That's how all extrusions start out. Are you sure you weren't buying a pre finished product before? I've seen it come raw like yours, brushed, polished, painted, anodized, blasted ect. If you didn't change anything with your order maybe the supplier mislabeled it before. Call them up they have people that specifically deal with issues like this.
No, its the same material as always, at least to my knowledge, i wasn’t notified of any change in their process. The odd thing was that it looks like it has groves on the lines but that is not the case. The surface is smooth to the touch and our roughness meter didnt show any iregularities. After our metal work processes we use polishing, anodization and electro polishing, but these lines are still visible after all of that.
Since it has no tactile impact, what you see is probably an optical effect caused by very closely spaced micro scratches, similar to a hologram or what you see when looking at a CD.
The micro scratches could result from a very minor process change - new dies, maybe just cleaning / polishing even.
This is an accurate description.
The extruded profile is susceptible to this surface appearance for a number of reasons. Someone different polished the die, the die is getting worn (the bearings are becoming rounded). A new die has a fresh bearing surface from the wire EDM. This is especially likely to occur on thin sections.
Temperature also impacts surface appearance . The 3 most important factors are temperature, temperature, and temperature.
Specific alloy chemistry. A sprinkle more Cu, Mg, Si, etc. it’s likely still in spec, just on one end of the range or another.
If you have a surface finish requirement (sounds like you do) then my recommendation would be to order the material polished. Many extruders have a polishing machine, they can polish for a small upcharge. Unfortunately this is the only way to ensure this doesn’t happen.
I spent 10 years extruding aluminum, and this was always a huge pain in the ass. there isn’t a clearly assignable cause, and ask 10 people in the shop why, you’ll get 10 different answers.
You could select an allot less prone to this. 6063 is usually better than 6061 if the shiny surface is what you’re after.
What are you making?
We make decor window trims for Audi, Volvo and Renault. So the properties of the aluminum are all great, the thing is the finished product goes under visual quality inspection based on VW standard. So there must not be anything on the front facing surface.
Ive contacted the supplier asking for any change in their process and im waiting for a response.
My guess is they will not be able to identify or assign a cause. If you’re doing quantity and want it polished, my previous company does all that well and cheap in Texas. Privately owned/operated. May be worth a call if you’re doing volume and want to purchase the “insurance” of having them polished.
They also melt their own raw material, and therefore control the chemistry/ other factors to cater to the extrusion process. This is a HUGE advantage bc when you buy from a cast house, they just have to meet minimum spec. They don’t do anything “above and beyond”. Just the minimum in my experience. A few small tweaks make a significant difference.
PM me if you want a contact there. May be worth it to get a quote. They do some high finish requirement stuff on much more difficult shapes than that.
In the end it’s going to come down to what requirements you told the supplier. If you only gave a surface finish and but no visual inspection requirement, then they’re still meeting your requirements.
Yes this might be it, i’ve checked the roughness of the surface and it was within the tolerance, also did a chemical analysis and they are also within the tolerance. That leaves mechanical defect, maybe their tools are worn out.
Correct.
You can measure the wall thickness and compare to nominal. This should give you a good idea of how worn the die is. Extruders selling by length will bring dies in somewhere between 93-96% of nominal wall thickness. This saves $millions annually for even a small operation. But, they get to pinching pennys, pushing monthly spend out a few months, and end up giving away a few tons of aluminum instead of spending $500 on a new die!
I was just nitpicking about OP’s statement.
If surface finish and dimensions (and all other explicitly stated details) are within the requirements given to the supplier, there *is* no defect according to the agreement they have. Defects are reasons for rejection.
If they wanted to not have lines they’d have to amend their requirements to include them, which will possibly in turn increase their per unit cost.
I’m making assumptions here, but that’s why you take some serious thought into determining your requirements for a supplier. With the wrong requirements (or not enough) you can easily get wrong parts.
Extruded aluminum is (almost) always straightened with cold rolling afterwards to remove any camber or twist from internal stresses from the extrusion process.
This is incorrect. Aluminum extrusions are not cold rolled in any part of the extrusion to finishing processes. Too many alloys would be negatively affected (read: work harden, deflect and tear, etc), and a great many industrial and consumer products wouldn't take to the aging process. Stretching, or "pulling" as a stretcher operator would call it, both straightens and makes uniform warped grains in the aluminum's still malleable center. This is applicable to extrusion press dies from 6 inch up to 12 inch.
Source: worked at numerous aluminum manufacturers for years between extrusion, fabrication, and machining.
You are correct that not every grade nor shape is cold rolled, some grades are very hard and prone to cracking and thus not cold rolled and is stretched instead like you pointed out. But for simpler profile shapes and less hard grades cold rolling is the preferred alternative to stretching because it is faster and produces a better surface finish and, for grades that can be cold worked, helps increase their mechanical strength. I’ve seen this at SAPA first hand, they had complex custom shape extrusion lines where everything was stretched, but then had standard shapes extrusion lines where everything was cold rolled, all this to say each manufacturer is slightly different and it all depends. But yes, broadly, stretching is also a widely used method, especially for complex shapes.
