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Defects in the Laser Cutting Process & How you Remedied them

PM2.5

Plastic
Joined
Oct 17, 2017
Hi,

I'm doing a Six Sigma defect reduction project with a company I just started working in as part of a distance learning course I'm doing. I'm don't have access to customer complaints as of yet and I don't feel I am in a position to contact customers to ask them directly what types of defects they are most commonly coming across when they receive our products.

I am looking for issues that people mainly come across when receiving laser cut parts. Some examples I have seen which are directly related to the laser cutting process include excess dross, sharp edges, poor quality holes, rough surfaces along the edges, parts warped due to excessive hear. Other defects include incorrect quantities, scratches on parts, missing holes. A lot of these errors appear to me to come from upstream processes so it's not typically operator error. Combination of a lot of things really and I'm trying to do some root cause analysis to improve things.

Would appreciate if anyone could give me other examples of errors on top of the above and even better how did you go about rectifying them.

Thanks.
 
I'm a pretty novice operator (1 year, no training) running a pretty old (1998) CO2 laser cutter so the input I have may not be applicable, but here goes anyway.

First- Read the manual. The whole thing. It goes over every function and how to correct any issue you could ever have.

One issue- Our laser does not have an auto focus head. There is a little thumbscrew you have to turn to get the focus where you want it. The previous operator only ever adjusted the focus to the condition the manual says to calibrate it to, but never adjusted the focus to match material type and thickness. We went from having to use Oxygen for everything and grinding off the dross, to using nitrogen on stainless and getting little to no dross on 12 gauge parts.

Make sure your operators know how to do a mode burn quickly and accurately. I guess your laser probably doesn't have any of the slope/centering/beam shape issues these CO2 lasers have, but we could have saved so much time if the operator just checked the beam and called our repair guy when it was a C shape that wouldn't cut even 18 gauge mild steel correctly.

A lot of corner issues can be resolved by rounding corners, if acceptable.

Pickled and oiled steel tends to cut better than regular hot rolled steel.

Our lasers also wouldn't cut very well on Mondays. Management assumed the employees were at fault. It turns out the resonators have a slight leak, so the pressure rises in the optical cavity and arcs start to form between the electrodes. We do gas changes every Monday now, even if it only has a few hours on it. One of our lasers has a bad servo board, and takes several hours to get to start, so we just leave it on. If the power fails, the machine stays off until it is absolutely needed, where we start the weird and time consuming startup process. This means it often sits for a couple of weeks, and if someone tries to use it without a gas change the pressure in the resonator is so high that it won't even make a beam, and just results in bright, visible arcing between the electrods in the resonator. Which looks kind of neat, but will totally destroy our electrodes.

Hopefully that helps somebody with something.
 
All the cut issues are not normally my problem, properly maintained lasers cut fine, my issue is the humans in the process.

Over here a good laser is a 1/3 million quid, then you need a big space. then they employee monkeys to run it seams to be the norm.

My key problems, in order of mine and my customer's importance!!

1. DELIVERY TIMES, what ever you say, fucking stick to it, this is the 21st century, you want me to outsource to you i need to know how much time you need, if its over 2 weeks, thanks will go else were! Its not use to me if its more than 2 weeks out or varies bettwen 3 days and 4 weeks. Equally if you have a material supply issue call, theres options, don't just ignore me. If your late delivering im online looking for a supplier for next months order because you clearly don't want the work!

2, QUOTATION. If i can not log on and get a qoute, yeah again i am not interested in using you, its too fucking slow to get back to my customer with a price if your going to take a week to quote from a dxf. I much prefer to do this myself as it reduces the fuck up rates immensely! Equally i get a lot of work by drawing parts and getting a price back to a customer before the rest of the world starts work on a Monday morning, help me feed there impulsiveness!

