Cutting Table Best Practise

Transcription

1 Cutting Table Best Practise Technical Bulletin TB Rev 0 Original Instructions Esprit Automation Ltd Placketts Mill, Church Drive Sandiacre, Nottingham NG10 5EE, United Kingdom Tel: +44 (0) info@espritautomation.com

2 Revision Status TB Rev 0 ( ) Page All Description of Change Initial release Manufacturer Copyright ESPRIT Automation Ltd Placketts Mill, Church Drive, Sandiacre, Nottingham, NG10 5EE, England Copyright 2017 ESPRIT Automation Ltd. All Rights Reserved No part of this publication may be copied in any form, including photocopying, electronic, optical and digital copying, or stored electronically, without prior written agreement. It is the policy of ESPRIT Automation Ltd to continually develop its products, and therefore, reserves the right to modify and amend its manuals in line with such developments, without prior notification. Trademarks Disclaimer Hypertherm Automation is a wholly owned subsidiary of Hypertherm, Inc. Hypertherm, Powermax45XP, Powermax65, Powermax85, Powermax105, Powermax125, HySpeed, MAXPRO200, HyPerformance, HPR130XD, HPR260XD, HPR400XD and HPR800XD are registered trademarks of Hypertherm, Inc. HSD130 and FineCut are trademarks of Hypertherm, Inc. EDGE and Shape Wizard are registered trademarks of Hypertherm Automation Nester, CutPro and True Hole are trademarks of Hypertherm Automation Telesis and PINSTAMP are registered trademarks of Telesis Technologies, Inc. Microsoft, Windows, Windows Vista and Internet Explorer are registered trademarks of the Microsoft Corporation HASP is a registered trademark of Aladdin Knowledge Systems Ltd Intel, Celeron, Pentium and Xeon are registered trademarks of the Intel Corporation AMD Athlon and Opteron are trademarks of Advanced Micro Devices, Inc. StruCAD is a registered trademark of AceCad Software Ltd Autodesk is a registered trademark of Autodesk, Inc. CAMduct is a trademark of Autodesk, Inc. E. & O.E.

3 Table of Contents Table of Contents Table of Contents... i Introduction... iii Purpose... iii Referenced Documents... iii Equipment Required... iii Materials Required... iii Safety Safety Information Hazard Warning Symbols Mandatory Personal Protective Equipment (PPE) Symbols Toxic Fumes Best Practise Cutting Table Operation Plate Positioning Cutting Table Maintenance i

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5 Introduction Introduction Purpose This document describes best practises for using cutting tables and how to position plate on them to achieve effective extraction. Referenced Documents N/A Equipment Required N/A Materials Required N/A iii

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7 Section 1 Safety This section identifies potential hazards in and around Cutting Tables and how to avoid them. The following topics are covered: Safety Information Hazard Warning Symbols Mandatory Personal Protective Equipment (PPE) Symbols Toxic Fumes

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9 Safety Safety Information Hazard Warning Symbols The following symbols can be found throughout this manual and on your machine to identify potential hazards. Warns that there is an electrical hazard present Warns that there is a risk of personal injury or mechanical damage present The following words are used in conjunction with the hazard symbols in this manual to identify the level of risk present. CAUTION Risk of mechanical damage WARNING Risk of personal injury or severe risk of mechanical damage DANGER Severe risk of personal injury Mandatory Personal Protective Equipment (PPE) Symbols The following symbols can be found throughout this manual and on your machine to identify the correct use of Personal Protective Equipment (PPE) when operating the machine. Opaque eye protection must be worn Ear protection must be worn Safety gloves must be worn Safety boots must be worn Head protection must be worn Instructions must be read READ Carefully read all safety messages in this manual and safety labels on your machine. Ensure that the labels on your machine are in good condition and always visible. Replace any missing or damaged labels immediately. Learn how to operate the machine safely and do not let anyone use it without proper instruction. Always keep your machine in good working condition. 1-3

