Cherry Pi III

by AndyCart May 27, 2014
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Hey Andy,
My class and I are building one of these and want to ask if there is a way you would recommend using a linear bearing slide over your rolling design on the sides.

Hi Richard

I would suggest you build the Cherry Pi IIIS instead. Much improved. As to linear slides. By all means if you can afford them but there is really no need



Love it want to build one, don't suppose you have other file formats? like STP?

Hi Andy

What are those white conectors on stepper motors conections.
I have some problems with small dupont ones.
Any link?

Thank you

Can you post, like, a pdf of instructions please? Great design.

What limits the build to be 190 x 190 mm?
Should I build it with longer rods? or maybe longer extrusions?
I'm planing to use to 220mm MK3 round heated bed, and I would like to use most of it's area.
Thank you!

(I'm building the s version)


Please, could you publish the CAD or source files for your version of Greg's Wade's Geared Extruder?



Im probably not the first one to ask but what your source for the metal balls?


Several builders have reported an issue with the non magnetic J Head effector. I've swapped it out on the 'Thing Files' page for a new version which should be O.K

I've come to the part in the build where I am trying to get the wires down the 2020 extrusion, how on earth do you manage that, there doesn't appear room for the heater wires, extruder wires etc. Is there a trick I'm missing.



Yes. The trick your missing is to drill a hole through the Z tower extrusion from front to back. I normally drill two 6mm holes very close to each other to form an oval. Take the heater, thermistor, fan, Z min, etc cables around the back of the Z tower and then through the hole just below the Extruder back to the front. The wires fit nicely in the front slot of the Z tower and I cover them with either 2020 cover strip or vinyl tape

Thanks Andy, that did the trick :)

Hi Andy,

Would it be possible for you to check the model for / reupload the Z_Probe_Effector_J_Head_Non_Magnetic piece?
I'm seeing a number of errors in the loop faces at the top as shown here: http://i.imgur.com/5KS0Qpy.jpg which currently makes it unprintable.


See my Cherry Pi IIIS page and try the extruder from there


Am I missing something, I have printed The Mini_V_Wheel_Adjustable and the Mini_V_Wheel_Rod_Non_Magnetic and the 3 holes for the self tapping screws don't appear to line up.



A very quick and stupid Question do you attach the 2 carriage parts together with self tappers (If so what size?) or some M3 button head screws

I use No.4 10mm self tappers

Hi Andy

Could you tell me what flange bearings your using, the parts say 6 x 16mm x 5mm x 4mm flanged bearings, and 3 x M5 45mm SHCS (top idlers). Which suggests that the bore of the bearing has to be 5mm, I would guess the outer is 16mm and the width is 5mm, but I can't find with suitable size.


I'm currently using F695ZZ bearings that are 13mm in diameter with a 5mm hole and are 4mm thick

Hi Andy,

I recently finished a Cherri-Pi III. I am having the same issue you mentioned here ( "http://forums.reprap.org/read.php?178,275926,page=3" ). Basically, my machine hesitates while updating display. This causes, small warts/blobs on the print. Otherwise, it runs very nicely. I am using Arduino Mega /RAMPS 1.4 with RepRap Discount Full Graphics Controller. Could you please tell me how you fixed it? Does switching to just plain "Smart Graphics Controller" fix it? Or, is there a way I can disable "graphics" mode on my full graphics controller and use it?

Thank you very much.

The only fix I could find was to use the plain LCD. The full graphics version puts too much load on the Arduino when used with a Delta. There's no real benefit to full graphics anyway.

That fixed it. Thank you! My prints are looking better now.

Thank you very much Andy. I have placed an order for plain smart controller. I agree that there is no real benefit to having a graphics controller.

Thx mate for the fast response! Ill sort the new files out. :) big thx

Hi Andy, very very nice design! But ive trouble to attach the Non Magnetic Rod Carrier on the carriages. The holes doesnt match to the carrier plate. Is this a known issue?
Please provide feedback so i can continue assembling :)

Check out my latest upload


Cherry Pi IIIS

Very well done. Thanks for posting the files.

