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dnewman

Core XY triple leadscrew system

by dnewman Jan 7, 2015
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I didn't see it, but what is the build volume on this design?

Why did you use linear rods instead of rails for the x and y axis?

Because for that span, they work very well for the price.

Do you think that linear rails would be better (if price wasn't an issue)?

Rails bolted to the frame along their length will sag less. So, for the present Y axis they would be a slight improvement. For the X axis you need to do the calcs to figure out what will be stiff enough. A piece of 4mm x ??? x ??? aluminum which the rail bolts to and is then suspended from the Y axis rails? At issue is not having sag.

Any ideas on where to get 430mm leadscrews with 5mm turned down ends?

508mm http://www.zentoolworks.com/product_info.php?cPath=16_15&products_id=125
355mm http://www.zentoolworks.com/product_info.php?cPath=16_15&products_id=141
304mm http://www.zentoolworks.com/product_info.php?cPath=16_15&products_id=160
203mm http://www.zentoolworks.com/product_info.php?cPath=16_15&products_id=139

So, you could cut down the 508 to get 430mm. However, call Zen Toolworks and see what other sizes they might have. And also determine if you want their large and bulky leadscrew nuts or not. I order them from them without those nuts and thus pay less than the prices linked to above. Their bulky leadscrew nuts are zero-backlash but, with the pre-load of a build plate, you don't need that anyway. And did I mention that they are big and bulky?

Im unable to find the pitch of that screw! Can u tell me the pitch and how many starts does it have?

I was considering building a much larger printer than I currently have but could not find a good design for my lead screws. This is exactly what I am looking for! I have just a couple of questions.

1) Have you had any issues with your belt tension? The only reason I ask is because on my current printer I have had a numerous issues.

2) Can this be expanded to a larger printer? My current build size is just over 200mm square but I was looking into building one with a print size of 350 or 400mm.

I've never had an issue with belt tension. For Z, it's easy to slide the Z motor to adjust if it is an issue. For the carriage, I used the tensioners related to the Core-XY design of which this is a derivative.

It can be expanded. People have done 1m x 1m x 1m printers (e.g., http://www.thingiverse.com/unknown/about ). However, they invariably need to use four Z leadscrews rather than three for the build platform. I do not know at what volume they find that necessary. Also, they have to stiffen the X and Y linear supports to deal with sagging over those spans.

i couldn't find 3mm aluminum plate around where i live, but i found some 3mm steel plates and i had them cut. I knew that they would be heavier than the aluminum but i didn't expect them to be THIS heavy :). Do you think that the nema 17 can carry the weight? I don't know exactly how heavy they are but im guessing about 1kg per z plate and the chamber plate is a little heavier.

Weight of the chamber plate doesn't matter, although the heavier the better as it adds overall mass to the frame. As to the plates for the upper and lower z stage, I myself have no way of knowing if yours are too heavy or not. You can always try them.

P.S. 2.5 or even 2.0 mm Al plate is probably fine.

Hi Dan,

What thickness is your lower Z-stage aluminum plate please?

Also, that SVG file does not have the holes for attaching the aluminum cross bar. Done intentionally I assume?

thanks,
Dave

3mm. Chosen because it's sufficient. 4mm is overkill. 2mm is a bit flimsy. 2.5mm might be okay.

Dan,

Any chance you can provide a part number of the "power entry" female plug you used? The part from the previous design (Core XY Cube) bill of material does not fit the laser cut mounting plate and I see from the pictures that you have used a different power entry part.

thanks,
Dave

EDIT: To be more clear, I only had the P2 and P3 pieces cut by Ponoko. I didn't catch the fact that there was another file (dxf) that likely is the right piece.... Regardless, if you do have that part number handy, I wouldn't have to cut new pieces.

EDIT: Ok, I went back and looked at the instructions and sure enough, you mention Mouser 16PJ522. Sorry about that! So, the BOM references a different part. I'll have to figure out which way to go....

