Cherry Pi Delta 3D Printer

by AndyCart, published

Cherry Pi Delta 3D Printer by AndyCart Dec 22, 2013
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UPDATE 13 April 2014
I have released details of Cherry Pi II with many improvements incorporated:-

This is my own variant of a variety of 3D printer designs available. I have used ideas from Kossel, Delta Pi, 3DR and, of course, Rostock. Many thanks to the designers of those machines for their brilliant ideas that I have shamelessly 'Cherry Picked' hence the name of my design!

The rods on my printer are 277mm from steel ball centre to centre. The towers are 800mm Bosch/Rexroth aluminium extrusion and the base frame extrusions are 250mm long as are, obviously, the top frame extrusions. You need nine in all.

The bearing carriers use 6 623 10mm x 4mm x 3mm bearings and slide directly on the extrusion. Nut traps for M3 nuts are included in the carrier. The rods connect to the carrier with a plate that fastens with 3 M3 bolts, again nut traps are included. The rod carriers and the effector plate hold 10mm x 5mm countersunk, cylindrical rare earth magnets and my rod end balls are 8mm diameter. My rods are 5mm carbon tube but you could use 6mm aluminium. My rod end balls have a 10mm M5 threaded rod and are the type used for the ends of gas struts, etc. the idea of the seperate rod carriers was to enable different rod attachment methods but the magnets and balls have worked out fine for me.

Update: (2014-01-03)
I have altered the delta rods and attachment mechanism and also designed a new effector plate. This time around I used 10mm spherical neodymium magnets and modified some M5 socket head capscrews with a 10mm ball end mill in my pillar drill. The magnetic attraction between the new spheres and the M5 SHCS 'cups' is about four times stronger than the previous version using 8mm steel balls and countersunk magnets. I've posted some images of the new design and also the .stl for the new effector plate. They should be self explanatory but drop me a line if you need further info.

Update: 21/02/2014

I have had some issues with the idler bearing belt guides - they disintegrated on me! I've posted a modified design on the 'files' section


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I am thinking about making this , Nice design

This is an awesome design!

I have never seen magnets used as rod ends like this. Very clever!

What is the approximate build cost?

Beautiful Delta and pieces, great job, man.

Hi Andy,

I'm building a delta style printer and plan to use this style of magnetic arm where the balls are magnets. My one major concern at the moment is how much wear these magnets can sustain before the (nickel?) coating wears off and they crumble to pieces or something.

Have you noticed any wear on your magnets with them riding directly in the bolt heads like that? Any idea how many hours of runtime or how much filament you've run with that setup?


Hi Hans

No sign of wear so far after about 4kgs of filament printed out. I did put a small amount of copper grease in each cup.


Hi Guys

For anyone who is interested I've uploaded an Sketchup file that shows the layout of the Cherry Pi. Actually it's the Cherry Pi II but it's basically the same, just a bit smaller.


Hi Andy,

I'm in the process of building all the parts. Can you give us a breakdown of how many of each item and perhaps a BOM somewhere? And if you have a picture/STL of the entire assembly, I can use that as a starting point to figure out where everything goes.



Hi Samer

3 x base
3 x top
3 x top cover
3 x bearing carrier
3 x rod carrier
3 x limit switch mount
1 x effector
3 x bearing pulley

And you're good to go. I printed with .4 nozzle 33% .3 layer


Awesome, thanks!!!!

Hello Andy,

I almost finished the mechanic and I bought the E3D hotend.
I see in the last image you posted the effector plate is bigger then the one is in the stl.
Could you upload the stl of the effector you assembled with E3D hotend?
Thank you

Hi cla

It's on there now. Sorry I must have missed it on the upload.

Hope you like my design.


Thank you very much.
The design is fantastic.
As soon as I have time I shall post some images of the structure

Hello Andy. I was wondering what plate to use for the Effector_Plate_Round_Ball so I can use a J-head?

Hi Andy
I'm glad to see your reply, looking forward to your perfect machine was born!

Good luck!


Hi ostrich12

I don't have a BOM for Cherry Pi yet. I'm about to build a second one and I will produce a build manual and images of the build and also compile a BOM. I was trying to hold off until I was happy with my prototype, which I now am, before spending a lot of time and effort on the manual. Watch this space!


Hi Guys

I've just uploaded the new .stl files for the effector that uses the hotend as the Z probe. Also a picture of it on my machine. Enjoy

hi Andy

Your printer is very good, I like very much, I do not know now automatic level device testing?
Can also add printer sharing all of the components list.

thank you!


