What is Vibro Finishing ?
In Vibratory Finishing the parts to be processed are charged in the bowl along with suitable Ceramic Media. As Soon as the machine is started a powerful spiral motion of the mass inside the bowl is generated. Now, because of the relative motion between media and the parts the necessary deburring, descalling, smoothening etc. is achieved. Hence we must make sure that the media and parts are moving freely inside the bowl.
Unlike tumbling where relative motion occurs only during half rotation and only at the top layer, in VIBRO-FIN Vibratory Finishing Machines there is continuous relative action through out the mass between media and parts. Hence we get the results much faster in VIBRO-FIN Vibratory Finishing Machine.
What are the major parameters in vibro finishing ?
The some of the major parameters that will affect the finishing performance are :
1. Initial Condition of Part :
"The best method of deburring is to avoid the "burr" – Manufacture parts as accurately as possible so that the burr formation is minimum. Sharpen the tools at proper interval. Keep proper clearances is press tools and regrind them at regular interval. Make sure that your mould has proper matching so that parting line is quite fragile.
Many time we try to correct mistake of earlier process using VIBRO-FIN it is quite difficult, time consuming and impossible at times. Because, what is Burr ? It is defined as loosely bonded metal film to the parent metal. Hence it is necessary that whichever layer we are trying to remove is loosely bonded; so that due to Vibratory force, rubbing off Ceramic and suitable compound we can remove it from parent metal.
Vibratory finishing is not a metal removing process, hence we cannot remove metal flow effectively, but it is best suited for removal of sharp edges, descaling, derusting, smoothening, polishing etc.
Hence lesser the burr, scale rust on the initial part through proper process planning of earlier operations better and faster results will be achieved.
2. Part Media Ratio :
In Vibratory Finishing media plays the role of cutting tools. Hence there must be sufficient quantity of media in the bowl. As the VIBRO-FIN Vibratory Finishing Machine is started, components start rubbing against the media. Hence if enough quantum of media is not available the desired result will not be achieved. The other important role of media is it prevents parts from hitting with each other. If quantity of media is lesser, then there will be part to part contact and hitting which can damage the part.
Hence in Vibratory Finishing Machine the quantity of parts and media based on the volume and not on weight. Generally part to media ratio varies from minimum of 1 : 3 to maximum 1 : 10 by volume.
If parts are quite strong, not likely to stick with one another and light deburring operation is required then part media ratio of 1 : 3 can be used. However if part is fragile, likely to stick with one another then higher media ratio of 1 : 10 should be employed. Also for polishing operation higher ratio is recommended.
Many times when parts are quite tiny and strong. Part to part processing is also possible. In this method the bowl is loaded only with parts and of required very small quantity about (20%) of Ceramic is added. On starting the machine these parts continuously rub against each other and necessary results are achieved.
3. Size and Shape of Media :
While selecting the media we must pay attention to its size and shape. The size and shape should be such that the media reaches all the intricate parts of the component. At the same time care must be taken to make sure that media does not clog any where. Otherwise removing the clogged media will be quite time consuming and laborious. The size should be enough to envelop the part properly and big enough to give proper hammering action for speedy deburring, descaling or surface smoothening. Variety of size and shape of Ceramic Media are available with S. M. Systems Pvt. Ltd. Thane.
Please see guidelines for selection of media & compounds for further details.
4.Dosing Compounds :
Dosing Chemical is as important as Ceramics. Some of the major objectives of dosing are :
Most of the compounds are mixed with water in the proportion of 20 gm. Compound in 10 liters of water, (i.e. very small quantity of compound is added in water).
However care must be taken that only required quantity of small amount of water is added continuously in the bowl. If excess quantity of liquid is poured then there will be splashing. The motion in the bowl will be very slow and proper spiral motion will not achieved.
For effective results of various compounds we must make sure that parts are not loaded, with excess grease or oil on them. Because it may break the formation of spiral motion inside due to its lubricating property. And will also damage rubber lining of the bowl.
Before using any compound in the bowl you must make sure that it doesn't affect the rubber lining adversely. Otherwise lining may swell and wear out very fast.
5. Duration of Process :
In Vibro Finishing the result obtained is directly proportional to the duration of the process. Longer the process time better and better will be the surface condition. However it is not true for indefinite time; because once the loosely bonded surface is totally removed further processing will not make much difference. Hence from trials process timing should be decided for best acceptable result.
6. Degree of Vibration :
It is quite obvious that higher the amplitude of vibration higher will be the impact. So according to the desired and result we have to set the degree of vibration. For deburring we need more vertical throw (adding bottom auxiliary weight) for polishing cation higher torrential speed will be more useful (adding to auxiliary weight). Also for delicate and fragile parts higher vibration can cause the damage. There should be optimum combination of vertical and horizontal throw for best result. Unnecessarily higher degree of vibration will increase load on the motor and consume higher power. Hence by experience proper vibrations should be adjusted.
How to select proper Media.
Guidelines For Selection Of Media And Compounds First is to select one or more of the following objectives :
a) Deburring :
Use higher size high abrasive media. Usually above 10mm. In case the components are very small 3mm or 5mm grey media can also be used.
b) Radiusing :
Use higher size high abrasive (grey) media. Usually 15mm or above (like triangles or cones).
c) Descaling :
In deburring cycly use descaling compound.
d) Finishing :
Use lower size low abrasive media usually below 10mm (Cylindrical shape) with finishing compounds.
e) Burnishing :
Steel Balls are recommended for very good results. For many applications corncob, saw, leather pieces etc. are used. Smaller size low abrasive ceramics can also be used.
While doing Ball Burnishing process make sure that balls are absolutely free from grease, oil & rust. The balls shine like Mirror, to get desired results. If balls are not of proper quality then polishing of the components will not be achieved.
It is recommended to clean/polish balls first.
For Ceramic Media Selection following point should also be considered.
In Vibratory Finishing there are no fixed mathematical formula. Operator must spend some time initially for optimum results. Experience of working with machine will be most valuable asset to get best results from the machine.