Molding and Casting Questions.

Whilst I would love to get a pressure pot, I don't have one right now, so have to work with what I have on hand.

1560584_10152591901478841_2453253152905591510_n.jpg


This is what I am thinking for the mold mod. Currently they are upside down and I load them before putting the top on and topping it up. As a result, I trap small air bubbles and I think (hope) doing the way shown in the drawing should solve those issues.
 
Whilst I love the detail, this can be so hit and miss.

A while back I mentioned modding the molds. I would then fill them from the other side to push the air out of small holes and end up with a perfect cast because pouring them the way I originally made the molds trapped air inside the tread area and each pyramid ended up with a small dimple instead of a peak.

This new method has certainly fixed that issue with both pairs from the last 2 pours having perfect treads.

10689707_10152686470273841_5568652794749478754_n.jpg


The issue is, either some air is still being trapped, or I am leaking rubber out the side of the mold. I am going with air at this stage given the pour level did not drop enough.

10649520_10152686470243841_5405972600337776734_n.jpg


As you can see here, the sole in the back is perfect. Even the air vents have remained attached to the cast. There is still a heap of flash where including some of the pour tube. The issue is the sole in front does not have a front inner wing.

I think I may be able to load the molds and pour new wings, trim and glue them to the perfectly formed treads and still get two sets of new soles from this project. Of course, the idea is to make each cast pair the same as the perfect sole I got tonight.

So far, just 25% success rate. I will get this up to 100% I promise.
 
Based on what I got from the last demold (yesterday), I think I will have a win here if I do the following -
1. Seal up all the little air holes I added.
2. Flip the molds back over.
3. Remove the plugs I made in the lid (which later became the base)
4. Add small air holes at the edges of the part but maybe upto 10 to ensure no air gets trapped.
5. Make the lid a bit more rigid so the centre can't "slump"
6. Pre-load the side "wing things" before putting the lid on.
7. Flood the molds and be prepared to waste a bit to get a fully formed part.

1909906_10152688133983841_1980186962678842977_n.jpg


Here is some perfectly formed tread :)
 
Had a bit of a break through tonight when I de-molded this part to discover it is perfect!

67197_10152781745888841_8951397366336219892_n.jpg

1656177_10152781745988841_864852706477720678_n.jpg


Now to mod the other mold and I will be done.
 
Thank you Azreal69. I seem to have a leak from the right sole mold or I do think I would have have been able to photograph two perfect soles. I think if I cut a channel around the part and fill that with pinkisil putty, I should be able to make a good seal and hopefully end the leaks. I'll look into that over the week end.
 
Since my last post, I have scrapped the previous right sole mold and made another.

I then ran a test with more of the cheap nasty polyester resin and it seems all is good now.

10380971_10152793359633841_8483172317172618337_n.jpg

10553521_10152793359588841_1203512248116365790_n.jpg

1461689_10152793359543841_7765942472823467550_n.jpg


I will need to give the molds a good clean up to get any residue left over from the polyester out and should be right to cast in the clear elastomer again.
 
robn1 said:
That's part of the incompatibility of platinum. They say it won't cure against sulfur or tin silicone at all. Some resins are a problem too, so you have to be careful what you make you master patterns with. I like using Tamiya spray paints on my masters, but Smooth-On platinum silicones had problems with it. A six hour cure rubber takes three days to cure against it. It's a shame too because I loved that rubber, 1-1 by volume mix, low shrink and long life. But I'll be damned if I can find a paint to use on my masters that it can work with.

I've been using Mold Max XLSII and it seems to be good stuff. No curing issues with any paint I've tried, and it's also low shrink and long life. Only problems are the 10-1 by weight mix and 24 hour cure time, but hey it works, and one day is better than three.

Like I say I've never used vacuum, I can't give much advice there. I do know the rubber is expected to rise several times it's volume while boiling, then fall back down when the air is released. How much vacuum and time is needed will depend on the volume and viscosity. I just mix it, pour into the mold box, and pressurize it. This is very effective at eliminating bubbles. But the master has to be pressure worthy, it won't work if the master will collapse under pressure.
Click to expand...


Hi, I have been using Mold Max XLSII but experiencing cure inhibiton problems on the mold keys after I created the second half.
I have used Mold Max 30 for a very long time now without any problems but it seems XLSII is very sensitive to mold release. I used Wax based and Ease release 200 but both resulted in mushy, uncured reg. keys and unusuable molds.
 

Attachments

  • xls-6.jpg
    xls-6.jpg
    285 KB · Views: 68
jevries said:
Hi, I have been using Mold Max XLSII but experiencing cure inhibiton problems on the mold keys after I created the second half.
I have used Mold Max 30 for a very long time now without any problems but it seems XLSII is very sensitive to mold release. I used Wax based and Ease release 200 but both resulted in mushy, uncured reg. keys and unusuable molds.
Click to expand...
Strange. I've used it with Ease Release with no issues at all.
 
jevries said:
From a bottle or spray can?
Click to expand...
The bottle, which may be the difference. I wanted to keep the release off my master when making two part molds so I applied the bottle version with a brush. I've used the spray but I can't remember if it was with XLSII or not.
 
This thread is more than 4 years old.

Your message may be considered spam for the following reasons:

  1. This thread hasn't been active in some time. A new post in this thread might not contribute constructively to this discussion after so long.
If you wish to reply despite these issues, check the box below before replying.
Be aware that malicious compliance may result in more severe penalties.

Similar threads

curiouslysophie
MC80 Liberty Questions
Replies
14
Views
864
rbeach84
rbeach84
CosmicQuest
Glueing and painting polypropylene and similar slippery plastics.
Replies
15
Views
564
CosmicQuest
CosmicQuest
ajamodels
TIME TRAVELLERS ROCKET AND BASE 1964
Replies
7
Views
375
joberg
joberg
Inlite
Moulding for rotocasting - advice needed
Replies
4
Views
541
JPH
JPH
ajamodels
THE PHANTOM PLANET ROCKET and base
Replies
5
Views
481
ajamodels
ajamodels
Back
Top