Need help with 1st time Core XY build

Hello guys, I have never used a CoreXY setup before, however I have put together Prusa i3 and a Delta kits. I am planning on building a new machine using Tech2C's Hypercube template and I would really appreciate if someone could answer couple of my questions.

1. To get a 400x400x300 build, what size of extrusions would I need to buy for both the printer and the bed? Please mention them in detail if possible.

2. I am buying from Misumi, this is the only place I know, are there any other place where I can get a better price?

3. I see that many people here built CoreXY printers but instead of using the typical T-Slot extrusions, they have used the hollow ones. Is there any specific reason to avoid the typical 2020 T-Slots?

4. Anything else should I know before ordering parts or starting to build a CoreXY machine? I remember someone warned me before I bought my Delta kit that they are too complicated for bed leveling, and they were right.

Thank you everyone in advance!

I only checked the printed parts of the Hypercube once, so I dont know for sure. But when you change extrusion profile/dimensions you may have to redesign many parts.
I had the same, when I chose T-slot against V-slot profile for my D-Bot.
You might get away with using 2040 Extrusion for most parts. Unfortunately, they don't offer CAD files for redesign. Maybe one of the remixes has some .STP file?

1) it's impossible for anyone to say how long the frame pieces should be without knowing exactly how big the extruder carriage is. You have some basic work to do and some decisions to make. See #4 below.

2) I buy 40x40 mm t-slot extrusions from local scrap yards for $2.50 per lb (about 1 foot per lb). Check your local scrap yards.

3) I don't think 20x20 is going to be rigid enough for a machine as large as you are contemplating.

4) You say you want to build for 400x400 bed. That's fine. Now if you're going to run dual extruders that are maybe 130 mm long, you'll need guide rail(s) for the x axis at least 400+130=530 mm long plus however much at the ends for mounting them (assuming end support, which I never recommend, and especially not for a 500 mm span). The means the frame members that run parallel to the X axis have to be at least that long, but probably longer because you're going to be mounting pulleys and motors. About that 400x400 bed...how are you going to heat it? Do you have funds for a custom heater? I ask because I have never seen an off-the-shelf 400x400 heater. How are you going to power it? How are you going to switch power to it?

This is how design works. One decision leads to another to another until the whole thing is defined. Changing one thing changes all (or many of) the downstream decisions. When you ask someone else to make those decisions for you, you're assuming that they had the same goals in mind that you do. Trying to change anything that someone else designed can lead to all sorts of problems and can be more difficult than designing the whole thing yourself. Using bed heaters as an example, many people discover that their cheapo printer kits have underpowered bed heaters and prints won't stick very well, or they can't get them hot enough to print ABS. So they get a higher powered bed heater and discover that their power supply can't deliver the necessary power, so they get a bigger supply. Then they burn up the MOSFET on the controller board or the board itself because it can't handle the extra current for the new heater. That's what can happen when you let others make design decisions for you.

---

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

400mm heater beds are definitely available... 400mm heater

These things are designed to heat oil drums so you can get them in nearly every size under the sun, and most sellers will custom make them as well on aliexpress. The one I linked is 220v, but obviously buy whatever voltage you are comfortable with using.

As for the other questions, Digital dentist raises some very valid points about design. Check the specs of your extrusion and see how much it will bow over that span. I would probably suggest chunkier extrusions then 2020 at that size. There isn't really any reason to choose one extrusion over the other. If it fits the design I don't see the problem. I personally use V-slot as it is readily available in the UK and we don't have decent scrapyards full of cheap extrusion on this side of the pond.

I would also ask if you need a bed so large? Making a bed that is smaller has many design advantages. Do you have specific items in mind that you want to print? Most people rarely make anything bigger then 150mm^2 footprint.

Edited 1 time(s). Last edit at 03/28/2017 08:30AM by Origamib.

Here's a useful article on using t-slot extrusions: [hackaday.com]

---

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

Thanks a lot everyone for your replies, what you have pointed out so far, I am already learning a lot. Ok so I have got more questions based on what you guys have pointed out. I should have also mentioned that I am salvaging most of the electronics and some other parts like smooth rods, bearings etc from my old Prusa i3.

@ o_lampe- I did a quick search and it seems like the V-Slot would be the best bet. Btw, why would the 3d models need to be redesigned if I just extend the length of the extrusions?

