and out of the system - sorry for not thinking of those items as well earlier -
Good luck -
Thursday, August 6, 2009
Need Help Extruding Rigid Tubing Using a Vacuum Tank
Buzz: You know Skip, we are working on extrusion materials from the last NPE show, but we often get questions that show the need for making sure just the basics are covered as well - like this one:
"We just got a vacuum tank and have had several jobs tool really well on it. On the past few jobs, we are getting a fold in the wall of the tubing that we cannot seem to work out. Materials are PP, PE and Nylon. I know that we are probably missing something simple. Any suggestions or resources that can help me trouble shoot?"
Skippy: Oh boy, I hope that our 30 years of extrusion experience can be of some benefit. We do this for a living, and would be glad to come in and help - Note these comments are not meant to criticize, but we will assume nothing -
Mentioned in your post:
"We just got a vacuum tank and have had several jobs tool really well on it. On the past few jobs, we are getting a fold in the wall of the tubing that we cannot seem to work out. Materials are PP, PE and Nylon. I know that we are probably missing something simple"
Buzz: Let's talk about a couple of these elements to see if you are in fact "missing something".
Skippy, ok, A) You got a new vacuum tank. Was this the only addition to the line, or did you get some new tooling with it to make particular parts as well? You mention the first few jobs ran "well" - were they in the same materials? Using the same tooling? Do you have a program in place to tear down the machine from job to job and a set up sheet that has been gone over to be sure that all processing conditions are "correct"? Are you running more or less lines now that in the past (see calibration - aka water)
Buzz: right, then B) Suddenly, you are having problems with the extrudate folding over in the wall of the extrudate - is it in one area only, or all around the tube - A fold usually indicates one of several things -
1) The wall balance versus the "draw down" is not correct.
When you shear off some material coming out of the die at rate, the parison (tube shape) pushed out should flow out roughly horizontally for a small way (until gravity kicks in).
Question? Do you clean the machine up totally from material to material (clean means all plastic out of the tooling to bare metal, pull the screens, pull the screw and clean all down to the metal?) If not, you might have material hung up in the barrel or at the tip of the screw, in the screens or breaker plate that isn't moving. Since the screw is imparting ribbon flow that must be converted into plug flow through the breaker plate, if you interrupt this plug, erratic and generally uneven flow through the balance of the tooling may occur. You might also have material caught up in one or more spider legs - causing whacked out flow that an operator is trying to correct with pin/shell relationships -
Once the material flows through the gate adapter in plug flow, through the spider and pin/shell in even distribution and assuming that your tooling is approximately 5 degrees above the correct melt temperature, then you should be delivering a "tube" out of the tooling that is ready for draw down and calibration -
Skippy: Good point, but it also might be
2) Die Gap - this is the distance between the Die Face and calibration. Assuming that the wall is even, then we would want the Die Gap to be even from every point on the die to every point on the calibration. Since the tooling is larger than the calibration, you need to back the tank AWAY from the die so that "draw down" can occur. The correct distance away will be somewhat variable based on
a) the melt temperature and "stiffness" of the melt"
b) the wall thickness versus the cross sectional area
c) the lot of material - yes I know that your materials should be fractional melt, but since they are "fractional" even a small change can affect the apparent "stiffness" of the melt at any given temperature.
In the materials that you mention, it is not uncommon for the OD and ID of the tubing tooling to be larger (in some cases up to 60% or more) than the final size of the tubing so that the material can be drawn down prior to entering the calibration. Are you using common tooling for all of the materials, or do you have different pins and shells for different sizes of tubing from different materials?
Also the die gap is established by making sure that the calibration and extrusion centerlines in both planes (side view and top down) are straight in line with one another. Vacuum tanks, takeoffs and cutting devices are notorious for vibration and will "creep" along the floor if able - is the line "in Line?" if not, you are perhaps not applying cooling evenly down line.
