Part shrinkage after cooling down.
04-15-2018, 04:33 PM,
#1
Part shrinkage after cooling down.
I'm a precision grinder. I grind everything you can think of. Over 25 years in the trade. Just started a job in a HVOF company doing their grinding. The problem I'm having is that the guy spraying 420 SS and other grades of stainless and carbide is giving me inconsistent amounts of stock. Sometimes it's .01 to .05 in carbide. That's very time consuming. He States that he doesn't know how much shrinkage he will have. My main question is, is it the parts being heated up and expansion in the parts (that can be calculated) or is it the material being sprayed that has a lot of shrinkage? I believe the shafts get up to about 225 degrees when finished.
Reply
04-17-2018, 02:04 AM,
#2
RE: Part shrinkage after cooling down.
(04-15-2018, 04:33 PM)Rage2371 Wrote: I'm a precision grinder. I grind everything you can think of. Over 25 years in the trade. Just started a job in a HVOF company doing their grinding. The problem I'm having is that the guy spraying 420 SS and other grades of stainless and carbide is giving me inconsistent amounts of stock. Sometimes it's .01 to .05 in carbide. That's very time consuming. He States that he doesn't know how much shrinkage he will have. My main question is, is it the parts being heated up and expansion in the parts (that can be calculated) or is it the material being sprayed that has a lot of shrinkage? I believe the shafts get up to about 225 degrees when finished.

Are you already do pre-heating before spray the powder??

Reply
04-17-2018, 06:36 AM, (This post was last modified: 04-17-2018, 06:36 AM by sprayloud.)
#3
RE: Part shrinkage after cooling down.
Mainly its the parts thermal expansion that can be calculated or determined experimentally ( measuring dimensions at elevated and room temperatures and spraying next part accordingly).
If its a spray-fuse coating, then things get tricky as coating shrinks quite a bit during fusing.
Reply
04-17-2018, 05:17 PM,
#4
RE: Part shrinkage after cooling down.
(04-17-2018, 02:04 AM)achmadarifudinh Wrote:
(04-15-2018, 04:33 PM)Rage2371 Wrote: I'm a precision grinder. I grind everything you can think of. Over 25 years in the trade. Just started a job in a HVOF company doing their grinding. The problem I'm having is that the guy spraying 420 SS and other grades of stainless and carbide is giving me inconsistent amounts of stock. Sometimes it's .01 to .05 in carbide. That's very time consuming. He States that he doesn't know how much shrinkage he will have. My main question is, is it the parts being heated up and expansion in the parts (that can be calculated) or is it the material being sprayed that has a lot of shrinkage? I believe the shafts get up to about 225 degrees when finished.

Are you already do pre-heating before spray the powder??

I asked the operator and he said he doesn't for fear of getting contamination on the part before the coating process.

They coat it with a bond coat then carbide.
Reply
04-30-2018, 10:52 AM,
#5
RE: Part shrinkage after cooling down.
(04-17-2018, 06:36 AM)sprayloud Wrote: Mainly its the parts thermal expansion that can be calculated or determined experimentally ( measuring dimensions at elevated and room temperatures and spraying next part accordingly).
If its a spray-fuse coating, then things get tricky as coating shrinks quite a bit during fusing.
I agree with this above. You can calculate the thermal expansion of the part (not the coating) and allow for this during the spraying, and the inspection of sprayed coating whilst hot.

if you accurately measure the cold part, and the hot part, you should know the shrinkage.

Sounds like you are in maintenance and repair, so maybe a large variety of diameters and parts sizes, and coating thickness, so its bit more challenging, but your coating operator should provide you with the correct information.
Reply
06-14-2018, 09:42 PM,
#6
RE: Part shrinkage after cooling down.
This used to drive me nuts when Sprayers would do this!.

Let the part cool before final measured and taken from the booth.

It may take 10-15 mins with compressed air blowing on it to get it to a stable temp/size. Its a margin of the time/cost involved if the part needs re-worked due to insufficient coating thickness.
Reply




Possibly Related Threads…
Thread Author Replies Views Last Post
  Nitrogen Cooling Neufeld 2 1,485 08-20-2019, 11:40 AM
Last Post: loriolo
  Reg: Cooling process. Dileep 2 3,425 10-16-2015, 01:05 AM
Last Post: Johnny_Blaze
  hvof cooling kschewe 0 2,792 07-16-2012, 06:10 AM
Last Post: kschewe
  brass coating over zinc part reg., prabu 2 3,861 11-08-2011, 09:40 AM
Last Post: xeviarjekel
  3MB gun air cooling Azraf Saip 1 3,194 10-21-2011, 09:15 PM
Last Post: LEN WOOD
  Coating shrinkage Guna 5 5,361 06-28-2010, 02:37 PM
Last Post: Gordon
  Porous Machined Surface on Part Lower Inner Diameter on Inco 718 Coating Surface Alexangel1226 4 7,771 03-19-2008, 02:05 PM
Last Post: Gordon
  Masking of Cooling Holes gshejale 4 7,043 01-20-2008, 10:09 PM
Last Post: plasmajet1990
  cooling jets karlos 1 6,517 06-14-2007, 12:49 PM
Last Post: Gordon
  SHRINKAGE OF ARC SPRAYED COATINGS Vijay Deshpande 3 9,119 02-12-2007, 11:25 PM
Last Post: Gordon



Users browsing this thread: 1 Guest(s)





Surface Engineering Forum Sponsor - Alphatek Hyperformance Coatings Ltd