MERGERS AND ACQUISITIONSVaritronics Inc., Plymouth, announced it has been acquired by a group of private investors based in Minnesota. The company had previously been owned by Brady Corp. and has been managed by David Grey, president and CEO. Grey will continue with the company, which will operate under the name Varitronics LLC.

DEBT AND EQUITIESProto Labs Inc., Maple Plain, has filed a registration statement with the Securities and Exchange Commission for a proposed public offering of $100 million of its common stock offered by certain selling shareholders and Proto Labs. Proto Labs expects that its portion of the offering will result in about $3 million in proceeds. Proto Labs will not receive any of the proceeds from the sale of the shares sold by the selling shareholders. The principal purposes of this offering are to facilitate an orderly distribution of shares for the selling shareholders and to increase Proto Labs' public float. Proto Labs intends to use the proceeds that it receives from the offering to pay the expenses that it incurs in connection with the offering and for working capital and general corporate purposes. The joint book-running managers of the proposed offering will be Morgan Stanley & Co. and Piper Jaffray & Co.

PERSONNELImage Sensing Systems Inc., St. Paul, named Kris Tufto president and CEO. Tufto, a board member since September 2011, had been serving as interim president and CEO since Aug. 14. Tufto will also remain on the board of directors.

Kohnstamm Communications, St. Paul, has named Greg Zimprich senior vice president of agency operations and strategic insight. Zimprich previously was director of brand public relations at General Mills Inc., Golden Valley.