Many thanks guys for your responses!

Quote Originally Posted by pippin88 View Post
I used West system with the 209 super slow hardener.

I got disappointing results. Better than raw steel tubing perhaps but nothing as good as some people report / claim.

It seems you need quite a thick pour (5mm plus) to overcome surface tension.
Epoxy is not a stiff material, so now you have 5mm of relatively soft stuff between your rails and the underlying metal.

I got indents from my rails in the epoxy despite waiting weeks for it to harden before mounting rails.

Overall I would not go for epoxy again.

There is no good cheap solution.

Send out for machining - $$$$$$$

Making the frame very adjustable is probably the best option. You can then do a lot with a machinists level and a good straight edge.
@pippin88

Yep, I intend making the frame (top rails) very adjustable, and take your point about not wanting to go for self-levelling-epoxy again, and I am actually undecided about using self-levelling-epoxy.

But can you perhaps recall where you bought the West Systems 105(209) epoxy and the rough cost?

There was another forum guy from Melbourne who also used West Systems 105(209) epoxy, but he stopped using this forum back in 2014, in his build:
http://www.mycncuk.com/threads/6626-...0662#post50662

Quote Originally Posted by Kitwn View Post
Andy,
Aluminium profile is very popular and based on the pictures we see on the forum is straight enough for directly mounting the rails. Problem is it costs an arm and a leg in Australia. My own machine has the rails mounted directly onto the steel section and relies on the straightness of the steel. It works OK for fully supported round rails but that may well not be good enough for Hi-Win or similar. The alignment of the rails to each other is done as pippin88 describes. Whether that's straight enough for you depends on what you want to make with it.

I'm not sure if anyone has tried a hybrid design with a steel frame and aluminium for supporting the rails. We're then into possible problems with differential expansion!

Kit
@Kit

My thoughts have been tempted from time to time to consider fully supported round rails, due to my understanding that they're more forgiving than Hiwins, but although I might not need the extra precision provided by Hiwin-type-profile-rail, I've been led to believe that they make sense in a cost-benefit and future-proofing kind of way, so will go with Hiwin-type-profile-rail.

Luckily enough, over the past few years I've bought some "bulk" lots of used aluminium off eBay, so fingers crossed may even have enough aluminium profile (90x45 -ish) for both the top rails and the gantry. I wouldn't have enough for a full frame of aluminium, and I really like the rigidity that a steel frame provides, so I may just go for a hybrid design with aluminium supporting top rails bolted to a steel frame. It looks to me like Jazz is doing something similar on his newest 600x900 machines?

As part of the process of aligning the rails, I'm now also thinking of using Milliput-epoxy-putty, that is readily available in Oz, similar to what Jazz explains in the following two posts:

http://www.mycncuk.com/threads/6382-...7754#post47754
http://www.mycncuk.com/threads/6382-...7815#post47815

Btw, some Milliput-epoxy-putty links are:

https://www.hobbytools.com.au/millip...low-grey-putty
https://www.milliput.com/howto.html

Andy