If you've been following along in the Improving Print Quality thread (https://www.forum.makertech3d.com/forum/3d-printing/improving-print-quality) then you know that the guide system included for the AXIS is sub-par, at best. We've had some very good attempts to address the issues with this system by @Gareth Owen . His additions and replacements are a great place to start with addressing issues with the guide system. However, I believe that if you really want to address issues with how the printer snags or wobbles along an axis then the best way to fix it is through a different mechanism.
My first attempt to address the guide system was to replace the guides with bearings fitted with cups to lower the friction between the moving body and the guide. This turned out to be fruitless as I was unable to design a setup that wouldn't interfere with other items on the printer.
What I settled on was cheap linear rails found on Amazon. I used two 250mm and one 300mm MGN12 linear rails. These rails are around $20/each. A set with a rail for each axis is about $55 as of the time this post. While this isn't an expensive proposition it does take the total invested cost in the printer up a significant amount. If you got all the upgrades when you got your AXIS and then add this on along with the metal coupler you're beyond the price of some budget entry level printers. I look at the cost of the printer and the upgrades I selected as more of a sunk cost at this point. Yes, I could have put that money towards a different printer, but hindsight is 20/20 and I can't go back in time to tell myself to do anything different. So in the end let's make this printer print better!
X-Axis Linear Rail
The first axis I wanted to address was the x-axis. It seemed like it was going to be the easiest. I ordered a 300mm rail. The first idea was to attach the rail to the base and the slider would attach to the platform. I decided against this as I felt that the length of the rail would stabilize the platform better. I'm not sure if it makes a difference. Ideally I think two rails spaced out on either side of the platform would make the assembly rock solid. The issue with this decision would be addressing the belt system for driving the platform. I thought that this modification would be too much.
Using the supplied files on MakerTech's GitHub for the AXIS printer I created sketches of where to place the slide on the base and where to put the rail on the platform. Designing and thinking this through was much easier than the actual execution. Looking at the hole layout on the base I selected the best place I thought for the slider. In actuality I was lucky I picked the spot I did. Guides for the belt system was only a cm or perhaps a little more from where it would mount. On the platform I centered the rail in both x and y directions. I had to revisit this and move the rail further toward the left side, away from the x-axis limit switch, to address travel issues.
Too low. The platform interferes with the pulleys.
This shows the rail centered on the platform. I ended up having to change this to move the rail more towards the right side (from this photo's viewpoint).
The slider on the MGN12 rails when attached to the rail sits low enough that the guide system for the belts has interference with the platform. A spacer is needed to raise the slider so that the whole system is raised. I guessed and created a spacer block 10mm high. This provided enough clearance but is perhaps a little higher than stock.
Z-Axis Linear Rail
After looking at the y-axis and z-axis I figured that it would be easier to tackle the z-axis second. It should also have a large affect on the quality of prints. I also figured it would be pretty simple as all it would require is to mount the rail to the Z-Axis Pillar (A) and the slider to the Y-Axis Gantry.
I went back to Fusion 360 with the models for the printer provided by MakerTech. I sketched out where I wanted to place the slider on the gantry. It was going to be simple, all it had to do was be center-aligned to the lead screw and placed vertically so that the mounting holes would be accessible. The rail should also be easy. I didn't need make a sketch for it. I just looked at how low the gantry would travel on the z-axis and then centered it on the pillar.
First appearances made me thing this was going to be great!
I thought that this solution was going to be simple and possibly the best upgrade when I was partially through assembly. I only wish I had "assembled" all the objects in Fusion before I got this far. I ended up with issues pretty quickly.
The belt, which normally travels between the gantry and the pillar, now had to get past the slider.
I was quite disappointed when I saw this. Some quick adjustments later and I came up with a different belt path.
The pulley on the stepper is just on there.
Add in a longer bolt with some spacers for the pulley, another longer set of bolts for the guides, zip tie the belt on, and we're ready to go!
At this point the y-axis appears ready to go. The machine is turned on and I home the axis. Everything works great, except for the z-axis! The distance between the slider and gantry is smaller than the original design this caused the lead screw to be pulled towards the pillar. As the gantry is lowered the lead screw cannot bend enough and it binds.
Doh!
To fix this issue I went back to Fusion and decided to take all the parts for the printer and assemble them in the correct orientation and at the correct location.