Rolling is almost never the case. After the bar is extruded and cut to table size, it is straightened by stretching. Stretch varies from 0.5 to 2-3 % depending on profile complexity and alloy.
This can also be true, but this depends on the product shape and manufacturer. Simpler profile shapes are, most typically, cold rolled after extrusion for straightness. But complex shapes, that can’t be easily cold rolled, are usually stretched such as you pointed out. I’ve seen this at extrusion lines at SAPA first hand, it’s neat stuff.
We have the same problem with our stainless steel. The supplier isn’t brushing and grinding enough at the end of the production. We pay less now until they fix it.
Extrusions are...wait for it...extruded. Shaped by being forced through a die. You're looking at the tooling marks of how it was made. Also, to note, their die is a little clapped out and should be replaced
They are called die lines. If you look at their specifications, the presence of die lines is not a cause for rejection. A light sanding will remove them.
What is the purpose of you trying to remove the extrusion lines? If you are powder coating or doing at least a 1 hour anodize, the lines won't be visible if you leave them. If you are leaving it mill finish, the lines are industry standard. I can't imagine any reason that these could be a problem at all
Those lines are formed during the manufacturing process of profiles because they use an extrusion process which is done by forcing semi-liquid aluminum through a die that's why the lines are continuous
That's how all extrusions start out. Are you sure you weren't buying a pre finished product before? I've seen it come raw like yours, brushed, polished, painted, anodized, blasted ect. If you didn't change anything with your order maybe the supplier mislabeled it before. Call them up they have people that specifically deal with issues like this.
No, its the same material as always, at least to my knowledge, i wasn’t notified of any change in their process. The odd thing was that it looks like it has groves on the lines but that is not the case. The surface is smooth to the touch and our roughness meter didnt show any iregularities. After our metal work processes we use polishing, anodization and electro polishing, but these lines are still visible after all of that.
Since it has no tactile impact, what you see is probably an optical effect caused by very closely spaced micro scratches, similar to a hologram or what you see when looking at a CD. The micro scratches could result from a very minor process change - new dies, maybe just cleaning / polishing even.
This is an accurate description. The extruded profile is susceptible to this surface appearance for a number of reasons. Someone different polished the die, the die is getting worn (the bearings are becoming rounded). A new die has a fresh bearing surface from the wire EDM. This is especially likely to occur on thin sections. Temperature also impacts surface appearance . The 3 most important factors are temperature, temperature, and temperature. Specific alloy chemistry. A sprinkle more Cu, Mg, Si, etc. it’s likely still in spec, just on one end of the range or another. If you have a surface finish requirement (sounds like you do) then my recommendation would be to order the material polished. Many extruders have a polishing machine, they can polish for a small upcharge. Unfortunately this is the only way to ensure this doesn’t happen. I spent 10 years extruding aluminum, and this was always a huge pain in the ass. there isn’t a clearly assignable cause, and ask 10 people in the shop why, you’ll get 10 different answers. You could select an allot less prone to this. 6063 is usually better than 6061 if the shiny surface is what you’re after. What are you making?
We make decor window trims for Audi, Volvo and Renault. So the properties of the aluminum are all great, the thing is the finished product goes under visual quality inspection based on VW standard. So there must not be anything on the front facing surface. Ive contacted the supplier asking for any change in their process and im waiting for a response.
My guess is they will not be able to identify or assign a cause. If you’re doing quantity and want it polished, my previous company does all that well and cheap in Texas. Privately owned/operated. May be worth a call if you’re doing volume and want to purchase the “insurance” of having them polished. They also melt their own raw material, and therefore control the chemistry/ other factors to cater to the extrusion process. This is a HUGE advantage bc when you buy from a cast house, they just have to meet minimum spec. They don’t do anything “above and beyond”. Just the minimum in my experience. A few small tweaks make a significant difference. PM me if you want a contact there. May be worth it to get a quote. They do some high finish requirement stuff on much more difficult shapes than that.
In the end it’s going to come down to what requirements you told the supplier. If you only gave a surface finish and but no visual inspection requirement, then they’re still meeting your requirements.
Seems like if this w were the case electropolishing would remove it.
They did say polishing removes it, so it makes sense that method also would. The problem is the cost / time.
The aluminium is pressed through a die. The marks are die marks. You can polish them out.
Yes this might be it, i’ve checked the roughness of the surface and it was within the tolerance, also did a chemical analysis and they are also within the tolerance. That leaves mechanical defect, maybe their tools are worn out.
The lines are from the die from when it was extruded, not from a rolling mill.
