Core-XY based on Rat Rig V-Core and Duet 2 Ethernet

grizewald

@snoozer said in Core-XY based on Rat Rig V-Core and Duet 2 Ethernet:

Thanks for the info. I can't wait to get the V-Core kit, its two weeks now I think since I ordered, I hope they will ship it next week. I will find out how well its designed then regarding tolerances and stiffness.

After watching the YT video with the Bondtech extruders I had a nosy on their website, they do pretty nice stuff, Bondtech just was never on my radar.

Jan

Jan, I built a RatRig V-Core at the end of last year. I hope they have improved their quality a lot since then. Sure, they will go out of their way (even using next-day DHL delivery to replace incorrectly manufactured parts), but I would have preferred not to have the problems in the first place.

One of the worst was that the threads which should be cut in the ends of some of the extrusions seemed to have been done by someone who was drunk:

alt text

Checking all your extrusions when you receive the kit will save you time and trouble. It is not possible to build the printer properly if the threads are not straight as the bolts bind in the thread before they can tighten against the plate that they mount.

Once put together, the frame is rock solid. You could probably park a bus on it without doing much damage. Getting it square when you put it together will entertain you for hours!

The supplied print bed is indeed 3mm and anodised. Unfortunately, they didn't countersink the mounting holes at the corners and this robs you of around ten millimetres of print volume at the front of the bed (and the back, if you don't get stopped by your part cooling fan hitting the back Z-rails first.) The bed itself is 33cm square. My actual print size is currently 300 by 275 by 290 (X, Y, Z). I currently have just a 32cm square PEI sheet (just 0.4mm thick) as my print surface. The plate is heated from underneath by a 30cm square silicone heater with 420W at 24V.

My intention is to replace the PEI sheet with a 31cm square Anycubic Ultrabase. I need to countersink the mounting holes on the bed first.

If you want more information about how I built mine and all the various parts I used, just shout and I will get my camera out this weekend and give you all the detail you want.

snoozer

@grizewald Thanks for the info, Much appreciated ! I was promised a tracking number last week but nothing yet. I got in touch again and apparently some supplies got stuck in customs....... hoping for a tracking number now this or next week. I am not really impressed with this to be honest, they could have done a better job communicating this.

Re quality of extrusions etc..... I have ordered under the assumption that I have to rework the ends anyway to make then square. I bought a router with routing bits that should allow to cut aluminium. I have read about kits like this (not Rat Rig now but other V-Slot stuff) where the extrusions have not been cut to length properly etc...... So before I assemble anything I will make sure all is correct length or at least same length where it needs to be and square.

Re the print bed. I an actually just waiting to see what comes with the kit. As you said, non countersunk holes is what I expected. The pictures show the heads of the bolts sticking out the top. @deckingman pointed me to a UK supplier for aluminium stuff. They don't deliver to Ireland, I have asked that already but DHL offers a "virtual" UK address, so they can ship there and DHL then sends it on to me. So I don't expect to use the original plate in the long run. My idea is to use a glass surface, the original Prusa Mk3 PEI I have on my printer is starting to crack and it generally becomes messy after only a few months. With the inductive probe I cant use glass on the Prusa without modifications. On the V-Core I hope to use a piezo probe which would work on any surface.

Well.......... I am hoping the kit will ship next week and be here about 7 working days later..... I am glad I have started this as a project with no time constraints, otherwise It would have been very frustrating.

Greetings from sunny West-Cork
Jan

deckingman

@snoozer Sorry to hear that you are still waiting. IIRC I had to wait a long time too for the initial batch of Vslot extrusion that I ordered from RatRig. When it eventually arrived, it was well packaged with no sign of any damage and all the ends were cut nice a square and accurately to the lengths that I had specified. So I had no problems on that score. I tapped my own holes so can't comment on that aspect but given that the extrusion already has the correct tapping size hole in the end, it's difficult to understand how they could get the tapping so badly wrong for @grizewald - they must indeed have ben drunk at the time

snoozer

Finally, got a shipping number...... Supposed to arrive 1st week in May........