3. PAYMENT, you want payment up front, cool im fine with that, even if i have done over 5K with you in the last 6 months, but don't penalise my delivery date because your account monkey is only in 1 day a week and needs to check the payment went through or it takes you 4 days to send a proforma invoice!

4. GET IT FUCKING RIGHT!! If i order 2B 304 i want 2B not brushed, if i order 2mm i want it cut in that not 3mm etc. By all means chuck in some spares if you wish, just bare in mind that unless that makes a complete assembly there as much use to me as well shelf filling!

So far i have used over 7 different laser suppliers here in the uk, 1 of them i still technically have parts on order 3 years later and they still have not worked out a price??? Others have either been nuts delivery times, shit quality or just too slow - painful to deal with.

1 Stands out, i ordered from them the first time last Monday, had the parts Friday morning and delt with my own quote online and paid as soon as i pressed order using there same online system, yep they were a little more costly than previous ordeals, but fuck me, if its like this every time theres going to be over £500 a month heading there way in orders and that’s growing too by circa £100 a month every year. I have the parts, i have a ever growing customer base, i can draw the parts, i just need a supplier that can hit a reliable time frame and i think i may have found the long term one! 5% cost premium is well worth it. Its the 21st century, i don't want to send emails asking were is it when its already late, i don't want to have to call and talk to you, i just want my parts in return you get your money easy right? Help me do it well and faster than my competition and its easy for my orders to increase. Fuck with the time line and make me miss trade shows with product and you get replaced.

FYI IP LASER is the online - webstore front software you want if you want to sell laser cutting online, its dead easy to use! Best of all it lets the customer set all the materials and part profile quirks, hence reduces loads of potential errors!
 
Another big thing we used to struggle with is how long it takes for the laser operator to notice bad cuts. We would often end up with full sheets of unusable parts, especially when parts are tabbed in (tabbed parts get removed as a full sheet and set aside until the operator gets to separating them). Now it's standard practice for us to frequently look at the sparks and the pierce pattern while cutting, and we pull the first part after a condition change and pull another part every 5-10 minutes for quality control, depending on the part and material.

The next thing is, what happens once you find an issue? In some cases the operators just spent longer deburring, or just slowed the feedrate to what worked. You need a method of reporting issues with the laser in a way that gets resolved. If you keep saying "you should be able to fix that" you'll get the same garbage unless you train them. It's the employee's responsibility to ensure good quality parts come from the machines, and the employer's responsibility to ensure the employees have the knowledge and tools to do so.
 
PM2.5 you need to define the accountability where it belongs and hold them accountable. I would need a bit more info:

1. What kind of Laser(s)? Stand-a-lone, FMS System???
2. Who does the programming? Some one in the Engineering Department or the Operator running the Machine? Or is the Operator supplied a Flat to "nest/program" at the Machine?
3. Do you do first article or first off inspection?

In our shop Engineering creates the Flat Pattern (DXF) to be nested by the Operator and generate the program at the Machine in our FMS System Lasers. If the parts are run in our Stand-a-lone Lasers the Engineering department programs the Part or Parts in the case of a multiple parts on the same sheet.

The Flats for our FMS Lasers (DXF file) are stored on a server in a customer directory identified by Part Number and Revision.

The Programs for the Stand-a-lone Lasers are stored under a Customer Directory and identified by program number. The Program Number is linked to a Set-Up Sheet provided to the operator in the shop packet. This has the Part Number and Revision Level.

In either case Engineering is responsible to make sure all the features of the Part are in the program, the Sheet/Blank Size is correct and Material type and thickness is identified.

Both departments run first off parts. The operator is responsible to assure all holes and features are in the part comparing to the Blue Print, the holes sizes are correct to the Blue Print and the Material and thickness matches the Blue Print and the parts has met the finish requirements defined or expected by the customer prior to submitting the first off parts for final review by QC. Both the operator and QC sign off the router. Note everything is compared to the Blue Print not the Flat supplied by Engineering. A double check if you will.

