Good job! Thanks for taking photos, sometimes I find it hard to visualise what people have done. The epoxy looks very neat, I would love to see some pictures of it when it's cured. How do you pour it? Just on one side and let it flow down the channel to the other, or fill both sides at the same time?
Did you weld the frame yourself? Looks very good.
I filled both sides at the same time. The magnets at the corners helped as they were 4.25mm thick, as i could clearly see how much i should pour to achieve 5mm thickness.
As the channels that connect the sides were very thin and i have not mixed enough epoxy, had to mix second time and pour in the channels.
if i was to turn back time, i would have used the same aluminum angle profiles, fix them with scotch only from outside and use cheap epoxy with a brush to make a kind of base, which would close the distance from the channel to the profile against spill. When dry and so secured, pour over the expensive epoxy :-)
Yes, i welded the frame , the process is described at post #43. My second welding job in fact. Good that i was careful there, now things are much more easier that could have been with not so careful welding. used a cheap 250A Mig which i obtained from ebay+C02, hence the not so smooth welds.
Yes the magnets seem a good idea. If I was doing the epoxy I think I would have also used the thin channels, so I am sorry it didn't work out as well as you intended but I am pleased you shared the results so others (me!) can learn from it.
Sorry i thought I had seen all of the posts but I guess I have missed a lot!
As Jim says, the epoxy looks very good and there's no way that frame is going to move.
I know that I have posted these before but this is the way I have done it. The epoxy is the Wests system Very slow cure. ..Clive
Now something very important. I will not move the frame at all. After a week has passed will solder the gantry and sides. Then will turn upside down the gantry and lay the upper side on the level surface of the epoxy. Then will pour epoxy on the gantry side plates that step on the Hiwin bearing blocks, connecting them together. Also pour epoxy on the lower side of the gantry beam. When dry, will turn the nagtry to normal position , rest the leveled side plates / epoxy on epoxy/ and pour the final epoxy at the top side of the gantry beam.
So with these steps i will achieve all hiwin rails lay on epoxy surfaces that are paralel to each other. The only thing left will be to ensure squareness of Z. I hope to achieve a quite precise machine.
Well, that's an obvious way to set up the epoxy on the gantry. You know, the kind of "obvious" that's only obvious when someone else says it!
I've been kicking ideas around in my head for the last week or two about how to align the Y rails for "constant spacing" if I put them on the top and bottom of the gantry bars for my new design. Easy enough to lay the gantry on its back and use epoxy to level the Y rails on the front face, but I couldn't work out how to do it where the fixing faces for the rails were not in the same plane. Easy enough if you have an accurate level surface to put the gantry on and do one rail at the time but how do you generate that initial level surface in a home workshop? So use one of the level surfaces you created when you used epoxy to set up the X rails! As I say, it's obvious once someone else has pointed it out...
In practice, any idea of how much out of true a typical length of, say, 50x50 or 80x80 steel tube would be? Are we talking about a mm or two, or significantly less than that? How much does the epoxy thickness vary, in other words?
Last edited by Neale; 28-01-2014 at 09:26 AM.
http://www.parkersteel.co.uk/media/p.../JPSBS0010.pdf I was looking for it yesterday when I wanted to look at how "true" my beam might have been. Don't forget you're also at the mercy of the stockholder and transport to keep the steel flat and not to induce any additional bending/torsion etc...Neil...
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Very interesting build, and good research for me. A weld bead causes shrinkage where it is deposited, so weld induced distortion is not so much due to the 'heat' that goes into the part, but is due to the fact that a weld, when solidifying, pulls on the adjacent parent metal. Apart from looking nice, I'm not convinced these types of bed frames, with massive members, need to be fully welded at the joints, from a stress point of view anyway - stitch welding would be perfectly adequate - having said that, the effect of inducing bending due to weld shrinkage is possibly only noticeable on smaller dimension square hollow section, less than 70mm say. The effect of weld shrinkage induced distortion may be mitigated where possible by welding to the perpendicular plane of the material, if that plane isn't as critical for flatness, and the design configuration suits it - I don't think it applies in this particular build case though.
Sorry to theorize in your build thread - being a noob, I guess I'm eager and this seemed an appropriate, and reasonable relevant place.
Last edited by CharlesJenkinson; 06-02-2014 at 09:00 PM.
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