Hi All

I've added auto bed levelling to Cherry Pi using Rich Cattell's Marlin version https://github.com/RichCattell/Marlinhttps://github.com/RichCattell....

I've designed a new effector to suit that holds the Z probe and microswitch. They are uploaded into the files area.


With regards to the effector magnets. Has anyone got any ideas for an alternative to milling the screws down to use them with spherical magnets? I've not got access to anything that would be able to create the shape needed for spheres on the screws.

Would reversing it work (I.e stick non-magnetic spherical balls to the end of the metal rods, then use some countersunk magnets attached to the effector plate)?

Hi RickM

I tried that first time around. If you can find some 8mm steel (not stainless steel) ball bearings you can use these countersunk magnets from http://first4magnets.comfirst4magnets.com - Partno F301N. Use a good epoxy putty to stick the balls to the ends of the rods forming a slight cup. My first version failed because I could only find SS ballbearings. Ordinary steel should be o.k. Make sure you print the correct versions of the effector plate and carriage rod carriers too. That said, all I used to mill the screws was an old bench mount pillar drill and a 10mm ball end mill tool that I got from Ebay for £5.00. You don't need a lathe or anything.


Finally making progress on my build :) After being stuck with the carriages I spent way too long fixing my Prusa i3. Turned out my x and y axis were having problems after I moved the printer to a different table. Had no idea it would be so sensitive to level changes.

In any case. I tweaked my marlin settings and printed a new carriage out and it fits great. I see what you mean about the curve acting as a spring now.

I've just got to print out the other 2 carriages now. My version of the Cherry Pi's going to be enlarges slightly. I'm using 350mm horizontal beams, and 900mm verticals. The build area if circular works out approx 250mm. I'm planning on having a Raspberry Pi under the bed, along side a RUMBA so that it can run a print server, and hook up a camera to it too :)

Are there any youtube clips of this machine in action? Looks good

The printed Tnuts that I mention below are actually very good. The printed part just holds the M5 half nut and a 1mm washer in place while the bolt tightens up. The actual load is on the nut and washer. Try them they are great!

Mintlin: not sure what you are asking re the 'square overhangs'. Which part? I didn't use any support for any of the Cherry Pi parts. You shouldn't need it.


Hi Andy, sorry I was looking at the L joint in your github repo :) which is not really required for the build.

Just a quick update regarding the t-nuts as it may be a help to anyone else building a Cherry Pi or similar delta printer. I tried a few different printed ones which worked ok, but felt a bit lacking in support. They do work, but just feel like they wont last very long. I've not got any ABS so had to print them in PLA - maybe they'd be stronger/better with ABS though.

I had a look at Montedis and the shipping charges for the UK were pretty high (sidenote: they also sell on ebay). I did some scouting around on some CNC forums and found a UK supplier called metallin who sell all sorts of t-nuts, and they are dirt cheap. I ended up getting these ones, which worked perfectly on the Bosch/Rexroth 20mm profile: http://www.metallin.co.uk/shop/t-slot-nut-5-st-m5-keyed.html?filter_name=ART02834http://www.metallin.co.uk/shop...

A pack of 70 cost me £21.12 including delivery which whilst still is quite expensive, it's cheaper than montendis who sell the same ones (http://www.motedis.co.uk/shop/Slot-profiles-accessories/Accessoiries-20-I-Typ-slot-5/T-nut-with-spring-ball-with-guidance-I-Type-slot-5::99999572.html)http://www.motedis.co.uk/shop/... but would charge £30.34 for a pack of 100 delivered.

TL;DR Metallin seems to be the cheapest UK supplier of T-nuts compatible with Bosch/Rexroth 20mm extrusions.

Hi Andy, how do you print the square overhangs for the brackets (top, bottom, L)? Do you use support structures etc? Thanks

Mintlin asked me to upload some images of prints from my Cherry Pi. I've just uploaded a couple. The 'sculpture' was printed in Chinese PLA at 0.2 layer height and the Treefrog in cheap ABS at 0.3.


Very nice quality prints Andy! Thanks for uploading the sample prints.

Hi Rick, Motendis has 100 for 13€. I dont know about the shipping to the UK, Regards Jean

Hi Jean,

Do you have a link for them? Cant seem to find any site for Motendis.



Hi Andy,

I don't suppose if you know of any decent alternative to the T'Nuts do you? I cant believe how pricey they are. It's going to cost about £40 to get 70 of them, which seems a bit much :/

I've been using standard M5 nuts which work ok for testing, but not sure I'd trust them for the final build.