During the run on a production order the operator is responsible to watch the product coming off the machine for defects, issues, changes and adjust accordingly. This inspection frequency changes based on the part running. A part with a +.001/-.000 hole tolerance will get check more frequent than a part with +.010/-.003 on a hole size. Risk Analysis is key and the hardest thing to teach.

You need to define expectations, rules and a play book for the departments to follow. Should some one drop the ball a Product Nonconformity Report needs to be generated. We do this for all issues across the board. The information is tracked by Department and personnel so we can watch trends and get them fixed sooner than later. This information is shared weekly in our Staff Meeting and in the weekly quality meeting. Each department head responsible addresses the actions required to make sure it cannot happen again. We started this program 15 years ago. the list was long but over the years we have closed the loop holes which cause problems, assigned accountability and gave the department heads the authority to make things happen. The list now averages 10 items a week of which 6 of 10 are internal issues and 4 of 10 are related to supplier issues outside of our plant.

Watching the trends, where the majority of the problems are helps identify the low hanging fruit to be acted on to get the greatest return in the shortest amount of time. Once the fires are put out it becomes a continuous improvement process. And it works.
 
I'm quite happy with the laser shop we use. Good comments above but one minor issue I had on one run is they put the tab right on the short edge were were gauging off on the press brake. I suppose I could have sent them a drawing as well as the DXF but it was a surprise.
 
^ yeah tab control would be great, but most of the nesting software i have ever encountered either leaves it wide open and tabs were it wishes or you give it a fixed spot. Lot of the bits i do and have had cut over the years there's oftern edges or areas were the tab can be with zero effort - no need to remove. Yet trying to relay that is more effort than a quick 2 secound hit on the belt sander! But sure would be great if you could specify prefered tabbing locations, can be a right ass if there right on a tight internal radius!
 
Yea, tabbing can get be trouble some. We do work for another laser shop that will send over the drawings and print showing where tabs need to be placed. Most instances if they are getting formed we put the tab around the bind line so it gets "hidden" in the radius. I have used that same method on our parts as well and it seems to work great. Typically we hit the "tit" off on the belt sander. Just a thing i like to try to do for people. I would recommend telling your laser house where to put the tabs. It may take a phone call, but i would rather you tell me you need it in a certain spot instead of just placing it randomly. Especially if you are doing the forming at your shop.
 
Great posts !
Agree 100% on what suppliers need to do.
Online-pricing, realtime quotes, deliver as agreed, deliver what is agreed.

And agree 90% of all suppliers of everything are useless in terms of building what they *should do*.
Automatic checking on consumables, cut current/material/etc, would lead to much better consistency.
Monitoring, automating, measuring, testing, improving stuff.
 
You guys running Lasers and Tabbing should look into reversing the Tabs. Leave the "Tit" on the slug to be thrown away. We came up with the concept years ago and Ncell incorporated it into their Software with the agreement we had the opportunity to run it for a year before it was included in their Software.

Yes it leaves a little divot in the remain part but less work. We have invested the time to educate our customers on the net effect on cost and most allow it.

We never Tab on a edge that will be used for registering the part 99% of the time. If we are tabbing Slots we do so on the ends of the Slot where the travel of the mating item will not be an issue.
 
Never ever realised you could do it in such a way as to achive that! That said the small divot would not probably be as acceptable on some of my parts. Anal customers!! but for some products i can see were that would be nice.
 
Problems I have had with four separate shops, one I used for about five years:

Inconsistent pricing, like 300% variations on random parts month to month.. And this was on reasonably large orders like $5K to $12K at a time.

Inconsistent tabbing and tabbing removal, we would send a drawing with tab marks and they would move the location to a bad place to make removal faster, then they would use a large belt grinder to remove the tabs which resulted in parts that would fit sloppy in the tooling because they had removed too much.

