The short answer is yes: “If you are an employer or self-employed. It is a legal requirement for every employer and self-employed person to make an assessment of the health and safety risks arising out of their work. The purpose of the assessment is to identify what needs to be done to control health and safety risks. Regulation 3 of the Management of Health and Safety at Work Regulations 1999.” (From the Health and Safety Executive Website - http://www.hse.gov.uk/risk/faq.htm#q8 ). Written by Businesswise Systems Ltd

This means that you need to consider the safety of your employees and other persons not in your employment arising out of or in connection with your undertaking. Failing to carry out proper risk assessments could result in accidents occurring and injury to people or property. Such damage might constitute criminal offences. This is so even if no harm was caused. In February 2016 tougher sentencing guidelines were introduced, including Corporate Manslaughter and Food Safety & Hygiene Offences. In the most serious of cases this could result in your business being closed and custodial sentences if a Director of a company is found to be guilty of “consent, connivance or neglect.”

Accordingly, be prepared. Seek advice and properly assess risk and procedures to protect your business, staff and persons coming into contact with your business. Businesswise Systems will be pleased to provide a free 30-minute telephone consultation and review your health & Safety needs. Please call on 07805 658299.

A DC servo drive is a device that controls a DC servo motor or a DC motor

When a motion controller needs to cause motion in conventional motors, it does so by producing a voltage which is equal to the current or the velocity demand that the controller has calculated is need to make the motor move. Depending on the way that the drive is set up, that voltage applied by the controller is equivalent to the current (current mode) that the drive will endeavor to apply to the motor or to the velocity desired (velocity mode).

The DC servo drive is normally a device that controls the current to the motor. There are two main types these are four quadrant or two quadrants. Four quadrants are famed for being more stable but are a lot less efficient. Quite simply when there is a motor command signal the drive uses the inductive nature of the motor to drive a pulsed width signal to the motor to control the current in the motor. All drives have a current control circuit and some also have a velocity control circuit. Where the drive aims to control velocity it must have some form of feedback normally these are Tacho generator or encoder. In the velocity mode the current applied to the motor depends upon the velocity where when the velocity is low the current will be high and vice versa. In systems with a motion controller current mode, where the current is proportional to the control voltage is the preferred option.

Following errors are what causes motion on motion control systems they are normal

When a motion controller needs to cause motion in conventional motors, it does so by producing a voltage which is equal to the current or the velocity demand that the controller has calculated is need to make the motor move. Depending on the way that the drive is set up, that voltage applied by the controller is equivalent to the current (current mode) that the drive will endeavor to apply to the motor or to the velocity desired (velocity mode).

This signal is proportional principally to the position error multiplied by the gain, it therefore follows that to cause motion there must be a following error. A following error is a normal for a servo motor that is moving. A motion controller operates on a regular time period often called a “sample period”, the position errors will accumulate and this causes a high demand voltage to be output. Depending upon the response time of the servo motor and drive this following error can easily equal the accumulated error from several sample periods. It is not uncommon for this error to be that of 5 or more sample periods. This is worth while considering when setting a following error limit in your motion controller, setting this too low may result in false tripping, set it too high and it may have a limited effect.

Motion controllers and automation systems use sensitive analogue signals. To protect these analogue signals from being influenced by other signals such as hum and whistle in the case of audio signals, an outer connection which is made out of foil or braided wire is often included around the cable or groups of conductors. This is commonly called a shield and its purpose is to provide a barrier reducing the amount of noise or other signals often called "crosstalk" that effect sensitive signals.However if current is allowed to flow in the screen it can actually make things worse therefore grounding a screen at both ends is not recommended this is called a ground loop

Ground loops can be avoided by connecting the screen at only one end. It is good practice to try and have all the screens connected to the same point this is often called start point and it should be connected to earth. It is very important therefore to ensure that the screens are connected at one end. People often think that a big machine made out of metal will not have a voltage across it and therefore connecting the screen at both ends will have no effect. Unfortunately this is absolutely not true especially where high-frequency signals from motors et cetera are concerned. High frequencies can regard solid lumps of metal as a very high impedance and therefore considerable voltages can occur across a seemingly solid lump of metal.

A good way of testing is to use an oscilloscope. However connecting screens only one end normally will eliminate all ground loops. There is a black art to getting rid of noise in digital and analogue systems, it can be extremely difficult to get systems to work especially in noisy environments. It is therefore recommended that noisy signals such as motor commutation are kept as far away from sensitive signals as possible. It is a good idea to put screened cables in a metal trunking as this enhances the screening. Connecting the screen at both ends almost always causes problems as does multiple connections to the screen which must always be avoided.

There are a minimum of two outputs from an incremental encoder that form the distance measuring part of the output signal. These are the A and B signals. These two signals are 90 degrees out of phase with each other. The encoder therefore sends out two signals each of which has a rising and a falling edge, counting each edge therefore gives 4 electrical pulses to each mechanical pulse. which is what quadrature means, most rotary encoders are rate in pulses per rev (PPR) and the output gained from this is the PPR x 4, for example a 1000 PPR encoder gives 4000 electrical pulses. These signals are decoded to produce a count up pulse or a count down pulse.

When the encoder is turned in one direction the A pulse leads the B and when the encoder is reversed the B pulse leads the A. The decoding device in the controller uses this fact to properly encode the distance measured by rotating the encoder. To make the signal more robust most encoders have tow more signals these are the Not A (A\)and Not B (B\) signals, there is nothing special about these signals they are simply the A and B signals inverted. The receiving device uses the polarity of both the A and A\ to determine the real status of the A signal as it does for the B signal. If noise is present in the A signal is is likely that the A\ will suffer the same disturbance and so the noise signal will have no effect overall.

Some encoders also have a signal that is only active for one pulse per revolution this is known as the Z pulse, the reason that this pulse is provided is that the exact rotational relationship is know relative to the mechanical position of the encoder. Normally on initialisation the Z pulse can be used so that when the axis moves off a switch away from home the Z pulse is used to reset or set the encoder counter to a known point normally zero.

Most welding applications are quite easy to setup and run, the PMC4 is an ideal motion controller for welding applications. Working with Plasma cutter or TIG welders is more challenging because of the startup conditions.

The startup phase of a Plasma cutter or TIG welder involves a high frequency signal and also a high voltage. In reality this is like a small transmitter, many welders also change the frequency cyclically, so they are likely to find a susceptibility in any wiring. Because of this susceptibility there is a need to shield all the cables and to make sure that even the motor encoders are shielded if not the encoders may become influenced by the startup signal. A very important thing is to ensure that electronic devices are shielded behind metal enclosures that are well grounded to a star ground. Only use shielded cables and make sure that they grounded at one end and connected to the star ground. it is also a good idea to shield the welding cables, but this must be done with great care as the shielding may effect the startup circuits of the welder. Maybe consider the use of flexible shielded trunking for the welder.