06. X gantry

The flatness of XY joiners aren't good , mines come wrapped, after mount on the plate and on rails ,twisted the gantry and the linear bearings don't slide well, I had to mill them.

My plastic “XY joiners” required some post processing. There was plastic drooping down from where unsupported bridges were printed. They touched the idlers and prevented them from spinning. A shot from my heat gun/lighter/torch and a little pressure smoothed the errant fibers and pushed them back into the main plastic part. A little bit of sanding or filing would produce the same result.

Is anyone else having problems getting the ends to fit on the 2020 extrusion. Both of mine were too tight to fit in, it could be my printer, but I had to edit the STL s and make the 2020 hole 20.4 mm on each side.

My 3D prints that I made were not good on this step. The 2020 extrusion would not fit, and I’m reprinting. Good idea to check before you enjoy the fun of putting the idlers together only to realize you will have to do it again.

no micro shims in my kit

I write this here up front, for everyone that wants to try the build like I did.

I did not follow the order described, as I read the warnings about the difficult belt inserts at the end.

Instead I first connected the gantry and the printed left and right parts. Then I screwed the metal plates onto the rails and placed the gantry on top. Then I started to insert the idler stacks by using a hex allen key from below the part through the adapter plate. This way I could add the belt while stacking the parts and it was totally easy to do so.

You might consider the help of another person to stack though, as the stacking while holding the allen key at the same time gets somewhat acrobatic at times :D Good part placement is key.

After the stacking and screwing the m5x55 through I attached the finished gantry to the metal adapter plates. This way the belts were already routed correctly.

(PS: To move the gantry for the rail alignment you can easily pull on both the loose belt ends on the side you want the gantry to go)

Material List is:

4 micro shims

8 Mini shims

8 Spacers 6mm

2 toothed Idlers

2 smooth Idlers

4 cap head screws M5 x 55

Make sure the X rail fits before doing this, mine was too tight and I had to reprint with 20.4 mm vs 20.2 as supplied, still required sharpy work to remove any overshoots. I should have printed this extra slow !.

(Just make sure you always have a shim each side of the bearing..)

Put the mini-shim between the two spacers, as the spacer is easier to position as a last piece..

Just a tip so you don’t do what I did, go ahead and put and m5 nut on the end so you don’t have to worry about them falling out when you do the next step.

I over tightened the cap head screws. The idlers did not want to spin freely. I backed the screws off a quarter turn and then they spun freely. You might want to double check all your idlers before you get to adding the belts.

Centring the little washer is tricky. I went the other way with another M5 bolt and then took the M5 bolt out and placed one in the correct way. It is easier to centre the last washer in between the spacers than the pulleys.

Would it be the end of the world if drop in Tnuts were used instead of slide in?

More of a pain to put on but once on… they should be just as secure as anything else right?

You should call the square nuts “square slide in T-nuts”. There are actual square nuts in the packaging that are used in other places. This would let you be more specific and direct the builder to the correct part with less confusion.

To make the insertion of the 2020 into the plastic Joiners easier, I beveled the sharp edges at the end of the 2020 with a small needle file.

The plates where not parellel so the rail did not align and did not drive smooth.

I drilled the 4 holes in both plates of 3mm with a 4 mm drill: aligned and smooth like sunshine!

In addition to Elco Jacob’s comment I would like to add that even if your printed parts are perfectly square and a snug fit to the 2020 extrusion and other parts, there can still be a problem with skewed plates that mount on the rail carriages. I don’t like solutions that are irriversable (such as sanding something down) without understanding what the actual cause is. So I looked closer into the problem. My parts were square and as good as you can expect from a printed part. Yet, when I tightened the bolts that hold the printed part to the extrusion, the plates skewed with their outer tips down by 0.15mm to 0.2mm left/right. What I did was test which one of the bolts could be fastened without the plate skewing. This were the top bolts. I then shimmed the space at the bottom bolts so it could no longer skew when tightened. This fix is actually closer to the real issue in my case, and is reversable and adjustable. Hope that helps!

If there is a gap, sanding the surface to make it flat will help. Loosen the screws from the previous step that hold the printed part to the extrusion. Press down so the plates make full contact with the flat surface. Then carefully put the assembly on its side and tighten the screws again. Finally, put the M5 nuts back on.

I think a crucial step that should be added to the guide is to ensure that the extrusion and the plates are perfectly parallel. If your printed parts have a small ridge (elephants foot from printing), it can cause misalignment. The result will be that your linear rails will start binding when you tighten the screws that hold the plates to the rails. The rails can slide very smoothly until you fully tighten.

To check and properly align: remove the 4 M5 nuts at the bottom of the plate. With the screws inside but loose, put the assembly on a flat surface and press down lightly. Check that there are no gaps between the plates and the surface or the plates and the printed part. If there is a gap, sanding the surface to make it flat will help.

obvious from remaining parts… but should call these m5 nuts out as m5 nylon nuts

Do we have to remove the endstops from the X rail before installing it on the 2020 extrusion?

yes all endstops need to be removed. See rails preparation step earlier.

Warning, missing step!

