Thread: Quite an Unusual one
looking like a really solid lump!!! How about drab (a sort of olive green) and "big bertha"? Well done. G.
where did you find that ball screw picture?
Olive green is a good idea. Some pieces black or and dark grey. I tried with the other green Mid Brunswick Green, but did not like it
Unfortunately someone took the name big berta . But lets make it alive, then the name.
Today started soldering the bed frame and bought the epoxy. As i stopped working at all except on the machine, money flows like water through my fingers. So i bought at the end the Spanish epoxy with very similar properties like the WS. from choice of three i choose the most similar. There were seemingly better though some data was not clear, from the one that could concern, i mean. 125eur with shipping for 5kg pack +1.6kg hardener.
Basically 90 min gel time, max isotherm 40C, compression strength 580kg/cm2, yellowish, contraction 0.1%, density 1.08 gr/cm3 which roughly translates to 6.5l so ~20eur /lit mix, I cross my fingers that it works ok.
It seems that the machine will lay on the floor with no legs. have to figure where to fix some hooks for the future and most importantly some plates to lift it using car jack. To level it for the epoxy pouring. Cause now it is unliftable already.
Last edited by Boyan Silyavski; 08-09-2014 at 11:18 PM.
where did you find that ball screw picture?
el martillo de ThoryavskiSpelling mistakes are not intentional, I only seem to see them some time after I've posted
But here is what happened:
The epoxy poured extremely well. It leveled well. And for 4 hours it was perfect. As gel time was 90min, i thought well, i cheated destiny. But no. After the 4rth hour it shrank in volume and there was not 20mm wide flat area in the center to munt the rail. I did the test 50mm wide channel, instead of the 40mm normal with WS 105+209. Read a lot why and it seems the reason is that the epoxy is low quality and contains non reacting solvents that vaporize when the hardening starts. On the long axis it was straight, so its not a mixing problem, anyways i mix it at least 5 minutes and change the can before pouring, so not my mistake. Repeated twice the test-same result.
So i took a risque and lost. My reasons were not that i am greedy, but the price difference multiplied by the future machines is quite some money. However i just returned the 5_1.6kg epoxy so the loss is about the cost of shipping, the time and 1 lit of epoxy.
1.Seems the biggest unaccounted problem for that purpose is the shrinkage, in other words the purity of the epoxy. Hence the price of good epoxies :-). Otherwise flatness and surface quality is more a result of good mixing and following exact mixture to the gram and temperature when pouring.
2. Judging epoxies from their technical sheets means nothing. It can seem on paper right but poor in reality
3. Epoxies with very high viscosity >700 cps of mixture maybe contain something that will evaporate later
Left on the picture is WS 105+209 at the time of pouring and cured. Also the spanish epoxy untill 4h. Right is the shrinkage when 8h passed
At the moment of pouring till 4h
The problem after 8h of curing, a bit difficult to be seen but the drawing above shows it better. On the second picture the shrinkage lines can be seen at the reflection distortion . Not that it could not have worked as we are talking about 0.3mm here and on the long axis was straight, but not worth the additional fiddling.
Last edited by Boyan Silyavski; 15-09-2014 at 10:43 AM.
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I don't think that you can blame the quality of the epoxy. It did what it was designed to do. I think that epoxies containing solvents are typically used for coating, so that they spread well - which is what your epoxy did! They are definitely not recommended for use as adhesives or fillers, mainly because of the shrinkage as the solvent evaporates. However, I didn't know this either until a couple of days ago when I read an article on the use of epoxies for adhesives and coating! Something to watch out for if anyone is looking for an alternative to the usual named brands.
This is specifically a casting epoxy, its not a coating epoxy. It specifically says 0.1% shrinkage in its technical sheet, and by no means its a cheap epoxy , its simply cheaper than imported WS epoxies.
I also read a lot of documents about epoxy and all say the same- 3 types of shrinkage, and exactly this type is due to non reacting solvents. This is not shrinkage due to temperature cause it happens after the initial hardening. From the company started to argue with me, saying this is not possible, it never happened, until the moment they understood that i know a lot of sh^t about epoxy and they agreed that this was because of the cheap solvents. That was the moment they agreed to break their policy of no return, once its opened.
What about adding a filler like ATH ?