CoreXY Dbot building

I'm curious if anyone has built or is maybe in the process of building this DIY kit here: [www.thingiverse.com]

I'm thinking about trying it but I'm curious about the process of buying all parts separately vs getting a kit. I would also need to figure out a way to cut the rails which are aluminum, other than that I believe I have the tools needed.

Apparently this printer is a version of one called a Cbot and it looks similar but the Dbot looks very clean and sturdy.

Thanks for any input

I like the D-bot, have seen it quite a few times in recent searches or/and discussions. Usually the vendor will supply the lengths of extrusion to your specification so one worry less I guess.
Good luck with your project and keep us posted.

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i like it. this might be my next build after i build atomX.

I am in the process of printing all the parts needed and have purchased all of the other items. I will be using an Ormerod designed extruder and plan to have 3 extruders and a diamond hotend in the future.
I will build everything first with a single extruder and then see how best to mount the extra extruders and perhaps a facility to hold 3 reels of filament.

One problem I am having is tapping qty14 5mm threads into the ends of the rails. My problem is trying to keep the tap vertical whist turning it. I am so worried that I will ruin the ends of the rails and will not be able to bolt the items together properly.

I'll update progress when I start to put it all together.

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appjaws - Core XYUV Duet Ethernet Duex5
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OpenSCAD version 2020.07
slic3r-1.3.0, Simplify3D 4.1.2, Cura-4.4.1

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appjaws1
I am in the process of printing all the parts needed and have purchased all of the other items. I will be using an Ormerod designed extruder and plan to have 3 extruders and a diamond hotend in the future.
I will build everything first with a single extruder and then see how best to mount the extra extruders and perhaps a facility to hold 3 reels of filament.

One problem I am having is tapping qty14 5mm threads into the ends of the rails. My problem is trying to keep the tap vertical whist turning it. I am so worried that I will ruin the ends of the rails and will not be able to bolt the items together properly.

I'll update progress when I start to put it all together.

I've seen this which could help to keep the tap aligned properly.

Thanks, that should help

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appjaws - Core XYUV Duet Ethernet Duex5
firmware 3.1.1 Web Interface 3.1.1
Ormerod 1-converted to laser engraver, Duet wifi
OpenSCAD version 2020.07
slic3r-1.3.0, Simplify3D 4.1.2, Cura-4.4.1

Same concept, might be a bit easier to use:

[www.thingiverse.com]

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appjaws1
I am in the process of printing all the parts needed and have purchased all of the other items. I will be using an Ormerod designed extruder and plan to have 3 extruders and a diamond hotend in the future.
I will build everything first with a single extruder and then see how best to mount the extra extruders and perhaps a facility to hold 3 reels of filament.

One problem I am having is tapping qty14 5mm threads into the ends of the rails. My problem is trying to keep the tap vertical whist turning it. I am so worried that I will ruin the ends of the rails and will not be able to bolt the items together properly.

I'll update progress when I start to put it all together.

So actually you have not even tapped a single extrusion yet?
I have tapped dozens of holes in them without even thinking of being careful on tapping. Did not ruin a single hole. With those precisely extruded 4.3mm holes it seems almost impossible to ruin the threads.

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vpt5566
I've seen this which could help to keep the tap aligned properly.

I use that and it works perfectly. Just put a bit of oil on the tap, and you'll get a nice set of threads.

WD-40 works great for aluminum tapping and I was surprised that online machinists were recommending it as pretty much everyone else on the net says it is useless for many other things.

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Edvardas
WD-40 works great for aluminum tapping and I was surprised that online machinists were recommending it as pretty much everyone else on the net says it is useless for many other things.

Thanks for the tip, any good advice for cutting aluminum rails in addition to thread tapping them? Is a hacksaw clean enough

Length-wise they should be cut by the vendor you have purchased it from. Hacksaw will not do a clean square cut. Maybe a miter saw could do the job but I wouldn't trust that. Maybe others have actual experience cutting aluminum with the miter saw and might say otherwise.

I would be interested in DIY-able ways to cut square/flush aluminum tube/extrusion.