Hi Andy,

I have a version of the CP3 that I put together prior to the update with the changed effector and center line. It has been very good. I have been "stress testing" it to see how fast I can crank it up. The first thing I notice is that under certain occasions, one or more rod can come off a magnet sphere and kill the print. As a test I simply tried to add some line from the center of my current effector to the appropriate carriage. I ran a faster print and had the same issue. I may try to to the same, but with a tensioning spring like you have put in. Out of curiosity, what kinds of speeds are you doing your prints in prior to the design change and after?

Hi Andy,

I finally have my CP3 together am just making some modificatins/tweaks. I like the design (I used original magnetic design). one question I have is that I am having a devil of a time getting autocal to work. I issue a g29, but the probe just goes to the bed once, then scoots back to the retract position, but then continues up past that position until one axis limits out. I have played with the z probe offset (setting it to zero with this implementation) and with the grid settings, but no luck. Are you using autoprobe successfully? If so, did you have to change the firmware to accomodate this design at all? I am just about ready to dig into the firmware, but thought I would ask first and see if this is a simple issue to fix (usually is).

Thanks for the design. I'll post mine once I am finished with a few add-ons.


Hi Paul

It's a fairly common issue. You need to set your values for the X Min and Y Min pins in Pins.h to minus 1 (-1). Re load the firmware and all should be good. I assume you have the probe micro switch connected to Z Min?


Hmmm. I just checked and the X Min and Y Min pins are already set to -1.

I notice in the firmware that there is still code for deploying the probe and retracting the probe, along the the handful of defines in the Configuration.h file associated with the two actions. Are they still necessary?

Hi Andy,
love the design, I built an original rostock and halfway through a similar one to this with twin rail and decided yours is way better.
i have just ordered a mill end 4flute solid carbide reworked. Are your 5mm bolts stainless or zinc plated? Does it make any difference?
What speed do i need to set the pillar drill?
Metal work not my thing!!
Thanks again for your postings your time is appreciated.

Hi. The M5 bolts have to be zinc plated (or plain steel) as there is very little magnetic attraction to stainless steel. Set you pillar drill as slow as it will go. I milled to a depth of 3mm from the top of the bolt. I've recently moved away from magnets to 8mm drilled ball bearings on the rods and 8mm 'cups' printed in the plastic effector and rod carrier. The whole lot is held together with an 80mm x 4mm spring and some Spectra line. The revised parts are included here on Thingiverse and a full write up of how to do it here http://forums.reprap.org/read.php?178,361141,page=4

Hi Andy,
What a quick response....just one question I rather liked the magnet idea and wouldn't have replaced it with springs etc
Why did you change it? Couldn't see a reason in the thread.

Hi. I get an email when the comments get added too! I try and respond as soon as I can as I know how frustrating it can be to wait for an answer if you are in the middle of a build!

The magnets are great but my supplier started sending magnets that weren't quite a powerful as previously. They still worked ok but sometimes a rod would let go on homing. Also they are quite expensive compared to the drilled ball bearings. My current iteration using 'balls and cups' is the best I have ever had. Rock solid, zero backlash yet still easy to dis-assemble if required.

Thanks , still deciding... which supplier, there were a few when i looked? Heres one i found. Is 1.4 KG the strength you had?
10mm dia N42 Neodymium Sphere Magnets - 1.4kg Pull (Pack Of 4)
£5.15 first4 magnets

Also new design assume cups are ABS, ....sorry if it is in some of the threads, only had a quick look.

The first4magnets onrs are fine. Just really expensive. I used them originally. I then found a cheap supplier in China. Quality dropped after about 4 orders. The 'cups' for the spring and string version are ABS on the effector and PLA on the carriage

Andy, the new spring assisted tension system looks great, cheers! I have a bunch of derlin ball bearings here I would love to try out on this as I'm just getting ready to print off a set of CP III parts and start the build.

Any chance you could modify the sockets to 13.3mm diameter if you have time and it's not too big of a job? I've already printed some test sockets and 13.3mm was a snug fit for these 1/2" bearings when printed at 0.3mm layer height.