10 Safety Toxic Fumes WARNING UK Law (COSHH Regulations 2002) requires that employers prevent or control the exposure of employees and others to hazardous substances at work. A hazardous substance is defined by UK Health and Safety Executive (HSE) as Any substance or a mixture or solution of two or more substances that present a potential to cause injury or ill health to an individual is it is inhaled, ingested or comes into contact with or absorbed through the skin. Proper precautions MUST be exercised to prevent the exposure of others in the vicinity to toxic fumes which may be generated whilst plasma cutting. The types of fumes produced are dependent on the material being cut and these can be identified by the employer using air sampling techniques. Certain chlorinated solvents such as perchlorethylene and trichlorethylene will decompose under ultra violet radiation to form phosgene or other gases. Care must be taken to avoid the use of these solvents on materials being cut with plasma arc cutting equipment. Containers of these solvents and other degreasing agents should be removed from the immediate area round the plasma arc. Metals coated with or containing significant amounts of lead, cadmium, zinc, mercury or beryllium can produce harmful concentrations of toxic fumes when plasma arc cut. Adequate local exhaust ventilation must be used or the operator must be supplied with special equipment to guarantee a supply of fresh air such as a respirator or air supplied helmet. Metals coated with materials which emit toxic fumes must not be cut unless: The coating is removed prior to cutting The area is adequately ventilated, or The operator is supplied with fresh air breathing equipment The HSE has issued documentation concerning Fixed Plasma Cutting processes. This information can be accessed via the HSE Website. The information provided covers a comprehensive range of materials that could be cut. Users of Fixed Plasma Machinery are advised in the first instance to refer to the following documents as well as other associated documentation referenced within these documents: HSE668/22 - HSE Information Document WL - HSE COSHH Essentials for Welding, Hot Work and Allied Processes WL15 - Arc-plasma cutting: Fixed Equipment HSG258 - Controlling Airborne Contaminants at Work: A guide to local exhaust ventilation (LEV) Reference is also made to HSE Guidance Note EH54 Assessments of Exposure to Fume from Welding and Allied Processes (ISBN ). For operations outside the UK, users are advised to contact their local / national Health and Safety organisation. Plasma cutting should only be carried out in an environment where a safe system of work has been adopted including proper risk assessments and provision of method statements associated with the machinery, materials and processes being used in the specific environment. ESPRIT machinery is designed to work in accordance with current HSE published good practice concerning the rate of extraction of fumes from the working area. In practical use this rate can be optimised by ensuring the minimisation of the open extraction area of the bed. It is important to highlight that it is only through the proper use of this machinery with a suitable extraction / filtration system that the optimum fume / gas control can be achieved. Proper maintenance and servicing of the entire system (machine and extraction / filtration) is vital to ensure the correct level of ventilation is achieved. 1-4

11 Section 2 Best Practise This section includes best practises for using cutting tables and how to position plate on them to achieve effective extraction. The following topics are covered: Cutting Table Operation Plate Positioning Cutting Table Maintenance

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13 Best Practise Cutting Table Operation The fume extraction cutting table is structurally independent from the machine and provides a stable support for the work piece. Scrap material and debris produced during the cutting process is collected in debris bins inside each module that can easily be lifted out for maintenance and cleaning. The cutting table is divided in to 1,545 mm or 2,060 mm long modules, which in turn and divided in to 515 mm long sections by vertical baffle plates. Each section is fitted with a pneumatic or mechanically actuated damper which open and closes to control the air flow in to the extraction channel which runs the length of the cutting table on one side. A damper actuating arm is mounted on to the gantry in line with the cutting torch so that only the damper in the section being cut over is open. During the cutting process the plasma stream is directed in to the debris bins where the majority of the kinetic energy of the cutting stream is dissipated allowing fumes to rise slowly. These fumes are captured by a downward flow of air around the edge of the debris bins that is generated by connecting a filtration system or extraction fan to the cutting table extraction channel. The figures below show a pneumatically actuated cutting table consisting of two modules, each divided in to 4 sections. Fig. 1. Three dimensional view of a cutting table with cutter bar assemblies removed for clarity. 2-3

14 Best Practise Fig. 2. Cross section along the length of the cutting table Module 2 Module 1 Section 8 Section 7 Section 6 Section 5 Section 4 Section 3 Section 2 Section 1 Fig 3. Cross section across the width of the cutting table Extraction Channel Fig. 4. Cross section of a table section showing air flow around the debris bin 2-4

15 Best Practise Plate Positioning DO... Ensure that 80-90% of the section(s) being cut over are covered. This will increase the capture velocity at the cutting table face to prevent fumes escaping. If the plate is not large enough to cover a section then use scrap material over the open area to increase the coverage. Position the plate approx. 50 mm in from the cutting table edge. This will allow air to be drawn in to the cutting table to capture fumes. Use the optimum cut process for the material being cut. Plasma cutting systems can cut thin gauge material at high speed, for example the HPRXD systems can cut 3 mm mild steel at up to 6,500 mm/min. When cutting at this speed along the length of the machine the torch will only be over a section for approximately 5 seconds before it moves over the next section. Depending on table coverage, plate positioning and the current condition of the cutting table (see below), this may not be enough time for all of the fumes to be captured before extraction moves to the adjacent section causing some fume to escape. It may not be possible to capture all fumes when doing long cuts down the length of the cutting table but lower amperage processes cut at slower speeds which will assist extraction. DON'T... Position the plate tight up to the edge of the cutting table. This will block the flow of air in to the cutting table. Also, the plasma stream may not be directed back in to the table causing debris and fumes to escape. Position the edge of the plate over one of the vertical baffles plates. As the torch traversing down the length of the cutting table it passes over the vertical baffle plates separating the table in to sections. To prevent loss of extraction as the torch passes over a baffle plate the damper actuating arm is made long enough to activate two dampers at the same time, thus creating a short overlap between sections where both dampers are open and extraction is reduced. Fumes can escape if the plate is positioned close to a baffle plate or when cutting along the width of the table over the top of one. Use the maximum cut process for the material being cut. High amperage processes can cut very fast but can also have negative impacts on consumable life, cut quality and extraction (see above). 2-5