Buzz: yes sir, and doen't forget
3) Lubrication - two of the materials - PP and PE have an affinity to move from being cohesive to adhesive as they get hotter - generally, most custom extruders use a lubricant (water or other proprietary) systems to lubricate the material as it enters the calibration. Is this system working correctly? Nylon is VERY sensitive to moisture - is your drying system capable, is the (lack of) moisture level very well maintained? It goes without saying that PP, PE and Nylon all require different pins and shells and draw downs to make the "same" size tubing. Anyone that tries to run all three from the same tooling perhaps can by sacrificing rate or quality. Best to optimize for each material and go clean to clean between materials on machines.
Skippy: yup, and this is key -
4) Calibration cooling - is it dependable and repeatable? Is it actually working? Your vacuum tank calibration cooling might be hooked up to
a) well water; coming up out of the ground, it is likely to be around 55 degrees all year round - good system if dependable in terms of gallons per minute
b) city water; likely to change temperature with the seasons - 55 or so in the winter to possibly 75 degrees of more in the summer. Again, are you sure that your supply in gallons per minute is known and repeatable?
c) some sort of internal water recovery system (cooling tower, chiller); do you do preventative maintenance on the system, again do you know day to day what the temperature and actual gallons per minute availability is
Once the supply of water is maintained, then it has to be APPLIED to the calibration in a known manner. I like to put gallons per minute meters in line supplying my calibration - for a couple of reasons -
a) once we know for instance that 7 gals per minute at 55 degrees on a part running 150# per hour at "X" feet per second through the calibration at 300# per thousand feet is running WELL, I note that as being critical to being repeated in the future.
Buzz: ok, all together now, b) are we ready for "silly?"
We often encounter plants with a problem like this, where everything is running well as in a) above, and then the process "goes south". I always ask what is "new at the line" - "Nothing" is generally the reply. Then I ask "what else is new in the plant?" and we find out that three other lines were being started at the same time, and the SUPPLY of water which was capable of giving me 7 gal per minute with valve open 1/4 is now being diverted into filling three more lines. A quick check on my gal per minute meter shows that at my line, we've dropped to 3 gals per minute and the parts are "folding" (too hot). I open the supply valve at my line from 1/4 to say 1/2, bringing my supply back up to 7 gal per minute and line settles out. Don't forget that when the other three lines eventually settle into production and turn their valves from FULL to fill to 1/4 to run that we will suddenly have TOO much water (check the gage) and have to make an adjustment again. One of these gages on every line allows each operator to know what effect others are having on his line, and what to do to get back in control rather than just "trying zone three for 5 degrees" etc.
Skippy: wow, just goes to show you that laying down the foundations is really important. Other simple thoughts include making sure that the water application in the tank is even - water rings get plugged up with rust, shavings, dirt etc, and make sure water is cooling all sides evenly.
Buzz: We haven't really talked much about how to set up the calibration, the materials of construction to seal around the tube after the calibration and from compartment to compartment etc, but have been focused on the "fold" probably happening with either uneven flow out of tools or uneven cooling in the Calibration.
Once again, we can be called upon for additional help, training etc in your plant as required.
Just our "two cents" -
"We just got a vacuum tank and have had several jobs tool really well on it. On the past few jobs, we are getting a fold in the wall of the tubing that we cannot seem to work out. Materials are PP, PE and Nylon. I know that we are probably missing something simple. Any suggestions or resources that can help me trouble shoot?"
Skippy: Oh boy, I hope that our 30 years of extrusion experience can be of some benefit. We do this for a living, and would be glad to come in and help - Note these comments are not meant to criticize, but we will assume nothing -
Mentioned in your post:
"We just got a vacuum tank and have had several jobs tool really well on it. On the past few jobs, we are getting a fold in the wall of the tubing that we cannot seem to work out. Materials are PP, PE and Nylon. I know that we are probably missing something simple"
Buzz: Let's talk about a couple of these elements to see if you are in fact "missing something".
Skippy, ok, A) You got a new vacuum tank. Was this the only addition to the line, or did you get some new tooling with it to make particular parts as well? You mention the first few jobs ran "well" - were they in the same materials? Using the same tooling? Do you have a program in place to tear down the machine from job to job and a set up sheet that has been gone over to be sure that all processing conditions are "correct"? Are you running more or less lines now that in the past (see calibration - aka water)
Buzz: right, then B) Suddenly, you are having problems with the extrudate folding over in the wall of the extrudate - is it in one area only, or all around the tube - A fold usually indicates one of several things -
1) The wall balance versus the "draw down" is not correct.
