SP FAQ - Seeding depth control
Yes! A further unique function of Cross Slot openers is that the downforce is controlled very carefully. In this regard the designers of Cross Slot openers realised at an early stage that when springs are used to push openers into the ground the downforces alter as the springs lengthen and shorten. There is no way of completely overcoming this mechanical shortcoming.
The problem is exacerbated because no-tillage openers are required to travel up and down much more than openers used in tilled soils because tillage smooths the soil prior to drilling.
Cross Slot openers are therefore pushed into the ground with individual hydraulic cylinders that act against one another and are cushioned by a common source of compressed nitrogen. The main advantage is that the downforces remain the same regardless of the position of the opener. So engineers were able to design in an extraordinary amount of vertical travel (45 cm or 18 inches) for each opener, which no other known no-tillage opener achieves.
Each Cross Slot opener has 450 mm of vertical travel and maintains the same down force throughout the entire range
An illustration of the extra-ordinary surface-following ability of Cross Slot openers through a hollow
They are neither. The hydraulic cylinders are also used to lift the openers off the ground for transportation, which eliminates the complication and expense of designing lifting mechanisms into frames and creates more space flexibility within a frame and facilitates close row spacing. Each Cross Slot opener is, in fact a self-contained modular unit requiring only to be connected to a tool bar of fixed height plus hydraulic, seed and fertilizer supply hoses.
Yes! Because they are all connected to the same source of oil supply, when one opener rises almost inevitably another opener will be going down. Thus openers exchange oil between themselves most of the time, which means that the overall oil pressure does not change much as the machine proceeds. In any case the overall oil pressure can be changed by the operator on-the-move, which gives the operator continuous control over downforces in response to changes in soil hardness across a field.
Mechanical springs simply cannot do any of these things.
Yes! Individual hydraulic cylinders on all openers also allow the oil pressure (and thus the downforce) to be constantly monitored and altered. Cross Slot machines have an electronic monitoring system (called Auto-Downforce or ADF) that measures the force required to push the openers into the soil to a given depth. The system automatically adjusts this force as the soil gets harder or softer, as happens constantly across any no-tilled field.
If the soil gets harder, for example, the force required for correct penetration of the openers will increase. Conversely if the soil gets softer, the force required will decrease. With tilled soils, the tillage process itself ensures the penetration forces are lower and vary little across the field. So there is no need for any form of automatic downforce control in tilled soils.
But in no-tillage, without an ADF system, it is impossible to accurately maintain a consistent depth of seeding. Therefore, with less sophisticated technologies a certain amount of hit-and-miss occurs as far as seeding depth is concerned, and this usually gets worse the longer the field is under no-tillage.
The Cross Slot ADF system monitors the ground hardness 10 times a second and adjusts the hydraulic pressure three times a second on the move. This equates to readjusting the downforce pressure about every metre or yard of forward travel.
No. The system can be over-ridden at any time.
In manual mode the system allows the operator to change the oil pressure manually on-the-move using the tractor's spool valves in the cab.
In automatic mode the control system tells the tractor hydraulic system to make the necessary alterations to the downforce pressure that the operator would have been making manually in manual mode. This removes yet another opportunity for operator error and is a major aid to helping maintain consistent seeding depth under no-tillage.
No other system achieves this degree of accuracy and automation.
A control unit for the Cross Slot automatic downforce (ADF) control system
Yes! The operator can return to manual at any time, or in the case of electrical failure, manual is the default setting.
Yes, several other manufactures now offer a similar system but Cross Slot's system is the original system and was first disclosed in 1993, at least 13 years before any competing systems.