CoreXY Enclosure, frame, and tips Questions.

Hi,

I am looking to build a core XY using this design:

[www.thingiverse.com]


I have a few questions.

1) It uses printed parts for the frame. Are their suitable metal corners that I could use instead, and are they worth the extra cost? I know for delta's getting the frame right is crucial. I also see that it uses cheap bearings with deldrin wheels. However, the open builds store offers premium polycarbonate wheels with bearings. Are those worth paying 3x the cost for? Finally it uses aliexpress-special lead screws, is there a great difference in quality? Which lead screws would you recommend.

2) For cutting extrusions, I have a table saw with a non-ferrous metal blade. But, how accurate do the cuts need to be? Im a novice at cutting. Would it be significantly better to have the extrusions cut at a machining shop if I suspect my tolerances if I cut them would be between 2-3mm?

3) It looks like the stepper motors would be inside any enclosure I designed to build. How have people dealt with that in the past?

4) I have plenty of 1.8 stepper motors. For a coreXY are .9 steppers worth the extra cost? (eg, having to buy them vs having them on hand)


Also, any other things you think I should know! Thanks

Edited 1 time(s). Last edit at 03/11/2017 11:36AM by Qdeathstar.

I've just finished the build of the same printer, but ( like many others ) have started to replace a few parts right away.
Especially the printed corner brackets don't make sense. I ordered metal corners in two different sizes instead.

1) The wheels will both do their job, but I've chosen to replace them with mgn12 linear rails. Therefor I had to redesign a few printed parts.

2) 2-3mm tolerance is too much. I got my extrusions cut to length for no extra cost. But I've chosen a profile that is cheaper and more common in Germany. ( 2020 & 2040 Bosch-profile Nut 6 )

3) the z-stepper would be underneath an enclosure and x-y steppers are outside too. I've seen CoreXY frames that are worse in that respect.

4) 1.8° steppers will do. Keep 0.9° on the wishlist for later.

Tomorrow, I can add some pics, if you like.

2) Cut them a bit longer, make a pack where you want the same length, align one end and cut them all at the same time at the other end.

Do not use printed corners. If extrusion is thick enough you don't need brackets either. I just finished a CoreXY build and all the frame joins (2040) are done like this:

[cdn.instructables.com]

The frame is sturdy enough and I expect it to be even better when I'll put the walls.

Printed corners look ugly and it is more work to be done with less gain.

Quote
Qdeathstar
Hi,

I am looking to build a core XY using this design:

[www.thingiverse.com]


I have a few questions.

1) It uses printed parts for the frame. Are their suitable metal corners that I could use instead, and are they worth the extra cost? I know for delta's getting the frame right is crucial. I also see that it uses cheap bearings with deldrin wheels. However, the open builds store offers premium polycarbonate wheels with bearings. Are those worth paying 3x the cost for? Finally it uses aliexpress-special lead screws, is there a great difference in quality? Which lead screws would you recommend.

Get metal corners from Ali express They are probably the same cost as the plastic. Also get linear rail from Ali express. They are easy to deal with and do not extend past the frame. So if you can move the motors inside the frame too you can attach the enclosure panels to the frame and not have a separate enclosure. My CoreXYNZ thread has links to the suppliers so you can do a quick price comparison


2) For cutting extrusions, I have a table saw with a non-ferrous metal blade. But, how accurate do the cuts need to be? Im a novice at cutting. Would it be significantly better to have the extrusions cut at a machining shop if I suspect my tolerances if I cut them would be between 2-3mm?

Accuracy depends on the way you put together the frame. If you can build in some adjust-ability then a millimeter here and there is OK. I would go with your table saw with a decent fence to get lengths the same.

3) It looks like the stepper motors would be inside any enclosure I designed to build. How have people dealt with that in the past?

Just make some ali brackets to attach to the frame, there are plenty of examples here. If you are not comfortable with making them I am pretty sure I have seen commercial items.

4) I have plenty of 1.8 stepper motors. For a coreXY are .9 steppers worth the extra cost? (eg, having to buy them vs having them on hand)

Go with the 1.8 degree and change them out if you are not happy with them.

Also, any other things you think I should know! Thanks

There are some great threads here so I,m sure you can find answers to most issues.
Good luck with your build and keep posting.

Quote
Qdeathstar
Hi,

I am looking to build a core XY using this design:

[www.thingiverse.com]


I have a few questions.

1) It uses printed parts for the frame. Are their suitable metal corners that I could use instead, and are they worth the extra cost? I know for delta's getting the frame right is crucial. I also see that it uses cheap bearings with deldrin wheels. However, the open builds store offers premium polycarbonate wheels with bearings. Are those worth paying 3x the cost for? Finally it uses aliexpress-special lead screws, is there a great difference in quality? Which lead screws would you recommend.