When you shear off some material coming out of the die at rate, the parison (tube shape) pushed out should flow out roughly horizontally for a small way (until gravity kicks in).
Question? Do you clean the machine up totally from material to material (clean means all plastic out of the tooling to bare metal, pull the screens, pull the screw and clean all down to the metal?) If not, you might have material hung up in the barrel or at the tip of the screw, in the screens or breaker plate that isn't moving. Since the screw is imparting ribbon flow that must be converted into plug flow through the breaker plate, if you interrupt this plug, erratic and generally uneven flow through the balance of the tooling may occur. You might also have material caught up in one or more spider legs - causing whacked out flow that an operator is trying to correct with pin/shell relationships -
Once the material flows through the gate adapter in plug flow, through the spider and pin/shell in even distribution and assuming that your tooling is approximately 5 degrees above the correct melt temperature, then you should be delivering a "tube" out of the tooling that is ready for draw down and calibration -
Skippy: Good point, but it also might be
2) Die Gap - this is the distance between the Die Face and calibration. Assuming that the wall is even, then we would want the Die Gap to be even from every point on the die to every point on the calibration. Since the tooling is larger than the calibration, you need to back the tank AWAY from the die so that "draw down" can occur. The correct distance away will be somewhat variable based on
a) the melt temperature and "stiffness" of the melt"
b) the wall thickness versus the cross sectional area
c) the lot of material - yes I know that your materials should be fractional melt, but since they are "fractional" even a small change can affect the apparent "stiffness" of the melt at any given temperature.
In the materials that you mention, it is not uncommon for the OD and ID of the tubing tooling to be larger (in some cases up to 60% or more) than the final size of the tubing so that the material can be drawn down prior to entering the calibration. Are you using common tooling for all of the materials, or do you have different pins and shells for different sizes of tubing from different materials?
Also the die gap is established by making sure that the calibration and extrusion centerlines in both planes (side view and top down) are straight in line with one another. Vacuum tanks, takeoffs and cutting devices are notorious for vibration and will "creep" along the floor if able - is the line "in Line?" if not, you are perhaps not applying cooling evenly down line.
Buzz: yes sir, and doen't forget
3) Lubrication - two of the materials - PP and PE have an affinity to move from being cohesive to adhesive as they get hotter - generally, most custom extruders use a lubricant (water or other proprietary) systems to lubricate the material as it enters the calibration. Is this system working correctly? Nylon is VERY sensitive to moisture - is your drying system capable, is the (lack of) moisture level very well maintained? It goes without saying that PP, PE and Nylon all require different pins and shells and draw downs to make the "same" size tubing. Anyone that tries to run all three from the same tooling perhaps can by sacrificing rate or quality. Best to optimize for each material and go clean to clean between materials on machines.
Skippy: yup, and this is key -
4) Calibration cooling - is it dependable and repeatable? Is it actually working? Your vacuum tank calibration cooling might be hooked up to
a) well water; coming up out of the ground, it is likely to be around 55 degrees all year round - good system if dependable in terms of gallons per minute
b) city water; likely to change temperature with the seasons - 55 or so in the winter to possibly 75 degrees of more in the summer. Again, are you sure that your supply in gallons per minute is known and repeatable?
c) some sort of internal water recovery system (cooling tower, chiller); do you do preventative maintenance on the system, again do you know day to day what the temperature and actual gallons per minute availability is
Once the supply of water is maintained, then it has to be APPLIED to the calibration in a known manner. I like to put gallons per minute meters in line supplying my calibration - for a couple of reasons -
a) once we know for instance that 7 gals per minute at 55 degrees on a part running 150# per hour at "X" feet per second through the calibration at 300# per thousand feet is running WELL, I note that as being critical to being repeated in the future.
Buzz: ok, all together now, b) are we ready for "silly?"