This showed me the difference I needed to fill with a spacer.
So, with this spacer printed I was able to get the z-axis moving without hesitation or wobble over the entire range of motion! Win!
Y-Axis Linear Rail
The final axis to tackle is the y-axis. This axis is turning out to be the most difficult. Finding a spot to place the rails so that the everything is in an acceptable alignment to the pulley and stepper is a bit of work.
Looking at the pictures above, you can see that the belt path is now different. The design will need to take this into account.
Current adapter for the tool carriage to the linear rail slider. The protrusions on the rear are for hex nuts to be inset and bolts threaded into for the attachment of the belts.
Further Improvements
I'm not a mechanical engineer. I can conceptualize things pretty easily, but getting that "down on paper" is an issue for me. This is especially true when working with CAD tools. I'm a software engineer by trade so for me this is the first time I've used these tools. That said, I solve problems all day (in code) and have to often come up with creative solutions. Sometimes they're not the best solution and I ended up meeting the "make it work" requirement. The same is true with my linear rail solution. I'll be posting all the work I've done in Thingiverse and providing links here. I'll do my best to provide any documentation. I hope others will read this, see my mistakes, highlight them, and we can work to address them. As I said in my opening, I have this printer and it isn't going anywhere. I might as well do my best to make it work. I believe that this solution is a cheap but highly effective way of improving the quality of what the printer can provide.
That said here are some things I think should be investigated and improved:
Address better x-axis mounting
I've offset the x,y plane towards the LCD. Come up with the best slider and rail position either by having the rail on the base and the slider on the platform are options as well as looking at better positions.
Better belt paths for x-axis
Better belt path for the y-axis.
There nuts on the back of the Z-Axis Pillar (A) are just enough out to hit the belt as it's traveling up and down the z-axis. This hasn't been an issue during smaller prints and is normally only noticeable when homing.
Re-evaluation of the tool carriage to linear rail slide adapter.
EDIT:
I realized I did not link to the linear rails that I'm using. I purchased them both from Amazon:
https://www.amazon.com/gp/product/B07GBNTJW3/ for the y and z axis
https://www.amazon.com/gp/product/B07Y2SNX4R/ for the x-axis.
If I was doing this again, I'd go for the 300mm rail for the z-axis and a 350mm rail for the x-axis. This would give more margin on how far the slides were able to move before exposing the internal bearings.
Hi @Michael G, I personally really appreciate the amount of work you have gone through to fix, document and post on the forums to help with the issues of this printer!
I was looking at your mod for mounting the rail to the Z axis. Would it not be easier to mount the new rail on the outside of the pillar and instead create a backplate and fix it onto the supports that are already in place using longer bolts? This would mean you wouldn’t have to change the position of the Y-axis pully and give you more available space.
This is just an observation thats all. Im yet to actually perform my first print as im still waiting on some cable so I can extend my thermal probe cable as I have the ones that are 20cm short (im hoping today I will be able to fix this and then finalise the setup and start performing test prints.)
My first attempt at over coming these issues will be to make the guides nice and tight and put bearing greese between the metal and plastic guides. im not sure how strong these motors are so im not holding up much hope tho.
Thank you @sebastian waters! With the pandemic putting a hold on my normal hobby (RC sailplanes) I've been able to really dive into 3D printing. I've only been doing this for for few months. However, since it is so interesting and there isn't much else to do, I have been able to invest a large amount of time into learning a lot of the ins and outs.
One thing I've noticed with communities surrounding other printers is the sharing of information. Since we're all together in a pretty small group, as it doesn't appear that Makertech is going to sell these outside of the Kickstater campaign, I figure that it's best that we all give back to the community the most that we can.
Perhaps the biggest reason that I try to be so communicative is that I hope that it helps me learn when I make a mistake or incorrect assumption. Your post highlights this. I did not consider putting the rail on the back side of the z-pillar. I noticed that I placed the rail too close to the bottom, probably by 3-5cm. While I don't print tall things I still should move the rail up. While doing this I'm going to have to investigate changing the placement to the other side in my modeling of the printer.
Just thinking about it, though, it would seem that this would be involved. The bracketing system would likely have to be two piece. A one piece bracket might not fit around the curves in the pillar. The problem with introducing multiple pieces is that it gives it more opportunity to flex, not to mention designing things which have to mesh together isn't something I've been able to get right in CAD.