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Quote
realthor
Length-wise they should be cut by the vendor you have purchased it from. Hacksaw will not do a clean square cut. Maybe a miter saw could do the job but I wouldn't trust that. Maybe others have actual experience cutting aluminum with the miter saw and might say otherwise.

I would be interested in DIY-able ways to cut square/flush aluminum tube/extrusion.

The railing called out for this build only comes in stock lengths from the store, 0.5m, 1m, 1.5m. The instructions show the cuts that need to be made so I'm not sure if the supplier will make the cuts.

For the non-motion parts you could get them pre-cut from Misumi. For the V-Slot required for the motion parts OpenBuilds only sells the standard lengths mentioned.

If you are comfortable doing some redesign of the frame you could try something along the lines of the way quadrap builds it. Here's an image depicting the layout:


You will have to drill and tap but the cuts can be imprecise.

Otherwise you might start searching for a shop that can do the cuts for you.

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Quote
realthor
Length-wise they should be cut by the vendor you have purchased it from. Hacksaw will not do a clean square cut. Maybe a miter saw could do the job but I wouldn't trust that. Maybe others have actual experience cutting aluminum with the miter saw and might say otherwise.

I would be interested in DIY-able ways to cut square/flush aluminum tube/extrusion.

Miter saw will cut just fine, but measure carefully, lock tightly (but don't crush the extrusion), and cut slowly. Also note a few pieces of V-slot I received had "twisted" ends that had to be squared off.

Also be aware, that due to the way the printed pieces are designed, a little bit short is easier to deal with than a little bit long-- the structural component comes from all the T-nuts in the rails, rather than the precision of the cut end butting up against the plastic printed part, so if you need a little bit of space between the end of the part and the end of the rail, it's not a big deal-- "square" is more important. That doesn't mean you should have 1/4" gaps, but a millimeter here or there won't be the end of your printer.

As far as I am aware, the sturdiness of the frame lies in the corner pieces butting together with the help of metal brackets. As long as plastic corners and brackets are used for a frame construction the rigidity and the squareness of the frame will be as good as the plasticity of the plastic in the brackets.

I would strive for metal corner pieces and those require flush cuts so that the butted parts end up making the frame stronger rather then weaker by pulling them apart a mm or two to make it square. That's why I went for the scout-tower-style frame (or you can look at quadrap 3d printer for the same idea). DIY reprap 3d printers should be DIY-able, so the designer should also think of how easy will the frame be able to be put together and how sturdy will it be.

I have great consideration for D-bot and its creator (and the C-bot and all the predecessors) but why plastic brackets in the corners.

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great question... why plastic brackets in the corners? If the objective to use plastic corner it to go cheap, them is better solution to simply make holes in the middle of the aluminium extrution and use screws to make the connection.

simple and overall a great solution:
[forums.reprap.org]

Edited 1 time(s). Last edit at 04/14/2016 06:20AM by filipeCampos.

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filipeCampos
great question... why plastic brackets in the corners? If the objective to use plastic corner it to go cheap, them is better solution to simply make holes in the middle of the aluminium extrution and use screws to make the connection.

simple and overall a great solution:
[forums.reprap.org]

Agree. Invest in a good tap that you will reuse time and time again rather than corner cubes and brackets.

But the problem of cutting perfectly square it seems to me that it's not that important any more when you consider tapping and screwing the joint together. Even if you don't completely close the gap, the bolt+aluminum around the tapped hole will be strong enough to prevent flexing. Now you can add some plastic brackets to make it stronger.

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realthor
I have great consideration for D-bot and its creator (and the C-bot and all the predecessors) but why plastic brackets in the corners.

Lots of repraps use plastic frame parts. A reprap printer is supposed to be mostly printable I believe.

I still think it's a good design and I don't mind the plastic corners as long as everything bolts together tight and the rails are cut well.

Yes, most of the printers use printed parts, but this does not means is a good idea to use plastic everywhere.
This is done because is easy to print, cheap and not a lot o person was access to a cnc to make aluminium parts.
My printer have lots of printed parts and recently i have build a cnc (mpcnc) was main goal replace all this parts with aluminium.