We often encounter plants with a problem like this, where everything is running well as in a) above, and then the process "goes south". I always ask what is "new at the line" - "Nothing" is generally the reply. Then I ask "what else is new in the plant?" and we find out that three other lines were being started at the same time, and the SUPPLY of water which was capable of giving me 7 gal per minute with valve open 1/4 is now being diverted into filling three more lines. A quick check on my gal per minute meter shows that at my line, we've dropped to 3 gals per minute and the parts are "folding" (too hot). I open the supply valve at my line from 1/4 to say 1/2, bringing my supply back up to 7 gal per minute and line settles out. Don't forget that when the other three lines eventually settle into production and turn their valves from FULL to fill to 1/4 to run that we will suddenly have TOO much water (check the gage) and have to make an adjustment again. One of these gages on every line allows each operator to know what effect others are having on his line, and what to do to get back in control rather than just "trying zone three for 5 degrees" etc.
Skippy: wow, just goes to show you that laying down the foundations is really important. Other simple thoughts include making sure that the water application in the tank is even - water rings get plugged up with rust, shavings, dirt etc, and make sure water is cooling all sides evenly.
Buzz: We haven't really talked much about how to set up the calibration, the materials of construction to seal around the tube after the calibration and from compartment to compartment etc, but have been focused on the "fold" probably happening with either uneven flow out of tools or uneven cooling in the Calibration.
Once again, we can be called upon for additional help, training etc in your plant as required.
Just our "two cents" -
Wednesday, July 29, 2009
- Bigger in your customer's eyes on a small budget -
Skippy: How do you act bigger with critical customer follow up without breaking the budget?
Buzz: As a small to medium size business (or even a small consultant group) you probably realize that in addition to the discipline of an active Customer Relationship Management program spitting out follow up activity, you have actionable follow up as well.
Skippy: Of course, plenty; from having meetings and teleconferences transcribed to keeping on top of customers critical time sensitive contacts to ordering supplies remotely, etc.
Buzz: Check out www.microtasking.net For a nominal charge, just about any customer or vendor follow up activity can be handled once or on a recurring basis on your behalf - think and be big on a small budget -
Buzz: As a small to medium size business (or even a small consultant group) you probably realize that in addition to the discipline of an active Customer Relationship Management program spitting out follow up activity, you have actionable follow up as well.
Skippy: Of course, plenty; from having meetings and teleconferences transcribed to keeping on top of customers critical time sensitive contacts to ordering supplies remotely, etc.
Buzz: Check out www.microtasking.net For a nominal charge, just about any customer or vendor follow up activity can be handled once or on a recurring basis on your behalf - think and be big on a small budget -
Wednesday, July 1, 2009
Profile extrusion info from NPE 2009
Skippy: Hi all - just back from a productive outing at NPE in Chicago -
Buzz: - I heard the show numbers were really down -
Skippy: Well yes, it did seem that the number of plastics personnel there were highly diminished from what we had observed the last 10 shows in a row back to 1979, but on the other hand, the folks that were there appeared to have a real reason to be there.
Buzz: and so the quality of the contacts was likely to be good?
Skippy: Right. I have a bag full of materials that are coming back from the variety of disciplines we are constantly going through - profile extrusion, thermoforming, injection molding both conventional and low pressure structural foam, and fiberglass composites.
There seemed to be a bigger focus on this show from the vendors on pooling the products (training, controls, common sense shop info etc) into more system wide solutions rather than just selling the newest loader, calibration, etc.
I will be assembling some of the materials regarding the profile extusion elements first and posting soon -
Buzz: - I heard the show numbers were really down -
Skippy: Well yes, it did seem that the number of plastics personnel there were highly diminished from what we had observed the last 10 shows in a row back to 1979, but on the other hand, the folks that were there appeared to have a real reason to be there.
Buzz: and so the quality of the contacts was likely to be good?
Skippy: Right. I have a bag full of materials that are coming back from the variety of disciplines we are constantly going through - profile extrusion, thermoforming, injection molding both conventional and low pressure structural foam, and fiberglass composites.
There seemed to be a bigger focus on this show from the vendors on pooling the products (training, controls, common sense shop info etc) into more system wide solutions rather than just selling the newest loader, calibration, etc.
