constructed in house or homemade vs self-made

Correct use:

"Assembled in house" or "constructed in house" is a phrase you use in science to say that your lab made something that you can't buy or order anywhere.

For example:

The filtration unit was constructed in house.

The bioreactor was assembled in house using glassware from Duran, Germany, and an impeller from Carl Roth, Germany.

"Homemade" means 

- something that you made 

- something someone made in their home

- something that was not made in a factory

For example: 

I brought a homemade cake to work. 

I'm wearing a homemade scarf, my mum knitted it for me. 

Origin of the confusion:

The German term "selbstgemacht" sounds confusingly like "self-made" in English, and this mistake is widespread in the German-speaking world.

The English term "self-made" is only used in one context: 

His parents were poor but he worked two jobs till he saved enough money to start his own business. Now he is a millionaire. He is a self-made man.

If you say "a self-made cake", it means the cake baked itself. A "self-made bioreactor" assembled itself.