Looking to build a delta - could use a bit of input

Hi all,

I recently built a Prusa i3 (laser frame with the twelvepro frame sides) and whilst I like it as a printer, I'd like to build a delta based printer. I've not had the best of time with the i3. Whilst building it wasn't a problem, the constant issues, changes, tweaks, maintenance, and weak x-axis had me looking around at ways to make a more reliable printer that would be less prone to silly little issues. Don't get me wrong, I know this is the case with all RepRaps to some degree, from conversations with other i3 owners, it seems to be a common trend that it's got it's fair share of design problems.

Having done some research on it, I'm thinking a fairly non-complex designed delta might be the answer here. So I've been looking at the Rostock, 3DR and the Kossel, as well as a few variants of each.

What I'd like to be able to do, is pull as much from the i3 as possible. Ideally I want to be able to print as much of the delta, using the i3, and then use the i3's RAMPS setup, heated bed, etc. Theoretically if I can plan it all out correctly, the only expense I'll have is PLA and a few vitamins for the delta such as rods, screws, bolts, etc.

What I really want is a push in the right direction from those who've been working with deltas already, and could maybe give me some feedback on the (possibly/likely incorrect) conclusions I've drawn about a few of the delta models:

3DR
I like the 3DR for its pretty tidy design, and love the fact that the base and top of the frame can be printed - but at the same time would be a bit concerned about the lack of a heated bed, and the fairly small looking build area. I love the way all the electronics, right down to the endstops get hidden away.

Rostock
Then with the Rostock, it seems to have a standard sized build area, supports a heated bed, but relies on a lot of wood cutting, and looks a little unfinished. On the plus side, no huge plastic parts to print, I guess this does have the benefit that you can use pretty much any mdf for the base, so might work out cheaper?

Kossel
The Kossel looks very rugged and strong, and looks like it'd be pretty cheap to make given it uses a simple aluminium box-section style frame. Just like the 3DR, I love the way it's all enclosed and nicely packaged. The only downside I can see from initial investigation, is the lack of a heated bed, however I'm not 100% sure what's going on as from what I can tell the Kossel mini does have a heated bed, does it not?

I'd really be interested to know if I'm correct, or way off the mark with the above, or if there are any other deltas I should be looking at as well as those above.

Also, for what it's worth, as I've seen a few queries about this - I'm not using this in a professional capacity, I built a RepRap solely to learn and contribute as a hobby.

Edited 3 time(s). Last edit at 12/18/2013 05:25PM by RickM.

I would suggest that having two printers is a pretty good idea. Until you get one fully running, you never know what you will need to fiddle with.

Hi RickM

I've just built a delta to my own design. I have previously built a Huxley and a 3DR. The 3DR is a super design but I found the build bed a bit small. There is a post with some pictures of my design, a Cherry Pi, further down the posts. You are more than welcome to my .stl files if you want them. I know I'm biased but it's a terrific printer and you could build it very cheaply given you have the bits from your I3. Just a few pieces of aluminium extrusion and some bearings, GT2 belt and pulleys, nuts and bolts. I use a 300mm granite chopping board as my build base with blue tape. It would be really easy to add a heated bed as all the electronics are in the base. My design is probably more kossel like than anything else but uses cheap Bosch rexroth extrusion and cheap 623 bearings (18 of them). I used magnetic rod ends but designed the rod carriers as a separate plate on the bearing housing so it's easy to use any rod type with a minor change. The rods use cheap 8mm threaded ball ends and 10mm countersunk rate earth magnets.

Good luck with whatever you finally go for.

Andy

As you look at Deltas be very sure you understand the print area and print height numbers for each design. A good way to sort them out is to figure out what the biggest cylinder is that you can fit into the print area. Looking at Max X,Y,Z can lead you astray. All of them have very odd shaped print areas.

Thanks for the feedback so far guys - it's much appreciated.

Now that I think about it, uncle_bobs recommendation to have two printers isn't a bad idea. I guess I can always sell off the i3, or strip it for parts for another printer later down the line once the delta is all up and running nicely. This is a damn addictive and expensive hobby!

@AndyCart your Cherry Pi printer looks pretty nice. What sort of costs did you have for the frame?

There are things that the i3 is adapted to doing, and things that the Delta should be better for. You see people doing tall print area Delta printers a lot. The i3 extruder and the Bowden tube on a Delta are very different beasts when you need to retract filament in a hurry.

There's a huge installed base of Kossel builders - in fact, I'm aware of 7 (including 2 derivatives) within the local RepRap group. Yes, you'll have more calibration to do, but it's not that hard, and the upside is a extremely fast, lightweight printer. Having built both a Legacy Kossel with strings, like the 3DR, and 2 Kossel Minis with belts, I have to say that belts are the easier option and now price-competitive.

You can add a heated bed to the Kossel, and I'm not sure why more people don't do this.
Trinity Labs has a heated bed for $35: (http://trinitylabs.com/products/12v-120w-kapton-heater-160mm-round)
Ultibots sells one for $25: [www.ultibots.com]
... and there are other choices if you want to go past the standard 170mm bed.

I added the Trinity one to my Kossel last week and it took 30 mins to install, with the only tool being a crimper. If you're seriously considering a delta, I would suggest checking the deltabot list on Google groups, and asking there if you have any more questions.

Thanks for your input brandonh.

I did see that someone had added a heated bed to a Kossel, and it looked pretty simple - he provided the mounting brackets on thingiverse as well (http://www.thingiverse.com/thing:37556). The more I look at it all, I am leaning towards a Kossel. The 3DR seems a bit too small to me, and the original Rostock looks functional, but not anywhere near as well finished as the Kossel looks.

I'll give the deltabot google groups list a look as well. Many thanks for posting!