I will be assembling some of the materials regarding the profile extusion elements first and posting soon -
Tuesday, February 10, 2009
Are you maintaining a “Three Legged Stool”?
Buzz - Hey Skippy - seat backs and tray tables up and locked please -
Skippy - say what?
Buzz - Well the travel in today's market is so bumpy and most of us don't have the luxury of having a 'Captain Sully' in the cockpit that it seems prudent to have seating that is firmly grounded.
Skippy - It goes without saying that we have a difficult marketplace at present.
Buzz - Yup, most companies (unfortunately) are in full blown ‘survival mode’; the mode consists mainly of gouging out ‘costs’ so as to live to fight another day.
Skippy - It is important to keep in mind though that doing this without enough introspection is akin to sawing legs off the stool you’re sitting on. You’ll want to maintain at least a ‘three legged stool’ with the three pillars necessary to provide stability over unknown terrain -
Buzz - which are?
Skippy -
A) [quality] sales - to existing and potential customers;
it’s easier to keep a customer than get one;
B) cash flow - you can be making sales and losing money etc.;
it never works out on ‘volume’ and lastly
C) human capital – are the right team members in place?
Buzz - Any suggestions?
Skippy - Rather than focus only on cost cutting, an honest internal assessment should be part of the operations mode at this most important time – does your team have a good handle on:
1. The existing problems that are currently facing your company?
2. The quality of key managers you presently employ?
3. The strengths and weaknesses of your company as seen through the eyes of your customers and employees?
4. The current climate of the company, such as morale and its status?
5. The planning that has occurred up to this point?
6. The attitudes of key managers toward the turn around and growth?
7. The story board material that presently exists(brochures, literature, selling aids, etc.)?
Buzz - Sounds like an assessment of these key factors prior to the coming rebuild is critical to take advantage of better company re-positioning and perhaps re-branding.
Skippy - right; and consider an independent audit. An outside consultant’s report can sometimes be not only revealing but also thought provoking. It may open the eyes of the most astute leadership. You must be prepared for real hidden problems that you might have missed. Moving forward before conducting an independent assessment can be deadly to your rebound and future growth.
Skippy - say what?
Buzz - Well the travel in today's market is so bumpy and most of us don't have the luxury of having a 'Captain Sully' in the cockpit that it seems prudent to have seating that is firmly grounded.
Skippy - It goes without saying that we have a difficult marketplace at present.
Buzz - Yup, most companies (unfortunately) are in full blown ‘survival mode’; the mode consists mainly of gouging out ‘costs’ so as to live to fight another day.
Skippy - It is important to keep in mind though that doing this without enough introspection is akin to sawing legs off the stool you’re sitting on. You’ll want to maintain at least a ‘three legged stool’ with the three pillars necessary to provide stability over unknown terrain -
Buzz - which are?
Skippy -
A) [quality] sales - to existing and potential customers;
it’s easier to keep a customer than get one;
B) cash flow - you can be making sales and losing money etc.;
it never works out on ‘volume’ and lastly
C) human capital – are the right team members in place?
Buzz - Any suggestions?
Skippy - Rather than focus only on cost cutting, an honest internal assessment should be part of the operations mode at this most important time – does your team have a good handle on:
1. The existing problems that are currently facing your company?
2. The quality of key managers you presently employ?
3. The strengths and weaknesses of your company as seen through the eyes of your customers and employees?
4. The current climate of the company, such as morale and its status?
5. The planning that has occurred up to this point?
6. The attitudes of key managers toward the turn around and growth?
7. The story board material that presently exists(brochures, literature, selling aids, etc.)?
Buzz - Sounds like an assessment of these key factors prior to the coming rebuild is critical to take advantage of better company re-positioning and perhaps re-branding.
Skippy - right; and consider an independent audit. An outside consultant’s report can sometimes be not only revealing but also thought provoking. It may open the eyes of the most astute leadership. You must be prepared for real hidden problems that you might have missed. Moving forward before conducting an independent assessment can be deadly to your rebound and future growth.