If you were using OpenSCAD I'd just get the source from you but I still haven't gotten around to learing the ins and outs of SketchUp yet and you'd probably still do a much better job than me if I did figure it out haha.

I'm excited for the much higher speeds! =D I'm using mechanical u-joints on my Mini Kossel right now and they work fine but I can't get much above 60mm/s without going way down in quality.

P.S. I'd be willing to pay you for your time or even fix you up with a set of these derlin bearings, I have lots here.

As always Andy you make these printers with intricacy and enjoyed this new update and want to see if I make this change in my printer sensor autonivel the z axis. If you have a printed piece to see the quality I appreciate. Hug.

Nearly finished the assembly. Couple of questions.
Any advice on getting the belts correctly tensioned?
I also had a look at your XYCore printer.
What is the material you have used for the bed?
Does it improve the sticking of PLA?
If it improves the sticking of PLA I would be interested in using it on the Cherry Pi.
Thanks in advance

Make sure the steppers are a the top of their slots. Pull the belt into a loop without the screw to lock it and then turn the screw into the belt loop with a driver. This should get it pretty tight. Then slacken off the stepper screws and push them down to really tighten. My belts 'twang' when I pluck them. The material is carbon fibre effect vinyl. Just google it. It make a great print bed surface for PLA on a cold bed. I print at 210 and it sticks great.

Thanks Andy.
I'm grateful for your design. It looks nice! I am planning to build one. I will post my photos as soon as I finish it.
Could you please post the STL file of the whole thing? It will be easier to assemble following it.

Good luck with your build. I don't have an STL of the entire machine. I can post you some detail images if you like but it's all fairly self explanatory once you print the parts off and look at the images. Check out the thread on the Reprap forum too.


Many thanks to Andy, i made a cherry pi III. I had a few problems, and i still have problems ;). My magnet balls have a 9,7mm diameter and i drilled my M5 screws with a 10mm ball cutter (sorry for my english).
So i think i have a play and thats why the pi is not printing flat (or do you know other reasons for that)? The printer is in the middle x0 and y0 and also on all three towers perfektly adjusted, but when i drive solwly from tower a to tower b the distance between the nozzel and the bed goes up and down. During a print i hear that the nozzel rubs on the last layer, but not all time. I love the disign and i hope i can solve the problem. I made a few pics but the upload does not work at the moment. How did you adjust the endstop position fow x,y and z, is there a option to make that in software? Because i had to release the complete top pracket for that. Sorry it is my frist delta and i have more questions...


It sounds like your DELTA_RADIUS is too large. What version of Marlin are you using? If, like me, you use Rich Cattell's Marlin fork then you can use the M666 command to adjust delta_radius, delta_rod_length, etc. You can also adjust the end stop offset (M666 X-1.5 Y-1.5 Z-1.7). Your best option is to post your questions on my thread in the Reprap forum (http://forums.reprap.org/read.php?178,361141) I don't think the 0.3mm difference in your magnets will matter that much.

Hi Andy.

Loving this whole project! I'm trying to find the microswitches in the size specified, but I am drawing blanks. I could modify the end stops easily enough, but I already printed the effector, and I'd rather find the right ones for that at least!

Can you recommend a source for the ones you use?

EDIT: I think I just found some!

I found and use these:


The only drawback is that I had to extend the trigger flap to reach the carriages.

I don't extend the trigger. I drill a hole in the top corner of the tower carriage and screw in an M3 8mm SHCS. It's normally just enough to catch the micro switch lever. There appears to be lots of variation in these switches. The first batch had levers about 5mm longer.

Hi Andy, I'm getting ready to start printing out the parts to make this beautiful printer you designed but on the top corner bracket there's no hole for locking it onto the extrusion. Can you upload the proper file when you get a chance? Thanks! :)

Hi Deltadroid

Good luck with your build. The part is correct. You need a 45mm M5 bolt for the top idler bearing pair. This passes through the hole (you need to drill it through the thin skin on the inside of the square hole for the extrusion) and locks into the top T nut. Double duty !!!


Getting on well with my build now, but can't find a suitable PSU.Where did you get the PSU you are using? All the ones I have found so far are too large to fit.

