New Build - Bolt Together CNC

[ardenum2]

Epoxy creeps over time.

I did epoxy levelling for my router. It has been disappointing. Requires about 6mm thickness to actually self level.
The rails and ball screw mounts have created indents in the epoxy over time.

It works fine for a wood router, but epoxy is not the perfect solution some people imply it is.

Steel filled epoxy designed for joint replication may be different, but you have to mold / install it in the final precision. A straightedge works for one rail bed, but doing two that need to be precisely on the same plane is not easy.

it seems that SC-15P is both steel filled and self leveling and de-airing, they showed some images of a flat surface covered with it to create an air bearing surface

[joeavaerage]

Hi,
if its steel filled, how is it still runny enough to self-level? As peteeng has already found even assuming a good solids ratio of 60% or better he still only got 18GPa.

I would not have thought had 18GPa is anything like enough to mount rails on.

Craig

[jaguar36]

I would not have thought had 18GPa is anything like enough to mount rails on.

As I said before, The epoxy layer is thin enough the stiffness doesn't really matter. If 4Gpa is fine, 18 will be even better.

Epoxy creeps over time.

I did epoxy levelling for my router. It has been disappointing. Requires about 6mm thickness to actually self level.
The rails and ball screw mounts have created indents in the epoxy over time.

I was hoping the supplier would have some creep rate data, but they don't appear to (which is slightly worrying). However as long as you stay below about 1/3rd of the epoxy melt temp creep is pretty minimal/non-existent. For SC-15P that should be around 90F, and my shop usually runs a good bit colder than that so I should be fine. Even if it does aned up creeping a few tenths, it would do it consistently, and therefore shouldn't have any noticeable impact.

I'm not set on epoxy yet, but it does seem like the best solution. What other issues did you have with it?

[joeavaerage]

Hi,
then try it and see. I'm sure it will work, the question is rather not IF it works but rather how WELL it works, both in the short and medium terms.
If it doesn't work to your expectations then so what? I mean you can scrape it off and try something else.

Craig

[pippin88]

As I said before, The epoxy layer is thin enough the stiffness doesn't really matter. If 4Gpa is fine, 18 will be even better.

I was hoping the supplier would have some creep rate data, but they don't appear to (which is slightly worrying). However as long as you stay below about 1/3rd of the epoxy melt temp creep is pretty minimal/non-existent. For SC-15P that should be around 90F, and my shop usually runs a good bit colder than that so I should be fine. Even if it does aned up creeping a few tenths, it would do it consistently, and therefore shouldn't have any noticeable impact.

I'm not set on epoxy yet, but it does seem like the best solution. What other issues did you have with it?

Even/consistent creep is a big assumption. What about different loads on different areas?

I pulled my gantry apart after I found the rails were not flat. I can't remember the figures, but it was about half to one millimetre over 1.2 metres or so.
This was after years of use and with visible indents in the epoxy from the rails.

For a woodworking machine it's ok perhaps, but don't expect perfection.

I don't think the claims of surface plate flatness are true in this application.

I used West system with the super slow hardener (it is not advertised as achieving surface plate flatness. The epoxies claiming super flatness / levelling are not sold in Australia)

[peteeng]

Hi - The epoxies that set flat have very slow cure to prevent surface creep and hot spots. They are similar to or the same as river casting epoxies. These are very soft due to the slow cure. As Pippin has found 1) they need quite a thick pour so surface tension does not dominate and pull the surface in various directions creating a chicken skin effect 2) thick so internal viscous forces are distributed and gravity can dominate... so the result is flatter. Total result is not good I think.... on another subject I went for a bicycle ride today along a new rail trail created nearby and they have refurbished one of the bridges. Makes me want to break out the furnace, rivet gun and buck.... or watch a Wallace and Grommet movie....Peter