Cherry Pi III Is Available

Hi Guys

I've added some new, detail shots to Thingiverse along with some updated .stl files and a guide to how many T nuts are required in the base of the printer.

[www.thingiverse.com]

Regards

Andy

nice job!

I like the look of the new spool holder ! The cable management thing look very usefull !

I also noticed that you doubled the cable to the spring. I only have one per side, work fine but I think I should have double it!

A thing I'm looking to add (some day... when I'll finish installing the power supply) is a connector + switch like you add on your CoreXY.

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- Sebastien Plante (nka)

I got those Belt ( [www.aliexpress.com] ), just FYI.

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- Sebastien Plante (nka)

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nka
I got those Belt ( [www.aliexpress.com] ), just FYI.

Same as the ones i got

I got these [www.aliexpress.com] lol

Hey all,

Just thought I'd pop my head in and say hi as I've started collecting parts to build my own Cherry Pi III. It'll be my first 3D printer, although I've backed The Micro on Kickstarter. I'm definitely going to need some help so I figured I'd introduce myself first!

So far the biggest challenge has been to locate parts within Australia as shipping really is a killer for anything from the UK or the US. I think there was one order I got quoted on and it was around US$100 just in shipping alone and it wasn't even a large amount of parts! I did decide to get my plastic parts from Andy... not only as a bit of a thank-you for putting this project out in the wild but because I think he'll take a fair bit of care to make sure they're on-spec. One day, when I get a bit more adventurous, I'd love to try and cast some modified versions of the components (removing unnecessary material due to added strength of aluminium) using the lost-PLA method... but that might be a bit down the track.

In terms of parts sources I'm going with:
- Plastics and some items I was unsure about (springs, bearings, etc) from Andy
- V slot, pulleys and mini v wheel kit from OpenBuilds
- GT2 belt and smart LCD controller (seems the same as the RRD one?) from BilbyCNC
- RAMPS, Mega2560, stepper drivers and NEMA 17s from MorelliTech
- Most of the fasteners from bolt.com.au if I can't get them at a similar price from Masters or Bunnings
- Power supply from RS (unless I can find cheaper)
- Centrifugal fan from Element14
- A few other things like aluminium tube from smallparts.com.au

It's a lot of different sources but places like RS and smallparts I can access in person, so it won't set me back on shipping.

My main goal is to have something with a good sized print area that can do some pretty reasonable resolution prints. The Micro is going to be cool to do small parts but I want to do some bigger stuff too.

One idea I've been tossing up is to build a large enclosure for it, just to a) absorb the small amount of noise it seems to make and b) to potentially warm up the area a tiny bit. I don't think I'll go full heat bed but I'm considering feeding a small, not-fan-driven heater to have a heated chamber of sorts. Would that cause any issues with the components?

I'm really excited, should be a great project and produce some nice parts!

Printing ABS on a heated bed at 80mm a sec NICE

ABS on heated bed

Edited 1 time(s). Last edit at 08/28/2014 06:30PM by KtB.

what is the size off that bed?

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- Sebastien Plante (nka)

Hi Guys

I found this LCD panel on Thingiverse. I've tweaked it a bit to make it fit Cherry Pi. I've also uploaded the .stl to Thinigverse.

Andy

Edited 1 time(s). Last edit at 08/29/2014 10:12AM by AndyCart.

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nka
what is the size off that bed?

Its the standard 200x200mm mk3 heated bed mounted on a di-bond sheet

Edited 1 time(s). Last edit at 08/29/2014 01:25PM by KtB.

Was just wondering, do you guys think the aluminium tubing is strong enough? I noticed a few people are using carbon fibre rods... Would it be worth filling the aluminium tubing with resin or something just to give it some added rigidity, or is the system fairly sensitive to the weight of the rods? The rods I've got are fairly light duty so I'm a tiny bit worried I guess... Wall thickness is less than 0.4mm.

I'm sure it'd be easy enough to swap to carbon fibre rods at a later stage if required, but figured I'd ask your opinion on other options before I begin assembly.

The acid test as to the suitability of the rods is when you have your 'spider' together and secured to the tower carriages. At that point you can try to manually move the effector to see if there is any play/flex. Given that you have six rods to share the load and the effector is extremely light you shouldn't have any issues. As you say, it's a simple swap anyway if it proves problematic. The tubes I use have OD 6mm ID 4mm so. 1mm wall thickness. They are perfect.

I bit the bullet and decided on pultruded carbon fibre arms. It's probably overkill but they happen to make them in 6mm OD 4mm ID and at a reasonable cost. It was less than AU$20 for 2x 1 metre lengths of it. Just wasn't too fond of the aluminium tube I had... There's a good chance they might have been fine, but I think over time they may have suffered fatigue with those thin walls, especially if I added a heated bed or something that would have seen a wide range of temperatures. Carbon fibre should be a bit more resilient, I think...