Thanks for the information. received the new mini v wheels today so with luck I should have the assembly complete by the weekend. then the fun will start with sorting out the software and calibrating etc.

Solved. I have the incorrect v wheels. I have the Solid V wheels not the mini V wheels.

Just started my build. I have completed building the frame and started on the carriages. I am unable to assemble the carriages to the extrusions. There is insufficient distance between the wheels. I have measured the distance between the wheels assembled to the carriage at approx. 35mm. From placing the wheels on the extrusion it looks like it should be more like 45mm. I don't think there is a problem with my current printer as all the frame components fit. I have also printed the rod carriers and they fit the adjustable carriers. Any idea what is wrong.

The dimensions of the carriage are definitely correct. I've personally built 8 Cherry Pi III printers and several people around the world have also completed successful builds. Check out the thread here http://forums.reprap.org/read.php?178,361141http://forums.reprap.org/read.... it may help if you can post some images of your printed parts and the extrusion you are using. The carriage is designed for the mini V wheels from Openbuilds and the extrusion needs to have a V slot. Normal T slot won't be suitable unless you re-design the carriage to allow for the lack of the V

I have started my build. I had a similar issue with the spacer rubbing a bit on the roller bearings for the carriages. Once I figured out the best combination of spacers/washers for the bearing it turned out great.
The only thing I had to change was how the rod holder portion connects to the wheel carriage. Originally, as I tightened up the tension it would skew the rod holder. This was because the two screws holding the rod holder to it were on the side that has only one v wheel. Once I modified it so that the rod holder was held to the carriage with two screws on the "two v-wheel" side and one on the "one v-wheel" side, then I would get no skew as I tightened it up. It stays pretty much square.
I'll post a remix with a few small changes once I get done. This is a really nice design Andy. Thanks.

Hi Andy
While i wait for my flanged bearings I have started to put the rest of the parts together. So far its going well but i have one question :)
I have just put the v-berings together and mounted them on the frame but have noticed that even though the rollers themselves are smooth they are a bit notchey when moving them on the extrusions. The ones I have are these which are supposed to be Bosch/Rexroth compatable http://www.aluminium-profile.co.uk/acatalog/20x20-Aluminium-Profile--KJN992888.html#SID=31http://www.aluminium-profile.c...
I was wondering how smooth yours are and if i have the wrong extrusion

I had an issue with the wheels being a bit tight. Turned out I had the wrong spacer between the two bearings. Once I got that sorted out the carriages run as smooth as silk on the extrusions. My exrusion is the same as the link you quoted so I assume the problem lies elsewhere. Have you checked the dimensions of the printed carriage against the .stl? Other than that I can't think why you have this issue.

Sorted they where to tight on the extrusion. The print dimensions where spot on and enlarging one mounting hole by a 1mm sorted the issue

Hi Andy, I have few quick questions.

  1. Would this hot end fit in your design? I have one in mail already. So, would be great if I can use it. I plan to remove the fan+fan mount as you have a centrifugal fan on the effector.
  2. Would a 300mm dia borosilicate glass fit in this frame? It is ok if I can't print to all the extra area. I found a good deal for 300mm round glass, so would be nice if i could put that on.
  3. While ordering OpenBuilds V wheels that are used in your design, I saw 20x20 rails (http://openbuildspartstore.com/v-slot-20-x-20mm/)http://openbuildspartstore.com... and ordered them. Now, wondering if that would make anything in your design incompatible.
  4. Would making the vertical columns little taller (another 200mm) cause any issue? (I will increase belt length/bowden tube length and any firmware settings appropriately). I need to build flutes in vertical standing position. I really need some extra height.

I like this design. I have collected most of the parts and almost have everything printed off to assemble. One question I had was about the autoleveling probe. Did you not implement one in this build? I cant see a reference to one.

Hi Diverp
Yes it's encompassed in the effector design. The hot end is hinged and this allows a microswitch (sames miniature one as in the towers) to detect the bed. It works great. Rich's Marlin fork with auto calibration finishes in about thirty iterations if the machine is put together carefully and the multi-probe that needs two similar readings usually only gives two taps i.e they are both the same.

