Quite an Unusual one

**Neale** · 15-09-2014

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.

**Boyan Silyavski** · 16-09-2014

Originally Posted by Neale

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.

Hi Neale,
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.

**ba99297** · 16-09-2014

Originally Posted by silyavski

Hi Neale,
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.

Syliavski i thought that a solvent free epoxy is a must at this procedure. Why you choose to buy an epoxy that contains solvent ( or i missaunderstood something?)

Vagelis

**Boyan Silyavski** · 16-09-2014

Originally Posted by Blackrat

What about adding a filler like ATH ?

I thought to do it , only had graphite at home. But truth is i want it perfect, so bought the West system epoxy at the end.

Originally Posted by ba99297

Syliavski i thought that a solvent free epoxy is a must at this procedure. Why you choose to buy an epoxy that contains solvent ( or i missaunderstood something?)

Vagelis

I chose to buy epoxy sin solvents but they sold me one with solvents :-)

**ba99297** · 16-09-2014

You mean the solvent was in the epoxy before you make the mix?
Good for you that they admit their mistake and you finally get your money back.

**Boyan Silyavski** · 14-10-2014

Hi,

The build is going on but i am stuck with epoxy problems. Mean BIG problems

.

Second time casting epoxy on the long sides and same problem. The area near the connecting bridges is sunk checked against straight edge. about 250mm wide visible inclination, not measured cause still not perfectly hardened but say 0.1-0.3mm . Each pour cost me 100euro

2.5kg of WS epoxy mix.

Now for a woodworking machine this will not matter, but spending so much money on it i would like to be as Perfect as possible. Hell, at least 0.05 precision or better, real life, not exaggerated. I was striving to something like the first machine i made 0.01mm, knowing that on such a big scale it would be difficult but worth to try.

So to achieve this i depended too much on the epoxy.

Whats the f---g problem then? Everything is perfectly prepared. 21C in the garage, 45mm wide dams, 10min careful epoxy mix, all by the letter. First time i thought the dam was flimsy and contracted at certain points. Not so the second time, everything is reinforced with steel/the bridges/ and hot glue / the 10x10mm dams.

I gave it a lot of thoughts and the conclusion is : the 1600mm long bridges are the culprit. The epoxy contracts , so the bridge epoxy contracts and takes away epoxy from the rails at the exact moment when its solidifying. cause i looked 100 times after 1 hour of pour, 2, 3 hours of pour -it was ok. It happens on hour 4 to 6. Or maybe it was my mistake that the connecting bridges had to be both ends, so when all contracts , contracts equally, like a ring i mean. No money though for further experiments . I believe though that even if ring is formed the right angle between them is the culprit.

So yes, there is a problem with 3000mm rails and 1600mm distance between them. Inherent problem i mean. Not reported by any body till now but hey, did anybody who made such a big machine take care to measure it against DIN 874 straight edge? Possibly no.

I blamed the air trapped, blamed the supports, blamed this and that, but on a smaller scale i did not have any problem before, +fixed all possible doubts. So yes its inherent, until somebody prove me wrong.

I see only 2 possibilities from here on.

1. Will wait to dry for 3-4 days and mount the rails using the straight edge/ 1m/ and shim. Then will have to buy the 2000mm straight edge to continue with the build and check the rails against each other. But if there is a twist , 2000mm straight edge will not be enough or at least would be very difficult to straighten things up. To the precision i would like, i mean.

2. I knew it when pouring second time, but was not sure.

. So may be third pour from scratch or half pour over this one. And on minute 45 / 21C/ cut the bridges simultaneously by some previously prepared method. Say a sliding plate or similar. The way in actual water channels the water flow is cut. Cause at this moment everything is perfectly leveled .