Large scratches from inserting into the machine, we had about $500 worth of parts that had been cut from a sheet or sheets that looked like it was dragged on concrete.. So rough that it changed the measurable thickness by 30%.

Poor palletizing, using broken poorly repaired pallets for a $12,000 order is moronic at best. Having $400+ worth of parts that I waited five weeks on destroyed because it fell through the broken pallet is rage inducing. And a single sheet of cardboard is not going to stop the nails in the pallet from scratching the crap out of my stuff. A half a sheet of OSB would cost like $5. 4,000 parts sitting top of a pallet in stacks of 200+ are NOT going to stay there unless you bundle them, five wraps of shrink wrap is NOT going to cut it.. And small parts need to go in boxes not just balanced on the boards of the pallet.

Ungloved hands on bare carbon sheet, I got one batch back that had to spend two hours in acid to get the rust scale off, the reason? The unloader was eating chips while unloading and was leaving salty sweaty handprints on each part. We found two empty chip bags in with the parts and visible chip crumbs on the parts.

Crooked parts, I don't know how it happens, but on average I get about .3% of the parts with the locator holes visibly misaligned with the outside of the part.. Like I stick a pin through the locator part and one part is sticking up 1/8".. I think my supplier would cut all the locator holes and then cut the outside of the parts, so if the machine jumps location a little or the sheet walks a little I have parts that have holes in the wrong spot.

Metal thickness variations up to 20%, which when you are doing wipe bending results in longer flanges and parts that get jammed in tooling resulting in damage.. Even when we requested and then demanded actual measurements of the actual sheet being used we would get a generic number off the chart, like 22 gauge was stated to be .0299" and then would show up at .0365" which is actually perfectly 20 gauge...

The wrong thicknesses ended up being the breaking point, we had almost $9k in extra costs to fix the mess up on a $6K order. I have my own machine coming in and we are going to see how hard this actually is.
 
^ Decent laser and its effortless have ran 2!! Its all the other shit that goes with it that my suppliers seam to fuck up. Cut the holes then the part profile then the next part, cutting all the holes in the sheet first is a no no!! Holes then part od and on a newish laser you will be within or under single digit thou's of location all day every day. Nothing fucks me off more than getting alu parts cut and there all lovely apart from were there was a bit of shit on a cut hole and they decided to randomly take it off with a angle grinder and a 40 grit disc meaning instead of selling the part i get to spend a fucking age removing the scratches.
 
Problems I have had with four separate shops, one I used for about five years:

Inconsistent pricing, like 300% variations on random parts month to month.. And this was on reasonably large orders like $5K to $12K at a time.

Estimators just guess at the linear inches of Laser required. Some are good at it and some are not. If you have the ability to provide them with a Flat DXF file you have the ability to tell them how many inches of Laser is required per part. Provide it on the prints. I see more and more of this from our customers today.

Inconsistent tabbing and tabbing removal, we would send a drawing with tab marks and they would move the location to a bad place to make removal faster, then they would use a large belt grinder to remove the tabs which resulted in parts that would fit sloppy in the tooling because they had removed too much.

That is just poor workmanship. That is a supplier quality issue. I hope you are rejecting the parts for replacements at no charge and asking for a corrective action.

Large scratches from inserting into the machine, we had about $500 worth of parts that had been cut from a sheet or sheets that looked like it was dragged on concrete.. So rough that it changed the measurable thickness by 30%.

Unless they have a Loader System they are using a Fork Truck to load the blanks. We made plastic covers for our Forks. They can pick up a 3500 lb bundle and not leave a mark. As set of Fork Guards lasts about a month if used properly.

Poor palletizing, using broken poorly repaired pallets for a $12,000 order is moronic at best. Having $400+ worth of parts that I waited five weeks on destroyed because it fell through the broken pallet is rage inducing. And a single sheet of cardboard is not going to stop the nails in the pallet from scratching the crap out of my stuff. A half a sheet of OSB would cost like $5. 4,000 parts sitting top of a pallet in stacks of 200+ are NOT going to stay there unless you bundle them, five wraps of shrink wrap is NOT going to cut it.. And small parts need to go in boxes not just balanced on the boards of the pallet.

