Front Lip Reproduction trial

[Woody928]

22 hours ago, munters said:

I was not clear in the last post

This is the Prototype to use for the mold not Urethane yet.

Im now building a box and then the endversion in Urethane with suporting brackets inside.(to adjust the angle the way i want it and give rigidity)

Oh right, either way still impressive work. 

Keep the good work up, I look forward to seeing the final product 

[moelk]

Looks great!

Well done!

[munters]

Next Step is done

Box with Prototype in it. fixed to the bottom of the box

Now I have to decide what kind of Polyurethane I will use. Im still for a Shore A 75 (hard/soft like Car tires)

I guess I will try it with that and if its not good, I can still do a second until I have the desired hardness.

 

For the Form(mold) I thought to use as well the Shore A 75 but Im asking myself if harder like shore A 90 could be better for the mold to reuse it more often

I know, the A75 should be good against UV light(sun) for about 10 years. then I can use the mold again.

 

 

[Captain Obvious]

Neat project. I'm no expert on molding parts, but it really looks like a tricky project to me. I got some questions and ideas:

Where are you going to put the parting line in the mold to separate it to remove the finished part? Are you planning to pour the mold in two stages and have the part line along the front and back faces of the finished part? If so, I would recommend against that. I think the part line would be much more hidden if it were along the top and bottom thinner edges of the part. A lot less post mold cleanup. But the problem is setting things up so that's where the parting line goes is more difficult.

I've seen where people pour the whole thing in one shot and them use a sharp knife to cut the mold open to create the parting line and get the original pattern part out. But if that's what you're planning, I think you're going to have a hard time blindly "aiming" for the narrow edge of the pattern.

Or are you just planning to pour up to the top edge of the pattern part and leave the whole top edge open?

Some other thoughts...

Make sure you use some sort of mold release on the stuff you don't want the silicone to stick to (like the wood and original pattern).

I worry that the cross section of the part is going to end up wavy in the finished part. Especially if you don't come up with a way to mechanically support the mold as you use it. The mold is somewhat soft and squishy and it's going to be like pouring juice into a fish. How are you planning to hold the two halves of the mold together as you pour?

And as for what material you make the mold out of, I'd go as soft as you think would be usable. It'll make it easier to get the finished parts out of the mold without tearing the mold. Honestly, I've never had great success on my first mold. I usually end up learning a lot on the first one and then making others based on my mistakes learned on the first one. In other words... I'd use something cheap and easy to work with and flexible for the first mold, because if you're like me, it won't be your final version. Then maybe use something stiffer the next time.  I mean, I wish you luck and hope so, but that doesn't happen for me. I'm not that good! 

[EuroDat]

Can't believe I missed this thread. Playing with PU rubber I can probably understand the challenges you are/will have in this project. Fun but challenging. The biggest job I have done was my 280Z turn signal lenses for the tail light.

The harder the shore the better. If you can get 80 or harder, I would use it.

Another suggestion, use shore 60 for your experimental phase. It flows much better and is forgivjng while you perfect your technique. The resin begins to set after 15 minutes or so and the harder the shore, the harder it is to work with. 

You will want a vacuum pump that will get close to absolute vacuum. 200mBarA will not be enough to get all the air out of 75 shore PU.

The container for the resin needs to be 4 times larger than the resin you are using otherwise it will boil over. 1 Litre resin = 4 litre container and a vacuum container to suit.

Lightly spray the mold with release agent. Don't overspray it, but make sure you don't miss any sections. PU really likes to stick to silicone.

[Zed Head]

I've worked with polyurethanes of the A scale hardness, 80 to 95A range.  They're pretty soft.  Found a good chart in the Wikipedia link.  Of course, making some small samples would give a good feel for the final product, and would be good practice to iron out process difficulties.  It's not uncommon for molds to be destroyed because of poor release.

https://en.wikipedia.org/wiki/Shore_durometer#Durometer_scales

[munters]

21 minutes ago, Captain Obvious said:

Neat project. I'm no expert on molding parts, but it really looks like a tricky project to me. I got some questions and ideas:

Where are you going to put the parting line in the mold to separate it to remove the finished part? Are you planning to pour the mold in two stages and have the part line along the front and back faces of the finished part? If so, I would recommend against that. I think the part line would be much more hidden if it were along the top and bottom thinner edges of the part. A lot less post mold cleanup. But the problem is setting things up so that's where the parting line goes is more difficult.

