How to control the blastig nozzle
03-05-2007, 02:11 AM,
#1
How to control the blastig nozzle
Dear all,
How to control the blasting nozzle.
How much wear rate of the blastign nozzles, I must replace new.
Thanks
regards,

William
Regards, William
Reply
03-05-2007, 06:57 AM,
#2
RE: How to control the blastig nozzle
William,

Which type of blasting machine you are using? Pressure type or Suction type? The nozzles are a bit different so as the design of the system. I assume you know the difference.

Before you talk about controlling, I think you should have a measuring system and do some data collection. It will be easier if you blasting machine only blast on 1 grit type e:g # 60/80/120..etc. some variable to be recorded:

1. Nozzle ID??
2. Blasting Duration (mins)
3. Operation (for you to have better understanding and tracking on the process)
4. RA on coupon (make a practise to every morning after check ID , spray a coupon using a fixed set parameter e.g: angle, stand-off, substract material, blasting pressure)
5. Operating Pressure (if the operating pressue drop over time)

A) For nozzle wear rate info:
Every morning, nozzle ball size (ID) checking is a must and record that down in the work log. Then it wears-off over time. With the data you have , e.g: 30 days periods, the nozzle wear off from a initial 0.300" to 0.500", then put every thing on the graph, you would be able to see, for a particular grit size, with X blasting pressure set, your wear rate is??? use the total blasting timing you recorded, else, you can use the # of days. if your blasting operation work load is average the same on daily basis.

B) Correlationship of nozzle wear with RA drop
You shd be a ble to observe there shd be a Surface finishing or roughness effect on the same substract material you blast when the nozzle wears-off.??Then base on your RA requirement, the control comes into play.

Which means the RA drop shd be the gauge for you to decide when you shd change a new nozzle. And the data would show you consistently on at what range of nozzle wear, the RA will fall out your RA limits, then you fix on the worn nozzle size to chenge.
For example: If you have verified that the nozzle wear from 0.3 ~0.5" you would not be able to get the roughness, then every time when you check the ID in the morning, once it wear till 0.5" then you change the nozzle, write up a SOP for that.

c) Reduction/ Salvation of wear nozzle
What I mean here is if you would want to enlong the life span for a nozzle which has e:g reahc 0.5"(scrapped condition), then you can look into changing of balsting pressure from mayb 3 bar to 4bar..etc. But you need to be very careful on this, exerting higher pressure though you can obtain the RA you need, but the higher the pressure, the grit blasted embedded to the substract would also be higher. That would give you interface ocontamination problem. Beware of that, do a cut -up to verify and sibstantiate that.

d) Alternative source of blasting nozzle
To enlong the lifespan and for better performance, you may source for boron carbide or tungsten carbide coating/ made nozzle, though much expensive, but it save you the time of changing and it last long.


A bit long winded, and the control is not as simple if you really want to do a proper one. Hope this is what you are looking for as this is how I control my blasting process. Hope it helps.

Regards,
Alex
Reply
03-05-2007, 12:11 PM,
#3
RE: How to control the blastig nozzle
Hi William and Alex

Can't add anything, other than to support Alex's advice above. Thanks Alex.Big Grin
Reply
03-06-2007, 12:50 AM,
#4
RE: How to control the blastig nozzle
Hi Alex and Gordon,
Sorry I have not written very detailedly.
Thanks for your advice and assistance.Ashamed0002
I use blasting parameters as follow:
Pressure Type: Suction
Blasting Air Pressure: 220~250 kpa
Grit type: #46 Al2O3
Roughness shall be Ra 1.5um~ 3.5um.
New nozzle ID: ~4.80 mm
Operation cycle: about 5 minutes each time.
Use for about 8 hours every day.

I will try to write down the parameter that you mention.

Thanks,
Regards,

william
Regards, William
Reply
03-22-2007, 12:59 AM, (This post was last modified: 03-22-2007, 01:41 AM by Gordon.)
#5
RE: How to control the blastig nozzle
William Wrote:Hi Alex and Gordon,
Sorry I have not written very detailedly.
Thanks for your advice and assistance.Ashamed0002
I use blasting parameters as follow:
Pressure Type: Suction
Blasting Air Pressure: 220~250 kpa
Grit type: #46 Al2O3
Roughness shall be Ra 1.5um~ 3.5um.
New nozzle ID: ~4.80 mm
Operation cycle: about 5 minutes each time.
Use for about 8 hours every day.

I will try to write down the parameter that you mention.

Thanks,
Regards,

william
Just one thing more, measure the Ra-value of your blasted surface, note which scale you are satisfied with - check every now or then if you get this value level, if not, change your blasting material if you feel its becoming too low. One thing more, keep in mind what you are blasting, especially the cleanliness of the work piece, which otherwise can contaminate whole your blasting media charge.
br bhe
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