Again workmanship...see above. Nothing changes until something changes.

Ungloved hands on bare carbon sheet, I got one batch back that had to spend two hours in acid to get the rust scale off, the reason? The unloader was eating chips while unloading and was leaving salty sweaty handprints on each part. We found two empty chip bags in with the parts and visible chip crumbs on the parts.

Food at the work station is a no-no...workmanship. We employee certain individuals who have acid on their hands without the chip. They know who they are and wear gloves we supply all day everyday. Reject and look for a corrective action.

Crooked parts, I don't know how it happens, but on average I get about .3% of the parts with the locator holes visibly misaligned with the outside of the part.. Like I stick a pin through the locator part and one part is sticking up 1/8".. I think my supplier would cut all the locator holes and then cut the outside of the parts, so if the machine jumps location a little or the sheet walks a little I have parts that have holes in the wrong spot.

More than likely this is from hitting a tipped slug. When the Nozzle hits a tipped slug at 1200 ipm the sheet is going to move. The key is know when to run with the head down and when you need to lift it. Nozzle strikes can be detected by looking at the Tip after the sheets is run. You can learn by doing this and if you see a strike you know that sheet needs to be sorted. Shit happens but it cannot get to the customer.

Metal thickness variations up to 20%, which when you are doing wipe bending results in longer flanges and parts that get jammed in tooling resulting in damage.. Even when we requested and then demanded actual measurements of the actual sheet being used we would get a generic number off the chart, like 22 gauge was stated to be .0299" and then would show up at .0365" which is actually perfectly 20 gauge...

My experience here is the way they inventory the Pallets of like material. If you combine 6 lots of .0635 Galvanneal you are going to have up to 6 different thicknesses running in the same order. Material management is critical if you are not ordering to the job and are pulling from inventory. Nesting can also cause a variation of this. If the dynamic nesting software allows parts to go in any direction on the sheet, grain direction will have the same effect on forming and angles.

The wrong thicknesses ended up being the breaking point, we had almost $9k in extra costs to fix the mess up on a $6K order. I have my own machine coming in and we are going to see how hard this actually is.

Good luck...how do I know all this...been around Lasers since 1979 in the Fabrication business. I have seen it all. Having a corrective action and root cause program is key to getting rid of these issues. When we got our first FMS System we had nothing but problems...funny after 6 months of running light on and lights out how smart the machines got.


^ Decent laser and its effortless have ran 2!! Its all the other shit that goes with it that my suppliers seam to fuck up. Cut the holes then the part profile then the next part, cutting all the holes in the sheet first is a no no!! Holes then part od and on a newish laser you will be within or under single digit thou's of location all day every day. Nothing fucks me off more than getting alu parts cut and there all lovely apart from were there was a bit of shit on a cut hole and they decided to randomly take it off with a angle grinder and a 40 grit disc meaning instead of selling the part i get to spend a fucking age removing the scratches.

Not sure what kind of "Shit Show" shops you guys are dealing with but I cannot remember a Laser defect ever reaching a customer. Sure there has been internal issues but they do not get out of the door...well that I can remember. If my Quality Manager wasn't on vacation this week I would ask him for a report on those work cells. All issues are tracked by department and operator...why so we can fix it!!!
 
Good luck...how do I know all this...been around Lasers since 1979 in the Fabrication business. I have seen it all. Having a corrective action and root cause program is key to getting rid of these issues. When we got our first FMS System we had nothing but problems...funny after 6 months of running light on and lights out how smart the machines got.