2) For cutting extrusions, I have a table saw with a non-ferrous metal blade. But, how accurate do the cuts need to be? Im a novice at cutting. Would it be significantly better to have the extrusions cut at a machining shop if I suspect my tolerances if I cut them would be between 2-3mm?

3) It looks like the stepper motors would be inside any enclosure I designed to build. How have people dealt with that in the past?

4) I have plenty of 1.8 stepper motors. For a coreXY are .9 steppers worth the extra cost? (eg, having to buy them vs having them on hand)


Also, any other things you think I should know! Thanks

I've not built a CoreXY, although I am heavily into the stages of designing one. I've also got a cartesian machine made with mostly openbuilds parts so I can comment on that.

1 -- The delrin wheels and bearings work superbly, but only if they are mounted solidly. In my experience, even thick PLA parts kept away from heat sources were not strong enough to keep the wheels aligned well. It works, but aluminium plates make a lot of difference. Contrary to popular opinion it is quite easy to make your own plates as the eccentric spacers mean you can drill the holes slightly off (within the offset of the spacers) and just adjust accordingly. When it comes to the wheels, the ability to place pre-load on them with the eccentric spacers is again a huge bonus. It makes them as accurate as linear rail in my opinion, although rail possibly wins out on speed and lightness. As for the bearings and wheels themself, cheap wheels are fine but quality bearings are a must. I started with cheap bearings but they don't deal well once tightened and often bind. The official openbuilds ones are very high quality. My opinion would be to source cheap Chinese wheels and spend on the bearings. Eccentric spacers can also be had cheap from china.

2 -- If you are relying on plastic corners to keep your frame square, then a chop saw is fine. If you want to do it properly I highly suggest you get them milled and bolt the extrusion directly to itself. You need very little bracing this way (if any at all) and you can be assured you are working with a very straight, true and square frame.

3 -- Motors inside the frame are fine. If you want high heat enclosures or you are worried about overheating, then take some precautions and add a heatsink to the motor and/or a fan. They're stationary so this makes it even simpler.

4 -- You can use 1.8degree motors, but as with a delta it makes for a nice improvement to go to 0.9 degree. it is not strictly necessary. Make sure you use 2 of the same motor.

Unfortunately the D-Bot requires printed corner brackets, because of the belt and idler routing through the slots. Don't see a chance to screw extrusions directly together. At least not for the gantry parts.

Then do a variation of it instead of compromising.

thanks for the response so far.

So, metal corners are worth it. I've seen metal stepper mounts and idler mounts on openbuilds, so they looks like they will work. I'll probably end up using the printed parts for the carriages, but i think i can get my delta to print them accurately enough.

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sigxcpu
2) Cut them a bit longer, make a pack where you want the same length, align one end and cut them all at the same time at the other end.

Do not use printed corners. If extrusion is thick enough you don't need brackets either. I just finished a CoreXY build and all the frame joins (2040) are done like this:

[cdn.instructables.com]

The frame is sturdy enough and I expect it to be even better when I'll put the walls.

Printed corners look ugly and it is more work to be done with less gain.

can you post some pics? And, O Lamp, more pics the better

I will, soon. It is hard to see things in the current "setup" (read tons of things around it make it hard to distinguish the printer in the pictures). I'm waiting for the acrylic panels and I'll some when I finish the electronics and wire routing (to be able to pick the printer from the current position).

Here are mine:







They are made to use as many original parts as possible, but I have plans to redesign the H-beam after I got some experience with this one.

Edited 1 time(s). Last edit at 03/13/2017 03:43AM by o_lampe.

Hi.

So, after reading around it sounds like the best idea for a larger core-xy (300mm) is to use three lead screws controlled by a single motor, a NEMA23? And that i should use MGN rails on the back of the machine for the Z axis.

Then, i can use some MGN rails for the y-axis and x axis as well.

Do they bolt on well to V-slot? I've heard T-slot is cheaper, but i cant seem to find it any cheaper than openbuilds v-slot. for the y-axis, do you use a mgn rail on the top and bottom on the extrusion? Are printed gantry's OK with MGN rails? I have access to a drill press and a table saw. Also, i saw someone who can cut the V-slot with 1mm tolerance, is that OK? Are there places that can do even better?

I did look on here for some could examples for builds, but mostly what you find is partially completed projects and untested plans for machines. Are there any links in specific you've found helpful? I know, for example, robotdigg sells a lot of parts specific to Deltas... any such site for CoreXYs?

