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irving2008
08-09-2010, 12:24 AM
Not exactly a machining problem, but I am looking for something that can be formed into a 150mm dia tube, 300mm long, that is non-porous and sufficiently rigid to withstand local deformation. I plan to use 3 x 150mm dia, 12mm thick MDF discs on a central spindle as a former to wrap this around. the nearest thing i have seen is thick acetate sheet (what would glue this to MDF?) but I cant find a large enough sheet locally - needs to be 500mm x 300mm at least and thats bigger than A3...

suggestions?

FatFreddie
08-09-2010, 12:34 AM
You can get larger acetate sheets at Wickes but 150mm might be a bit of a tight radius to bend it to.

How about pipe? http://www.tlc-direct.co.uk/Products/FD61350.html for example

irving2008
08-09-2010, 12:41 AM
Good suggestion... only issue is I need another one 200mm diameter as well and that pipe is 156mm external which is too big, . Thanks anyway. I looked in B&Q at polycarbonate sheet but even the thin stuff wont bend that much... laser printer transparency sheets would do (I'd use two overlaid to give stiffness), if i could get it it bigger...

i2i
08-09-2010, 12:41 AM
pipe does sound sensible, but you could use laminate sheet and that comes in 8' x 4'. Contact adhesive works well.

ecat
08-09-2010, 12:54 AM
Finding things is a bit of a trawl at this place but it is always worth a look...
eg

http://www.modelshop.co.uk/product/Clear_PETG_0.5_x_800_x_1000mm_RS20113 too thick maybe?
http://www.modelshop.co.uk/product/PVC_0.18mm_x_1300mm_x_1m_black_RS30135 not strong enough?

... lots to look through :)

irving2008
08-09-2010, 01:01 AM
I dont believe it... that place is not 100y from the arches where I park my car if I have to take it into the office... and I never even knew it existed... guess where I'm going tomorrow at lunchtime :lol:

ecat
08-09-2010, 01:06 AM
heh, cool :)

Bit expensive to actually use but ask if you can play with their laser cutting bed while you're there, pictures or it didn't happen ;-)
http://www.modelshop.co.uk/article/show/18

spluppit
08-09-2010, 01:22 AM
another one you can try if you get no luck.


http://www.davis-plastics.co.uk/index.html

compfranon
08-09-2010, 02:23 PM
Could you use acrylic tube 150mm dia x 3mm wall thickness, available here

150mm Dia x 3mm Wall x 1000mm Long Acrylic Tube (http://www.trentplastics.co.uk/online/index.php?act=viewProd&productId=366)

irving2008
08-09-2010, 02:53 PM
Thanks for that... they do 150 and 200mm tube. But its expensive stuff if you have to buy in 1000mm lengths... I'm going to "4D Modelworld" in the next hour to see what they have.

irving2008
08-09-2010, 09:08 PM
OK, got me a 660 x 680 piece of 1mm styrene sheet for 3.15... it will form to a 150 or 200mm cylinder (will use some MDF formers) and can be glued with contact adhesive. That place is a treasure trove of interesting stuff for modelling... hard o get stuff like wire mesh sheet in small sizes (both mesh and sheet size) at reasonable prices.

Had a look at the laser and a long chat to the guy that operates it. Got a video on my phone that I'll upload shortly (once I've figured how to get it off the phone). They do acid etching as well. They also do on-site white metal and resin casting from own patterns.

ecat
08-09-2010, 10:07 PM
Excellent news \o/

I've not used the place myself, just one of the many links I've collected during my, err, feasibility studies. Yes, feasibility studies is a good description for projects that never quite get started ;-)

irving2008
09-09-2010, 12:10 AM
:lol: What do you call a project that you've spent money on acquiring the parts, yet it still never quite got started??? I've a few of those too :)

Jonathan
09-09-2010, 12:14 AM
Hmm, all this talk of thin plastics has got me thinking what to use to make machine bellows. Any ideas? Was there anything that looked suitable in that shop irving?

irving2008
09-09-2010, 12:19 AM
well the styrene comes in 0.5mm thick and thats quite pliable. If were scored right it might work without cracking... also PTGE sheet in 0.5mm. another idea would be styrene/PTGE strips glued to a fabric hinge.

Jonathan
09-09-2010, 12:25 AM
Interesting. I think making fabric hinges could rapidly get tedious though.
I'm getting really fed up with the swarf/dust/milling cutters dropping on to my Y-axis screw. The swarf builds up them makes a horrible noise from the oil being soaked up...can't be good for it.

Did you mean PFTE, not PTGE? I can't seem to find any info on PTGE. I think PTFE could be good since I've got some thicker sheet and it's very flexible.

ecat
09-09-2010, 12:55 AM
Keeping the dust out...

This guy planed his ballnut and used draught excluder
http://www.cnczone.com/forums/showpost.php?p=261621&postcount=70

and this guy uses some sort of split pipe device + some sort of flexible plastic
http://oneoceankayaks.com/madvac/machine_frame.htm, see last two pic's on page

both look to be good ideas

irving2008
09-09-2010, 12:57 AM
PETG (http://www.modelshop.co.uk/product/Clear_PETG_0.5_x_800_x_1000mm_RS20113) is what I meant

ecat
09-09-2010, 01:03 AM
:lol: What do you call a project that you've spent money on acquiring the parts, yet it still never quite got started??? I've a few of those too :)

A-ha. That would be the proactive purchasing of serendipitous supplies.

irving2008
09-09-2010, 01:32 AM
Here's the video I took of their laser. It was making sample cuttings - basically a collection of 25mm squares of various materials, ply, balsa, card, etc etc, with the power & pulse rate used and an example of the cut you get by 'machining' a 20 x 10mm rectangle. Depending on the power/pulse rate this can be a mere scorching of the surface to a complete blast through and all depths in between.


http://www.youtube.com/watch?v=fWkdg16AcvE