The Importance of a Panmixer
Yes - panmixers are expensive. The speciality engineering of rolling metal to form the circular pan combined with the high-cost motor that drives the paddles to rotate at a high torque ratio to blend the aggregate properly all day everyday for years - that does come at a cost.
But what is the alternative?
MIXING BY HAND
Mixing concrete block mixture by hand, employing labour & using spades, is certainly sufficient for personal brick-making. In fact, much of the time it is a cost-effective solution for entry-level commercial brickyards.
However, there are three major drawbacks to this old-school method.
It is labour intensive; It adds to the cost in an already-labour driven process of brickmaking
It can be a slow procedure to mix piles of aggregate for the machinery - most of the time this is where the bottle neck occurs, limiting the daily production while the machinery waits idle
It will not be as uniformly mixed as with a panmixer, which will result in brick strength variances across batch productions (possibly even within the brick / block / paver itself)
The idea behind this method is to take your aggregate (sand/grit/crusher dust) & blend it with a ratio of cement. Spades are used to "turn" the drymix repeatedly with 2-3 people at this mixing station. Once the colouring shows sign of uniform distribution, the water can be added & the turning process repeated until the mixture is also of uniform moisture.
Clumping may occur during the adding of water & typically the spade is used to pat down the mix to break the coagulated balls before being turned again into the rest of the mix.
The metaphor to use here would be to compare a concrete mixer to a cake mixing bowl, except there is no whisk - you are simply turning the bowl to get the moisture propagated throughout.
Concrete mixers are designed for usage with a wet mix slurry. The only requirement is that the mixture is uniformly wet & keeps turning to prevent the mixture from hardening before use.
A concrete mixer does NOT blend different aggregate types. The use of pre-mixing by hand with spades is required & the concrete mixer can take over by turning the mixture with the water. However, because brick-making is typically a "dry" mix process, the propagation of water in this manner seldom works. Moisture must be forcibly distributed otherwise parts of the mixture will simply be more moist than others.
The effects on the brick-making process output is markedly seen after curing when bricks show less strength than their counterpart bricks, made from uniformly mixed aggregate. This is due to the "weakest link" effect: if part of the brick lacks the strength provided by the concrete mixture, all of the brick strength fails by that weak point during the tests (pressure test, modulus breaking point, etc).
Using a panmixer will ensure that:
The aggregate of one or more types is uniformly blended & mixed
The cement is uniformly distributed evenly throughout the mixture
The water content is thoroughly propagated
The speed of the cycle is superior to other methods
The consistency of the speed as well as mixture product is kept for all batches
So if you have a brickyard & you are thinking of expanding - first get a panmixer to maximise the efficiency of your current machinery & optimise the quality of your current concrete product before increasing your production through additional brick machinery.