Local 3-D printing startup 3DLT is partnering with a Pittsburgh company to get its designs to consumers in retail stores. Covington-based 3DLT on Tuesday announced the partnership with Pittsburgh-based PieceMaker Technologies. 3DLT is a platform for 3-D printing as a service, with an online marketplace of designs that can be sent to its network of affiliate printers to be created and shipped to consumers. The startup in March collaborated with Amazon.com to pilot a new section on the e-retailer’s…