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



  • @deckingman

    Just watched your video of the 5x BT extruder upgrade. Its all V-Slot mechanics your are using ? Must be a good system if you are still with that. I have read about ppl having issues with flats spots on the wheels when the printer is sitting for a while, you never had that ? Did you deliberately chose to load the wheel lateral on the X axis or did your design just work out better with the space you have available this way and the loading direction is accidental ?

    I did check the Aluminium supplier you suggested, no shipping to IRL, same with a couple of other suppliers from the UK. A friend of mine lives part time in Newcastle, I get him to bring one back for me. The price really is reasonable in compare to what I find local.

    How is your glass plate held in place ? It looks almost as if you have a slot in system ?

    Thanks
    Jan



  • @snoozer So many questions ....

    Yes it's all OpenBuilds Vslot.

    No, I've never had a problem with flat spotting the wheels. There is only one reason why that can happen and that is if the wheel doesn't rotate freely and scrapes along the rail. It's exactly the same as locking the brakes on a car (before the days of ABS) and then the tyre scrapes along the road.

    IMO there is only one reason why the wheels may not rotate freely and that is due to poor assembly. The eccentric spacers must be adjusted so that when a carriage is fitted to a rail, if that rail is then tilted, the carriage will slide under it's own weight. At the same time, there must be no "play" in the carriage.

    I have had occasions when using OpenBuilds gantry plates, even with the eccentric spacers backed off completely, the carriage is still too tight. That is an unacceptable situation. One solution that I have used is to enlarge the small hole that takes the wheels on the other side of the gantry plate. This allows the bolt with the non-eccentric spacers to move slightly further away from the rail which then gives the necessary clearance. One other thing that can make the wheels bind is over tightening the lock nuts. However it is achieved, the wheels must rotate freely on the rails and not bind.

    Regarding the lateral loading of the wheels on the X carriage, I guess you mean the fact that the wheels are either side of the rails, rather than being top and bottom. There are three reasons for this. One being that I use two parallel rails. The carriage has 6 wheels in total, 3 per rail with two inner fixed wheels, and one outer adjustable wheel. This arrangement helps to keep the rails parallel. The second reason is that I always like to have the wheel bolts supported both ends, like an axel. Rather than having the bolts fixed at one end only, which means that they could flex. So it's easier to have a top and bottom plate with the "axels" fitted vertically between them, rather than using a single plate which would need bosses hanging down to support "axels" running horizontally. The third reason is that with wheels top and bottom, the hot end would have sat too high unless I had spaced the rails further apart to allow it to sit lower. This would have meant losing even more Y travel. Although the engineer in me would have preferred to have the wheels top and bottom, this works well enough.

    The glass is clamped to the bed using two "L" shaped sections of aluminium extrusion. These have slots in the side through "T bolts" screw into the edge of the aluminium plate. So I press down in the extrusions then tighten the bolts.

    Hope that all makes sense.



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

    IMO there is only one reason why the wheels may not rotate freely and that is due to poor assembly.

    Don't forget junk bearings! Though far less likely on a good quality OpenBuilds wheel.



  • 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



  • @snoozer I did find that when I ordered my first lot of VSlot from RatRig, that delivery wasn't as quick as I would have liked. Subsequently, I've bough all my OpenBuilds stuff from Ooznest here in the UK. That doesn't help you though......



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

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

    IMO there is only one reason why the wheels may not rotate freely and that is due to poor assembly.

    Don't forget junk bearings! Though far less likely on a good quality OpenBuilds wheel.

    Well I wouldn't want us to fall out over it, but I'd argue that fitting junk bearings falls under the heading of poor assembly. Junk bearings seldom start life as being smooth and perfect and then fail a short time after - they are usually junk to start with and it's pretty easy to tell. Likewise Delrin wheels can sometimes have seams or casting marks that need to be dealt with by the application of fine grit abrasive. Washers and other metal parts can have burrs which need to be removed. Bits of swarf or grit can sometimes be found and need to be removed. For sure these things could all come under the heading of "defective parts" but they should be checked and either discarded or rectified as part of the assembly process in my opinion.



  • @deckingman

    I got my steppers, Duet 2 and Titan Aero from Ooznest, they don't have a V-Core kit and as a 1st self build I thought I go with a mechanical kit to not get lost in my project....... Once I get all work OK I will check what path to take next. I have my eye on getting a CNC mill, but that's not yet a fully formed plan, just an idea to have better resources for future builds..........

    Jan



  • @snoozer I have found the service from Ooznest to be first class and have no hesitation in recommending them. Of course, they don't do a 3D printer kit so I understand why you chose RatRig.

