Not sure if I'm a boffin but here it goes
Things to consider.
You aren't just heating lacquer you are heating lacquer and can this will take longer.
Your lacquer may need time to cure , does it just need to hit x temp or does it need to mantain that temp.
As someone mentioned focusing and angling of lights or products may be an answer, I would also imagine placing a reflective layer around the inside of the machine and on surface of conveyer belt may reduce overall energy absorbed by insignificant entites.
The manufacturer says hit 250c as fast as possible and all should be good, from what i understand we are not the only one with this problem but others have no problems, i need to find out how those people are curing it.The lamps may be slightly less efficient (or slightly more) at higher power ratings but this doesn't really resolve your issue.
If your goal is to have the lacquer harden and you don't directly care about heat production then I would look at the actual curing process of the lacquer.
What you might find is that there is a an amount of time required at a certain temperature needed to cure. Increasing the heat may not resolve any issue. You need o contact the manufacturer of the lacquer, or investigate alternative solutions.
You might have to invest in an industrial oven so the cans can effectively bake for 1-2 hours (or maybe just 5 minute etc.). 12seconds might not be enough for most regular lacquers.
You might find that passing the cans through the heater multiple times does the trick.
Russian Customer no idea what they are putting in itWhat i want to know is what products are currently being sent out in cans with wet lacquer still in them?
Try and see a 24K if you're feeling brave, so much heat haze from thoseGet some 5K fresnels on the go! They are some hot and blinding mofos!