Thank you for your feedback :) , i ordered the 36 gt pulleys cause i don't feel like experimenting, it was a headache enough sourcing all the parts from your and tempo's BOM, its my first printer build ever but i think i can handle it.... Thank you guys so much for contributing to the community, especially with such an exceptional build :)

If you have not already purchased it, I would recommend that you NOT purchase the LCD display in the tempo BOM. That lists a FlashForge display and the connectors on it point in the wrong direction. There will be interference with the electronics box.

You want the Wanhao LCD but unfortunately they are out of stock. I am trying to source it now.....

For the record, I use the WanHao displays since they save me a little time. I had a couple of FlashForge ones and removed
the pin header and put on new ones oriented the direction I preferred. With the WanHao's I don't have to spend time doing that.

I also wanted to mention that I just bought 5 of the short-xy plates for the extruder. Big Blue Saw priced them out at 5 for the price of 1. So, instead of an $88 water jet job, I will be receiving 5 of them.

If you have any interest, I would be happy to sell one or more at my cost.

Let me know and I'll have a picture on my Flickr page once they arrive.

Hi,

I'm available to knock ideas around with you as well. I'm about 75% into this build.

Here is my Thingiverse page: http://www.thingiverse.com/thing:864017

There is a link to Flickr with pictures mentioned in the description.

I've only run into one significant problem so far. I used the motor brackets from tempo's build but want to mount the electronics box on the "back" of the printer frame. There is significant interference between the two so I am going to, in the short term, incorporate some spacers to make it all work.

Good luck with it.

Dave

Hi-Z Core XY triple leadscrew
by vronp

Ok then thx, i will order them. In the meantime i found some 8mm to 5mm bore adapters, but i have a 1032 tooth belt... will it fit the 32 teeth pulleys or will it be too loose?

You'll have to measure the diameters of your pulleys and do the math to determine the actual belt length needed. Once upon a time, I had the math all written up for calculating it but I don't know if I ever posted it anywhere. I still have it at home but I'm traveling at the moment.

An issue with bore adapters is that unless they were carefully machined, they tend to be ever so slightly off-center. I don't think that'll make much difference here if they are, but it's something to be aware of. In the Core-XY designs that wind up fishing line on spools, it's a very serious issue as you get steps/mm values which change as the spool rotates.

Dan,

Are there settings that need to be tweaked if the Z-axis pulley diameters end up being different than what you specify?

I'm looking at engineering things a bit differently and using GT2 pulleys with an 8mm ID:

http://www.sdp-si.com/eStore/Catalog/PartNumber/A%206A51M074NF0608

Well, I have to bail on this idea. My hope was to use straight 8mm lead screws the entire length but it looks like I won't be able to find a pulley with a small enough diameter to clear the frame.

So, one more question on this topic please. It seems as if you had wished to have a turned down length of the lead screw longer than what you originally specified.

If you did it all again, and maybe you are, what turned down length would you use?

Thanks once again Dan.

Turned down length of mine were fine. It just meant I had to make taller idlers than I originally expected.

So you're saying that the pulleys have such a large diameter that they hit the horizontal frame members which support the bottom plate? How many teeth did they have? Up to 36 should be fine unless they have really tall rims. The 36T GT2 pulleys I used still had 8mm of clearance. Only gotcha would be if you used thicker vertical rails pushing things further back on one end.

Yes, your assessment is correct. I was looking at these:

http://www.sdp-si.com/eStore/Catalog/PartNumber/A%206A51M074NF0608

The pitch diameter is around 47 mm.

It just occurred to me that I could drop the pulleys and idlers "below" the horizontal frame members. The frame is the "standard" 20x20.

What I was trying to do was avoid the lead screw machining. Open Builds sells 1000mm long lead screw. I was thinking about using a stop collar above the bottom plate with some form of bearing.

I believe the final length of my leads screws will be in the neighborhood of 650mm. I do have some concerns about the rotational inertia involved but on the other hand, I don't have a solid feel for these steppers and what they are capable of swinging.

