FT5 CoreXY Conversion

by Rajaa Jun 28, 2017
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Hi Rajaa,

First off, nice work! I recently bought an FT-5 kit and will be building it as CoreXY printer right off the bat using this project! ;-) (This will be my 6th 3D printer, so I'm comfortable doing that. ;-) )

A couple of things to note:
1) The right_idlers1.stl part currently has a 3mm hole for the bearing screw instead of a 5mm hole.
2) The left_idlers1.stl part currently has a 4mm hole for the bearing screw, instead of a 5mm hole.

I know that I can fix them before I re-print them, but thought you may want to know so you can update the files on here. ;-) (I actually -didn't- fix them yet, but since I printed with 4 outlines, I should be able to drill them out to 5mm without an issue. I can always modify and re-print them too...)

Anyways, everything else seems to be as described/designed.

Now I'm just waiting for my online purchase of M5 bolts and bearings to arrive, then I'll be all set to build my CoreXY FT-5... ;-) (Metric bolts are not readily available in the US as of yet...)


Thank you, and thanks for the notes. Actually the Left_idlers1.STL is fine (it's 4.5mm) I made it this way so the screw will tap the plastic (no need for a nut). The Right_idlers1.STL was 4mm, so I updated the files to 4.5mm.
I provided the STEP files as well in case anyone wanna edit the files easily.
Wish you all the luck with the new printer! :)

Hi I have some polycarbonate carbon fiber filament on the way and have been meaning to build this. So it is time ha.

My question is I see idlers in your design but then I see you have the flanged f695zz bearings in there. Are these to replace all the idlers? Or am I missing something?

Hi! good luck with it! The answer is in the Summary, check the attached pic here:

Oh shoot my apologies, I missed this. Perfect thank you, that means I have everything I need ordered.

Also is it possible for you to upload a STEP file of each component? I need to do some modifications to some parts to work with my enclosure. I will not release anything, and can gladly send back my minor adjustments.

No problems! The answer is in the summary as well, in that link you will be able to choose any format :) check the attached pic here:

I am very unfamiliar with fusion360. I downloaded the file but it appears your assembly is one large part?

I am very fluid in solidworks and if I could get the parts in STEP file I can easily convert them and modify them in Solidworks, which was why I was asking.

Is that possible? Converting STL files is a lengthy and usually inaccurate process with solidworks.

It's not one large part, you can view any part alone even when you just open and view the link online: http://a360.co/2Bv5o4T
And when you download it from the same link you can choose STEP or whatever. But anyway i'll attach the files for you individually in a while :)

Thank you!

I am sorry hate to be complicated but I am so lost on how to get individual files pulled from the assembly lol.

No problem my friend :) now you can find the STEP files in the files section (with the STLs).


I will share my findings later :)

I see the steppers mounted at the front in a lot of these corexy designs. Is there a reason for putting them up front rather than in the back?

The reason is just to keep it open wide in the front side, otherwise the belts cross will make it hard to see/access.

Did you put anything between the two idlers that are mounted on the left/right idler brackets?

I used a little printed tube/washer (spacer). And I used it without a spacer as well and it worked fine, the idlers stayed in place. It's better to have a spacer tho.

Awesome thanks! I'm putting it together and I love the design.

Good luck, glad to hear that!

can you send me the firmware for the ft-5 core xy build

Here's mine, but you may need to teak things up according to your own build :)

Hi, I have a question: Where do you mount the X endstop? I can't see the mounting on the extruder carriage?

Hi, there is a hole in the bottom of carriage. You have to print the small part and install it there.

I see it now, thankyou very much! - I hope to actually do the build next weekend :)

You're welcome! Good luck with it :)

I notice none of your pulleys or steppers are mounted in sheer. Do you have any problem with deflection of the parts?
I'm just waiting for my pulleys and an IR height sensor right now, while I print off the rest of the parts, but I sorta feel like I should be building on top of your design, with double sheer for all parts (maybe my prints are just weaker than yours?).

I'm going to adjust the steppers mount now to make them more solid as well.

Hi, the carriages have a very thick screws mount (base). With PLA it was very strong. Even another guy used PETG.
My next design will be printed with CF-PLA.
For the stepper mounts, check the video I talked about it (short answer is no as well even if you can flex it with your hand).
Maybe your outlines are low or not bonding well.
I hade another design for all the parts like cage, but changed it to this.

I just built this one https://www.thingiverse.com/thing:2373745 , and so far so good. And it's nowhere near as rigid as this is. But I plan to take steps to improve it despite having no issues so far.


Looks nice, but I think the bed needs more support.

Very nice work! Are you happy with the print results after conversion?

Happy 200%

I assume that you found that tapping the plastic was strong enough? Or would you recommend using something like the heat-set inserts?

Right, I found it really strong with plastic only in my design.
I didn't need heat-inserts yet.
The plastic in the carriages is more than 18mm tho, so it's thick.

Looks great! I am designing my own CoreXY Printer, and I was wandering how you worked out the positioning of the pulleys so that the belts ran exactly parallel, as I can't find measurements of how the belts sit on the pulleys. (I would just use you measurements, but I am looking to use 16 toothed pulleys for higher accuracy).

I've put the belt on the pulley, and took the measurement of the final diameter (the pulley with the belt on it), then used that diameter in the design. Everything is aligned 100%.
Did I understood your question correctly?

Yep, that answered my question. I was hoping there was some clever way to work it out, but guess I will have to probably get the belts and pulleys before getting my final designs printed.

Actually I think that my way is the clever way, as you measure exactly what it is in real life. But if you are looking for the measurements, here's the info you need (check the pictures)
16t GT2:

GT2 belt:

Just a simple Google search :)

That is probably the best way, in case the pulleys aren't exactly to spec. I have worked out the way that you can do it using a pulley's outer diameter (see: http://www.york-ind.com/print_cat/york_2mmGT2.pdf) and dimension 'i' on the drawing (see: http://openbuildspartstore.com/gt2-2m-timing-belt/).
So the diameter of the belt on a pulley is the Outer Diameter + 2 x i.

awesome work , eager to start this. what type of filament did you use?

Thank you! I used PLA PrimaSelect from 3Dprima.se.

Love the elegance of this design.

Thank you! Glad to hear that!

looking forward to see next version

Maybe tomorrow or a couple of days :)

What size of idlers are you planning on using for the smooth and the toothed pulleys?

2GT 20 teeth, and the similar size of toothless one.

3mm bore or 5mm?

Thanks. Can you tell me how many of each smooth vs toothed?

You're welcome :)
6 toothed and 2 toothless.