It was surprisingly simple, since I find poster tape works fine to attach the glass to the tabs on the Kossel - no new parts needed. I just had to crimp the thermistor and bed heater wires, attach the heater (it's adhesive-backed), and enable the heater by defining a thermistor type in Marlin.

Hi RickM

The extrusion was about £1.06 per metre and I got them to cut the nine 250mm and three 800mm pieces. I think total including shipping and cutting was £24.00. Cheap as chips really!

Andy

Quote
brandonh
I just had to crimp the thermistor and bed heater wires, attach the heater (it's adhesive-backed), .

I do not trust crimps, it's just a hang up I have. I'd go back and put a bit of solder on the connections ....

I do like beer at a wide range of temperatures, so I'm not completely bad ...

Quote
AndyCart
Hi RickM

The extrusion was about £1.06 per metre and I got them to cut the nine 250mm and three 800mm pieces. I think total including shipping and cutting was £24.00. Cheap as chips really!

Andy

Nice! I couldn't quite tell from the pictures, is it openbeam or something similar? I've only managed to find 1 UK supplier so far (http://www.technobotsonline.com/construction-kits/openbeam.html). The prices seem pretty reasonable though, although saying that I've not priced anything up yet.

Also could I just ask about what the sound is like on yours? I've seem from a few people that their openbeam based deltas can be a bit loud - it's not a major concern however, but it'd be nice to plan it out so that there's not too much noise.

Hi RickM

My printer is a bit noisy, steppers are at 32 microsteps so that helps a bit but with the belts, and the bearings running on the aluminium extrusion it's definitely not as quiet as the 3DR. That said it's nowhere near as noisy as my Huxley. I'm sure if you used 20mm stainless steel square tube for the towers it would be quieter. There seems to be some reason steel on aluminium gets noisy!!!

Andy

I thought it might be. I guess the channels along the aluminium resonate and cause the sound. It's no big deal. In fact it'll give me something to do - try to make it quieter

I've done a bit of research into the frame and think I'll be going with standard 20mm slotted aluminium. It's cheap and lightweight. I've found what looks to be a pretty reasonably priced supplier, who offers cutting to size, so I wont need to worry about picking up any power tools or fancy saws to cut them up. For anyone interested, it was the first ones on this page: [www.aluminium-profile.co.uk]

I've found a few people's projects on thingiverse that have used the same style 20mm bars, and have provided stls for the frame, which I can print out on my i3.

From what I can tell it'll be a lot simpler to plan this out than a standard printer will be. If I'm not mistaken, I've now just got to sort out how best to mount the three axis to the frame, and then things like belts vs threaded rod, etc

I stumbled upon something potentially useful for the future. Basically I was looking at types of aluminium extrusion, wondering if you could do some sort of wheel based rail, without needing to attach something like openrail, or use expensive openbeam/makerbeam type extrusions.

Today I found these: [www.motedis.co.uk]

They fit inside the 8mm gap of a standard 20mm x 20mm t-slot (the Bosch/Rexroth stuff). They're a bit pricey when you add delivery, but theoretically you could use 4 (or maybe even just 2?) and create a track on the sides of the standard 20mm beam. Because they are plastic, and they'll be running on the actual beam gap they should be significantly quieter, and not cause damage to the aluminium, which is from what I can tell, a bit of an issue with standard bearings.

I think to begin with I'll probably just use the standard metal bearing option that Andy's used on the Cherry Pi, but might have to have a go with the rollers at some point!

My experience: I have a Prusa i2 and a mini Kossel. I have not had any parts that I could not print on both (the i2 printed the mini, and the mini has printed over 10 other mini's). I've no idea what you print or plan to print but bigger is not always better and in this case it might just be wasted space. My i2 takes up roughly 2 square feet of desk space whereas I have the mini sitting on a 16" long x 12" deep wall shelf. It has a 160mm diameter print surface and unless you are printing "plates" (multiple parts at the same time) I think it's plenty. The main reason I don't print plates, one part pops loose, and you could lose the whole plate.

Something to consider.

Yup, completely agree jaydmdigital.

When I first started thinking about it, all I could think about was to make the build size as big as possible. But given I'm building it primarily as a hobby and not for one specific work purpose, I started to jot down a few ideas of what I'd like to achieve with the build. So far I have the following goals:

- All parts easily sourced from either local UK national hardware/DIY shops (e.g Wickes, B&Q, Homebase, etc) or via low-cost online providers (e.g reprapdiscount for electronics kits that can be shipped globally) where not possible.
- As many parts as possible should be printable, unless it has a significant effect on the build quality (i.e I wouldn't use printed structural supports).
- Use the Bosch Rexroth 20x20 profile extrusion, which is easily available across Europe, and is very cheap. This will also be mostly, if not completely compatible with any 80/20 builds, which I understand is fairly readily available in the US.
- If it's significantly cheaper, use a standard MK2 heatbed, and not a circular custom one as these seem to be expensive.


For the heatbed, I'm just trying to decide if I want it to overlap the frame, (e.g like a Rostock Prisma) or have it contained within the frame (like a Rostock Max). I'm leaning towards having it inside the frame. Whilst it means the footprint of the frame is slightly larger, it allows for a lot more future improvements, with things such as an integrated enclosure - something I do want to attempt at some point. Plus it will provide more space under the bed to keep the electronics nice and tidy.

I've still got some planning and shopping around to do. If I can find a decent quality and decently priced circular heatbed and piece of glass it'd be ideal, but the only PCB based heatbed I've found so far is the Onyx which is pretty pricy, and thats before shipping costs to the UK. I've found a few rubber silicon based heaters that I need to look into as they may be a lower cost option to consider.

For a round heatbed you could do a diy job: [forums.reprap.org]