16 Best Practise DO... Full plate coverage (Ideal) Use a full size sheet to cover the cutting table, e.g. a 2 m W x 4 m L sheet on a 2 m W x 4 m L cutting table. This will leave a small gap all round the plate for air to be drawn in to the table to capture fumes. Short plate with fully covered sections When using a plate that is shorter than the cutting table, try to cover full sections. Narrow plate with open area covered When using a plate that is narrower than the cutting table so less than 80% of the width is covered, e.g. a 1.5 m plate on a 2 m wide cutting table, use scrap material to cover the open area. Small plate with all open areas covered When using a plate that is shorter and narrower than the cutting table so less than 80% of sections it sits over are covered, use scrap material to cover the open area. 2-6

17 Best Practise DON'T... Short plate with open area uncovered When using a plate that is shorter than the cutting table do not overlap in to uncovered sections if you intend to cut in these areas or close to the vertical baffle plates. The open area will be too large and fumes may escape. Narrow plate with open area uncovered When using a plate that is narrower that the cutting table, e.g. a 1.5 m plate on a 2 m wide cutting table, do not leave the open area uncovered as fumes may escape. Small plate covering multiple uncovered sections When using a plate that is shorter and narrower than the cutting table so less than 80% of sections it sits over are covered, do not leave the open area uncovered as fumes may escape. Small plate covering multiple uncovered sections When using a plate that is shorter and narrower than the cutting table so less than 80% of sections it sits over are covered, try to cover a few sections as possible. Do not overlapping slightly in to one or more sections without covering them as this will leave large open areas where fumes may escape. Small plate with edge over vertical baffle plate When using a plate that is shorter and narrower than the cutting table so less than 80% of sections it sits over are covered, do not line up the plate with a vertical baffle plate without covering the adjoining section as this section will be fully open and fumes may escape. 2-7

18 Best Practise Cutting Table Maintenance It is difficult to define what regular cleaning is as different duty cycles, thickness ranges and cutting amperages will all affect the required interval. In some applications, customers may have to clean out the cutting table every week whilst other light users may do it on a monthly basis. Regular cleaning out of the cutting table is very important. The cutting process generates a significant amount of slag and metal waste. Poor housekeeping in this area can result in reduced extraction efficiency leading to emission of fumes into the working area. As the debris bins in the cutting table fill up the distance under the plate for the plasma stream to dissipate its kinetic energy is reduced leading to fumes raising at high speed relative to the capturing air flow. Additionally, if slag is allowed to build up excessively, then the fabric of the cutting table may become permanently damaged. The lift out cutter bars can become welded into the cutting bed if regular cleaning is not carried out. Excessive slag will also reduce the air flow in to the cutting table allowing fumes to escape. DO... Regularly check the condition of the cutter bars. Damaged cutter bars will prevent plate from sitting flat on the cutting table. Replace any that are damaged or unserviceable. Regularly check for correct operation of the extraction dampers. If the dampers are not opening fully then extraction in the respective section of the cutting table will be reduced and may lead to fumes escaping. Ensure that the dampers are being actuated correctly and check for any debris inside the cutting table preventing the dampers from opening fully. Regularly remove all of the cutter bars and gratings and clean out the slag containers. Excessive build up of slag and metal waste in the debris bins will cause the plasma stream to deflect upwards closer to the surface of the cutting table at a higher velocity than the capturing air flow. DON'T... Allow excessive build up of slag on the cutter bars. This will block the flow of air in to the cutting table. Allow excessive build up of slag and metal waste in the debris bins. This will reduce the distance that the plasma stream has before it hits an obstacle, thus increasing the velocity of fumes rising out of the cutting table above the capturing air flow. 2-8

19 Best Practise DON'T... Excessive build up of slag Extraction possible Extraction is still possible through the cutter bars but support for the plate will be poor as the cutter bars are uneven. The cutter bar assembly has been "welded" together and will need replacing. Excessive build up of slag and debris in bins Extraction impeded Whilst the gaps between the cutter bars are still open the debris bins are very full. This will deflect the plasma stream upwards quickly leading to fumes raising at high speed relative to the capturing air flow. Complete build up of slag No extraction possible The cutter bars have been completed covered in slag and have fused together creating an uneven surface and preventing air from being drawn in to the cutting table to capture fumes. 2-9

20 Best Practise ESPRIT Automation Ltd Placketts Mill Church Drive Sandiacre Nottingham NG10 5EE Telephone: +44 (0) Fax: +44 (0) Web: Or us at: Machine Installation and Service Machine Sales Consumables and Spares Parts Software Support