Oh, something else I thought of too. When placing the linear rail for the y-axis with the z-axis on the outside of the pillar it might really create some weird offsets. Again, I'll have to see how this models out in CAD.
Hi @Michael G. I myself wouldn't design the plate to go around the curves of the Z pillar. i would just design the plate to fit into the slots for the nuts on the original linear guides.
As i mentioned before just longer bolts would be needed to attach the plate.
The large slot in the plate would be were i would attach it to your new linear rail.
on the bck side there are also some holes for the nuts to be inserted aswell.
I'm a little confused. There aren't any nuts on the linear guides. I just realized that I didn't link the rails I used in the OP. Doh! Here's the 250mm I'm using for the z-axis and will be on the y-axis: https://www.amazon.com/gp/product/B07GBNTJW3/
If you look at the second render you can kinda see, but there is a space between the gantry and the slider.
In this render you can see it as I've marked it as green. It's 4.59 mm from the slider to the gantry. That puts the nut for the lead screw directly inline with the stepper motor shaft. The problem with the 4.6mm (I rounded up) is that it's not thick enough to pass the belt through. I thought about making pulleys that would allow the belt to go over and under, but then I'd have to buy a new belt.
I've been working on the design for the Y-Axis adapter/spacer and I may be able to solve the issue there. The idea I'm currently pursing is moving the whole stepper so that it bolts to the back side of the gantry, similar to how the extruders mount. I'd then make pillars coming off of the adapter plate long enough so that the attachment for the belt was pushed further back to be in line with the pulley on the stepper motor. This would also require coming up with an extension for the pulley on the end of the y-axis.
Sorry i didnt explain my idea very well. The bracket i was suggesting in the image would mount onto the original linear guides that Makertech provided for their original build.
Sorry for the crude picture. i havent had time to put together full rending of the model in fusion 360.
@sebastian waters oh, on the gantry.
I thought about this but any solution seemed to to require multiple parts.
OK. I understand now! I'll have to mock something up in Fusion.
You're right, this will help with the y-axis spacer/adapter.
Hmmm, now that I'm looking at the model in Fusion and thinking about it this would be a large torque moment from the gantry on the adapter piece. Four M4 bolts holding it to the plate would be sufficient to keep it from breaking but that would put a lot of stress on the plate that interfaced with the slider. I'd be worried about deformation over time and it being a little easy to move about as the printer moved around while printing.
I still am going to play around with this idea. I had thought about using all these bearings that I have sitting around from my earlier attempts at replacing the guide system. I was going to place them at those four attachment points so that the belt could ride over them. I figured I'd just order a new belt on my next Amazon order.
Something like this?
@Gareth Owen yeah sorry bad initial explanation.
The plate would only be helpful when mounting the linear rail @Michael G is using on the outside of the Z pillar.
Now that i have the dimensions and step files for the Zpillar itself. I can easily designing a new single component that could be used as a new linear guide. the only issue would be the accuracy and tolerances of the print itself.
Gareth if you want me to put something together im happy to do it. im currently just doing my first prints and trying to calibrate the printer as i have only just been able to finally extened the thermo wires.
@sebastian waters I'm unable/unwilling to try anything until the rigid coupling arrives.
Currently, I'm still thinking about ducting for the heatsinks
I borrowed your idea and successfully upgraded my X and Z axises. I took a slightly different approach on the Z-axis. I used a 2 carriage block system so the belt could go between them. My X-axis is made of a T-Track I had laying around and some T-bolt posts I managed to print and polish smooth.
I have models and drilling templates if anyone is interested. I made a few other mods along the way. I should probably put it all up in my own thread. But for now, here are some images:
There's two spacer pieces that attach between my two mount pieces and the carriages (the 2 aluminum pieces partially hidden by the gantry). My rail is mounted just like yours.
Most cool!
What type of rails are those? They don't look like the "typical" linear rail that you see on a lot of printers.
Yeah, the X-axis rails are T-Track. They're meant for woodworking tables and the like ... my design is a simple hack with what I happened to have on hand. The Z-axis is the same rail you have ... the 12mm x 350mm rail with 2x MGN12H carriage blocks. Here's another pic of the Z
(the giant pipe nipple is just a 2lbs weight to keep the thing upright when the bed is at its extents ... it also seems to help steady the z-axis a bit).