The origin of the Mini-Jector goes back to 1946 and the development of the model #40 "Wasp" bench-top machine by Moslo Machinery of Cleveland, Ohio. The original Mini-Jector utilized the "V" mold system used today for the current machines. This machine used a rack and pinion driven by a steering wheel (from a Greyhound Bus!!) to power the injection ram.

The original machine was subsequently joined by the model #45, which used a large air cylinder to power the injection ram. Then came the model #50, which had a hydraulic power unit and a hydraulic cylinder to power the ram. The hydraulic unit used was a Vickers Power Pack, as used on tractor-portable agricultural implements. The "Wasp" series "V" mold principle, in which the nozzle force wedges the mold into a "V" slot in the machine base, offers a simple mold construction and the 15° included angle on the mold sides amplifies the vertical nozzle force by a 4:1 factor for mold clamping. (The "V" principle was also used by press maker Watson-Stillman on a small machine).

The model #60 machine utilized a lever-operated toggle clamp in a horizontal plane and the vertical heat cylinder of the "Wasp" series. These were dubbed the "Hornet" series and used more conventional molds. In 1955, W.O. Frohring, a scientist with a PhD in nutrition (he developed SMA baby food, the first artificial baby formula), purchased the Mini-Jector line from Moslo Machinery, who had developed larger production machinery and wished to divest the small product line. Mr. Frohring's son Roger had a small custom machine shop, and his son Glenn was just getting out of engineering school at the Case Institute of Technology. He felt this product would fit well with the existing shop and a budding engineer.

The entities of the three formed Newbury Industries Inc. in 1957. A vertical clamp line for insert molding (model #70VC95) was added that year as was a hydraulic toggle clamp installed on the model #60. Roger Frohring died in an accident in 1958 and W. O. Frohring passed away in 1959, leaving Glenn to operate the business alone.

A fully-automatic machine (model #65HA100) was added in 1960, and a horizontal machine (model #82HA200) was added in 1961. The business grew rapidly during the early 60's, but it really took off in 1964 with the addition of the model #H3-75RS, a 75-ton clamp machine that incorporated a reciprocating screw plasticizer. At its peak, this machine was produced at a rate of 20 units per month. The vertical machine line was boosted to 30 tons and became the single most prolific product of the company. In 1968 the H6-150RS, a 150-ton clamp machine, was introduced and was the leading seller in that size range in the United States.

Eventually, machines with up to 700 tons of clamping force (from the acquisition of the IMPCO machine line) were built. The small Mini-Jector line was no longer economical to produce in what was now a large facility with 185 employees. The last real Mini-Jector #45 was produced in 1987.

In 1993, Newbury Industries was sold to Heico, a Chicago-based holding company who, in 1996, sold the Newbury line to Van Dorn (now Demag Plastics Group). In the years prior to the sale, over 10,000 machines had been built by Newbury Industries.

At the time of Newbury's sale to Heico, Glenn Frohring retained the Mini-Jector name and the rights to produce small machines similar to the originals. Mini-Jector Machinery Corp. was founded, and a new line in the spirit of the "Wasp V-mold" type machines was developed. Later, vertical machines, models #70 and #75, plus a new fully-automatic model #60 were added using state-of-the art controls. The model #55 machine was the first and only bench top screw-type machine on the market.

By 2004, machine demand was reaching the limits of a cottage industry business, and Glenn was approaching the "big 7-OH." RAF Fluid Power, who had been one of Mini-Jector's key vendors, supplying hydraulic, pneumatic, and electronic equipment, decided to purchase the Mini-Jector line. In doing so, they brought to it their wealth of expertise and much-needed capacity. RAF created Miniature Plastic Molding internally to manufacture the line but wisely retained Glenn as a consultant. The future is very bright for the product line, and many new innovations are in the works.