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View Full Version : Reinforced plastic beams for x-axis rails ?



flanagaj
19-10-2011, 11:11 AM
I am trying to think out the box here so that I can move away from using steel for the frame. Having read a fair bit, I have concluded that steel is far from ideal for cnc rails due to the following.

1. Resonance
2. Thermal stability

As a result I have looked at casting the rails using epoxy granite and reinforced plastic beams. Both of which will have excellent damping. I am waiting on the tech literature for the recycled plastic beams as I am not sure what the thermal stability of them is.

http://www.lankhorst.co.uk/hst/l18a10n/lankhorst.nsf/Main/LH%20UK~Products~Marine%20engineering~KLP%C2%AE%20 Steel%20reinforced%20beams%5EUK?open&lang=UK

Interested to hear your thoughts on this.

Thanks

blackburn mark
19-10-2011, 11:47 AM
As a result I have looked at casting the rails using epoxy granite and reinforced plastic beams

im assuming when you say "rails" you mean the frame or rail beds ?

i like the idea of epoxy granite, i dont like the idea of casting around the plastic I beams.... if your going to the trouble of casting a base anyway why go to the bother of using the I beams..... if its about keeping the "volume to weight" ratio down id be tempted to just cast around foam or polystyrene blocks

flanagaj
19-10-2011, 01:39 PM
im assuming when you say "rails" you mean the frame or rail beds ?

i like the idea of epoxy granite, i dont like the idea of casting around the plastic I beams.... if your going to the trouble of casting a base anyway why go to the bother of using the I beams..... if its about keeping the "volume to weight" ratio down id be tempted to just cast around foam or polystyrene blocks
Sorry, but having reread my post it was not very clear. I was thinking of

a) casting the rails using epoxy granite

b) using the plastic i beams for rails

Both a and b would then have a 50mm * 40mm machined aluminium section attached which has been precision milled to hold the linear guide rails.

The other option and I would love to explore it, would be to make the rails using composite materials. eg foam which has been layered with carbon. Carbon is super stiff and I suspect you would end up with a very stiff and light rail ?

Thanks

Swarfing
19-10-2011, 06:28 PM
The plastic beams you are referring to in that link is the same thing as plastic decking. Have a look here
http://www.ebay.co.uk/itm/Recycled-solid-plastic-decking-brown-thick-deck-board-/390303558245?pt=LH_DefaultDomain_3&hash=item5adfe7aa65

This stuff still flexes but good over short lengths. Might give some a try myself.