There are no instructions for installing the X rail to the 2020 extrusion.

Do we have to remove the endstops from the X rail before installing it on the 2020 extrusion?

ps Make sure the m5 nuts are in contact with the steel plate when done, if not you are too loose.

Georg makes an excellent comment. I would only add that the best way I found to be sure the m5 screws were as loose as possible yet still tight enough, was to loosen the m5 screws until you can twist the plastic part (about x) and just barely be able to move it off the steel plate. Then slightly tighten until you can no longer make any gap between the steel and the printed part. This will prevent any unwanted movement when printing, but keep the parts loose enough so they doesn’t cause too much noise in the y axis and reduce bearing wear.

Thanks for the top Georg. I ended up doing a lot of sanding as it seemed like I had printed the plastic parts at an angle (which is likely as the printer I used was not high quality). But ultimately, I succeeded in making the parts flat, so when mounted on the metal holders they didn’t force the rail carriages to in rest crookedly on the Y-rails.

Problem: with the M3 screws from the gantry plates to the rails being loose, the gantry moves very smoothly. But when you tighten them, it makes unpleasent noises. Then do the following:

1. Untighten the M5 screws a little (printed parts to gantry plates), not only should the idlers move very easily, but it also influences the rails. If tightened only a little too hard, the wagon on the rail is tilted and doesnt move freely anymore.

2. If not enough: remove the gantry from the printer and the plates from the gantry. Place the plastic parts (with the M5 screws pushed in, be careful not to let them fall out) on a flat surface. If it wobbles on the surface or has a gap between the surface and the printed parts, do the following: Put a piece of sandpaper on the surface and move the printed part on it, so the underside is sanded and gets flatter. Keep the other printed part on the surface so everything is flat and repeat on the other side. This improved things for me. Although still not as good as with loose screws.

In addition to the above comments I found that it was extremely easy to tie a thin piece of string to any small piece you can feed through the rear slot and then tie the other end of the string to your belt and simply pull it all though like mule tape. The zip ties I had lying around were too short to easily do this process by themselves but with some string it easily fed through the first time.

That trick is amazing. Should go into the step description.

Daniel is correct I used the magnets for the z axis arms and it worked to pull up the nut enough to engage it! Nice tip, especially if you don’t have a m5x14

The M5 x 12mm will work just fine if you use a decent power magnet to pull the nut to the top of the extrusion while tigntening down the bolt.

I also struggled a bit here. The X-Endstop part is rather flimsy, and I followed Murray’s suggestion to put a shim underneath to support the end stop as to bot break it apart when tightening the M5 bolt. Like many others I also needed to use a 14mm long M5 as the 12mm provided couldn’t reach the square nut in the extrusion.

Where does the Y end stop go?

Other stated that it should be an M5x14 but I was able to used the default m5x12 with the 3d printed parts from rat rig themselves without any modifications. With that said YMMV

I had an extra 6mm shim washer left over which I put between the endstop block and the left XY joiner to fill the gap and not break through the bottom of the stop as the bolt was retightened. I sanded the stop so that it fit and slide easily off the end of the rail (there is a right way and a wrong way to put the stop block on, its bottom groove has to align with the rail).

I’m a bit disappointed with the endstop arrangement, The adjustment part on the EVA can’t be adjusted once it’s assembled (I’m using a BMG extruder option), so not sure why it’s made adjustable. The switch is held in place by screws that screw into the plastic arm and I overtightened one so I then needed to add a nut on the other end. It would be a better to go with nuts from the start I think. Then the switch lever contacts only the very outer corner of the block which also has the problem others have described as a very thin plastic base. I redesigned my block to eliminate these last two issues as I felt the end stop will become unstable over time if I left as it was.

As Daniel noted, be careful screwing this piece down as it is very thin. On top of that, check for a lip between the XY joiner and the linear rail. In my case, the joiner was too short. I didn’t notice until screwing down the piece and it cracked under almost no force. The linear rail stuck up above the joiner by about 2mm. That lip combined with the very thin piece almost guaranteed that the endstop wasn’t ever going to be secured very well.

Agree with Tom’s comment, this really should be a m5 x 14. However, I was able to use the 12mm by tipping the printer on its side, causing the square nut to come closer to the rail.

It’s roughly clear this is the left side of the gantry… but should be pointed out in the docs. Should also point out not to tighten this down to tight. The plastic holding this endstop is really thin where it bolts down and i cracked mine… and yup, an M5x14 was nice upgrade here Tom. Forgot to mention the picture at the top of this page does not show the end stop. Nor does the picture at the bottom or subsequent steps.

The M5 * 12 isn’t long enough, use an M5 * 14

EVA is a modular carriage platform for MGN style linear rails used on 3D printers. The main goal is to support a wide variety of hot ends and extruders in common use on a variety of 3D printers including the Rat Rig V-Core-3. You can find all the EVA details, printable parts and guides at the EVA web site https://main.eva-3d.page/ The build guide for EVA on a Rat Rig V-Core 3 with Bondtech BMG extruder and E3D V6 hot end is included in section 8 of this build guide.