My two cents worth. The blast cabinet from what I have seen is a suction cabinet, so, one of the major problems is the contamination of the grit, along with the grit getting finer with use. Providing the your cfm does not change / drop, is fixed, then the media is the only variable. Course grit is not your solution. Depending on what you are blasting, the coating thickness that you are trying to remove will to most extents be governed by the grade, type of media and finally the availability of the media. All media breaks down and get smaller. The speed at which that happens depends upon the media being used, also the material that is to be blasted and the final profile that needs to be achieved has to be considered. Suction cabinets are not very efficient, speed wise in blasting, this is due to the air speed and the grit acceleration onto the job. That is where a pressure system is much better, even with the same air flow. Nonetheless if a suction cabinet is what we have then we make the best with that. There has been mention of crushed glass, glass bead, copper slag, aluminium oxide and steel shot. All of which will work, there has been no mention of garnet. Garnet is a very viable alternative, had good recycling capacity (about 4 times in a suction cabinet). Now the grit size of the blast media. Course grit is required for when there needs to be a thick coating removed and or heavy rust removed. The course grit has much more impact energy onto the job to break down the 'coating'. The down side is the ability of the grit particles to get into the smaller cavities of the job. Ideally you would need a smaller particle size to get into the small rust pores, crevices, not break down and last forever. As the grit size is reduced, recycling the contamination % increases and provides a cushioning effect of the media against the job slowing down the blasting process.
Two things are required. From the job that you have in the cabinet, I would recommend, if you can get it GL80 steel shot. This will last the longest and is quite fine, used by powder coaters not to generate a course profile on the 'steel' so they don't have to put too much power to make the job smooth. The other advantage of the smaller grit is the number impacts per square inch, weight of the grit which speeds up the blasting. Finally the contamination MUST be removed on a regular basis to stop the cushioning of the media against the job. This also helps in the visibility when blasting. I have constructed a fine mesh screen to remove the fines and dust from my media so blasting stays consistent and saves as much media as possible.
One of my pressure cabinets I use plastic media to blast clean paint sprayer pumps prior to repairs. This is the fastest way that I have found to clean paint pumps. The plastic media is very pricy but vital to clean the metal parts from paint without damaging or marking the metal components. Contamination, blasted paint and or fractured media particles make visibility poor and slow down the blasting speed. All of which we want more speed. Sorry about being so long winded
It mentioned vibration hoppers to improve feed. In my case I could test that by screwing a sander to the hopper and run it to see if media flow improves and adjust air pressure + qty of media in the hopper to try and find the sweet spot where it runs decent.
the blue twin comp will run at about 28cfm and will run a a pot with an open 6.0mm blast jet no problems cfm wise show us a picture of your pot
Just get a pressure pot and afix it to the bottom of the cabinet you have. I have done several and they work just the same. I even have photos of two of them, somewhere. I even have a thought that I have placed the photos on this forum somewhere
Just get a pressure pot and afix it to the bottom of the cabinet you have. I have done several and they work just the same. I even have photos of two of them, somewhere. I even have a thought that I have placed the photos on this forum somewhere
If we are talking the very same air supply, then a pressure setup would be better in blasting than suction. However this relays upon getting the right size nozzle, through which grit passes to obtain the pressure whilst blasting. It is the at pressure air volume that determins the blasting rate. The rate of blasting is directly proportional to the amount of grit and the speed at which it impacts upon a job. A suction system cannot accelerate the grit which is syphoned up to the same speed as a pressure system, period. Unfortunately in blasting there is no substitute for horsepower. More air, more pressure, more grit means faster blasting. The point of a cabinet is that the grit / mess is contained. I still have my first cabinet, suction and tried to use it with a 3hp compressor
. Painfully slow. I upgraded it to a pilot operated air control valve with 1/2" air lines and fed it from a 11kw screw compressor (60+cfm 7 -8 bar) and it worked much much better. This is however a massive upgrade. General rule of thumb a No2 nozzle (1/8") at 100 psi blasting pressure requires 26cfm at that pressure. Depending what you are blasting this is slow. Next nozzle up No3 (3/16") at 100psi requires 57cfm. This is better, but as you can see it is basically double what you had before. My first setup (pressure pot, which I still have) had a No2 nozzle in it and was frustratingly slow. Compressor was a 7.5kw screw. It was upgraded to a 11kw where now on site I use the No3 nozzle to do blasting on boats shafts props rudders prior to applying prop speed.