Contact Jetguy and ask his experiences with using leadscrews that way. I believe he tried similar once with thrust bearings.

Rotational inertia isn't an issue: you don't turn them very fast.

What matters is the ratio of pulley teeth between the Z-motor and each leadscrews. Each leadscrew must have the same toothcount, but the count can be different between the pulley on the Z motor and those on the leadscrews.

Ok, great, thanks for the info.

Ahhh i seem to hAve bought the 32 teeth pulleys and their bore is 8mm... I dont have the patience to wait for other ones to come in the mail as im located in europe, so do you think that printing the gt2 pulleys in petg will get the job done?

I would guess that you'll have backlash if you do that. These drive systems (e.g., GT2) are all carefully designed such that the belts and pulley's have extremely low backlash. But part of achieving that is correct angles, pitches, tolerances, etc. If you 3D print a pulley, it'll drive the belt back and forth but even being off a bit will lead to backlash and even perhaps slippage at moderate speeds. You can try it though.

Hi Dan,

Where did you find the long threaded (presumably) nylon spacers for the electronics box?

thanks,
Dave

Digikey. Below is a URL but I don't know if it will get mangled or not. Search there for "nylon standoffs". You'll find them under "Board spacers, standoffs".

http://www.digikey.com/product-search/en?pv1678=1&pv29=38&FV=fff40020%2Cfff803ee&k=nylon+standoff&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

Sometimes I can find them on Amazon as well. The knurled thumb screws I got from McMaster-Carr. McMaster-Carr also carries standoffs / spacers, but charges too high of prices for them.

E.g. Digikey 1820K-ND, HEX STANDOFF 6-32 ALUM 2-1/4" ($1.04 apiece)

FlashForge sells a Creator Pro extruder stepper with the following specs. I was planning to use this for the extruder and perhaps the z-stage if necessary.

Rated Voltage: 4.83V DC
Rated Current: 0.84A
Phase Resistance: 0.75 ohm±10%(20℃)
Phase inductance: 9.3mH±20% (1kHz 1V rms)
Holding torque: 1.28N.m MIN (Two phase on/rated current)
Shaft diameter: 5mm
Shaft length: 17.7mm
Motor depth: 34.3 MAX

$14.50 gets you the stepper motor many of us use for X, Y, and Z. Available in the US from ultimachine.com,

https://ultimachine.com/content/kysan-1124090-nema-17-stepper-motor

Will that also work on the extruder?

Yes but it will approximately double the mass of the extruder requiring you to move it around with much lower acceleration. Would also require a design change to your XY carriage as the motor is much longer than an extruder motor.

Dan,

How is the rail-stop.stl piece used?

thanks,
Dave

Many rails do not have stops. Stops to prevent the car from sliding off and losing all of its tiny ball bearings. So, depending upon what is at either end of your linear rail, you may need to have a stop to prevent the car from coming off. Enter these rail stops. You bolt the rail down and also bolt one of these at either end of the rail which needs a stop. The stop bolts to the extrusion using a long 3, 4, or 5mm bolt and extrusion-frame nut. (Well, for 5mm you may need to ream the hole out; I don't recall.)

Dan,

Your discussion surrounding the Z-axis stepper mentions a lower current motor would likely work. There is a reference to modification of the Pololu A4988 that is required otherwise.

Is the modification the EEPROM change you mention? And if so, would I need to make that modification on the X and Y axis if I use that motor for X/Y as well?

thanks,
Dave

The issue is that the "standard" botstep stepper drivers shipped with MightyBoards can only supply a maximum of 0.77A, and that's if you modify the firmware to allow a digipot setting of 127. The firmwares for MightyBoards limit it to a digipot setting of 118 which limits to 0.72A.

So, if you use stepper motors requiring more current, then you have to use different stepper drivers. And the MightyBoard doesn't use a standard pinout. Thus, in all likelihood, you must modify whatever alternate stepper driver you use. For example, if you use a Pololu A4988, you have to modify it. See, e.g., https://www.flickr.com/photos/d-newman/sets/72157654553957262 .

