What are the “strengths” you are referring to? Exoslide bearings only support one axis and with two, I have support for both axes.
There’s actually a bit less off centre force on the vertical Exoslide due to the fact that my custom adapter plate weighs less than an Exoslide bearing - this off centre force (really torque) is handled by the lower Exoslide. If you were to look at it from the side, it looks like:
Unless you place a matching mass on the other side of the assembly, you’re always going to get an unbalance force (torque) regardless of the number of Exoslides that has to be balanced. So, this is not an out of specification design; the Exoslide documentation kind of references this but they really don’t provide any design guidelines. I’ve run an earlier version of this design for 800+ hours without any issues.
The primary reason for this approach is to integrate the Micro Swiss NG hot end along with the Super Pinda inductive sensor as well as the movement belts. If I put the vertical Exoslide on the other side, I wouldn’t be able to get as compact a package as I have here. You might get a better idea of how everything goes together in this image (which has the NG hot end but no shroud along with the Super Pinda and belts in blue):
Anyway, I’m very confident in the design (it’s gone through enough iterations and a fair amount of testing with the previous design which turned out to be not square because the .step file was wrong). I just did a search looking for people who are doing what I am doing and can’t find any
Anyway, it sounds like you’re about to go down the same path with only using two Exoslides on an axis - you’ve said you’re not putting your design into a CAD system which may be an advantage because, as I’ve said repeatedly, the .step model has errors in it and Giles at Exoslide is not responding to my emails regarding this concern.
The inaccurate .step file and the non-existent support from Exoslide is what concerns me.
Well, I’m glad to hear you are getting it to work.
What I meant was that exoslides would work better the closer the load is to the wheels that are taking the load. With the configuration you are using, the print head weight has a lot more leverage on the vertical exoslide, as it is approximately 20+mm away from the wheels, vs about 10 mm away if between the print head and extruder. The further away the weight is from the load bearing wheels, the more it will want to pull the top wheels in, and push the bottom wheels out. Since you have the horizontal exoslide on the bottom, it will want to push the horizontal one down. Sounds like you got things resolved though.
The only way you remove all side forces is to place the toohead in line with the centre of the 2020 Rail (which is usually impractical). It doesn’t come through in the crude drawings here, but by using a Custom Support I actually bring the nozzle in 5mm closer to the centre of the 2020 Rail than if I mounted the NG to an Exoslide directly using Micro Swiss’s adapter:
I only found out about this plate this week from Micro Swiss. As well as being further out, it makes my challenges of cleaning up the wires more difficult and there’s no way to easily mount the Z axis endstop sensor.
It’s been a lot of work, but I think I have a reasonably elegant solution that works.
FYI. Here are the concerns about Exoslide I passed onto Giles who seems to be the owner/principal.
He told me:
What parts of the ExoSlide STEP file are not consistent? It was created from deleting features of the full model, and should be accurate except for missing filets and drafts on the exterior.
Here are my concerns:
The big problem is that you seem to have simplified the model so that the position of the mounting screw bosses are not accurately represented. There is a rib that runs by the bearing bosses that runs along the width of the .step model – I think this is why I had the twisting problem that I reported before. If you look at this image, for me to get proper mounting on the toolhead I had to put shims in (which intersect with the Exoslide .step model) in CAD:
Next, the width and distances between the screw and bearing bosses seems different on the actual part do not match the .step file. I’m not sure if this is shrinkage from the moulding operation but it made putting a Super Pinda sensor between the bosses challenging.
The bearing tightening screws on both sides of the Exoslide are not represented in the model which made coming up with keep out areas more work than they should have been and also made getting the Super Pinda location difficult.
So, if you’re not making custom plates or using a CAD system then you should only be attaching pieces to the topside M4 heat insert nuts.
I don’t mean center of the extrusion, but center of the wheels. Having the exoslide between the hotend and extrusion would allow the weight to be closer to the wheels that are taking the weight.
I picked up the bed plate today. We will see how it works. I went with 1/4 inch plate. That was the thickest aluminum plate that the shop had. Also bought a saw blade and a few needed drill bits.
I am going to order a few items yet, CRTouch, some cabling, extruder, probably hotend if I don’t have a spare in my parts drawer, and some foil backed insulation. I now have all the components needed to begin construction though, so that is exciting!
CRTouch? Why not a genuine Antclabs BL Touch? I’ve never used a CRTouch but I’ve seen people complain about them on various forums over the years. The Antclabs original seems to be the best.
On the point of toolhead accessories, are you going with a toolhead controller? You’re going to have some pretty long wires running from your main controller to the toolhead.
I have a CRTouch on both of my Ender 3s, and they’ve both been flawless. Supposedly the CRTouch is slightly more accurate, but the price and the metal probes vs the nylon tip on the BLTouch is what sold me on them.
No toolhead controller on the hotend, doesn’t seem to me like there would really be such a benefit considering the extra cost, plus extra hastle with firmware. If there is problems, then I guess I’ll cross that bridge then.
Since I am a night owl, I made some construction progress yet today. The base frame is largely built. Only the end cross members are tightened. The middle ones will be tightened after the bed has had the mounting holes drilled.
I adjusted and assembled two carriages, and temporarily clamped a 2020 extrusion to them so I could test for any binding while moving along the rail, and it passed that test with flying colours!
Tomorrow other things will be keeping me busy, but next week sometime, progress will hopefully resume.
The gantry frame is now largely assembled. The top cross member is only temporarily mounted for testing. Once the needed brackets are designed and printed, it will be mounted in a lower profile configuration.
Bed mounting will be one of the next steps, followed by the designing and printing of a lot of different brackets.
Progress for today was the design of a few brackets; the prototypes are printing now. I also got the bed plate drilled, bolts installed, and the heat mats attached. Tomorrow, hopefully I can get the bed completely mounted, as well as test fitting the prototype brackets.
Yes, it will be. It’s already pretty hefty when moving it around.
The printer is going on a shelf above my workbench. The shelf above the shelf that the printer will be on will hold the filament spool on its roller. I will use a 4mm inner diameter PTFE tube to route the 1.75mm filament down through the shelf to the extruder, with enough slack to permit a full range of motion. It will be the same basic system I use to route filament to my other three printers, which has worked well.
Well, it was something of a project all by itself, but the bed is fully mounted, and by my best estimate, is about as level as it is going to get. Hopefully things don’t change too much once heated.
The prototype brackets are mounted. There are some design changes needed, primarily to do with the x axis sagging. I don’t plan on implementing a dual z lift unless absolutely necessary.
At this stage of assembly, the printer weighs around 16-17KG.
It’s been a bit since the last update. Not really a lot of visible progress since then. Most progress has been on the digital workbench; designing various brackets, then testing and iterating from there.
Life has been pretty busy as well, and is about to get much busier, as harvest is about to start on the grain farm where I work.
I did receive a few more components today that I had to order in, some of them because I had underestimated the amount needed or forgot about needing them earlier.
Time for the next update. After a fair amount of design iteration, and barring me discovering some sort of major flaw, the motion system is done. Testing will need to be done once wiring and electronics are further along, and refinements might be necessary, but for now I am happy with the base design.
The extruder stepper still needs to be mounted; I haven’t quite decided exactly where I will place it yet. Designing a mount for it will be one of the next steps, along with designing the electronics housings, and the rest of the cable chain mounts.
It doesn’t look like I will have much free time to work on it for the rest of this week either, so progress updates will likely continue to be fairly infrequent for a while.
I went with 1/4 inch plate. That was the thickest aluminum plate that the shop had. Also bought a saw blade and a few needed drill bits.