Jan

deckingman

@snoozer said in Core-XY based on Rat Rig V-Core and Duet 2 Ethernet:

Finally, got a shipping number...... Supposed to arrive 1st week in May........

Jan

That's bad. You must be very unhappy about how long this is taking. How long will it be between you placing the order and receiving the goods?

snoozer

As I said before, I treat this as a project so the time is not really an issue but ofc its not satisfying to have these delays. However....... the delivery has arrived at my local depot this morning. If I am very luck the delivery will be made today otherwise tomorrow.

I have ordered the kit on the 27/02/19, that makes it over 2 months. Gave me time to play with the steppers and the Duet 2. RatRig could have done a better job communicating the lead time but I also accept there are sometimes issues out of their control as well such as customs.

I will post pictures of the unboxing and show details about the quality of the extrusion cuts etc......

Hope to be able to update here this evening or tomorrow !

Have FuN!
Jan

PS: I was actually tempted to order an Anycubic Predator for the meanwhile to have something to play with. They are unbelievably cheap and have not so bad reviews and they can print big. I might still do that for a fast-print large nozzle machine. I hate changing nozzles between uses. I have the "Nozzle X" in my Prusa for everything but played around with 0.6 and 0.8mm nozzles as well with good results and FAST !!!!!!

snoozer

The kit has arrived. No visual damage on the outside. This evening I will open the box and check the content. I have other obligations 1st so probably wont start the build until the weekend.

Have FuN!
Jan

snoozer

Hello,

today was the day I started the build. I was positively impressed with the precision of the extrusion cuts. I have no precise squares and I can measure the length only with a ruler but the extrusions of meant to be of same length really exact. The threats in the extrusions also worked flawless where straight. I had to remove some metal shavings but hey, that's OK. Here a pic of all that came in the box (except the tools etc on my workbench ofc).

And the extrusions:

I started at 10:00 with assembly and have the metal work done now 18:30. The instructions could have been better but its not a Prusa, I have seen to late that there has to be a washer between the bearing in the rollers. Had to remove them cause I had seen that to late. I am not yet 100% sure the cube frame is actually square yet. I will have to do some adjustment. I have used a ratchet strap to tie all together before tightening all bolts but the X gantry does not hit the ends equally, one side is approx 1mm off at the front and the other end 1mm at the back. Not shure what way would be a good procedure for that, suggestions are welcome.

Here the state I am at so far.

Now printing a tool mount in Colorfabc's Carbon Filled XT-CF20. I will continue the build tomorrow. Time for pints and friends now.

to be continued.....,,

mrehorstdmd

You can get things squared up by measuring diagonals across each parallelogram in the frame. If they are square the diagonals will be the same.

snoozer

@mrehorstdmd

I know how to measure it, just I have no clue yet how to adjust it. I was thinking of criss crossing the frame work with adjustable wires....... but that would only bend the extrusions, not fix the actual adjustments.

THX
Jan

mrehorstdmd

I'd square it up as I assemble it instead of trying to assemble it first then make it square.
Since the XY relationship is critical, I'd start at the top of the frame and get that part square before bolting the rest of the stuff to it. Match the bottom square to the top, then add the verticals. If the frame is also the Z axis, get those verticals square with the top first then add in the other two. Check squareness of everything with each frame member that you add.

Keep in mind that a 1mm error over a span of 500 mm is only a 0.11 degree error.

deckingman

@snoozer Your X gantry issue is most likely caused by unequal belt tension.

snoozer

@deckingman

This is the plain mechanic only sitting idle, no belts yet hooked up. The actual frame is the issue I think. Once I have finished printing parts for the V-Core on my Prusa I use the steel table that I have for the Prusa to check the V-Core frame is level and square. My "workbench" is a rather light Ikea desk, probably not really flat and level.

Jan

snoozer

@mrehorstdmd

The think is that I am not really clear how to "adjust" anything. The angles are set by the extrusions and the corner plates. The extrusions length is a perfect match, there is no visual difference. I will try if I can somehow make the double-t nut fix at different angles I suppose. Are those double-t nuts a good way to do it actually ? From feeling while assembly it felt much better to work with the drop in single t-nuts that came with the kit.