There's a great thing on here T Nuts you can print they use an M5 half nut and washer. Way cheaper. You would, of course need access to a printer though. http://www.thingiverse.com/thing:28788http://www.thingiverse.com/thi...

M5 T-slot nut substitute

Awesome! I wanted to start something just like that with basically the same "cherry picking" you did here. I already have a smaller delta (pretty much a standard rostock) that i am very happy with, so now i'm starting a BOM to make my own, bigger, more powerful design.

How are those alum. extrusions holding up? I was thinking of taking something bigger, maybe 30x60mm with the longer part pointing to the middle of the platform to make it more rigid, and i will probably use some 60° or 120° alum. extrusion pieces to make the top and bottom more rigid too. Do you think that is overkill?
One thing that would really be cool would be to have some kind of simple elevator where the bowden driver and spool sit on that would move up and down in sync with the print head to minimize the bowden tube length. Maybe just some sort of "autofollowing" the height of the head with a "tracking sensor", so you could have it controlled by seperate controller/driver and would not need to modify the original controller boards and the gcode generator to add it to the machine, but that would be Stage 2 in my project.
Anyway, thanks for the ideas and insights i can grab from your project here. Now, keep on printing... :-)

The extrusions are holding up fine. I mounted the extruder at half travel. Bowden is about 400mm. So far it's all been o.k. Speed and print quality are good. If I built again I would probably beef up the sizes too. Not enough of an issue to bother changing though. 30 x 30 would have been better.

Good luck with your project.


Hi Andy,
On the topic of speeds... what kind of Travel and Print speeds (to the nozzle size) are you getting at the moment? Also, would you be able to upload a picture of the print quality if you can be bothered? Thanks mate!

Hi Mintlin. I've recently swapped out my Jhead for an E3D. Excellent piece of kit btw. The Jhead was oozing like made during hotend warmup. The E3D doesn't suffer from this. It has a 0.4 mm nozzle. I normally print at 50mm/sec travel speed is 150mm/sec. I have had it up to 300 but it shakes the frame a bit and makes little difference to the length of time to complete a print. I've uploaded an image of a twisted heart vase I did at 50mm/sec, 0.2 layer, spiral vase. It took about an hour and the quality is superb (that was on my oozey Jhead) the E3D it actually better but I've no pics. The machine is quite happy printing at 100mm/sec but the quality on small items isn't as good. It rips through the Cherry Pi's bottom brackets pretty quick at that speed though!

Hi Strelly

Look in the .stl files and you will find limit switch mount.stl. This is a plate of three microswitch mounts. They slot into the extrusion profile and are secured with an M3 screw. There is a nut trap in the mount. They can locate anywhere under the top bracket. The limit switch itself is secured to the mount with two self tapping screws.



Thanks Andy,

Thats great info. Do you have a link for the limit switches you used?

From a calibration point of view do these switches need to be accurately placed on the extrusion; so the each carriage contacts its limit switch at the same time?


Hi Strelly. You could calibrate that way but it would be quite fiddly. My version of Marlin supports the M666 Endstop offset function so I use that. It makes calibrating a flat build plate very easy.

Hey Andy,

Love the design! I'm just collecting up the parts needed to make one.

Could you do into more detail about the endstop location please? I've got a good idea about the design from the photos but cant quite work out what you've done with the endstops!


Hi Runninfarmer.
The new effector is no smoother, it's still a ball and cup joint it's just that the ball is now the magnet not the cup. It's way stronger now though. It takes about 1kg to break a rod lose. My effector with the fan is about 150g. The ball mill was sourced on Ebay. I typed 10mm ball end mill in their search box and got lots of hits. It was about £5.


Is the motion smoother with the new magnetic cup design? I like the newer design since it's easier to obtain the regular sphere magnets, but wanted to know if there were other advantages? Also where did you get the balll mill to drill out the cups?

RickM seems to be having issues with the size of the carriages. I have just uploaded a couple of images that show what they should look like. Hope it helps. Part of the print is a small circular ridge which sits against each bearing ans stands it off the carrier a little to centralise it on the edge of the extrusion face. I printed mine at 0.3mm layer height and they came out fine.

Thanks Andy,

I'll dig out the callipers as I can only think that a missprint might be the cause. I've got a gap of about 1cm so something must have screwed up with my i3 when I printed them.

You have got all six bearings in the carriage haven't you? Sorry but it was just a thought.

