Results 1 to 4 of 4

Thread: Casting 18ct gold issue - please help!

  1. #1
    Join Date
    Jun 2017
    Posts
    13

    Default Casting 18ct gold issue - please help!

    Hi all,

    We've been casting wax and resin in 18ct yellow and white gold now for 18+ months with no issues at all, but in the last month every cast we do is coming out with imperfections.

    We thought we had a gas porosity issue initially, but I'm not so sure if that is the problem now so I'm desperately trying to trouble-shoot.

    We always cast with either new metal, or a 50/50 mix of scrap and new. We've tried replacing our investment in the hope it may have been a simple contamination issue, but no joy.

    We've tried lowering the temp of the melt (multiple times,) we've replaced the furnace (assumed our old one wasn't reporting correct temp,) we've tried delaying the quench, lowering flask temp ... I'm out of ideas.

    Does anyone recognise this type of porosity (is it even porosity?) I've attached a picture which shows the type of imperfection we're seeing - they're large-ish, irregular shaped holes. There's no cracking, and no peppering of micro-grain holes.

    Any help would be SO appreciated. My husband is the casting expert, but he's not too tech savvy, hence me posting with my poor terminology.

    Thank you!

    Click image for larger version. 

Name:	IMG_7175.jpg 
Views:	12 
Size:	32.2 KB 
ID:	13305

  2. #2
    Join Date
    Mar 2011
    Location
    Manchester UK
    Posts
    863

    Default

    Are you casting the wax and resin together ? I know its the obvious one and I'm sure you have thought of it but have you changed anything to make it change in the last month ? It looks to me light when the resin is not burnt out correctly but its difficult to tell without more information.

  3. #3
    Join Date
    Jun 2017
    Posts
    13

    Default

    Quote Originally Posted by josef1 View Post
    Are you casting the wax and resin together ? I know its the obvious one and I'm sure you have thought of it but have you changed anything to make it change in the last month ? It looks to me light when the resin is not burnt out correctly but its difficult to tell without more information.
    Hi Josef, thank you for coming back to me! The main sprue is wax and sprued pieces are resin. The burnout cycle used hasn’t changed and is.
    Ramp:300 to 100 hold 3hrs
    Ramp: 225 to 550 hold 2hrs
    Ramp: 215 to 780 hold 4hrs
    Ramp: 100 to 500 hold 1hr min.
    Investment used is SRS CADCAST
    3D resin used is Powerresins WAX with DLP printer. We have recently bought a new batch of the resin but can’t remember if this issue has exactly coincided with this.
    Thanks

  4. #4
    Join Date
    Mar 2011
    Location
    Manchester UK
    Posts
    863

    Default

    The first one looks a bit high I think it should be room temp but i could be reading it wrong
    I think that investment is something like this for a 3"x 3" flask
    room temp to 230 for 1.5 hours
    hold at 230 for 3 hours
    then climb at 150degC/hr to 630 (this is the important bit to burn all the resin out you can go to 850 with the investment if other things will stand it) but see the air bit below
    then soak flask at casting temp for min of an hour

    500 seems low for flask temp but if your getting good results before with it then cool

    If the investment is a gray colour when you take it out from the kiln and not clean white, you may need to get more air into the kiln don't increase the temperature. I've seen people drilling holes in the kiln to get more air in. If you have a look on the internet there's loads on there about the subject.
    The main prob with resin is burning it out properly its a bit of a pain. Also spruing can cause problems if your using wax sprues if it 'blocks' the wax in behind the resin it can boil and cause problems.

    Hope this helps a bit and keep us posted on your results.
    Last edited by josef1; 17-03-2022 at 03:27 PM.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •