Need opinions (and any promotional help) on 3d printer and its RPi electronics - Page 1
Forum section: electronics / projects

author: mobadr
author_rank: Newbie
timestamp: June 27, 2017, 04:55:39 pm
content: Hello everyone!My name is Muhammad, but you can call me Mo. I'm a Mechatronics Engineer and have a PhD in Robotics, and currently, I'm trying to earn a living by making 3d printers and hopefully other open source robotics stuff.I'm working on a portable 3d printer with foldable printbed and quick-detachable toolheads, I'm almost done with the electronics, and the rest is to be done soon.I need your opinion whether you think this project would sell. I'm quite passionate about it and I'm sure that I cannot see it objectively.You can find information on the electronics on my website (https://www.cannyrobots.com/) and onhttps://hackaday.io/project/25607-stepzero, I'm planning to sell the electronics on tindie (one prototype is already there) while working on the printer itself.The printer itself is going to have the dimensions of 250x225x55mm when folded and the toolhead removed (one toolhead can be stored within the folded printer. The build volume will be 150x200x170mm. I expect to be able to sell it for about £650-£850.Do you think the compact electronics and/or the compact and portable printer offer a feature that would be useful? Would people pay that price for such a device?Many thanks for all your inputMo

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 27, 2017, 06:06:12 pm
content: Quote from: mobadr on June 27, 2017, 04:55:39 pmif i'm representing of all potential buyers. then no it will not sell at that price, find another project, such as giant 3d printer at a cheap to sell to universities, make your preliminary study first before doing anything you should know that. oshw 3d printer market is flooded already with many cheaper options, sorry to say that... you are welcome...

author: janoc
author_rank: Super Contributor
timestamp: June 27, 2017, 06:32:49 pm
content: Hello Mo,I have to agree with Mechatrommer - printers with that small build volume certainly won't sell for 850 GBP. I have bought my Mendel90 (the Nophead's version) for less than that - two years ago. It has a 200x200x200mm build volume. And that was before the flooding of the market by the cheap Chinese printers that sell for $200-300.I am also not quite sure what is the point behind the replaceable "toolheads" (extruders?) on this class of printer - do you think that someone would want to swap extruders that often that it would justify this complication?If you are trying to go the way of the printers that claim to be also a CNC mill, drill, pick & place and what not thanks to the replaceable heads, don't. Those machines are universally crap - a typical 3D printer frame is not stiff enough for a mill, pick & place without feeders and vision is useless and drilling can be done easier and cheaper using a normal drill stand. These are machines that are jacks of all trades but masters of none.I had a quick look at your electronics too - what is the point of building an 8bit AVR based board today when you can have much more capable boards like the Smoothieboard for less, never mind the flood of the cheap Chinese boards? Even the $200 Monoprice printer includes a 32bit controller already (STM32F103 based, I believe). 8bit AVR/Arduino based controllers are universally considered obsolete, the 32bit controllers allow much better motor control, smoother acceleration/deceleration, better curves etc. thanks to the higher computation power, especially in floating point. And they cost more or less the same as the AVR based ones.One can always hook up the RPi to it (like I have done with my Mendel in order to not have to bother with SD cards), even when it isn't an RPi HAT, so that wouldn't be a selling point for me. Furthermore, many are happy with running the printer from an SD card or using a laptop, so having a "hardwired" RPi adding $35 to your already expensive BOM is silly, IMO.I would say you need to stop building and first do a market survey to find something that isn't available yet and actually fills a need. You can't really compete with mass-produced machines assembled by people working for 10% of your salary.

author: Nusa
author_rank: Super Contributor
timestamp: June 27, 2017, 07:10:46 pm
content: I think the market for THAT kind of portability is rather small, especially when you consider the roll of filament and other accessories you still have to take with it. One of the 3dprinters I currently have doesn't fold (other than a removable spool arm) and measures about 30x30x20 cm with a similar build volume. It's portable enough as is to transport in a car trunk or seat. And it's even cheaper today than when I bought it...I could replace it with a newer model for about $200US now. So I agree with Mecha that you're well out of the price range unless you have some really unusual and desirable feature in mind.As for electronics, 8-bit arduino-based solutions are already well developed and available exremely cheap. There are many offerings out there. They'll be around for a while yet, but the more serious hobbyists have been moving to 32-bit ARM-based controllers. (e.g.https://www.duet3d.com/is one of the better offerings), So you're a bit behind the times there as well, although I gather you did it mainly because of your planned size constraints.

