Where should the compactability of the moulding sand be consistent – at the mixer or at moulding machine?
On the transportation route from the mixer to the moulding plant there is a large number of external influences and of internal reactions subsequent to the mixing process, affecting the sand. These influence the compactability with always different intensity, until it arrives at the moulding plant. The answer to the question where the compactability of the sand really matters can only be: At the moulding plant! Though it is obvious that for this, the compactability must be determined also at the moulding machine (and not at the mixer),
we do know that very often the question is put why just Michenfelder is so far the only manufacturer who succeeded to master this challenging task.
We are pleased to explain why this location of the sand testing system is exactly the right one and that the measurement there is not belated at all and why controlling the compactability with Michenfelder does work so extraordinarily well and that consistent results directly at the moulding machine can be guaranteed.
The key to success is interlinking and control-technical coupling of the sand testing system at the moulding machine with the continuous moisture control system with super-fine resolution at the green sand mixer. As moisture and compactability correlate, this system is in the control concept, as a finely reacting adjusting device, of dominant importance.
The moisture measuring and control system already ensures, because of the correlating behaviour of moisture and compactability, pre-stabilisation of compactability.
When now the sand composition changes the system registers the smallest deviations from the set compactability value and adjusts by feedback to the moisture measuring and control system in the mixer permanently and in finest steps the required water amount to the slowly changing sand composition maintaining automatically the compactability at the moulding machine on a constant level.
Beyond that, the various changes occurring in the sand when conveyed from the mixer to the moulding machine, due to follow-up saturation of the bentonite, evaporation and temperature effects, varying dwell times, sand aerators and conveying belt transfer points can, till today, only be registered fully automatically and reliably offset by this particular arrangement and interlinking of the modules of the Moulding Sand Management System FoMaSys.
By means of this system arrangement it is possible to warrant across all production phases an extremely narrow fluctuation range of compactability of s = ± 2% directly at the moulding machine. With reliably and sufficiently pre-moisturised used sand this system arrangement produced during daily routine consistently a standard deviation which, with s = ± 0.8 – 1.5%, is still much better. No other system can achieve this. For the capability of a modern foundry to operate with regard to sand with permanently low scrap rates, it is thus of critical importance at which point in the process of reconditioning the moulding sand possesses consistently the best mechanical properties. This point is not the mixer, but the moulding machine.
Process-integrated moulding sand management directly at the moulding machine
There is a choice of two different on-line sand testing systems. The proven VEDIMAT, with which the compactability and the green compression strength are determined and the brand-new ONLINE-SANDLAB (currently still in the internal pilot period).
New ONLINE-SANDLAB with wide range of measured variables and, for the first time, process-integrated permeability testing
During the Moulding Material Conference (Formstofftage) at Duisburg, Germany, in February 2014, the prototype of the new ONLINE-SANDLAB with process-integrated permeability measurement was presented for the first time
With this new ONLINE-SANDLAB Michenfelder (r)evolutionises the monitoring and control of moulding material parameters and complements the modular Moulding Sand Management System FoMaSys. In a compact automatic testing unit for conveyor belt installation there are several devices combined for the determination of a so far unequalled multitude of quality-relevant variables for sand preparation. For the first time, also permeability testing has been relocated away from the laboratory into the sand preparation process. This relocation allows action and reaction based on an enormously enlarged and directly at the moulding plant generated database in real time.
Measured variables and functions
The following measured variables and functions are available when using the sand testing systems VEDIMAT and SANDLAB
(VEDIMAT = V / SANDLAB = S)
With stand-alone operation:
- Compactability V,S
- Shear strength S
- Compression strength V,S
- Permeability S
- Moisture and temperature S
In combination with process control system MiPro:
- Shear strength with record of deformability graph S
- Compression strength with record of compression strength drop graphV,S
- Content of fines V,S
- Bentonite equivalent S
- Use of comfortable monitoring, analysing and evaluation tools V,S
- Remote maintenance for rapid error analysis or measured-data evaluation V,S
When connected to moisture measuring and control system in the mixer:
- Fully automatic control and stabilisation of compactability directly at the moulding machine V,S
- Profit from use of two independent systems, complementing each other perfectly V,S
- Use of the Moulding Sand Matrix – the navigation system for sand reconditioning V,S