But in the case of these corners is a different story, you do not need a cnc and a a screw is more cheap that the printed piece.
There is no reason to use plastic, a simple M8 screw will do a far better job that any printed pieces you put where.

Edited 1 time(s). Last edit at 04/14/2016 12:40PM by filipeCampos.

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vpt5566
Lots of repraps use plastic frame parts. A reprap printer is supposed to be mostly printable I believe.

i have a friend who bought one of the early repraps. he's a competent sysadmin and is scientifically-minded. he only bought it because it was exciting, new, open hardware and he wanted to explore it. most of his time however was spent on printing replacement parts to keep it functional. when it broke beyond self-repair, which it did frequently, he used a soldering iron as a drill to make holes in order to put rods back into place in order to at least be able to bootstrap his way back to printing.

bottom line: the reprap is *NOT* a good role model on which to make any design decisions. many of the parts that my friend made on his would explode into a tangle of spaghetti after a few months, due to the tension inherent in PLA as it cools: that was sufficient for the parts to self-destruct.

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vpt5566

Thanks for the tip, any good advice for cutting aluminum rails in addition to thread tapping them? Is a hacksaw clean enough

take a deep breath, and read what i wrote here:
[reprap.org]

basically, because i've used 10,000 RPM 125x1mm cutting discs before, i'm familiar with how to ensure that i only cut the metal, not anything else. they are however sodding dangerous. if you cannot get hold of pre-cut extrusion, i strongly, strongly suggest you reconsider the word "can't" and look harder.

a hacksaw will not be clean enough (actually pretty much nothing will except possibly a bench-mounted professional circular saw or a workshop band-saw) - what you can do, however is, using either a file (if you are patient) or an angle-grinder (if you are not so patient but are competent to use an angle-grinder) just cut to 1 or 0.5mm excess (or whatever level of competence you have with a hacksaw) then mark all four edges off to the right length and file down until it's both accurate and clean.

i found that i almost certainly needed to file both the edges outside and in after using the disc cutter: a hacksaw will be the same. you should get a bunch of keyfiles, this will allow you to clean burrs off the *inside* of the extrusion which would otherwise completely prevent you from putting nuts into the extrusion.

basically you really really really should be looking at getting pre-cut extrusion, or seeing if you can find someone with workshop tools. even if it costs more, if you make a mistake then *that* will cost you more.

Edited 2 time(s). Last edit at 04/14/2016 02:59PM by lkcl.

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vpt5566

I still think it's a good design and I don't mind the plastic corners as long as everything bolts together tight and the rails are cut well.

you won't mind until it's assembled and you push the box at one corner and you go "oh my god did i just *really* believe that plastic without any kind of diagonal bracing could be entrusted to provide rigidy?? whyy????"

so, if you don't believe me that it's going to shock you how much play there will be, what i suggest you do is: assemble just the frame, then put it on the floor. put two feet on the front bottom bar, then place one hand on the left top and the other on the right top bar. then, TWIST the top like you're unscrewing a jar lid. you will *easily* get around 5 to 10mm of twist with very little effort, and with quite a bit of force you will have about 15-20mm of travel. shearing will be just as bad - left/right and forward/backwards.

now, to fix this there are a number of solutions: (1) use a technique that edvardas showed me - you drill holes into one extrusion and bolt it to the other one - for this to work you need dead-flat ends. the link's on the page i sent in the previous message about the sandwich200. (2) use diagonal bracing. a bar in each of all *six* yes all six faces is needed, and of course you can't put one in the top core xy so you'll end up with "rotation" about the top still being possible or (3) place right-angle corner brackets in as many corners as you're happy to buy brackets or (4) use hardboard, MDF or perspex to "fill" the rectangular spaces. or (5) use corner-cubes.

all of these you can see discussed and video'd on the sandwich200 forum and the wiki page - links are [reprap.org] and [forums.reprap.org] edvardas and fa-mas and others kindly helped prompt discussions and gave extremely useful input, and the frame for the sandwich200 is also aluminium extrusion.

