Will any of the reflect collection attachments harm my mixer?
All the attachments have been designed to prolong the life of your mixer. We have worked hard to make sure that the attachments are in balance and do not put any more load on the motor than the ones provided by the manufacturer. The amount of drag our accessories produce is far less than that of a flex edge beater and almost identical to the manufactures flat beater.
I have heard that they may invalid the manufacturers warranty.
The warranty varies across different countries but generally the warranty covers parts and labour for a period of between 1 and 5 years depending on the model. In the UK, the general conditions (https://www.kitchenaid.co.uk/static_assets/pdf/KA/KA_SDA_uk.pdf) we have read states “The contractual warranty ceases to apply in case the purchaser or a non-authorized third party modifies the appliance.” The most common interpretation is that this does not refer to using an accessory or attachment.
The mixer manufacturer wants you to buy from them and not the competition. There are many accessory manufacturers and to date we are not aware of any cases where the use of any of these accessories has affected a warranty claim. In 2009 KitchenAid claimed that flex edge beaters raised the internal temperature of the mixer beyond that of using the standard beater in an attempt to put customers of buying them. Three years later they bought out their own.