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pugzor
Was just wondering, do you guys think the aluminium tubing is strong enough? I noticed a few people are using carbon fibre rods... Would it be worth filling the aluminium tubing with resin or something just to give it some added rigidity, or is the system fairly sensitive to the weight of the rods? The rods I've got are fairly light duty so I'm a tiny bit worried I guess... Wall thickness is less than 0.4mm.

In race car suspensions, unsprung weight is usually bad. (Unsprung weight is the parts below the suspension springs, like the wheels, hubs/axles, control arms, etc.) Ditto for a Delta and everything from the carriage to the tip of the hotend. The more mass involved, the more momentum that must be overcome to change directions quickly...and therefore your maximum print speed.

I read an interesting thread in an engineering forum where they claimed that tubing was stronger than solid material in some aspects because the round interior wall somehow added strength. Most of the force into a Delta's rods is straight through the tubing, with minimal twisting or bending forces. Next time that you are poking a plastic sippy straw through a juice box, think about why the straw does not break even though you can pinch it closed or fold it in half with minimal effort.

My only fear with 0.4mm thick aluminum walls would be if there was enough "meat" there to tap for threads. If you are using glue to hold the ends on, I personally would not be afraid to try the aluminum rods out. I have been tempted to hit up McDonalds for drink straws to make up a set of rods just to see if they would work.....

Totally understand that! I was concerned about the extra weight that would have been added in filling the tube too... I was even thinking at one stage that expandable filler foam (used in patching walls) might have been a nice solution, as it would have added support inside without adding a lot of weight. I'm unsure how it would stand up to temperatures in the system though and if it would have actually adhered to the aluminium enough to stop flex, or if it would have just separated if there was any bend in the tubing. It's not the most rigid material but it's quite strong for what it is.

Really the main concern was the effect on thin walled aluminium tubing over a long period of time. 0.3xx mm wall thickness just seems a little bit too susceptible to fatigue... but then again I tend to over-engineer everything I touch. Carbon fibre tube, although protruded with unidirectional fibre (I would have preferred wrapped weave!), would actually provide a solution even lighter than aluminium tube with the same OD/ID, but should be a lot more stable over time with a heavy duty cycle. Well, that's my thinking anyway, I don't actually know the properties that could tell me for sure. I'm sure 6mm OD 4mm ID of either aluminium or carbon fibre would both be fairly similar in performance and life expectancy.

I personally think that you are over-thinking the whole heat and mechanical stress issue.

The thing that I like about Andy's CP implementation with the spherical magnets is how easy it is to change out rods. I have two different sets, and can change them out (obviously with a printer re-calibration) if I need longer rods to print a wide part or shorter rods to print a tall/narrow part. Since the end mill bit is already paid for, I might as well make several sets of rods to recoup my investment.

Expanding foam is evil. I have seen people warp window and door frames by using too much of it, and could picture it blowing the welded seam out of cheap tubing just like a water pipe freezing in the winter. There is much to be said for sandwich core construction with foam at the core, but I don't think it is a good idea in a tube.

If you want weaved CF, you could always get a 4mm OD aluminum tube, wax it up as a mandrel, and put some bi-axial CF sleeve over it. Wet out the sleeve with epoxy, cover it with electrical shrink tubing, heat the tubing until it shrinks (who needs an autoclave!) and let the epoxy dry. When done, slip the aluminum tubing out from the inside, cut the shrink tubing from the outside, and wet sand to finish. Or, you could go one step further and search this site for the DIY filament winder that someone posted the designs for last spring.

Personally, I think that pultruded CF is overkill for strength on my Delta.....

Actually swapping out the rods with the new design is nearly as easy. The Spectra just loops over the screw in the effector base. All that is required is to pop the rods out and unhook the Spectra. An 'extension' loop of Spectra added and the process reversed. The Spectra, unlike normal string, doesn't seem to lock up in a knot so it's easy to undo the extension loop later too. In fact the line is so slippery I have to secure the knots in the loops with CA to stop them pulling apart. There is probably a fancy knot I could use but two half hitches and a drop of glue works fine.

Haha, it's all good. I can't wait until mine is assembled! Really looking forward to it. It's a bit of a tease having the stepper motors sitting on my desk right now...

BTW, I was worried how I was going to join the GT2 belt, but then had a better look at your Thingiverse pics Andy and saw the neat little clamp (for lack of a better description?). The pics you've got up on Thingiverse are almost as good as an instruction manual Andy!

Probably the next most awesome thing, for me, will be to reproduce all of the plastic parts in aluminium. Very cool video on the lost-PLA process here [www.youtube.com]

Only 4 more orders to come in! Unfortunately that just happens to be most of the parts haha. I'm picking up the power supply tomorrow but then I've got to wait for all my misc bits from the UK, the electronics from China and a few bits (like the v-slot) from the US.