Saturday, January 31, 2009
"Pita" Management
Skippy – Hey Buzz – Happy New Year. Had someone inquire about "Pita" Management:
“Hi In the molding process when you allow raw material to flow fluently from the extruder at the beginning or end of work you get what we call here a "Pita" It is a big round and hard melted raw material. This raw material is out of the stock but not handled by the shop order and due to that after a while cause mismatch in stock. I would like to hear how do you handle that in your plants and if you have any suggestions for me. Thanks in advance.”
Buzz – Happy New Year as well. Hmm, this question could be looked at two ways – are we talking about the handling, use or disposal of the “pita” or the raw material allocation and subsequent quote effects side?
Skippy – why not both?
Buzz – Ok, from a material handling only point of view, it depends on the condition of the material as is extruded -
In custom shops running multiple materials, it is often that the barrel was given a light coating of a petroleum based product to seal the pores of the barrel. It is a given that your tooling was likely coated with something as well and that you have de-"greased" it etc as you hung and heated up -
A new run of material will pick this up and it is not in your best interest to have petroleum or silicone based products introduced back into your run mix from internally generated scrap - pitch it.
On the other hand, once you are up and running, with a good melt temp, the material can be handled at nearly the correct make up consistency, cool the material by mass quickly, remove water if present and run through granulator being careful to have the resultant regrind not too gummy/sticky - if you generate enough of this due to jamb ups, string ups, etc you may want to consider a "hot granulator" designed to take excess material at or near melt temp . . .
Skippy – okay, how about from a raw material variance standpoint?
Buzz – well, the amount of shop generated regrinds and virgin is a problem that is easy to overcome in your MRP or ERP process with a little examination of your particular system, some history analysis and a slight 'adjustment percentage' to your allocation table from the BOM..
It sounds like you have two major issues -
The first is COST for quoting, and the second is ACCURACY for material allocations.
Material allocations (probably the more important on a month to month basis):
------------------------------------------------------------------------------------------------------------------
Assuming that you have a costed bill of materials for each product, each would call for "X" pounds or kilos of plastic per some measure - thousand feet, 100 meters etc. Unless you have a VERY sophisticated MRP system, you probably have variances month to month in virgin to regrinds before any losses -
There are several losses that occur that belong in the BOM but generally are excluded until the problem becomes so large that it is hard to miss -
1) "Pita"s or start up scrap or jamb ups etc are all "losses" unless recaptured as I indicated in the original reply. If they are ground up and re-run, no loss exists and no variance is expected. For this exercise, we will assume that they are always losses
2) scrap that is lost in and around the granulator - it is rare that material isn't spilled on the floor and swept up, or vacuumed up when cleaning a granulator and going from one material to another or regular maintenance - what happens to it? Unless you re-wash, dry and reuse, again, loss
3) In extrusion, and vacuum or thermoforming versus injection molding, saw shavings, and tool cut offs end up on the floor as saw dust, trims etc. These can be or are losses as well unless recovered.
The closest MOSTLY correct answer is to do a scrupulous study by product - measure all inputs, all saved product, all by product wastes and losses as above, then calculate the % of loss as a measure of the total amount of material consumed and either
a) Increase the raw material per measure in each BOM by the same percentage or
the NEXT most correct answer is to do a scrupulous monthly study on the weights of all final products (net) by raw materials, and using the following formulas -
Beginning inventory + Purchases - minus ending inventory is Material Consumed. (Gross)
Material Consumed - net weight of all saved parts for shipment is Actual Material Used for Product and what ever is left is what was LOST.
LOST/Material consumed is the percentage that each Bill of Material should be increased by (average) to predict material allocations more closely.
--------------
Quoting:
--------------
This same exercise for a year would probably yield that your losses in aggregate are likely in the 1-3% range in a fairly clean well run shop. In this case, you would want to increase the raw material cost component in your quotes by the same or slightly more (slightly more is more likely to leave a little wiggle room until you find all the losses) than the aggregate loss. In this way, you know you aren't going to automatically get a "SURPRISE" loss in margin of 1-3% at year end.
Note that none of this discussion focuses on Regrind availability or max percentage usable. These discussions are beyond the scope of this simple answer.