author: thm_w
author_rank: Super Contributor
timestamp: June 28, 2017, 12:02:22 am
content: Quote from: janoc on June 27, 2017, 06:32:49 pmAlmost all of the cheap printers I was looking at are still using the Atmega2560 or similar. I agree its ridiculous but they are hardly considered obsolete, people are still pumping them out.Maker select V2 is same as wanhao i3, and they use an atmega 2560 or similar.MP select mini is the one using STM32F103, but I guarantee its for cost reasons. Thats a low pin count very cheap processor ($1, for atmega its more like $3.50).

author: janoc
author_rank: Super Contributor
timestamp: June 28, 2017, 07:06:35 pm
content: Quote from: thm_w on June 28, 2017, 12:02:22 amOf course they do use the AVR ones - all the R&D is long amortized, just copy an existing board design, load Marlin or GRBL on it and done. If you want a bottom of the barrel price, it is a nobrainer. They are obsolete in the sense that they are not really being developed further and most new designs are moving to 32bit platforms already.However, we are speaking about anewprinter design that is trying to compete with the $300-400 Wanhao - but costs 800 GBP and doesn't really bring anything better (some parts are even worse, like the build volume) or new. A better controller board would be a start if I am to pay the higher price.And re Mini - it could well be for cost reasons, on a $200 printer every dollar counts. But regardless of that that controller has much more computing power and includes wifi & color LCD. So building an AVR-based board into a more expensive machine makes little sense.

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 28, 2017, 07:39:15 pm
content: Quote from: janoc on June 28, 2017, 07:06:35 pmmarlin is still developed and extended until recently...https://github.com/MarlinFirmware/Marlinthey expanded it with the bells and whistles that i dont need. the marlin version installed in my machine are from 2-3 years back i have no problem with... time to wait for the next stepper motion is more than what the 8 bit processor can do... i believe movement to 32bit mcu is just a marketing buzz... and colorfull lcd doesnt give better print, larger code and development effort, requires many pins, and variety of hardware configuration and complexity, increased cost makes it unworthy in OSHW imho. 20x4 lcd and an encoder switch can do the job, and alot better than PC-USB dependent machine model flooding the market. i dont get the idea why those chaps are still developing no-monitor model while lcd-oshw fw is already available

author: janoc
author_rank: Super Contributor
timestamp: June 28, 2017, 09:18:19 pm
content: Quote from: Mechatrommer on June 28, 2017, 07:39:15 pm32bit boards are certainly not just marketing buzz. E.g. delta or some more esoteric geometries (scara ...) are pushing the capabilities of a 16MHz AVR to its limits already. Hardware support for encoders on something like STM32 allows for proper closed loop servo drive, eliminating problems with "missed steps" or the extruder bumping into something and getting out of position or even easy stops and restarts => more reliable and flexible printing.Higher computational power allows faster and better quality printing too, because the G-code trajectory interpolation can be smoother, you can do look-ahead, you can do fancier acceleration & deceleration curves, better maintain the extruder pressure, better PID for the heaters all the while having a responsive LCD or some other user interface.Of course, one can argue that 20x4 character LCD and a clicky encoder is all user interface one needs but a small touch screen display is not much more expensive and can display a lot more information in a more readable form. Is it needed? No. But it is a nice to have user comfort thing. We have also moved over from text terminals to graphic interfaces - not because the terminals couldn't handle it anymore but because GUIs are often easier to use. Just look at the $200 Monoprice printer and compare it with something like a Prusa i3 which has only the character LCD.And then you can have niceties like proper hardware USB (and not just a UART to USB bridge) and ethernet support. Good luck finding that on an 8bit board.The current 8bit controllers do the job if if all you have is a carthesian machine, but e.g. handling both printing and a display at the same time is a tall order for them already, never mind networking.BTW, Smoothieboard and Smoothieware are both OSHW and OSS, respectively:http://smoothieware.org/

author: C
author_rank: Super Contributor
timestamp: June 28, 2017, 10:38:00 pm
content: Quote from: Mechatrommer on June 28, 2017, 07:39:15 pmIf you look on You Tube, you should be able to find some tests what I think are good tests that show some problems with existing 8-bit mcu. If the hardware is not up to increased speed, then better mpu might not help much.One test is watched appeared to show that the 8-bit processor could print faster with less errors in the 3D print when data came from the SD card instead of serial port. Still increased did not make a huge difference in total print time.With lack of CTS in hardware this makes some sense this could happen. This also creates the question of how hard is it to download from PC serial port to SD Card and then do the 3D print. Cures a lot of problems with out the need to move SD Card from PC to Printer.I think a lot of 3D printer users would not want to hack hardware for hardware CTS. Some would not even want to upgrade software for this change.Think the basics of OP's question is simple.OP's electronics is less capable then a RAMPS board and will most likely cost more. At same time I do not see a big need for a portable printer that prints takes hours to complete and at same time costs more.

