In the 1980's I read a short story in an anthology. The short story was called "Hey Diddle Diddle". It was about some guys in a space station (I think) one of which pilfered equipment to make a machine that made milk from, if I recall correctly, paper. Googling for this has not helped me as there are other stories called Hey Diddle Diddle that do not seem to match this one. If possible the name of the anthology would be very helpful also.
"Hi Diddle Diddle!", a novelette by Robert Silverberg; first published (as by "Calvin M. Knox") in Astounding Science Fiction, February 1959, available at the Internet Archive. The story was reprinted in Silverberg's 1975 collection Sunrise on Mercury and Other Science Fiction Stories, and in two 1969 anthologies edited by Harry Harrison, namely Blast Off and Worlds of Wonder. If you read it in the UK, I guess Blast Off is the most likely place.
He saw by the sly looks on their faces that they were completely hooked. There hadn’t been a really good gag at Lunar Base Three in a couple of months, not since a computer man had programmed one of the heavy-duty robot drudges to give hotfoots. Mason could hardly wait until the first quart of milk came from the synthetic cow.
[. . . .]
Maury Roberts and Nat Bryan stuffed the waste-paper bale onto the intake platform, while Sam Brewster’s hand hovered over the electronic keyboard that controlled the entire operation. He thumbed a switch. The machine hummed. The bale of paper moved ponderously forward, into the jaws of the shredders.
From there the shredded cellulose proceeded to the first stomach to be mangled and pulped into a soggy semiliquid; then on to the second stomach for further breaking-down, then to the wringer in the third stomach, then to the fourth, where digestion proper could begin. Translucent feed lines spurted enzymes into the system at the properly programmed intervals. Counters clicked; gears meshed. The effect was imposing.
According to Mason’s computations, the process, vastly accelerated over its natural counterpart, would take about three hours from waste-paper to milk. The time was 0540 hours when the first few drops of yield came filtering through the udder. At 0650, after Maury Roberts had run some quick chemical tests and after the yield had been refrigerated, the six bleary-eyed experimenters gravely toasted each other with milk that was milk to the last decimal point.