Ok, that Pololu mod site stipulates Rev E, G, and H boards. Okay with D ?

You don't have a rev D mightyboard. You have a rev E mightyboard. FF only sells rev E mightyboards. The rev E refers to the electronics and how they are layed out. It does not refer to some FlashForge internal revision code.

Ok, well, I think I'll try to locate a lower current motor in light of the fact that you thought the Z stage didn't require a lot of torque.

Hold on there. I wrote that I MAY have been able to use a lower torque motor. I could well be wrong, I've not tried it and I've not done the measurements and calculations to see what roughly is required. So, if you simply try some other motor be prepared that it may not work. If I were going to simply try a lower torque motor, I'd perhaps try one of the stepper motors used for the extruders. That way, if it doesn't work for the Z axis, I still have a use for the motor (extruder axis).

Dan,
It looks like you have built a few machines now with the basic configuration. Can you comment about any concerns where the belts cross each other?
http://openbuilds.com/threads/triple-c-bot.1255/page-2#post-18445

They cross. It's no big deal. They don't mind rubbing. However, it does seem to rub the fur the wrong way on some folks. (Particularly people who have never built or used one.) It's just not worth worrying about. As to the best place for them to cross I have no opinion.

And no, I do not find belt dust on the table below where they cross on my bots. The belts see far more wear running over the pulleys and from any contact with pulley flanges then they see passing by each other. It most definitely will not be a source of belt wear and most definitely will not cause print artifacts. The belts are not under extreme tension.

Dan,

Your "X lasercut carriage" doesn't appear to match the piece on 393155 (xyplate-short.dxf).

I'm looking at this picture: https://www.flickr.com/photos/d-newman/14521954744/in/album-72157645313526624/

There is no picture of this piece on the Flickr site for your triple lead screw design so I really don't know what you used there.

Would you please advise?

thanks,
Dave

  1. That's not a laser cut carriage, it was machined out of 3mm aluminum plate.
  2. It doesn't match any published build files. Indeed, there are no build files for it as I designed it the old fashioned way (pencil, paper, straight-edge, etc) and handed the dimensioned drawing to my-father-the-retired-machinist.

Hi Dan,

I want to use that xstageshort.dxf file from 252041.

I wonder why you cut a slot in place of the through hole in this picture on the older design:

https://www.flickr.com/photos/d-newman/14590689804/in/album-72157645313526624/

Did something not line up correctly with the through hole?

With a slot you can use different belt fasteners, a taller motor stack, etc. It's more flexible is all.

Hi,

Did you use these idler brackets?

http://www.thingiverse.com/thing:364426

Unless I am missing something I don't see these on the tempo502 CoreXY Cube project. I want to be sure I am using the parts you used and also make reference to this on the remix I created today.

thanks,
Dave

Core XY Idler & Motor Brackets for 2020

Yes, those are the brackets I used (Thing #364426)

Hi,

Very nice design. I want to build this to accommodate parts that are 21" tall. Do you have any concerns at that height? I was thinking I would build the aluminum frame with centered side spans.

thanks,
Dave

These frames built with 20x20 extrusion are very rigid, especially if the lengths are cut with adequate precision and squareness. However, at that overall height, 0.75 meters or more, I'd worry about twisting moments. For that, centered side spans may not help much and you might be better off with some diagonal elements. I know that Jetguy on his large bots has ended up needing to use diagonals. He's posted about them to the 3dprintertipstricksreviews @ googlegroups.com list starting with his first for the NYC MakerFaire in 2013. (P.S. Jetguy lives in NC and does frequent some of the makerspaces down that way.)

Thanks, I'll look into that.

Say, do you happen to have a formula for calculating the cage height based on the maximum height of the parts desired? Or perhaps you can tell me what max height this design can create and I'll just add on from there.

I read through everything but that didn't appear evident....

Wow, this is a really nice looking setup. You paid attention to the aesthetics for sure! I love the green acrylic.