Hi rmwebs

Yes. They should be snug. To the point that the carriages flex a little when you insert the aluminium extrusion. The curved side was designed to act as a spring to allow that flex. I used 20mm M3 socket head caps screws. My carriages wouldn't slide down the extrusion under their own weight but needed very little force to get them moving. I designed that way to allow for a little bedding in of the bearing against the aluminium. The published design was the third iteration to get the flex just right. Measure the cad and make sure yours are to spec.


Hi Andy,

Quick query regarding the carriages. Are they supposed to fit snug? Mine seem very loose to the point where it looks like they're going to wobble around a lot. I've got a fealing there should be some sort of plastic ridge looking at your photos, my bearings seem like they arent far enough out....if that makes any sense at all.

What size screws should be used for them?

Many thanks

The main structure is all m5 10mm and t nuts. 60 in total.

Thanks Andy. Very much appreciate your effort.

The m3 bolts used on the bearings in the carriage and to attach the rod carrier are 20mm and 10mm (from memory) I'm away from home on business at the moment so can't check. I'm pretty sure that's correct though.

Hi Mintlin. I doubt it, but then 600g is probably too heavy for a delta effector anyway. You would lose the main benefit I.e speed due to the low inertia of the lighter effector. I would go with a Bowden setup. My hotend is a Jhead and even with the new 40mm fan and mount/duct I have fitted its probably less than 100g


Hi Andy,
Another question: how strong are those spherical magnets setup? Will the rig be able to hold about 600g of end effector (direct drive) weight?

hi Pauloblank

No problem. I use Sketchup. The files are on my Github https://github.com/Andycart/CherryPihttps://github.com/Andycart/Ch...
By all means use them.

Great design! I also like to mix good ideas from different machines. I got prusa printers and are now interested in deltas (smaller footprint, fewer parts). I may use your design as a reference for mine. Maybe a smaller 3DP between yours and the cool 3DR. Would you mind to share your CAD files? sldprt, igs, sat, whathever, would help very much ! Thanks a lot !

Hi Rick
Yes they are exactly those LEDs from IKEA. I can't believe how good they are for so little money !!! I also now have a spare 12V PSU !!!
Good luck with your build. I can really recommend the latest iteration of my delta rods. The 6mm aluminium tube was from B&Q and mine are cut (aluminium tube length) to 250mm. With the M5 cap head screws I used, once they were milled into a cup on the heads, my total ball centre to ball centre was 277.5. The magnets were the 10mm spheres from firstformagnets,com. I have used them a couple of times now and they are very fast and reasonably priced.

Love the latest update Andy. Those lights at the top wouldn't happen to be the £11 Ikea LEDBERG ones would they? Recently picked up a pack for a Prusa i3 and they are fab :)

Just about to order by aluminium from KJN to start building a delta based on yours!

Hi Woodcam. I got them from http://sgs-engineering.comsgs-engineering.com. My rods are now in their third iteration. First was 5mm carbon fibre tube with 8mm ball bearings fixed with CA. That worked great but the ball bearings were stainless so not as magnetic as I wanted. Second was with the threaded studs from sgs. I made some adapters to fit the 5mm thread to the 5mm CF tube using some 6mm aluminium tube from B&Q. That worked ok too but I had the rods popping off the magnets if the hot end hit a raised bit of extruded filament. Third iteration is using 10mm sphere magnets and 6mm aluminium tube rods. The rod end have an M5 10mm socket head cap screw which threads into the 6mm tube. The head has been turned using a 10mm ball end mill in my pillar drill to form a cup for the magnet. This is the final iteration. It's actually quite difficult to separate the cup from the magnet.


Andy, where did you get the threaded ball studs - I can find 10mm x 5/16-18 ball studs (Maxum Hardware) but not 8mm x m5????

Hi Mintlin. As RickM says they are 20x20. I got them from KJN. They are Bosch Rexroth profile. That said you could use any 20x20 profile or even steel square tube ala Delta Pi (a great design)

Thanks for the reply Andy. I will look into your thread that RickyM posted. This design is looking to be quite cost effective to produce as well. Keep up the good work!

If it helps, there's a discussion thread about Andy's Cherry Pi on http://RepRap.orgRepRap.org - He's using the Bosch 20mm extrusions IIRC: http://forums.reprap.org/read.php?178,275926http://forums.reprap.org/read....

Fantastic. Thanks!

Great design Andy! Truly cherry picked. The aluminium extrusions you've used, are they 20x20 or 30x30 profile?