We’ve seen many production sites in the last years and all of them have one thing in common: lack of spareparts and very low stock level.
But as every story we need to start from the beginning:
when a lithium battery cell manufacturer decide to move with one or multiple equipment suppliers, in most of the cases (especially for new camers) he doesn’t have any idea about which are critical spareparts and how often they need to replace into the machine. It’s even hard to obtain these info from equipment suppliers since in many cases they have a rough list and estimated working life for each critical component. But, as you know, theory and reality not always meet each other. It’s not easy for equipment maker have constant feedback from manufacturing plants about the working life of critical parts and even some indication about the failure modes, this for sure would improve they capability to support the end user but in many cases they still with assumption and theoretical values.
The scenario is worst if we consider production plants with prototype equipment: due to tight timeline and in some cases limited budget the R&D or equipment testing team in supplier site is not able to test the working life of new components and the critical ones so in many situations they are not able to provide any estimation even due to absence of history for that dedicated equipment functional group.
So, without experience is very difficult understand how many spareparts the cell maker need to purchase and the frequency.
Is it a real pain?
The answer is yes. Let us make some example:
if we look at mechanical notching machine, theoretical working life of notching tool before resharpening is about 1Mln cycles, but practically this depends on electrode composition, thickness, quality of mechanical assembly (this could affect heavily the working life) and maintenance frequency into the machine. So let’s say the working life could be 1Mln +/- 30%.
How long a notching machine takes to reach 1Mln cycles?
For an high speed notching machine, the throughput could be around 300-350 notch/minute. So we can say in 2-3 days the notching tools end their working life and must be resharpened. So as you can see the frequency here is high but the limiting factor is not just the working life: have you ever re-grind a notching tool for lithium battery manufacturing?
Very few in the world are able to do that. Everytime we aware costumers about that and everytime the answer is: “ahhhh don’t worry we have already a supplier which can resharp this kind of material”. The results at the end is a desperate run to search a good supplier to avoid long production stops. Koreans are masters on that, and in europe very few facilities are able to do this job, delivery time? Even 2 weeks.
But the working life of a notching tool is not infinite, after 10 to 20 re-sharpening cycle, it becomes unstable in cutting and you loose accuracy and quality so you need to search for a new one. Even here the research is desperate, but usually who is able to re-sharp is even able to design and manufacture a new one.
And this is just the example of notching tools, but we can talk for days about others like:
- Cutting blades: same issue of notching tool. The challenge is to obtain a perfect cutting edge on the blade surface to avoid to damage electrodes during cutting. Any small surface defects on the edge of even 20-30um could trigger equivalent or even bigger defects on electrode cutting edge which can results in shortcircuit or particle generations so affect the working life and health of the battery cell itself.
- Horn and anvil for utrasonic welding: 6-10 weeks delivery time. High cost, the validation of a horn follow many steps and micro crack in the body of the horn due to the manufacturing process can affect heavily welding performance and welding quality. Else, the welding pattern on horn and anvil surface is not easy to manufacturer and required anti adhesive treatment.
- Winding spindle/mandrel for winding machine: circularity and other geometrical tolerance are very tight. Here we are talking about hard metals and in some case tungsten carbide. Small misalignment in the winding spindle shape can trigger material misalignment during winding cycle affecting heavily machine OEE and yield.
- Lamination roller in lamination and stacking machine: surface treatment and manufacturing tolerance are the main issue. Lamination rollers must be perfect from geometrical and surface roughness point of views to avoid material misalignment and create high local pressure points which can trigger shortcircuit in the battery cell.
- Special belts with silicon coating
- Forming tool for pouch forming: tolerance and manufacturing has same complexity level of a notching tool.
- Sealing bars for pouch sealing: the bars are made of soft metals to allow high heat conductivity. The manufacturing process is costumized and foreseen to work the bars at high temperature (simulating working condition). Planarity, surface roughness are the main key tolerance to allows a good sealing line on the pouch; any misalignment or defects could trigger wrinkles and other functional defects.
- Grooving and crimping tools in cylindrical cells
and many others…
If we look at emerging markets for lithium battery like europe, India and why not, even USA this is a big issue for battery produceder and in most of the case underestimated.
So the first step is for sure the experience, but a deep study of manufacturing process in each equipment can identify in advance the most critical components.
Then commercial agreement with equipment suppliers which foreseen the shipment of some volume of spareparts at fixed frequency and/or deep partnership with local or strategic suppliers could minimize this issue and avoid any quality drop in the production. All these activities must be in charge of manfuacturing and production team in pre-operation phase. Start to face this kind of issue in production is to late and can trigger huge waste of money and delay in product delivery.
Else, locally we need a huge development of supply chain to minimize the delivery time of this components and allows to get local suppliers avoiding to belong to the well known Korean and other asian suppliers which foreseen in some case long delivery time due to shipment of components overseas.
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