hey all just did a quick search on the boards, has anyone vac formed using uhmwpe (as opposed to hdpe)?(yes this is a stormtrooper helmet question)
I'm going to get a couple of sheets and have a play around with it
hey all just did a quick search on the boards, has anyone vac formed using uhmwpe (as opposed to hdpe)?
I'm going to get a couple of sheets and have a play around with it
Sounds good. How does it compare in price to other plastics like HIPS, PVC or ABS?UHMWPE (Ultra High Molecular Weight Polyethylene) exhibits excellent wear characteristics due to its low co-efficient of friction (second only to PTFE). It has the highest known impact strength of any thermoplastic, and it's molecular stability allows it to perform very well at cryogenic temperatures. UHMWPE has FDA approval for use with food products.
UHMWPE has long been in severe abrasion situations and has come to be regarded as the premier material in these applications in industraies such as pulp and paper, mining and conveyors. It provides optimum properties at a minimum cost.
How thick would you go for a Stormtrooper helmet? I've just go into the fun of Vac Forming and found I need thicker (currently using 1.5mm PVC and HIPS) for what I am doing if I want any real body to the parts.
That has to be even more of a pain to paint than to a HDPE helmet ...
Hey Cavx yeah I have found a bit on the net about it. It is a thermoplastic which suggests it can be vac formed but I just wonder how easily and how well it will take detail.
It's more expensive than ABS and HIPS but I think if it's anything like hdpe it will come off the forms easier.
I'm looking at 2mm at this stage. I've done some vac forming in 2mm ABS and HIPS before, anything thicker is WAY to thick and anything thinner is a wee bit too flimsy for my liking although you get better detail....
I think I'll just buy a couple of sheets and have a go :o
I'm hoping to get white uhmwpe. At this stage I am having trouble sourcing HDPE in New Zealand and in sheet formDarth Lars said:
Some questions:oota goota said:
Q1. How thick do you want the wall thickness?
Q2. How tall are your bucks?
The buck I used today is under 3" (75mm tall) and temp pending, it will stretch the 1.5mm I'm using to about 0.5mm in some parts. I learned that if I don't heat the plastic too much, I can maintain at least 1mm wall thickness, but at the expense of some detail. Actually this slight loss is advantageous as if the buck does not have a 100% perfect surface, you won't see it.
A Stormtrooper bucket is going to be quite tall (10~12"?), so I would think you might want a thicker piece to start.
thanks cavx yeah you might be right. I have no idea how much the uhmwpe will stretch or how thin it will get. I'm thinking it will probably get down to about 0.5mm we'll see!
The general rule of thumb is that the plastic will half its thickness during this process, but there does not seem to be a way of working out how much height you can get away with. If your choosing this type of thermal for its durability, then it might defeat the purpose if the wall thickness is just 0.5mm. ideally you would want at least 1.5 or 2.0.
When I had my prototype acoustic tile made, the guys that made it for me out of ABS said that they needed 10mm due to the shape and amount of difference between the high and low points. The end wall thickness is about 3mm.
I have been amazed with how thin the plastic I have used can get and in some cases, I even got tears which compromised the seal on a few pulls. You don't want to be getting these on a Stormtrooper bucket or any other parts to the armor.
the reason why I'm trying to uhmwpe is I'm hoping it's going to be more flexible than ABS or styrene and come off the forms more easily.....I'm might just have to keep looking for hdpe ....so yeah I might have to look at 3mm or so thanks dude!
I am going to source some 3mm PVC in grey for a part I am working on. This part is just 100mm tall and the 1.5mm HIPS I used is stretched pretty thin and I had a few tears on earlier attempts, so thicker material needed here for sure.
Be curious to know how that works out. I've tried to vac PVC before but had no success the vac former couldn't pull the plastic down as easily....
What are you using for a heater? I am using a quarts wall mountable twin strip unit rated at just 1500W on high mode. I actually have two of these and based on what I have seen so far, will probably do a vertical mount with a heater on each side to get heat into the thicker plastic. If using thin plastic, will just use one heater.oota goota said:
In my original hot box, the heater was some 800mm away from the plastic and I just could not get the plastic hot enough to make a really good pull. And my early experiments also took the best part of 50min to get the plastic up to temperature.
After a heap of experimentation, I discovered I get the best results with the heat mounted just 75mm off the plastic. 100mm might actually be slightly better as I have burned [discolours] the plastic and also made it too thin as a result.
These parts are both made from 1.5mm PVC. I found that if the plastic does not get too hot, that you get a really smooth finish with really nice white [part on the left] at the expense of some detail. If the plastic gets too hot, it does slightly discolour but gives awesome detail. The wall thickness becomes too thin IMO to be used as an actual part. You could thicken that up by slush casting a resin, I guess. I'd rather go with the thicker plastic and make the part right the first time.
wow they look great cavx. I've got access to a home made vac former made of steel with a vac chamber etc etc. So it's a good machine although the heating unit is a bit smaller than the frame that holds the sheet so it doesn't heat particularly evenly. I can get round that but I think it's not powerful enough to heat PVC of any decent thickness properly
I've have to check the distance between heater and plastic.I've an idea its about 75mm
Still no word about the uhmwpe yet
I'll have to take a photo of the heater(s) I am using. I bought each for $15.00 new at Bunning. They are a wall mountable twin bar 1500W quartz heaters and at 75mm, one takes just 2:30 to heat 1.5mm PVC to temp where it slumps. I also now heat from above, so no risk of melting plastic into the heater.
My Platen is 600mm x 600mm with 19 x 19 holes spaced about 20mm apart. My frames are 50mm wide leaving a center of 500mm x 500mm. Because most plastic comes in 2400mm x 1200mm sheets, I got the supplier to cut them into 600mm x 600mm for me. Rather than just clamp, I drilled through the plastic and secured everything with small bolts and tee nuts. I also ran some rubber door seal around the Platen.
Shortly I am going to order more 600mm x 600mm frames, but these will have much smaller cutouts of maybe 400mm x 300mm for smaller parts so I can conserve plastic. I am also thinking about using my router to rebate the cutout so the plastic sits into the MDF. I hope to only need one frame and not two for these smaller parts. I have a packet of 15mm flat heat screws that will be prefect for this.
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