@ the_digital_dentist- No dual extruders, just single. I was thinking of buying a 500w pc psu to power everything, that should work to power the heater, hotend and the rest of the printer right? What can I do to not fry my board (MKS SBASE 1.3) when using the bed Origamib suggested?

@ Origamib- There are many times I have designed a headphone frame or a quadcopter part but could not print on my 200x200 prusa or delta. I know 400x400 is a bit large, probably 300x300 would do just fine but I was hoping to somewhat future proof it. Btw what did you mean by "how much it will bow over that span"?

Thanks!

0.5W / cm^2 is sufficient heat to get the bed up to 105C ABS print temperature in a few minutes. For a 400 x400 bed, you're looking at 1600 cm^2 so an 800W (or more) heater should do the job.

I just built a machine with a 300x300x8mm aluminum bed and used a 750W line powered heater. It gets to 105C in 4.5 minutes. I can wait 4.5 minutes for a print to start. If you put glass on top of the bed you'll be waiting a while longer for the surface to get up to print temperature, and it may not heat evenly.

For a print bed I wouldn't mess around with anything but cast aluminum tooling plate on a three point leveling scheme. Put a layer of PEI on it, and a high powered heater and you'll never have problems with first layers not sticking to the bed.

You will definitely want to use line power for your bed's heater- it requires a lot less current than a low voltage heater so you won't have trouble finding flexible cable to bring power to it. You can switch power with an inexpensive SSR that won't even get warm in operation, so no heatsink will be needed. You can use a lower power rated supply which will cost less and might even be fanless so the machine can run a little quieter. I bought one of these Meanwell 200W 24V supplies for my CubeX Duo and I just ordered another for the new CoreXY machine: [www.ebay.com]
They are relatively small and fanless and provide more than enough power to run everything except the bed heater. These things are actually cheaper than the no-name "LED" supplies from China that have no QC, no protection circuits, and no warranty.

Here's something to consider before making controller board decisions: [smoothieware.org][]=mks
The MKS boards use the drv8825 motor drivers. You'll need to add diodes to the cables to make them work well. See: [www.engineerination.com]#!

---

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

Quote
scarecrow2k6
Thanks a lot everyone for your replies, what you have pointed out so far, I am already learning a lot. Ok so I have got more questions based on what you guys have pointed out. I should have also mentioned that I am salvaging most of the electronics and some other parts like smooth rods, bearings etc from my old Prusa i3.

@ o_lampe- I did a quick search and it seems like the V-Slot would be the best bet. Btw, why would the 3d models need to be redesigned if I just extend the length of the extrusions?

@ the_digital_dentist- No dual extruders, just single. I was thinking of buying a 500w pc psu to power everything, that should work to power the heater, hotend and the rest of the printer right? What can I do to not fry my board (MKS SBASE 1.3) when using the bed Origamib suggested?

@ Origamib- There are many times I have designed a headphone frame or a quadcopter part but could not print on my 200x200 prusa or delta. I know 400x400 is a bit large, probably 300x300 would do just fine but I was hoping to somewhat future proof it. Btw what did you mean by "how much it will bow over that span"?

Thanks!

The heated bed I linked is 220v, 600W so your 12v PC power supply will not work. only use a 220v heater if you are aware of the risks and will be using more safety measures then usual. Make sure wiring is spot on and use thermal fuses. Consider multiple thermistors.

All materials will sag and bow under their own weight if they are allowed to, the question is by how much. Any decent supplier of extrusions or metal components will be able to tell you this. You may find that over 400mm that simple 2020 extrusion will be lower in the center then at the supported ends. This is why I suggest to consider your printer size. If you are not comfortable with a mains powered bed, then you may struggle to heat it with 12 or 24v power supplies. The added cost of larger extrusions for the larger design may also be off-putting to you, depending on your budget. Sometimes it's better to go smaller and design your parts well. Just something to consider really.

After giving it some thought it seems like I will get more headaches dealing with parts than to actually build the machine. @the_digital_dentist, what size of extrusions did you use for your 300x300 build? @Origamib, I will listen to you and go lower on the build volume. I will definitely do some research on the heater you mentioned and also the power supply. Thanks!

I used 40mm square extrusion for all three of my builds, and screwed the frame members directly to each other. The latest machine is quite tall (1.4 m) and wobbles more than I find acceptable, so I will be adding some bracing. The previous builds were smaller and rock solid.

---

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