basically i went for a combination of the above techniques: diagonal bracing, hardboard, corner-cubes in the main frame and finally right-angle triangular metal-folded brackets which are easy to get on abay for the Top CoreXY. the only reason why i have 2mm of travel when doing the above twisting test is because i have a couple of plastic pieces which i need to adjust that have protruded 1mm too far, which stops me from being able to clamp the frame together, creating a 1mm gap along both the left and right sides. the actual TopCoreXY part is staggeringly strong.

so.

yeah.

if you want to trust bits of plastic for rigidy - using a material that is brittle and its strength degrades over time depending on exposure to U.V. light, and, in addition, has a glass melting point of 60C, go ahead.... "explore that space" as the Zen Yogi Masters say....

With the C/D-Bot design, most corners can (and should) be done with 90 degree metal brackets. You could design around the printed motor mounts if you wanted, since a NEMA-17 mount and a couple metal brackets would work there as well.

It's the two blocks in what I consider the "back" of the printer that have pulleys embedded in them that are probably best off as printed parts, and once they're printed / assembled, they're pretty solid. If you're worried about TG, print out of PETG or something fancier.

By the way, I consider people who apply unnatural torque to their printers in ways the printers will never, ever experience in their operational lifetimes to be the equivalent of someone who tests their car by driving it into a brick wall. There's "reasonable" load (static and *actual* dynamic forces), and then there's gorilla testing-- I don't care that my printer frame can't withstand 200 Nm of rotational torque on the top half of the frame, because it's not going to happen when I'm printing.

I am in the middle of a C-bot build now.

I cut the frames with a powered mitre saw using a cheap non-ferrous blade.
Using a couple of pieces of MDF as a long base and a fence, and a block of wood clamped down as an endstop to ensure lengths are repeatable, I found I could cut the aluminium very easily and very accurately.
It is potentially dangerous - the use of a power tools always is. Observe safety precautions such as goggles etc, clamp everything down and keep your fingers out of the way. Don't rush!

I now have the cube assembled.
I have bolted it down to 18mm plywood for rigidity, mainly when carrying, and am pleasantly surprised by how rigid the frame is.
I have not used metal corners.
The D-Bot may be different, but with the C-Bot, there is a lot of plastic around those corners to hold things rigid.

I have built to for a 10"x10" print bed. I would imagine if building a very large printer things may be different.

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ian_in_the_midlands
I am in the middle of a C-bot build now.

I cut the frames with a powered mitre saw using a cheap non-ferrous blade.
Using a couple of pieces of MDF as a long base and a fence, and a block of wood clamped down as an endstop to ensure lengths are repeatable, I found I could cut the aluminium very easily and very accurately.

cool! that's a good idea

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I now have the cube assembled.
I have bolted it down to 18mm plywood for rigidity, mainly when carrying, and am pleasantly surprised by how rigid the frame is.

great! it's surprising how effective just filling in a face is, isn't it?

I modeled double size corner brackets for my D-Bot build and it made a definite difference in rigidity.
Regarding materials, I believe the author recommends using PETG instead of PLA or ABS.

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KDan
I modeled double size corner brackets for my D-Bot build and it made a definite difference in rigidity.
Regarding materials, I believe the author recommends using PETG instead of PLA or ABS.

You can use PLA, my printer is all PLA parts and it has some hairline cracks in parts but I believe they are mainly cosmetic.
ABS would work well for printer parts but it is more difficult to print than PLA due to higher temps, fumes, warping, etc.
PETG is a nice middle ground which is strong and slightly flexible but not too flexible.

Nice to see you here David.
I actually used PLA for most parts too - except for my extruder motor holding bracket which I printed in ABS. All other motor mounts have a laser cut cork gasket between the motor and the parts to insulate the PLA from the heat of the stepper motor. I've done this before and it worked perfectly... the PLA part never even gets warm.

Edited 1 time(s). Last edit at 07/01/2016 02:58PM by KDan.