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RFQ - Two Molds, Secondary welding required

Nate_D

Plastic
Joined
Feb 25, 2016
I need two molds made from aluminum. Molds will be used in a composite resin infusion process and will need a 3" flange welded around the outside once cut. Flange location is non critical, just needs to be somewhat near the top of the mold and the welds all solid.

I have two files for each mold. One without the flange and one with the flange to show approximate location (again, exact location not critical).

Upper Mold & Lower Mold
Tolerance: +/- 0.005"
Material: Aluminum 6061
Flange width: 3"
Flange Thickness: 3/8"

Exterior dimensions of upper mold (without flange): < 36" x 8" x 2.75"
Exterior dimensions of lower mold (without flange): < 40" x 6" x 3.5"

Due to software limitations, current files do not have a radius at the interior edges. A 0.5mm radius can be added at all interior edges for machining purposes.

I only have STEP files, no dimensional drawings. Please email me at [email protected] .

Pictures with and without flange

Screen Shot 2016-11-14 at 10.37.30 PM.jpgScreen Shot 2016-11-14 at 10.38.12 PM.jpgScreen Shot 2016-11-14 at 10.38.26 PM.jpgScreen Shot 2016-11-14 at 10.39.00 PM.jpgScreen Shot 2016-11-14 at 10.39.11 PM.jpg
 
Couple of notes.
1. fix your location
2. why weld a flange around the top after machining and then expect to hold .005 ?
 
Couple of notes.
1. fix your location
2. why weld a flange around the top after machining and then expect to hold .005 ?

+1 (or whatever it is kids say). If you want to keep the precision of the mold you can try adding a "picture frame" feature that is just a sheet of material cut with the outside profile you want, some ctsk holes for fasteners, and a relieved profile mate to the top of your mold parts with tapped holes to receive the retaining fasteners. Properly done it'll keep your mold accuracy and be easily replaceable if needed.
 
Couple of notes.
1. fix your location
2. why weld a flange around the top after machining and then expect to hold .005 ?

1) I'll change it. Location is houston.

2) it would seem to be the most economical way to make these molds. If I add 3" to all sides of the mold that more than double material cost. I'm open to suggestions on a better way to achieve the end result.
 
+1 (or whatever it is kids say). If you want to keep the precision of the mold you can try adding a "picture frame" feature that is just a sheet of material cut with the outside profile you want, some ctsk holes for fasteners, and a relieved profile mate to the top of your mold parts with tapped holes to receive the retaining fasteners. Properly done it'll keep your mold accuracy and be easily replaceable if needed.

There will be a 29hg vacuum pulled on the mold, so the flange-mold mating surface would need to be air tight. I suppose I could tacky tape the underside, but that's just more places where an air leak could happen.

Is there a particular reason that welding the flange would not work? If it's the wall thickness of the mold, that can be increased.

Thanks for your help
 
Aluminum can move a lot while it's getting welded, and the resultant cool-down stresses can show up as warped surfaces. A well designed bolted surface will maintain its integrity when being attached. Tons of ways to seal the interface, so don't let that be a deterrent.
 
Aluminum can move a lot while it's getting welded, and the resultant cool-down stresses can show up as warped surfaces. A well designed bolted surface will maintain it's integrity when being attached. Tons of ways to seal the interface, so don't let that be a deterrent.

Gotcha. What about welding prior to machining?

Designing another set of parts that need to be machined is my last resort here. It will also add to the machining of the molds, as all four sides will need to be drilled and tapped. That might end up being the only way to do it. It just seems like it would add a significant amount of cost to the project.
 
Gotcha. What about welding prior to machining?

Designing another set of parts that need to be machined is my last resort here. It will also add to the machining of the molds, as all four sides will need to be drilled and tapped. That might end up being the only way to do it. It just seems like it would add a significant amount of cost to the project.

Nate, the nice thing about a picture frame is you only have to drill and tap the top of the part, so extra setup isn't needed. The picture frame itself is just cut from a flat plate, a simple job. Or even easier, just four straight bars, with the butting sections sealed with some adhesive or other "goo" similar to that used along the lengths.

You don't need massive numbers of large fasteners to hold the frame or plates in place, the loads from the vacuum directly on the plates should be rather small unless I don't understand your bagging technique. Perhaps 1/4-20 flathead cap screws every four inches should be fine.
 
Nate, the nice thing about a picture frame is you only have to drill and tap the top of the part, so extra setup isn't needed. The picture frame itself is just cut from a flat plate, a simple job. Or even easier, just four straight bars, with the butting sections sealed with some adhesive or other "goo" similar to that used along the lengths.

You don't need massive numbers of large fasteners to hold the frame or plates in place, the loads from the vacuum directly on the plates should be rather small unless I don't understand your bagging technique. Perhaps 1/4-20 flathead cap screws every four inches should be fine.

I see what you are saying. Makes sense. The load on the mold and flange is minimal. The top of the molds are concave and convex though, so the picture frame would need to have the same profile, right?
 
Nate, It seems that the cost of the additional material would be minimal when compared to the labor to bolt on or weld a flange. We machine a variety of aluminum rotational molds and resin transfer molds, many of which with the runout left in the solid.
 
Nate, It seems that the cost of the additional material would be minimal when compared to the labor to bolt on or weld a flange. We machine a variety of aluminum rotational molds and resin transfer molds, many of which with the runout left in the solid.

Looking into the material cost just now, it isn't as big of a difference as I had thought. I'll revise this RFQ and have new files prepared. Thank you guys for your insight on this.
 








 
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