Are there any build guides specific to using MGN rails? The one i linked to uses rollers and so i'm not sure but i would suspect the measurements for the cuts would be different if you are using three lead screws and mgn rails?

Edited 3 time(s). Last edit at 03/16/2017 07:22PM by Qdeathstar.

If you use larger cross section t-slot like 40x40 mm, and the ends are milled square, you can screw them directly to each other without all the ugly and expensive corner brackets. I cut the frame pieces a few mm longer than needed then mill them to final length and square. When I screw them together, they make a square, rigid frame. Saw cuts won't do for that type of construction. I think you can order extrusions from Misumi cut and milled to length. Otherwise, find a local makerspace or even a local machinist who has a mill in his garage. As for the source of the t-slot extrusion, I prefer to check local scrap yards where I buy 40x40 and some 40x80 mm stuff for $2.50 per lb (about 1 ft of 40x40). You might want to check your local scrappers and recyclers.

MGN is a specific family of parts made by HiWin, a Taiwanese company. They make good quality stuff, but there are 100 or so Chinese factories churning out cheesy knock-offs and calling them the same thing. The problem with buying MGN rails is that it's hard to be sure you're getting the real thing or one of the crappy knock-offs. The generic name for the MGN type of thing is "linear guide". Many companies make them, with some of the best ones being Japanese. You can buy THK, NSK, and IKO linear guides for exorbitant prices new, or you can buy them used via ebay, often for just a little more than the HiWin knock-offs. The "12" part of the designation is just the width of the guide rail. They come in many sizes. You can use almost any size rail for a 3D printer because they are designed to take much higher loads than they will ever see in a 3D printer.

A lot of people design printers starting with the frame, then try to find parts that will fit within their frame design. That might be OK for a commercial product where you have specific goals for the size and appearance of the machine, but you're building a one-off, not 100k machines. That means you have a lot more freedom in your part selection. I build machines in the opposite direction, by accumulating parts for them and designing those parts in. Start at the extruder carriage, figure out everything you want there (multiple extruders, fans, lights, motors, etc.). That size and you target XY print size will then determine how long the guide rails have to be. Don't worry about exact lengths- guide rails can easily be cut down to the length needed. Start shopping ebay for rails that are at least as long as you need and have the number of bearing blocks that you think you will need. it doesn't matter if the rails are 12 mm wide or 30 mm wide. Just get what is available at a reasonable price. Once you know how long the rails are you can start to plan the frame to hold them. The rest of the design sort of just flows until you get down to details like mounting limit switches, routing cables, etc., then the process can get a little slow again.

3 lead screws and two linear guides should be fine for the Z axis, and it's always a good idea to use a single motor to drive multiple screws. I'm building a tall coreXY machine that uses a belt driven Z axis. One advantage of using a belt drive is a complete elimination of Z axis artifacts in the prints (I hope) and arbitrary length for minimal cost difference. It can be easier and cheaper to construct a belt driven Z axis, but you have to deal with problems like the bed dropping when power to the motor driver is cut off (unless you don't mind the bed dropping). There are different ways to fix that, some of which can drive the cost back up to about the same as using lead screws.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

When you say scrapyard, do you mean the place where I drop off scrap metal like copper? I've been there several times as an electrician turning in copper and I've never seen any tslot or heard about them selling it.

When I ask about it, do I ask "do you sell t-slot" or is there another trade name?

Would you consider 4 guide rails and two belts running up the z axis to be superior to the lead screws? Do belts really make a difference in z banding if you use the optimal z-height for your lead screws?

Quote
Qdeathstar
When you say scrapyard, do you mean the place where I drop off scrap metal like copper? I've been there several times as an electrician turning in copper and I've never seen any tslot or heard about them selling it.
When I ask about it, do I ask "do you sell t-slot" or is there another trade name?

Yes, that's the type of place you want to go. They might not know what it is called. Just tell them you need aluminum materials for a project and ask them if you can look around. They always sort the metals and can show you where the aluminum is stashed. Wear old clothes, bring gloves, a tape measure, sturdy shoes, and cash.

Quote
Qdeathstar
Would you consider 4 guide rails and two belts running up the z axis to be superior to the lead screws? Do belts really make a difference in z banding if you use the optimal z-height for your lead screws?

I don't know if it would be superior- I'm just getting my belt driven Z axis to the point where I can run some test prints. 4 guides is overkill, and if there's any minor misalignment will likely cause the mechanism to bind. The guides are there to prevent lateral and twisting motion of the bed. Two should be plenty.