    Re CNC mill. I guess it depends a lot on what you want to do with it. Most of the OpenBuilds designs that I have seen are more what I would call CNC routers, rather than milling machines. For operations such as drilling, you need a lot more Z travel. I'd be a bit concerned about the rigidity of the column on those OpenBuilds designs that I've seen which have a reasonable amount of Z travel.

    If a router type CNC mill will do what you want then fine - go for it. If you want to do more than mill slots and shapes, then I think you need cast iron slide ways, with "T" slots that you can clamp a vice to, a very rigid column, precision ground spindle, adjustable jibs, etc. Personally, I need to machine mostly small aluminium or brass components and for my usage case I'm looking at buying a "proper" milling machine then maybe converting it to CNC at a later date. The conversion shouldn't be difficult - at least for a 3 axis machine. It's more less just a matter of replacing the hand wheels with stepper motors I'd have thought.



  • So I checked with Rat Rig last WE, they came back to me and the V-Core kit is apparently shipping this week. I hope the wait has an end soon now......



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

    ... machine then maybe converting it to CNC at a later date. The conversion shouldn't be difficult - at least for a 3 axis machine. It's more less just a matter of replacing the hand wheels with stepper motors I'd have thought.

    Slightly OT now, but, have had the same thought - seems the low end machines come with lead screws instead of ball screws so may have to replace the screws or accept some backlash. At least that was my conclusion.



  • @bearer

    I know in Mach3 you can work with backlash compensation, seen a bunch of stuff on YT. I believe in the F360 CAM module there is also something regarding backlash that can be configured. With a dovetail guide on a machine it would be a tight enough fit that you dont have it "bouncing" around and its likely to only come into play on changing direction. On an actual milling machine (remembering back to 1st apprenticeship) you only operate in one direction for cutting, not back and forth because the tool rotation and the type of cut dictates which direction to cut. Its not like a router. The move back is usually not a cutting move but instead a move to get the tool of the surface and fast travel and then re engaging. If you move in the axis that is responsible for your surface measurement then yes, you must take backlash or play into consideration. If you cut a perimeter around a part then you would have to compensate for backlash as well but you should be able to measure that and it should not change unless your lead screw or the lock is wearing out.

    For me personally I am looking into a CCC (Cheap and cheerful China) type CNC router. 200-300mm bed size will do for me. Mostly light aluminium and sheet plastic stuff and engraving front panels etc.....



  • @bearer

    And one thing I have totally ignored in my post above, a proper milling machine would have linear encoders on the axis as such, not on the drive. That would by default compensate for positioning errors cause you have a closed loop system. Still you would take out the backlash play I guess by moving over the point and move back to accurate position you have the load on the correct surface on you drive. Closed loop steppers would not solve that in the same way cause that reading is not aware of the actual position of the work piece but only of the drive.

    Jan



  • @snoozer Ahh, those comments about "actual milling machines" and "apprenticeships" take me back almost 50 years - long before the days of computers let alone CNC machines. Long before linear encoders and DROs (Digital Read Outs) in fact. But yes, you are absolutely right about backlash. It was always assumed that any machine (mill or lathe) would have backlash so any cut was always made by moving the tool to a position beyond the start point, then commencing the cut from the same direction.



  • @deckingman

    My 1st apprenticeship was in 1986, not yet 50 years. In the workshop for apprentices we had DROs on the milling machines (Deckel, a well known German brand) and you could program the machine to cut out the feed after x mm but not real CNC there yet,we where supposed to learn 😉 I have also a vague memory there was mechanical sliders that could be set to cut out the feed...... just vague memory, can't remember exactly how that worked.

    Jan



  • @snoozer We are going off topic but as it's your thread, I guess it's OK. I pre-date you a bit - my apprenticeship was from 1969 to 1975. In the days when men were men, boys were boys and calipers had vernier scales. Calculators hadn't been thought of so we used slide rules and log tables.☺



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

    @snoozer We are going off topic but as it's your thread, I guess it's OK. I pre-date you a bit - my apprenticeship was from 1969 to 1975. In the days when men were men, boys were boys and calipers had vernier scales. Calculators hadn't been thought of so we used slide rules and log tables.☺

    Takes me back a bit as well Ian I started my apprenticeship in 73 finished it in 77 but did get to use a bridgeport CNC Mill at college in 76 ish. (did actually do some real CNC Work in 78 sort of time whilst working in an Industrial engineering department for a large engineering company.

    Doug



  • @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.



  • @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



  • @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 ☺



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

    Jan


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