Jump to content

Recommended Posts

Well I went out the shed for an hour, had to come in as it was brasic out there, to give machining the worst blank I had a go. It's the bottom blank in this photo.

 

HDPE2%20012_zpsxqbiooni.jpg

 

To be honest I did not have high hopes as the blank was bent,anyhow I gave it a go.

 

This is how it turned out.

 

hdpe3%20004_zps0fl2gqgu.jpg

 

hdpe3%20005_zpsmh3dovtv.jpg

 

hdpe3%20006_zpsbkf34mgp.jpg

 

So a few lessons learnt, I need to make a bigger blank at least 6 or 7mm larger than I want. Or just make the blanks to any size and have the needle the size it cleans up to. They need to be a lot longer than I need also. The first option is the best for me as I can have the needles all the same size then, makes the machining of them easier as I can just set a jig then away to go.

 

TC

Link to post
Share on other sites

Is this stuff usually injection moulded or "roto molded" do you no?

I have just found a video of the making of milk bottles with HDPE. The HDPE is heated to 170 degrees then a measured amount it placed in a mould of two halves then compressed air forces the HDPE to the shape of the mould.

 

http://www.bottle2bottle.com/making-hdpe-bottles.asp

 

http://www.bottle2bottle.com/tourplayer3.html

 

TC

Edited by tiercel
Link to post
Share on other sites

Well I went out the shed for an hour, had to come in as it was brasic out there, to give machining the worst blank I had a go. It's the bottom blank in this photo.

 

HDPE2%20012_zpsxqbiooni.jpg

 

To be honest I did not have high hopes as the blank was bent,anyhow I gave it a go.

 

This is how it turned out.

 

hdpe3%20004_zps0fl2gqgu.jpg

 

hdpe3%20005_zpsmh3dovtv.jpg

 

hdpe3%20006_zpsbkf34mgp.jpg

 

So a few lessons learnt, I need to make a bigger blank at least 6 or 7mm larger than I want. Or just make the blanks to any size and have the needle the size it cleans up to. They need to be a lot longer than I need also. The first option is the best for me as I can have the needles all the same size then, makes the machining of them easier as I can just set a jig then away to go.

 

TC

i saw something online with regards to the cooling stage, maybe you could use a metal mould and cool it down gradually in the oven :thumbs:

Link to post
Share on other sites

i saw something online with regards to the cooling stage, maybe you could use a metal mould and cool it down gradually in the oven :thumbs:

 

:laugh: Me and metal just do not get on I'm afraid. If I can't router or plane it we just don't mix, and one of us ends up in the bin. The size of the blank takes about 3/4 of an hour to cool but because it is a billet, it needs pressure on two sides top and side to stop the warping. I have an idea for the next mould if it will work is another matter. :laugh:

 

To be honest I am enjoying the challenge, it's something different.

 

Right back off out the shed for another half an hour, till my hands stop working.

 

TC

Edited by tiercel
  • Like 1
Link to post
Share on other sites

 

i saw something online with regards to the cooling stage, maybe you could use a metal mould and cool it down gradually in the oven :thumbs:

 

:laugh: Me and metal just do not get on I'm afraid. If I can't router or plane it we just don't mix, and one of us ends up in the bin. The size of the blank takes about 3/4 of an hour to cool but because it is a billet, it needs pressure on two sides top and side to stop the warping. I have an idea for the next mould if it will work is another matter. :laugh:

 

To be honest I am enjoying the challenge, it's something different.

 

Right back off out the shed for another half an hour, till my hands stop working.

 

TC

 

you could make a vice type contraption clamping the sides then the same for the top :thumbs: think i'll stick to buying in the plastic ones looks too much agro for me :laugh::laugh::laugh:

Link to post
Share on other sites

Have you considered using polymorph plastic? That stuff is bloody hard and can be easily reworked, added to etc but I'm not sure about machining it.

Nope, never heard of it till I read this post.I will have a look.

 

Thanks.

 

TC

 

Edited to add: Just seen the price on it. I think that is a non starter. Empty milk bottles are free. :D

 

TC

Edited by tiercel
Link to post
Share on other sites

Well the HDPE does machine very nicely indeed.

 

008_zpsfrd1kh0b.jpg

 

But I need to get the melting and casting of the blanks right. I think I am not leaving the HDPE long enough under the heat and it is not bonding right.

 

009_zpsxx8nw9bp.jpg

 

I will try it again this weekend and give it longer to bond.

 

TC

Link to post
Share on other sites

Leave the hdpe under the heat till it goes shiny, clamp under as much pressure as possible then leave plenty of time to cool, pulling it too early is what causes the warping. Best way to finish it ive found is to either flame bake it over a candle constantly keeping it moving. Or heat a metal spoon up or similar and rub it over the hdpe, again its got to be continous or else it will create melted points along it, hope that helps

  • Like 1
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...