Out of interest, is there anything really stopping us adding extra height to the build volume? I'm guessing the main limitations would be the amount of v slot and -gt2 belt you've got to play with, along with wiring length, but is there anything else? Was just playing with the idea of trying to make the print envelope 300mm high instead of 250mm.... Is that achievable?

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pugzor
Out of interest, is there anything really stopping us adding extra height to the build volume? I'm guessing the main limitations would be the amount of v slot and -gt2 belt you've got to play with, along with wiring length, but is there anything else? Was just playing with the idea of trying to make the print envelope 300mm high instead of 250mm.... Is that achievable?

Hi Andrew

The main limitation, with 2020 extrusion, is the amount of twist in the towers. Going from 600mm to 650mm to get that extra 50mm of build height will be fine but much more and you would really need more substantial extrusion.

Andy

Has everyone just been directly wiring in a mains cord to their PSU, that basically goes from the PSU straight to the wall? Has anyone played with the idea of throwing a fused IEC plug into the mix? I know it's all home brew but I have an unhealthy passion for trying to make my gear look consumer grade...

I'm running an ATX power supply externally for the moment, but did pick up one of these for when I go 24V in the future:

http://www.amazon.com/gp/product/B008X10HHE/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1

Nice! Yeah, that's what I was thinking too vreihen. [www.jaycar.com.au] Think I might build it with a hard-wired mains cord to begin with, but once I can print out some parts, I'll make a nice little add-on box to mount an IEC connector onto.

Andy, do you think there'd be enough belt in the quoted "4 metres" to add that extra 50mm of height? I got my V Slot today and I just want to make sure before I cut, haha. I'm not too worried if I don't, I'd prefer to build with a lower build height than have to acquire more GT2 belt at this stage!

If you cut it too long, it's not that bad, you can just lower the top braquet (without the top).

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- Sebastien Plante (nka)

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pugzor
Nice! Yeah, that's what I was thinking too vreihen. [www.jaycar.com.au] Think I might build it with a hard-wired mains cord to begin with, but once I can print out some parts, I'll make a nice little add-on box to mount an IEC connector onto.

Andy, do you think there'd be enough belt in the quoted "4 metres" to add that extra 50mm of height? I got my V Slot today and I just want to make sure before I cut, haha. I'm not too worried if I don't, I'd prefer to build with a lower build height than have to acquire more GT2 belt at this stage!

Hi Andrew

For the standard build with 600mm tower extrusions I cut my belts to 1220mm so if you go to 650mm towers you need to cut three at 1320mm. So yes, you should get all three from a 4M roll of GT2.

Andy

Well the GT2 belt is only used for the 3 vertical movements, right? I think it's going to be REAL close on whether I can do this or not with my existing GT2 belt... I think it mostly depends on whether or not I have exactly 4 metres.

Got my v slot today! Something funny about receiving several pieces of extrusion from the other side of the world. My parts from Andy should be in my hands tomorrow morning too. Just waiting on the electronics and am yet to source a build plate. In the mean time, assembly can begin!

A quick question and it's not terribly related to the Cherry Pi, but one of my pulleys from OpenBuilds is slightly damaged. 2 of the teeth have chunks missing on them (I'd say it reduces the height of the teeth by 1mm but for only 1/3 to 1/2 of each tooth). Should this still be fine to use?

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pugzor
I think it's going to be REAL close on whether I can do this or not with my existing GT2 belt... I think it mostly depends on whether or not I have exactly 4 metres.

I managed to use some cable ties as a belt extension to close the loop in my first delta printer. It also provided a free ratcheting belt tensioner as an added bonus! Just make sure to put it in a location where it it does not roll through the pulley or sprocket.....

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pugzor
A quick question and it's not terribly related to the Cherry Pi, but one of my pulleys from OpenBuilds is slightly damaged. 2 of the teeth have chunks missing on them (I'd say it reduces the height of the teeth by 1mm but for only 1/3 to 1/2 of each tooth). Should this still be fine to use?

It should... since there's more than one teeth holding the belt (180 degree loop)... but if it skip, you'll have to change it.

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- Sebastien Plante (nka)

Got my parts from Andy today! *dances* It sure is a bright yellow Andy haha. Should be good though. Everything arrived intact other than the feet on one of the tower bases. Are they needed or can they be removed?



Just waiting for my electronics from China and I should be all good to go.

Ends up I was actually supplied with 4.5m of GT2 belt so I was well and truly safe for adding on the 50mm to build height. I've cut up my carbon rod, extrusion and GT2 belt now so really, it's just about soldering and assembling. Can you tell I'm a bit excited?