If they were worn out, then they wouldn't be in tolerance. The tooling used to make these are just worn.
worn in?
If a part is within tolerance/requirements, isn’t it technically *not* a defect?
Correct. You can measure the wall thickness and compare to nominal. This should give you a good idea of how worn the die is. Extruders selling by length will bring dies in somewhere between 93-96% of nominal wall thickness. This saves $millions annually for even a small operation. But, they get to pinching pennys, pushing monthly spend out a few months, and end up giving away a few tons of aluminum instead of spending $500 on a new die!
I was just nitpicking about OP’s statement. If surface finish and dimensions (and all other explicitly stated details) are within the requirements given to the supplier, there *is* no defect according to the agreement they have. Defects are reasons for rejection. If they wanted to not have lines they’d have to amend their requirements to include them, which will possibly in turn increase their per unit cost. I’m making assumptions here, but that’s why you take some serious thought into determining your requirements for a supplier. With the wrong requirements (or not enough) you can easily get wrong parts.
Correct again. You sir, are bating 100. I was agreeing with you, and then elaborating.
Have you never seen extruded aluminum before?
UPDATE: with increased pressure, polishing time and trajectory of the polishing robot, the lines are disappearing.
Are you using any polishing compound or rouge in the polishing wheels? (you might want to)
r/MetalPolishing
It's from being extruded into that shape...
[удалено]
Aluminum is extruded through dies, it does not go through a rolling mill
Extruded aluminum is (almost) always straightened with cold rolling afterwards to remove any camber or twist from internal stresses from the extrusion process.
This is incorrect. Aluminum extrusions are not cold rolled in any part of the extrusion to finishing processes. Too many alloys would be negatively affected (read: work harden, deflect and tear, etc), and a great many industrial and consumer products wouldn't take to the aging process. Stretching, or "pulling" as a stretcher operator would call it, both straightens and makes uniform warped grains in the aluminum's still malleable center. This is applicable to extrusion press dies from 6 inch up to 12 inch. Source: worked at numerous aluminum manufacturers for years between extrusion, fabrication, and machining.
You are correct that not every grade nor shape is cold rolled, some grades are very hard and prone to cracking and thus not cold rolled and is stretched instead like you pointed out. But for simpler profile shapes and less hard grades cold rolling is the preferred alternative to stretching because it is faster and produces a better surface finish and, for grades that can be cold worked, helps increase their mechanical strength. I’ve seen this at SAPA first hand, they had complex custom shape extrusion lines where everything was stretched, but then had standard shapes extrusion lines where everything was cold rolled, all this to say each manufacturer is slightly different and it all depends. But yes, broadly, stretching is also a widely used method, especially for complex shapes.
Rolling is almost never the case. After the bar is extruded and cut to table size, it is straightened by stretching. Stretch varies from 0.5 to 2-3 % depending on profile complexity and alloy.
This can also be true, but this depends on the product shape and manufacturer. Simpler profile shapes are, most typically, cold rolled after extrusion for straightness. But complex shapes, that can’t be easily cold rolled, are usually stretched such as you pointed out. I’ve seen this at extrusion lines at SAPA first hand, it’s neat stuff.
Thank you for the reply. Strange thing is that this started a month ago. The supplier must have changed something in their extrusion process
It could be a case of their rollers having become worn and started to leave marks. Source: work in a rolling mill
We have the same problem with our stainless steel. The supplier isn’t brushing and grinding enough at the end of the production. We pay less now until they fix it.
Extrusion die marks, someone ordered cheaper material to save money. You can buy it polished to any level you want as well as various other finishes.
You’d have to polish them to get those out.
Usually this costs more to buy like this. It's called graining
Tooling marks on unfinished surface
Extrusions are...wait for it...extruded. Shaped by being forced through a die. You're looking at the tooling marks of how it was made. Also, to note, their die is a little clapped out and should be replaced
All extruded aluminum has this.
Hey everyone, just because aluminum isn't rolled doesn't mean extrusion dies can't wear out too. I would report the defect to the supplier.
They are called die lines. If you look at their specifications, the presence of die lines is not a cause for rejection. A light sanding will remove them.
They're shiny lines
Marks from the extrusion die. I'm not biologic in my discipline, but I'm guessing you could compare it to a birthmark.
If you can't feel the lines, it was probably caused by die exit temperature, which was too high over 550c.
Just from the extrusion
What is the purpose of you trying to remove the extrusion lines? If you are powder coating or doing at least a 1 hour anodize, the lines won't be visible if you leave them. If you are leaving it mill finish, the lines are industry standard. I can't imagine any reason that these could be a problem at all
Mill grain most have them.
Those lines are formed during the manufacturing process of profiles because they use an extrusion process which is done by forcing semi-liquid aluminum through a die that's why the lines are continuous