Will Press Fit and Powder Coat Work Together for My Sheet Metal Part?

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Discussion Overview

The discussion revolves around the feasibility of powder coating a sheet metal part that includes a press-fitted steel spacer. Participants explore concerns regarding the thermal expansion rates of the materials involved, specifically A572 grade 50 sheet metal and either 1020 or 1018 steel, during the powder coating process at elevated temperatures.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Eric expresses concern about potential failure of the press fit due to differing thermal expansion rates between the A572 sheet metal and the steel spacer during the powder coating process.
  • One participant suggests estimating the stress developed due to thermal expansion differences using a formula involving the modulus of elasticity and coefficients of linear expansion.
  • Another participant indicates that the thickness of the sheet metal may not significantly impact the outcome, suggesting that the combination of materials should be acceptable.
  • A later reply emphasizes that thermal stress can develop regardless of material thickness and clarifies that thinner gauge steel may heat up more quickly than thicker materials, potentially affecting the fit.
  • Eric reiterates his initial concerns and expresses a belief that the expansion differences will not be significant enough to cause the spacer to dislodge.
  • Eric concludes by stating his intention to run test samples through various processes to determine the best approach.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the potential risks associated with thermal expansion and press fit integrity, with multiple viewpoints presented regarding the adequacy of the materials and the necessity of testing.

Contextual Notes

Some participants highlight the importance of testing due to uncertainties in thermal behavior and material interactions, but do not resolve the specific implications of thermal expansion on the press fit.

emagray
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Hello all, I need some help with a sheet metal part I am going to produce. The part consists of 12ga A572 grade 50 sheet metal and a 1020 or 1018 steel spacer that will be press fitted into a laser cut hole in the sheet metal. After assembly the part will be powder coated where I know temperatures in the oven are normally 300~400 degrees. Will there be a problem powder coating parts that are pressed together? More specifically I am concerned with there being a difference in expansion rates between the different materials causing the press fit to fail when exposed to those temperatures. I think it should be fine since both materials are low carbon steel and should have similar expansion rates but I wanted to post here for some input/assurance.

Thank you!
- Eric
 
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You can estimate the stress developed as follows:

stress = E * [ alpha(A572) - alpha(1020) ] * (Tf - Ti)

E = modulus of elasticity (should be about the same for both)

alpha = coefficient of linear expansion for your two steels

Tf, Ti = final and initial temperatures.

Try to limit your stress to 60% of the yield stress of the weaker of the two.
 
I would have greater concern if the sheet metal were of thinner gage, but your combination will probably be okay. Run a test piece through the process to be sure.
 
pantaz said:
I would have greater concern if the sheet metal were of thinner gage, but your combination will probably be okay. Run a test piece through the process to be sure.
Thick or thin material can still develop thermal stress. Notice the thickness does not appear in the formula I listed.
 
edgepflow said:
Thick or thin material can still develop thermal stress. Notice the thickness does not appear in the formula I listed.

I should have been more clear -- I wasn't thinking about stress, I just meant that thinner gage steel would absorb heat more quickly than the spacer, which may allow the hole to expand faster than the thicker section of the pressed-in piece.
(I know, that's not phrased in the best technical verbiage, but I'm tired, and I think you'll understand my intent.)
 
emagray said:
Hello all, I need some help with a sheet metal part I am going to produce. The part consists of 12ga A572 grade 50 sheet metal and a 1020 or 1018 steel spacer that will be press fitted into a laser cut hole in the sheet metal. After assembly the part will be powder coated where I know temperatures in the oven are normally 300~400 degrees. Will there be a problem powder coating parts that are pressed together? More specifically I am concerned with there being a difference in expansion rates between the different materials causing the press fit to fail when exposed to those temperatures. I think it should be fine since both materials are low carbon steel and should have similar expansion rates but I wanted to post here for some input/assurance.

Thank you!
- Eric

I don't think the expansion will be so much a difference as to allow your spacer to fall out, not at that temp.
 
Thank you all for the help! I think I am going to just run a couple samples through different processes and see what works best =)
 

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