Not sure what kind of "Shit Show" shops you guys are dealing with but I cannot remember a Laser defect ever reaching a customer. Sure there has been internal issues but they do not get out of the door...well that I can remember. If my Quality Manager wasn't on vacation this week I would ask him for a report on those work cells. All issues are tracked by department and operator...why so we can fix it!!!

Well I reported my issues multiple times and I honestly think it never got past the sales rep.. The way the company was setup I really did not have access to anyone else to complain... We spent about $120K with them over about four years. A few times I would get pissed about the lack of assistance and send a dozen quotes off to other companies, the problem I ran into is very few ever responded to quote requests from out of state.. The few that did often had quotes for a small part that was running 70 cents from the current supplier and they would quote around $8.00 even with a full load of parts... I expect price differences but more than 10X higher? :nutter: I had a few that came in at the same or lower but only had local pick up or only shipped UPS or offered a sample piece and never delivered.. Bizarre stuff.

I demanded something be done about the parts cut from the wrong thickness material and basically their solution was to not pick up the phone for a few weeks and not respond to emails. I don't think I was being a problem customer seeing as I had worked with what arrived every time until that point, and asked for corrections via email for the next batch..... If you're running a laser cut house. Be sure to watch the emails your sales reps are getting in or have a complaint submission form that goes directly to you..

And when I said I had problems with incorrect thickness we are talking actual measured thickness of flat parts with a micrometer not results after forming, in my book if you have steel that has a 22 gauge sticker on the roll or stack and lab documentation, but it measures perfect nominal thickness of 20 gauge, then it was mislabeled, having thick stacks of paper saying it is right does NOT make it work.. I was running other parts in a punch press and blanking dies and my local steel sheet varied at most a few thousandths over 20+ separate orders over eight years.. I actually save samples of each order for reference, the difference between most batches is hard to pick up with a micrometer.. A 7 thousandths thickness variation on a product that is only 29 thousandths thick is basically unworkable, it is 20% more metal.. I can't think of a product that allows for that much variation.
 
Well I reported my issues multiple times and I honestly think it never got past the sales rep.. The way the company was setup I really did not have access to anyone else to complain... We spent about $120K with them over about four years. A few times I would get pissed about the lack of assistance and send a dozen quotes off to other companies, the problem I ran into is very few ever responded to quote requests from out of state.. The few that did often had quotes for a small part that was running 70 cents from the current supplier and they would quote around $8.00 even with a full load of parts... I expect price differences but more than 10X higher? :nutter: I had a few that came in at the same or lower but only had local pick up or only shipped UPS or offered a sample piece and never delivered.. Bizarre stuff.

I demanded something be done about the parts cut from the wrong thickness material and basically their solution was to not pick up the phone for a few weeks and not respond to emails. I don't think I was being a problem customer seeing as I had worked with what arrived every time until that point, and asked for corrections via email for the next batch..... If you're running a laser cut house. Be sure to watch the emails your sales reps are getting in or have a complaint submission form that goes directly to you..

And when I said I had problems with incorrect thickness we are talking actual measured thickness of flat parts with a micrometer not results after forming, in my book if you have steel that has a 22 gauge sticker on the roll or stack and lab documentation, but it measures perfect nominal thickness of 20 gauge, then it was mislabeled, having thick stacks of paper saying it is right does NOT make it work.. I was running other parts in a punch press and blanking dies and my local steel sheet varied at most a few thousandths over 20+ separate orders over eight years.. I actually save samples of each order for reference, the difference between most batches is hard to pick up with a micrometer.. A 7 thousandths thickness variation on a product that is only 29 thousandths thick is basically unworkable, it is 20% more metal.. I can't think of a product that allows for that much variation.

If we don't respond to our Customers we are off the Quote List and removed from their Vendor Data Base. We I have an issue with a Supplier they don't get paid until the issue is resolved...no matter what!!! The way into a company when nobody listens is to not pay the invoice. They will call you and you don't have to waste the time trying to call them.

If you fabrication services...I know a shop...
 








 
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