Venting in Green sand Moulding 1) Horizontal venting: In flask less Horizontal moulding, 1-2 mm strips are provided on parting line to remove mould and core gases. This much I know 2) We you used to do this horizontal venting on the parting line in Side-frame Bolsters steel castings by GS. 3) How about vasuvent? 4) Well i throw the first ball of this inning ....how important is igniting the gas while poring metal (gas cuming out from the vents )specially in 45O jolt squeeze.express your view wether it is necessary or not necessary. 5) Yes sir, it's very much IMP. Some big foundries are using the same while pouring high bunch_wt products in No-bake also. According_to me it's veryyyyy IMP. 6) Is there any formula to calculate area of vent in cope to volume of casting or area of casting...vents r difficult in hpml flskless molds. 7) It is important to light the vents. If not done gasses collect and there are minor imploded which cause metal penetration resulting in poor surface finish. implosions 8) In HPML or conventional machines cope may undergo venting machine for vents at appropriate preset locations. it can be add on accessory. Machine manufacturers can throw more light on this. Ignition while pouring is must if you look at good surface finish 9) It is very important to Igniting the gases from poring metal.if it not do,then there is no Quality. 10) Could you please be specific sir? Which part of quality will get affected Pl? 11) If gases in poring metal ,then blowholes in casting, quality get affected. 12) My observations regarding Gas ignition:Gas coming out between drag mould and pallet :- No effect on casting whether it is ignited or not. It gets ignited with sound if a spark or liquid metal droplet from adjacent mould comes in its contact. Gas coming from contact face of cope and drag:- Observation same as above. Gas coming out from vents on top face:Vents which on prints in which no metal enters - No effect.
Vents which in fact are flow offs:- If gases from these gets combusted with sound it may affect surface finish of casting on cope side and on vertical wa'll. If these vents are increased in Number then it does not matter whether it is force ignited or not. 13) Agreed. Like to include : Venting is necessary but not necessary to ignite for cope and cores which may cause pin holes on castings surface, effect on metal filling of edges of small wall thickness like in impellers or motor body fins or lugs etc. Sand permeability also helps to reduce gas in moulds during pouring from moulds. Venting very necessary for all types of moulding i.e. flask or flaskless moulding. This is observed by me 14) OK. I just read this about igniting the vents. Though this is a generally accepted practice and even in my company. I fail to agree that lighting the vent is necessary to reduce BH or better surface finish, or anything of that sort. Does it mean - that by igniting- more gas is released from the mould? Simple fluid dynamics says - NO. Basically the gas is ignited so that it does not pollute the atmosphere with carbon monoxide (CO). Upon ignition it becomes CO2 (Carbon dioxide) which is much less harmful than monoxide. 15) And by the way I have even tried taking 2 days melts without igniting- vents. There was no difference in the quality of castings. Venting is important- but igniting- them for quality reasons - I disagree. 16) Agreed as we also not ignite the gas. You are right about burning of CO to CO2. 17) In European foundries with high pressure moulding lines and pouring furnace (press pour) only human being is one sitting in control room of presspour. Other (s) are those who come to fill liquid metal in presspour. There is no body to ignite Gas etc. And there is no automatic system to do this job. 18) Agreed 19) It's better to keep permeability of molding sand in between the range. Sand itself should be comfortable to release the gases. Looking after AFS & distribution in standard range. 20) What is the difference between a vent and a flow off? 21) Vent is provided for escape of gases. Flow off is basically for taking cold metal. But before liquid enters flowoff gases escape through the same. However, if pouring speed is high liquid metal enters flow offs ahead of gases. Expanding gases then push liquid metal out of the flow off resulting in spurting. If temperature of liquid metal is low it solidifies leaving behind gases which results in blow hole right below the flow off. 22) in such case should we reduce pouring speed?
23) Vents are provided to remove the core gases & metal should not enter in to them where as flow offs are provided to remove mould gases & sometimes cold metal also. 24) Don't reduce pouring speed while pouring keep Basin full. Check runner and getting system otherwise will get cold lap or metal not feed the end point of castings. Another problem. Venting and flow off need to determine whether required or not for castings. All depends on method of every foundry practice. 25) Pouring time, Choke area , has to be calculated as per A. F. S. Gating risering book. Vent area should be two times choke area. Now a days for flaskless molding lines only blind vents are provided. But for H. P. M. L blocks&heads venting is necessary told by other experts. 26) The permeability of the sand must have been controlled in such cases 27) There were standardized 14 Flowoff in Green Sand Molding system for Railway Wagon Side-Frames... when we tested in V-Process we had to reduce to just 8 that too on the insistence of the BESCO Methoding expert.... With 14 flow offs the metal didn't reach till end. 28) These were the first Side Frame castings by V-Process in India under my supervision 29) Now Crescent Foundries Kolkata makes Counter Weights regularly by V-Process , they are in a process of expansion of their V-Process capacity now to 7ton single piece. I was their initial consultant for adaptation of V-process in their first project. 30) ✅ Very precise of you sir... And throwing light on how we foundryman go by myths... We were discussing about igniting gas at parting line only.... How could ignition or no ignition in air affect quality of casting inside mould? Who ignites the gases on HPML? 31) The only advantage of igniting the gases is.. safety of workers ....by way of fire or suffocating. ... 32) That means providing flow off is more a liability 33) Keeping basin full take care of lots of problems 34) Flow off reliable in thin wall castings flaskless moulding where vents for riser less or big castings with flask or mould box. We have this practice. Also close vents with steel wool to avoid any metal flush when completing pouring. 35) What are the precautions to be taken to keep the flows off & vent ? On pattern 36) I known , avoid direct flow up on pattern to avoid sand drop
37) Which vent area pl? 1. Core or mould? 2. Where to measure this area? 38) Vent area of mold 39) Mold venting area. We measure at bottom. 40) Area of the drill hole or peirced opening