Thanks for the kind words. I have a nearly finished even larger 625mm (outside height) but don't have details on the specifics of working out the height. I'll see if I can add that to the instructions. You can sort of reverse engineer them from this slide,

https://www.flickr.com/photos/d-newman/15693200543/in/album-72157647713563474/

Basically, if

  1. You do NOT mount the electronics on the underside,
  2. Do not use corner brackets above the bottom chamber plate,

then the outside vertical height boils down to

outside height = B + E + C + Zu + 75 + E
outside height = B + 2E + C + Zu + 75 mm
where

E = extrusion vertical height (e.g., 20mm for 20x20 extrusion),
B = height of bottom corner brace (e.g., 35 mm),
C = chamber plate height (e.g., 4 mm), and
Zu = length of the Z axis leadscrews above the chamber plate (e.g., 470 mm).

That 75 mm is a combination of things, some relating to component choices:

  • 19 mm inside corner brace
  • 43 mm tall flanged shaft support block for an 8mm linear rod (which this holds the center of that rod at 21.5 mm below the 19 mm tall corner brace)
  • use of the TR_Y.stl bracket on the 8 mm linear rods to support the two 8 mm linear rods for the X axis (http://www.thingiverse.com/thing:252041/#files)
  • use of the XY extruder carriage of this bot and direct drive extruder with the particular height it holds the nozzle above the print surface

Note you can go higher and be okay: if the extruder nozzle is too high above the build plate, then you just lower the flanged shaft support blocks thus lowering the Y axis linear rods and thus lowering the X axis linear rods and the extruder carriage.

Core XY cube
by Unknown

Do you plan to post your 625 mm build here? If so, I may wait until you do before I begin. I plan to use the BOM posted by tempo502 and tweaking as necessary to match the design changes.

A picture of it, maybe but nothing more.

Did you buy the belt as a closed loop ?

I have a 2m timing belt , and would be keen to do something similar . However , mine isn't a closed loop.

Closed loop for the Z axis. For the XY axes (Core XY axes), two open belts are used. I just buy whatever is the least expensive form of getting the necessary length, be it closed or open.

Great thanks. Is your bottom plate 3mm Aluminium ?
What fittings are you using to mount the threaded rod onto the bottom plate and pulleys?

These and many other questions are answered in the Instructions section and within the comments of the photos in the Flickr album. (E.g., thickness of the metal plate is in the comments to the photo showing the metal plate installed; 4mm.)

Hey this build looks super great! I have a question though... Why do you have be leveling springs? Couldn't you use the lead screws to level the bed?

Why introduce needless complexity? The bed gets out of level over time (or the surface treatment does or whatever). Changing the lead screws minutely means having to turn the bot upside down, loosen the pulleys on each one, then turn it back over, tram the build surface to the extruder, then not disturb any of that, turn the bot back over, then tighten down all the pulleys without disturbing the lead screws. Pretty complicated and not likely to work the first couple of times -- you're likely to discover that
something moved a tad and now isn't trammed.

You have to loosen the pulleys since otherwise, turning one leadscrew any amount turns all the others. And you have to keep all the pulley's sync'd with the belt.

So that makes more sense. However, if there was a mechanism to disengage the pulleys from the platform then you could double up on the benefit of triple lead screws. Regardless of that this is a very nice build. I hope my bot looks like that when it grows up.

Comments deleted.

What's the build area on your machine? Is it the same as the base design?

In XY, same as the base machine. In Z it's however tall you choose to make it.

Interesting. Are you the same "Sailfish" Dan? The stepper motors + code have no problem with steps and the larger distances?

D

Yes and depends. Depends upon what firmware you choose to use. Jetguy has his 4foot by 4foot by 1meter corexy bot using Sailfish and it works fine. Even then incredibly large numbers of steps can be broken into two (or more) moves but we're talking, IIRC, things exceeding 524287 steps in a single move along any one axis.

You are awesome! Love the way you think and make your OWN design. and how you improved the Z stage with 3 screws. Keep up the great work!