John's Alu Profile build

**pippin88** · 10-09-2020

Is your steel angle truly 90 degrees? Often they are not and that could cause issues for your alignment.

**JAZZCNC** · 10-09-2020

Why did you epoxy the whole base.? You will need a base board or fixture plate and that will need to be surfaced so it seems like a lot of wasted epoxy to me.?

To me sitting the rails on profile to raise the gantry defeats the point of the concrete base as it introduces a weak point which could have been avoided by creating raised sides by shuttering up and filling with concrete, then epoxying just the raised surface. You could have then fit tooling plate to the surface for the rails to fasten too, it could also have been used to fine tune out any errors.

But I suppose the beauty of concrete is that you could still do something like this if you wanted without too much hassle.

**Evengravy** · 04-10-2020

Hey jazz. I mainly did it this way to have a nice level surface to measure from to align x travel but you're right, it's not the most efficient use of epoxy for sure.

I've spent quite a bit of time aligning everything.

Front to back I'm within 20 micron on the left Y rail (measured rail block to epoxy) in the right side within 50 micron. If I were to do it again I'd cast the y rails as raised concrete sections as you say jazz. It'd be closer then. The error is coming almost exclusively from the profile, but, I'm happy enough. I'm going to try hand scrape the alu Y rail on the right hand side to get it down to within 20 micron. It's bowed up 50 micron in the middle of travel. Not a massive amount but can be improved a little. These figures are front to back, in smaller areas the accuracy improves significantly.

On the X axis I'm within +/- 5 micron left to right so all good there. At those levels I'm reaching the limits of my measurement tools/technique.

I'm planning to drop a cast Alu plate on here fixed with threaded anchors soon ish. But I want to get the alignment as close as possible before I do that. That's really why I epoxied the entire top. Maybe not the ideal (cost effective) way but it gives me peace of mind when measuring. The project is on hold atm as I get the electricity supply sorted so will pick it up again soon. I'll really need to insulate the space too given the weather has gotten so wet here.

Comments are bang on though, could be done more efficiently and if I were to build again I'd cast the Y rails from concrete. Basically I had these already done and the thing running before designing the base so didn't want to start again redesigning bits, but so far it's working out alright. It's a learning experience so I expected that to be honest.

**Evengravy** · 05-10-2020

@Jazz

Thinking ahead to fixture plate. What grades would you recommend for cast plate? It's not something I've purchased personally and suppliers on this side of the water are much more limited than the UK. Am I correct in thinking it would be cast machined 5083? something like this:

https://www.impactirl.ie/product/cas...00-en-aw-5083/

**Evengravy** · 05-10-2020

Originally Posted by pippin88

Is your steel angle truly 90 degrees? Often they are not and that could cause issues for your alignment.

They're aren't exactly 90 degrees as you'd expect, you're right, but since I'm bracing both sides of the rail there is scope to adjust allignment each side, so it isn't really an issue in my case. Alignment isn't an issue so far, bar the time required to dial it all in. Chasing microns is slow going.