Customer control of supplier's process

We have created a product and provided information to our customer about its critical characteristics and how we control out process to the machine type level.

Our company has hundreds of this type of machine. As long as we use the same "recipe", it does not matter what machine we run the product on, we will get the same result.

Our customer is pushing us to guarantee them that we will run their product on the same machine every time, and has hinted that they want the same operator to run it every time too. They want to know exactly every maintenance step we do, etc. We do not feel that this type of information at this level is so critical that it needs this level of micro management. Next they will want us to guarantee that we only make the product when there is a full moon, it is exactly 70 degrees outside, and Joe the operator has had spaghetti and meatballs from his favorite restaurant before starting.

Any ideas how I can convince them that we are capable of defining and controlling what is critical and that if something is found to be a risk we will add it into our control process?

Thanks for your help.

Why not offer to run a few validation production runs?

You can report which machines you used, the characteristics of the products produced. When all the products come out the same and you can show that it doesn't matter which machine, or operator you use.

Yep. Dazzle them with data.

What type of process? Is it machine dominant or tooling dominant?

They can have it run any way they want, everything comes with a price...

It is wire bunching. It is highly dependent on the tooling and operator's setup.
Thank you!!