Tiercel 6,986 Posted January 31, 2015 Author Report Share Posted January 31, 2015 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. 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. 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 Quote Link to post Share on other sites
Tiercel 6,986 Posted February 1, 2015 Author Report Share Posted February 1, 2015 (edited) 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 February 1, 2015 by tiercel Quote Link to post Share on other sites
NELS0N 457 Posted February 1, 2015 Report Share Posted February 1, 2015 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. 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. 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 Quote Link to post Share on other sites
Tiercel 6,986 Posted February 1, 2015 Author Report Share Posted February 1, 2015 (edited) 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 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. 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 February 1, 2015 by tiercel 1 Quote Link to post Share on other sites
NELS0N 457 Posted February 1, 2015 Report Share Posted February 1, 2015 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 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. 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 think i'll stick to buying in the plastic ones looks too much agro for me Quote Link to post Share on other sites
gnipper 6,570 Posted February 1, 2015 Report Share Posted February 1, 2015 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. Quote Link to post Share on other sites
Tiercel 6,986 Posted February 1, 2015 Author Report Share Posted February 1, 2015 (edited) 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. TC Edited February 1, 2015 by tiercel Quote Link to post Share on other sites
atomlab 104 Posted February 4, 2015 Report Share Posted February 4, 2015 (edited) .. Edited February 4, 2015 by atomlab Quote Link to post Share on other sites
Tiercel 6,986 Posted February 5, 2015 Author Report Share Posted February 5, 2015 Well the HDPE does machine very nicely indeed. 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. I will try it again this weekend and give it longer to bond. TC Quote Link to post Share on other sites
youcanthide...BANG 1,051 Posted February 6, 2015 Report Share Posted February 6, 2015 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 1 Quote Link to post Share on other sites
Tiercel 6,986 Posted February 6, 2015 Author Report Share Posted February 6, 2015 Can melted HDPE find it's own level? Does it liquefy enough to flow? If I heated it in a mould would it find it's level by volume, or does it not get to the stage where it can flow? TC Quote Link to post Share on other sites
youcanthide...BANG 1,051 Posted February 7, 2015 Report Share Posted February 7, 2015 I doubt it mate, too sticky really. Check the first three videos of this blokes channel, might help you out http://m.youtube.com/channel/UCPM2-F1VXmtYvHBh-5jOQaw Quote Link to post Share on other sites
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