I hope this simple explanation works. Good luck.
“Hi In the molding process when you allow raw material to flow fluently from the extruder at the beginning or end of work you get what we call here a "Pita" It is a big round and hard melted raw material. This raw material is out of the stock but not handled by the shop order and due to that after a while cause mismatch in stock. I would like to hear how do you handle that in your plants and if you have any suggestions for me. Thanks in advance.”
Buzz – Happy New Year as well. Hmm, this question could be looked at two ways – are we talking about the handling, use or disposal of the “pita” or the raw material allocation and subsequent quote effects side?
Skippy – why not both?
Buzz – Ok, from a material handling only point of view, it depends on the condition of the material as is extruded -
In custom shops running multiple materials, it is often that the barrel was given a light coating of a petroleum based product to seal the pores of the barrel. It is a given that your tooling was likely coated with something as well and that you have de-"greased" it etc as you hung and heated up -
A new run of material will pick this up and it is not in your best interest to have petroleum or silicone based products introduced back into your run mix from internally generated scrap - pitch it.
On the other hand, once you are up and running, with a good melt temp, the material can be handled at nearly the correct make up consistency, cool the material by mass quickly, remove water if present and run through granulator being careful to have the resultant regrind not too gummy/sticky - if you generate enough of this due to jamb ups, string ups, etc you may want to consider a "hot granulator" designed to take excess material at or near melt temp . . .
Skippy – okay, how about from a raw material variance standpoint?
Buzz – well, the amount of shop generated regrinds and virgin is a problem that is easy to overcome in your MRP or ERP process with a little examination of your particular system, some history analysis and a slight 'adjustment percentage' to your allocation table from the BOM..
It sounds like you have two major issues -
The first is COST for quoting, and the second is ACCURACY for material allocations.
Material allocations (probably the more important on a month to month basis):
------------------------------------------------------------------------------------------------------------------
Assuming that you have a costed bill of materials for each product, each would call for "X" pounds or kilos of plastic per some measure - thousand feet, 100 meters etc. Unless you have a VERY sophisticated MRP system, you probably have variances month to month in virgin to regrinds before any losses -
There are several losses that occur that belong in the BOM but generally are excluded until the problem becomes so large that it is hard to miss -
1) "Pita"s or start up scrap or jamb ups etc are all "losses" unless recaptured as I indicated in the original reply. If they are ground up and re-run, no loss exists and no variance is expected. For this exercise, we will assume that they are always losses
2) scrap that is lost in and around the granulator - it is rare that material isn't spilled on the floor and swept up, or vacuumed up when cleaning a granulator and going from one material to another or regular maintenance - what happens to it? Unless you re-wash, dry and reuse, again, loss
3) In extrusion, and vacuum or thermoforming versus injection molding, saw shavings, and tool cut offs end up on the floor as saw dust, trims etc. These can be or are losses as well unless recovered.
The closest MOSTLY correct answer is to do a scrupulous study by product - measure all inputs, all saved product, all by product wastes and losses as above, then calculate the % of loss as a measure of the total amount of material consumed and either
a) Increase the raw material per measure in each BOM by the same percentage or
the NEXT most correct answer is to do a scrupulous monthly study on the weights of all final products (net) by raw materials, and using the following formulas -
Beginning inventory + Purchases - minus ending inventory is Material Consumed. (Gross)
Material Consumed - net weight of all saved parts for shipment is Actual Material Used for Product and what ever is left is what was LOST.
LOST/Material consumed is the percentage that each Bill of Material should be increased by (average) to predict material allocations more closely.
--------------
Quoting:
--------------
This same exercise for a year would probably yield that your losses in aggregate are likely in the 1-3% range in a fairly clean well run shop. In this case, you would want to increase the raw material cost component in your quotes by the same or slightly more (slightly more is more likely to leave a little wiggle room until you find all the losses) than the aggregate loss. In this way, you know you aren't going to automatically get a "SURPRISE" loss in margin of 1-3% at year end.
Note that none of this discussion focuses on Regrind availability or max percentage usable. These discussions are beyond the scope of this simple answer.
I hope this simple explanation works. Good luck.
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