Ahh. I see now. Looks good. Thanks for the clarification.

Well i must say so far I'm very impressed with this delta i have sourced about 95% of the parts and finished most of the printed parts but i cannot seem to find the 16mm x 5mm x 4mm flanged bearings anywhere. Anyone got a source for them ?

Sir, thank you for your design and parts list. I am trying to order the parts and noticed you have 61 M5 screws (8mm). Probably most go to put the frame together. Is 8mm correct length? They seem too short considering thickness of extrusion and plastic parts. Kindly let me know if 8mm is correct or not.

8mm are fine if you use the printed T nuts I just happened to have them in my stock. 10mm would be better maybe. I have just restocked with 10mm as I have just completed my 5th CP III and run out of 8mm

Two sandwiched together for each of the belt top idlers :-)

I'm loving this printer! I'm looking up sources for parts, daydreaming about building my own.
Looking at your BOM, I see 6 x 16mm x 5mm x 4mm flanged bearings, but I can't figure out where they would fit. What are you doing with them?

Some people reported a problem with the extruder body. It was 'tilted' on the print bed. I've checked my version in Cura (layer view) and re-uploaded the known good version.

That extrusion won't work with the v wheel carriages. It hasn't got the 'V' chamfer on the edge of the slots. Not sure about the ball end. What sort of movement will they allow. The original magnet/cup design gives virtually unlimited movement in all directions. You could use the Cherry Pi (original) carriages with that type of extrusion. Just make sure you get good quality 623 bearings

hi,what aluminum extrusion you are using?

I use Bosch/Rexroth as it has the V groove on the slots

Hi ekaggrat
All the parts shown in the images of the printer were printed on a Cherry Pi (Cherry Pi II). The speed and quality are great. I use Cura and set the base print speed at 60mm/s, the outer perimeter at 45mm/s, the inner perimeter at 50mm/s, and the infill at 80mm/s with a 33% infill and 0.3mm layer height. My machines use a 0.4mm nozzle and I normally print PLA at 210 degrees C. The only part that is different is the effector I print that on another machine that has a heated bed and use ABS with a 0.2mm layer height.
I built a 3DR when it was first released, it was a good machine but I had issues with the filament drive spools where the filament overlapped all the time and threw the steps per mm off slightly. Could this be your issue? I also wanted a machine with a larger print bed. Cherry Pi III uses a 250mm diameter bed and I get, more or less, 200 x 200 x 250 build area.

thanks for the response... i think the prints that you have also have a little amount of banding ( the grey parts specially ).. i will be doing a little more testing before i figure out the issue...

They do. I think it must be the PLA I was using as the orange parts have no trace of it. Maybe I was running it a bit too hot. Given it was printed at 100mm/s it wasn't too bad and for the part in question I felt it was acceptable. It was my prototype draft design.

can you show some same prints from this machine... how do you compare the print quality to the 3dr ? i recently completed a 3dr and i am seeing some horizontal banding in the prints!! i dont know hat is causing that

The mini V wheels are from Open Builds. Very smooth. No play. Highly recommended.

Very nice design. From where did you supply the V derlin bearings? How do you assess them? Do they have play? Is it noticeable into the quality of prints? Thank you.

Thanks. I notice in the new file that there is some skirt on the narrow arms of that part. I had printed off the previous versions and notice some very slight warping (even with a heated bed and PLA). It wasnt enough to worry about, but I assume those were put in to help counter that same thing? I'll try the newer file with bigger skirt and see if that helps eliminate that warping.
Thanks again

Exactly that! Good luck

Good looking design. I assume that the Bottom printed corner mounts are the same as in your Cherry Pi II build? I noticed they werent in this compilation, but probably haven't changed since the CPII?

Hi Diverp
I hadn't even noticed they weren't included. They somehow got missed off the upload. They are there now. But yes, they are the same. (more or less)

I source all my parts on EBay or make them myself (rods, rod ends, printed parts)

Hi Cherry ! Enjoyed the equipment and information.
You can tell where I find parts or mounting kit for this printer ?