I've seen where people pour the whole thing in one shot and them use a sharp knife to cut the mold open to create the parting line and get the original pattern part out. But if that's what you're planning, I think you're going to have a hard time blindly "aiming" for the narrow edge of the pattern.

Or are you just planning to pour up to the top edge of the pattern part and leave the whole top edge open?

Some other thoughts...

Make sure you use some sort of mold release on the stuff you don't want the silicone to stick to (like the wood and original pattern).

I worry that the cross section of the part is going to end up wavy in the finished part. Especially if you don't come up with a way to mechanically support the mold as you use it. The mold is somewhat soft and squishy and it's going to be like pouring juice into a fish. How are you planning to hold the two halves of the mold together as you pour?

And as for what material you make the mold out of, I'd go as soft as you think would be usable. It'll make it easier to get the finished parts out of the mold without tearing the mold. Honestly, I've never had great success on my first mold. I usually end up learning a lot on the first one and then making others based on my mistakes learned on the first one. In other words... I'd use something cheap and easy to work with and flexible for the first mold, because if you're like me, it won't be your final version. Then maybe use something stiffer the next time.  I mean, I wish you luck and hope so, but that doesn't happen for me. I'm not that good! 

Hello Captain

Thanks for your inputs. Im braking my brain with what if then else questions...

I guess I will learn as you said. Yes, soft mold (shore A30) means easy to take it out, but needs always a box to use it.

Over Shore A50 no box is needed, but it will be harder to get it out. I tend to have it harder to get it out but easier to replicate.

Below the Prototype are studs to the bottom wood and give marks where to open the mold

yes I will poor it at once I don't want a mark somewhere.

and where the studs are, (below every mounting bracket) I will putt pipes in the mold to get the air out  and to be able to "overfill"

(I will poor it the opposite side from the top to the bottom of the lip )

One will be used to pour it in. There I will use a 2cmx5cm pipe to fill it. when every pipe has material it should be fine.

I don't know yet if the center or the side is better, but I think the side.

Those are all the Ideas I have a t the moment and hope more knowledge will be shared. Here or with the guys I will buy the PU from.

The next few Days will give more ideas.

 

 

[munters]

I got the first answer from the guy I buy the PU from and he suggests to use

1. Silicone Shore 28 for easiness but always a box needed to support the mold 

2. Silicone shore 50 to 60. Still easier to use, but hard enough to use it without a box.

3. Polyurethane 50 to 60. a bit harder to use, not as precise texturing as Silicone but much cheaper.

The lip itself he thinks 80 would be good.

[EuroDat]

I would go for a silicone shore A 50 or 60. And one with a platinum catalyst instead of the tin catalyst variety. The tin catalyst silicone will work, but it feels oily and attracts dust and grime. Its not as durable as the platinum silicones.

+1 on your supplier advice for sh. 80. The harder the better for wind resistance. Sh 80 will still be flexable.

Have you looked at the website from Alumilite. They use to have some interesting how to videos. Good to get you thinking about how to go about it.

https://www.alumilite.com

Edited February 2, 2018 by EuroDat

[munters]

Zed Head

Thanks for the scale I used a similar one.

Eurodat cool site I will study it.

The product I most properly use is from the netherlands I think called Eurosil

This is what he wrote about the new material

Eurosil 50 – require NO RELEASE AGENT!, easy casting, high quality, no shrinkage, durable,

[Captain Obvious]

Good luck with the project, and here's to hoping it works out great.

One thing... Just because they say "no release agent" required, it's not always true. A little bit, even if it's just as insurance won't hurt!  

[EuroDat]

7 hours ago, munters said:

The product I most properly use is from the netherlands I think called Eurosil

This is what he wrote about the new material

Eurosil 50 – require NO RELEASE AGENT!, easy casting, high quality, no shrinkage, durable,

I think they are Belgium. They are about half an hour from were I live in NL. They had a good forum for members. Don't know if it is stil active. I use a company here in NL called Formx for the silicane rubber.Smoothsil 950. It worked really well and lasts a long time before twaring. I always used a very light coat of release agent.

http://www.formx.eu  Nice instrctions and info on mold making here too.