I'm not sure what "optimal z height" means, but either one should be workable. I think the main reason people have Z wobble problems is unstraight screws, off-center motor couplers, and a flexible frame and/or guide rails. Any bend in the screw or offset in the coupler will create lateral forces on the guide rails. If they are flexible, or if the frame they are attached to is flexible, they will allow lateral motion of the bed and create z wobble in the prints. Belts don't create any lateral forces, so even if the rails and/or the fame is a little flexy, you probably won't end up with z wobble (but you should still make the frame as rigid as possible).

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Optimal Z Height: [www.prusaprinters.org]

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Helps you to select layer height in a way, that Z axis moves only by full step increments. Z axis isn't usually enabled during inactivity. If the axis is disabled during micro-step, axis jumps to the closest full step and intorduce error. This effect is occuring to some extent even while leaving the Z axis motors enabled. This is most usefull to machines with imperial leadscrews but also for unusual layer heights with metric leadscrews.

If you could take any pictures of your z axis (just for ideas) that would be great aswell!. i found your topic

Thanks for the other info!

Edited 2 time(s). Last edit at 03/17/2017 11:10PM by Qdeathstar.

Hi.

On Craigslist I saw some IKO 12mm rails and bearing 18" long for 60$ for four


Is that a good price if they are in good condition?

Edited 1 time(s). Last edit at 03/20/2017 02:25PM by Qdeathstar.

Yes, probably a very good price. How many rails and how many bearing blocks?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

4 rails and 4 blocks. (one block per rail) I'm going to go and look now. If they slide nice, i assume they are good?

Edited 1 time(s). Last edit at 03/20/2017 06:12PM by Qdeathstar.

Yes. Make sure they are smooth from one end to the other. Be careful about removing the blocks from the rails- older designs will spill the balls all over the place and it will be a nightmare to collect them, clean them off, and get them back into the blocks.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

You guys are lucky to have Craigslist... You don't get second hand rails in the UK, or proper places where people dispose of this stuff....

I have a smallish update..

I was able to get the rails, i've i've mounted one of them on a section of misumi 2020 extrusion for testing. Eventually im going to use this as my X gantry.

When designing the x gantry, do you think it is necessary to plan on putting guide rail on each side of the extrusion? (i have enough pieces) or will that over constrain the movement of the x axis? Also, to T-nuts autoalign inside the t-slot or do i need to be especially careful on how i mount everything? There are a lot of holes in the rail (12) do you think it necessary to put a bolt through every hole?


I have also been able to figure out the basics of building a frame on inventor. It isnt too scale or anything like that, but its a cube of misumi 2040 extrusions, which is what i plan to build the frame out of.




and a picture of the rail attached to the t-slot




How do you know if you can slide the guides off without damaging them? The guids are IKO mhd12SL and i did look at the datasheet but it doesnt seem to mention anything either way..

[www.lineairegeleiding.nl]

page A-58 seems to bee where it talks about my rails. Also, when it says "mounting on top" does that mean i should only use these face up? Or is it just that the screws are oriented on "top" of the rail, but that the rail is OK if it is positioned so the rail hangs sideways?

Edited 1 time(s). Last edit at 03/28/2017 07:05PM by Qdeathstar.

The rails will work fine in any position, though lubrication may have to be done more often in some positions. Some blocks are designed so the balls are captive and some are not. Unless you have a good reason to separate the rails and blocks I would say don't do it. If you must, you can carefully slide the rail out of the bearing block by turning it upside down (rail up, bearing block down). Do this with the block in a tray to capture any balls that fall out. Put a loop of wire or a zip tie at each end of the rail to prevent accidents until you get the rails bolted down and have mechanical end stops in place.

A single linear guide and bearing block should be sufficient for the extruder carriage.

Edited 1 time(s). Last edit at 03/29/2017 02:50PM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Thank you for your response

A lot of name brand rails come with the blocks packaged separately with a plastic insert that is the same size as rail. With that insert is easy to install or remove the block w/o dropping any ball bearings. If you have a 3d printer you can make one to match your rail.

Well, i am slowly figuring out assymblies. I got the rail and extrusion modeled for the x axis



And it moves pretty I tried making a video using inventors video capture setting but for some reason the video turned out all choppy and grainy....



Now i'm going to work on the xy frame

The only problem i am really having is that constrains on assemblies seem to be gooey, eg, the model will move out of my selected constraints if i make a new constraint.. Still trying to figure out why.

hi.

i am moving forward with my build. My question is does the belt from the stepper to the first pulley need to,be parallel or is just between pullies that everything needs to be parallel?

Any belt-section between stepper and gantry has to be parallel. Also between rear corners and gantry.
From stepper to the back of the frame and between left and right rear corners doesn't matter

Edited 2 time(s). Last edit at 04/24/2017 03:00AM by o_lampe.