budget molding... how to mold help w/ High-Density Polyethylene

[blackpinesnake]

I have a link to a cage I would like to replicate. I would like to do it myself and does not have to be exact. I've done injecting molding but not sure where to start w/ this. I can figure out the hardware stuff, just would like to see what you think about making this a garage project, quality not a huge priority as I will fill in bubbles and sand to smooth. Only the face is visible anyway. What do you think?

http://lllreptile.com/store/catalog/...1-vision-cage/

Thanks for all help,
Clay

[dpryor]

Are you talking about molding a 24x14 container as a garage project? That's going to be a pretty big mold and press to run it in.

[One of Many]

Chances are that this part is either blow molded or rotomolded. The opening is finish routed out after molding.

There are some videos around the web for both types of molding.

Youtube rotomoulding concepts

Not exactly a home process.......

DC

[blackpinesnake]

I think the concept is simple engineering. Do not see why it could not be a home project. The heating of seems to be the only real issue. Maybe mold a steel mold and install the heating elmiments into them then cool w/ water... Best at home idea I can figure. I've done metal casting in h/s... seemed like an easy concept as well. Thanks for the advice. Exactly what I wanted. Could probably just cut the opening out with a router or something?

Clay

[Wiseco]

Or maybe you could do it with thermoforming. It's pretty simple. And for the window in the face, you could bolt or anything else to the front of your thermoformed sheet.

Also, thermoforming would be simpler than rotomolding.

Here is how it's done :
http://www.offshoresolutions.com/pro...rmoformed4.gif

[One of Many]

Thermoforming for this size would take roughly 40"x48" blank due to the depth of draw IF a snap back box or bubble is used to prestretch the material. Depending on the starting and formed thickness, you could choke it up a bit smaller.

The dimensions won't allow for a female die due to thinout at the bottom. A straight drap would take a much larger blank, but the aspect ratio could cause webbing at the corners. Regardless of which method, the draft for the height of the die would need to be generous on at least three sides, even with air eject. As you can imagine, there is a lot of wasted material in these choices.

Probably a better option for a home shop. Although it would take a large vaccum pump and tank volume, not to mention an automated cycle.... truck size machine to make the part. I'd guess about the same size of machine to rotomold.

How many cages to get the machine to pay for itself, after including material and labor in the units selling price?

For low production, I wonder if there is a self skinning dense foam that could be used in a break down mold.



DC

[Wiseco]

Originally Posted by One of Many Thermoforming for this size would take roughly 40"x48" blank due to the depth of draw IF a snap back box or bubble is used to prestretch the material. Depending on the starting and formed thickness, you could choke it up a bit smaller.

Hum I don't think so man. Plastic can stetch did you know that? So for his 24" X 14" cage, it could be thermoformed with a sheet close to the same size. Just to make sure the sheet thickness is right for the job.

I still think thermoforming would be your best guess.

Here is an example :
http://fr.youtube.com/watch?v=5jOxhQ1lhV8&NR=1

You could find more on youtube.

[One of Many]

I have spent many years in the thermoforming trade as a toolmaker in past careers.

The general rule for a female die max depth of draw is 2:1 bottom to sidewall dimensions in order to maintain reasonable material thickness at the bottom of the part. You can only cheat that so far with a helper to push the material into the cavity. This part is a 22" draw on a 24x14" cavity opening. There is not enough plastic there to pull it down that far. The majority of the material will chill off at the top, before it has a chance to thin. What is left by the time it gets to the bottom will either be paper thin or more than likely open a hole.

We would usually blow a bubble for high aspect ratio parts like this. That gets the material stretched out and the die comes down into the bubble to allow the material to wrap around it as the bubble collapses. The vacuum does not kick in until the upper die base touches the material.

DC

[Wiseco]

Oh... ok then. I think you know your job! theheheh! Sorry to have doubted about you.

I based myself on video I saw, this is why I was doubting. But as I'm in injection-blow molding trade, I know some of blowing process and I tought thermoforming would be the best way to do his project without spending too much cash.