welding steel base or just getting aluminium extrusion

**EddyCurrent** · 19-12-2017

It sounds like you need to invest in some tools such as a straight edge, engineers square.
I attached one of the long X rails using a straight edge to get it straight, then it was easy to space the second rail from it. Once you have the bearings fitted and a gantry cross beam attached you can feel if the bearings are tight at any point in the travel and make adjustments to the second rail.
Here's how I squared the rest up; http://www.mycncuk.com/threads/6565-...5217#post55217

**JoeHarris** · 19-12-2017

That is pretty much how I did my y axis with the rails onto extrusion.

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**mekanik** · 20-12-2017

I am getting the impression that you haven't done your basic research (ie wadding through the vast amount of information in the build logs) the epoxy leveling procedure and rail installation has all been well covered, and Boyan went into this when he started his build. you can't build an accurate machine without certain items(ie precision straight edge and square) no offense is intended by my comments.As Clive has said if you proceed as outlined in the video you will just duplicate any errors in the ally rail.
Regards
Mike

**Neale** · 20-12-2017

By the same token, the guy bolts his rails straight to the top of the extrusion. No particular reason to believe that this is any straighter than the side of the extrusion - the surface will be influenced by errors in the supporting components, etc. However, errors in work on the machine will be in depth rather than profile accuracy, so perhaps up-and-down errors are less important for a lot of work.

For a router intended for mostly work in wood or plastics, though, will the errors be significant? If you are going to be making sign boards, doing lettering, cutting out stand-alone shapes which do not have tight manufacturing tolerances, is it worth chasing the last micron? I'm not saying you should ignore any errors, but you need a sense of proportion here. If your ballscrew/ballnut/bearing assemblies give, say, 0.05mm backlash, how much better than that do you need to be in the supporting structure?

Steel is different - my own 1.8m support rails dipped by 1.5-2mm in the centre, which is why I used epoxy - but in practice, how accurate are these aluminum extrusions?

**Clive S** · 20-12-2017

Steel is different - my own 1.8m support rails dipped by 1.5-2mm in the centre, which is why I used epoxy - but in practice, how accurate are these aluminum extrusions?

I have built several router type machines with the heavy duty profile 90x45 with the L type gantry layout with the rails top and bottom with no issues. So in my conclusion they are fine for the majority of diy builds and work very well.

**reefy86** · 20-12-2017

Was just a thought after watching that video, i know i will be needing straight edges and engineer squares but most of these videos on youtube are just some guy pointing his camera at an engineer square and going up and down which lasts 20 seconds long lol. i am still reading on here and watching other people tips and tricks but all i can picture in my head is getting one rail on and have it as straight as possible on one side and bolt it down and then use the gantry to slide up and down to get the second rail inline and then bolt that down and then just use engineer squares against the aluminium beam and side plates to make sure thats square

**reefy86** · 20-12-2017

Originally Posted by EddyCurrent

It sounds like you need to invest in some tools such as a straight edge, engineers square.
I attached one of the long X rails using a straight edge to get it straight, then it was easy to space the second rail from it. Once you have the bearings fitted and a gantry cross beam attached you can feel if the bearings are tight at any point in the travel and make adjustments to the second rail.
Here's how I squared the rest up; http://www.mycncuk.com/threads/6565-...5217#post55217

read through your thread mate and i have a better picture in mind now so thank you, after reading about your problems with the bk12 bearings is this something i am going to run into when buying from zappautomation? mine will be the bk15 and bk17 not the bk12.

**Neale** · 20-12-2017

Originally Posted by reefy86

Was just a thought after watching that video, i know i will be needing straight edges and engineer squares but most of these videos on youtube are just some guy pointing his camera at an engineer square and going up and down which lasts 20 seconds long lol. i am still reading on here and watching other people tips and tricks but all i can picture in my head is getting one rail on and have it as straight as possible on one side and bolt it down and then use the gantry to slide up and down to get the second rail inline and then bolt that down and then just use engineer squares against the aluminium beam and side plates to make sure thats square

You are going to need to be able to square the gantry once the machine is up and running, by adjusting home positions for each end of the gantry. Whether you do that via software or manually (home one end as part of the usual homing sequence and then adjust the second end manually) doesn't really matter but you do need to be able to do this. Probably the easiest and most accurate way to check that the gantry is square is to use the machine to make four holes in a square pattern in a piece of suitable material (I use MDF and make the holes a firm fit for the shanks of a set of identical drills). Measure the diagonals and adjust the home positions for the gantry until those measurements are as close to each other as you can make them. Any machine which uses two motors/ballscrews on a single axis will need to be able to do this.

**reefy86** · 23-12-2017

Hope you all have a good Christmas guy's

**reefy86** · 28-12-2017

is it possible to combine a 4th axis capable of cutting up to 200x200mm to my design? i am struggling to figure out how i would without having to adjust the z height, my plan was to adjust the width of the machine to allow me do add a t track to the side of the machine which does not affect the spoil board so i can adjust the 4th axis length so maximum cutting for the 4th axis would be 2400mmx200mmx200mm. So far my z height already has a cutting height of 200mm so if i was to somehow add the 4th axis i feel as if i would now need to adjust my z height to around 300mm and i have no idea how weak it would make my z axis doing this.