Jan

PS: I wonder, would it be better to leave 0.5 - 1mm room in the corners for the upright posts or is squeezing the horizontal extrusions agains the uprights (what I did) the way to go ? I am thinking leaving room could give maybe room for adjustments, on the other hand assuming the extrusions profile are the same fixed measurement all around squeezing it should result in a square.

mrehorstdmd

The angles should be set by the square cut ends of the t-slots and the plates should only reinforce the corners.

You can test the t-slot for square cuts by standing the t-slot pieces up on their ends on a table. Stand them next to each other. It will be obvious if they aren't square because the pieces won't stand parallel to each other.

If the ends are square, you can tap the center hole at each end of each piece, drill tool access holes, and bolt the t-slot directly together using button head cap screws whose heads fit in the t-slot. If any corner reinforcement is required, add plates later. If the cuts aren't square you might be able to shim the ends where they bolt together using strips of metal from a beer can.

alt text

If the plates have to be used to force square joints I'd probably use a rafter square to adjust for squareness of each joint as I proceed with the assembly.

alt text

I tried to include a couple images, but they don't seem to be working today.
Here are links:
https://cdn.instructables.com/FYM/776V/IA57RRJB/FYM776VIA57RRJB.LARGE.jpg
https://www.amazon.ca/Empire-Level-2990-Magnum-Rafter/dp/B0002YSAX8

snoozer

@mrehorstdmd

Thanks for explaining that so well. I did not stand them all up individual, but I have stood them on the cut all side by side and they looked straight. I put a metal ruler across to see if they are all same length and they where. If that's 100% true now IDK but nothing was obviously out of line. The V-Core does not really work the way you showed in the picture. Here how they intend it to go together:

Sure I could drill the parts and put them together as you suggested. I have had it on my steel table now and it stands straight, no wobble nothing. Another thing that came to mind is that I did not check the end mounts of the X axis if they are square to the actual X extrusion. Those are 3D printed, there is obviously a change they are a bit off.

Jan

Alexander Mundy

Maybe a little late, but to square the ends of extrusion I use a table style disc sander. A cheap one will work as long as you get the table and slide 90 degrees to the sanding disc which isn't tough with a spare piece of extrusion and turning it 90 degrees at a time and lightly touching it then observing the sanding marks and adjusting according. Once all extension ends are square I take a spare piece of long extrusion and put 2 set of t nut/ washer/round spacer/washer/bolt and space them apart so the shortest piece of extrusion in the same length group barely fits to make a jig. Then lightly sand the rest in the group to the same length checking often for go/no go in the jig. This will get you extremely close to the same length extrusions without a caliper long enough to accurately measure them.

mrehorstdmd

There's probably enough slop in the fit of the nut-strips in the t-slot to allow the joints to be assembled squarely. Pick up either a machinist's square or a rafter square and have another go at it. You can test the square for squareness by drawing a vertical line with it placed on a board, then flip the square over and check that the line you drew follows the edge of the square. Even cheap plastic rafter squares are usually square. Machinist's squares are "adjustable" and should be checked before first use.

What are those corners made of?

snoozer

@mrehorstdmd

The corner plates are made of aluminium.

http://www.ratrig.com/hardware2/openbuilds/plates/90-degree-joining-plate-black.html

I don't have a square of any kind here, I checked with the frame on a piece of cardboard and drew a line, turn it around and the line matched. Sure it may not be a 100% solution but I move forward from here now with the belt installation. I have a square next week and check again then.

PS: I do actually have the print bed which is square, yes I need to do a bit of adjusting. I better do that now before moving to the belts.....

snoozer

That was a lot easier than I thought, I have no experience with these extrusions, there is indeed enough play with those double t-nuts to square it up. Also the holes in those corner plates are bigger then the bolts, so there is some play there as well. It was only out by approx 0.5mm on a distance of about 320mm.