One of the most popular questions of surface finishing is how to calculate the tumbling machine capacity. Since barrel tumbling machines and vibratory finishing machines are the most used equipment. In this article, we only focus on these two types of mass finishing equipment.
For a given size of the machine, one needs to determine machine capacity. Especially this machine is an old model or from another manufacturer. Base on that, we can calculate how many Kg of parts and media to put in the barrel.
In most case, you have to decide the right machine size according to the number of parts finished at one time, parts conditions and production conditions. Therefore we know how many parts per Liter. With the above information, we can estimate the machine capacity.
1. Calculate the size of the machine with a given machine size
Manufacturer design and produce mass finishing machines by machine total volume. The total volume of the machine represents the capacity fully occupied by media. However, in the real condition, the theoretical volume will never achieve because media and parts need free space to get the movement.
1.1 Vibratory Finishing Machine Volume calculation:
The operating channel of vibratory finishing machines is toroid. When the volume of a vibratory bowl is unknown, it is possible to estimate the bowl’s volume using the following formula:
Volume = ¼π2(R + r)(R – r)2
where R = diameter of the vibratory bowl, and r = center drum diameter
Vibratory finishing machines real capacity is about 80-90% of theoretical capacity.
1.2 Barrel Tumbling Machine Volume calculation:
For barrel tumbling machine, calculation of tumbling machine is quite simple:
Volume = ¼π2RL
where R = diameter of the side length and L = length of the barrel
Barrel tumbling machine real capacity is about 50-60% of theoretical capacity.
2. Calculate machine volume with parts conditions and production conditions
2.1 Media to Parts ratio
The final step is to decide media to parts mixture ratio. To maximize your output, you always want to put extra pieces in your vibratory bowl. However, too many parts in a vibratory bowl result in parts on parts impingement. So here we make some idea regarding media to parts ratio:
1:1 Media and parts are mixed in equal capacity. The small amount of media will make parts on parts hit and scratch a lot. This can work out when the surface mark is not a problem.
3:1 The average ratio use in the vibratory finishing process. However, with vibratory finishing machine with internal separation, you need to have a higher ratio of 4:1
8:1 8 times and higher media to parts ratio suggest for delicate parts. This mixing ratio also used in vibratory polishing and burnishing process.
For an easy calculation, we use 3:1 media to parts ratio which is used in most parts. The mixture ratio is a volumetric ratio.
2.2 Parts condition
2.2.1 Standard parts Volume Calculation
The part’s length, width, and height should be measured correctly. When we get the dimension, we can decide parts volumetric displacement.
For example we have a part of the following dimensions: length = 20mm, width = 5mm, height = 2mm. Volume of this part is: volume = 20*5*2 = 200 mm3.
Here comes another question: How many parts can be put into one-liter capacity? This load number can be determined as follows:
One Liter capacity: 1 Liter = 1000 mm3
1000 mm3/Liter ÷ 200 m3/pc = 5 pc/Liter
2.2.2 Delicate parts and Soft parts Orthographic Projection
When deciding parts loading capacity, it’s important to estimate with orthographic projection. This is essentially important if a part is fragile and soft. To prevent parts impingements, they cannot finish in high volume.
For vibratory finishing machines, we suggest using parts orthographic projection to calculate parts load rate. Therefore, parts size can be considered as a sphere which just holds the parts. Using this calculation, X= length of the parts; Y=width of the parts; Z=height of the parts.
The volume of a sphere is Volume = (4/3)(π*r3)
where r=√x2+y2+z2, r is the radius of the sphere and be considered as the item’s volume measurement
2.2.3 Very Heavy Parts
Parts heavier than 4kg should be finished in a divided chamber or processed one by one to prevent damage.
Vibratory Tub with dividers allows several big parts processed independently at the same time. This ensures 100 percent protection against part-on-part damage.
2.3 Production condition
When we have the 8 hours working time, we have the cycle time of the process, plus 20 minutes of handling time, we will know the total shift per day. Some factories work more than 10 hours a day, so we can do extra shifts every day.
3. A case duty: How this works out in real life
|Real condition||Working hours||Handling time||Processing time||Parts per day||Parts to media ratio|
|Data||8 hours||30 minutes||2 hours||3000||1:3|
|Real condition||Part size||Delicate parts||Parts Material||Parts requirement|
Calculate how many parts per hour that you need to run, how long it will take to run them, the media to parts ratio that the parts need, parts size and how many parts will fit in one liter to come up with the size of machine you need.
You know that you have 3000 parts to finish per day.
Your shop runs 8 hours per day.
You know from the sample tests that the part will be done in 2 hours.
You calculate it will take 20 minutes to load and unload.
So now the total process time per shift is 2 hours 20 minutes.
You know you can do 3 shifts per day. So each shift is 1000 parts.
The part made from steel so we use 3:1 media to parts ratio.
You measure your parts size, 20x10x4=800 mm3
and 1000 of them are 1000X800=800 Liter
Media and parts total capacity 800X4=3200 Liter
3200 Liter done in 3 shifts, each shift about 1100 Liter
Consider machine put 80%-90% capacity full of total volume, and then a 1200 Liter machine is suggested.
You can also use 2 sets 600L vibratory finishing machines for deburring instead. Or you can set your work time as 16 hours per day. In that case, one set 600L vibratory tumbling machine is enough for the work.
In this article, we discussed how to estimate mass finishing machine capacity including rotary tumbling machines and vibratory finishing machines. Firstly, we can calculate an existing machine capacity based on the surface dimension. Secondly, we know how big size machine is best for our production according to parts conditions and production conditions. Last, we discuss a real steel part and select the proper vibratory machine for deburring.