author: Nusa
author_rank: Super Contributor
timestamp: June 29, 2017, 12:07:48 am
content: Quote from: C on June 28, 2017, 10:38:00 pmThe feature is generally present, but it's SLOW by an order of magnitude or more over what the PC can do! The Arduino isn't clocked fast enough to run the SPI bus to the SD card at a speed high enough for fast file transfers, nor does it have enough available RAM to implement proper buffering between the USB port and the SD card. Sneaker-netting the SD card to the PC is simply the practical solution. For just reading the file during print, the speed is sufficient.

author: janoc
author_rank: Super Contributor
timestamp: June 30, 2017, 07:40:54 pm
content: Quote from: Nusa on June 29, 2017, 12:07:48 amAlso don't forget that none of the Arduino/AVR based boards have native USB, they are all running over an UART-to-USB bridge of some sorts, slowing things down even more.

author: Nusa
author_rank: Super Contributor
timestamp: June 30, 2017, 10:20:06 pm
content: Quote from: janoc on June 30, 2017, 07:40:54 pmThat's not true, there are a number of Arduino/AVR CPUs with native USB on chip. Check out the Arduino Pro Micro or Arduino Leonardo for examples. Of course, reduced part count doesn't necessarily mean it's the cheaper solution. Nor is native vs external usb implementation going to have any real effect on the speed of operation.

author: janoc
author_rank: Super Contributor
timestamp: July 01, 2017, 10:43:12 am
content: Quote from: Nusa on June 30, 2017, 10:20:06 pmOf course there are AVRs which have native USB, I know that. However, I have been talking about AVR basedboards, which is a different thing. Most you will see are derived from RAMPS, Sanguinololu, Melzi and similar, thus are using ATMega2560, ATMega1280, ATMega1284 which don't have native USB. Unfortunately Atmel in their infinite wisdom has put the USB phy only in a handful of chips and they all have rather limited peripheral selection and pin count, making them unattractive to use in printers. They are also quite expensive.Native USB vs UART won't have impact on the speed of printing, certainly. There the bottleneck is rarely the serial port but the physical constraints of the machine.However, I was replying to a post talking about uploading data to the SD card from the PC while it is in the controller. Even my 250kbps Mendel90 with a Melzi board takes ages to upload any larger sized file like that. That's 1/5th of the bandwidth of low speed USB, with most MCUs having native USB phy being capable of high speed - 12Mbit/s. And it is certainly still a lot slower than the achievable writing speed of an SD card, even when driven over the slow SPI interface.

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 01, 2017, 10:59:56 pm
content: Quote from: janoc on July 01, 2017, 10:43:12 amthe same with rigol ds1000z when saving data (csv) to usb drive (pc to usb drive uploading is not available), i know data to usb-pc transfer is a lot faster, so i made a program for it. heck i mean why make something that is not its true purpose as the selling point like its the most important aspect of it? why use the slow feature when we have this at $5 or less?...i have no problem printing directly from usb, the 8 bit avr is not throttling, but my space will not make it so convenience, and i dont like the idea of "PC has to be on and ready for 10++ hours of printing", and "when the PC got hanged due to i'm playing with other unstable program, the printing will stopped making the half-printed abs/pla will go to the trash". so my preferable solution will be the above device, and very little movement to transfer sd card few meters away, should be good enough as a slight fat burner to my body... and while printing independently, i have peace of mind using my pc, and switch it off anytime i want to... ymmv..and the golden question is... even if it has usb natively in cpu, it has all the whistle and bell for the purpose, resulting the end product price is more expensive than competition, are you going to buy it?

author: janoc
author_rank: Super Contributor
timestamp: July 02, 2017, 09:33:47 am
content: Quote from: Mechatrommer on July 01, 2017, 10:59:56 pmWho said it has to be more expensive? The Monoprice Mini is a $200 printer with a color display, 32bit microcontroller board with both native USB and wifi.Now I am not saying that this should be a benchmark, because most will not be able to harness their economies of scale, but it should give you an idea and the machine is out there, being sold, so it cannot be ignored. Most printers with 8bit controllers sell for at least double and many print significantly worse and have all sorts of worse reliability issues than the Mini has.That's the whole point - those "bells and whistles" can actually cost less if you do your homework. The controller board is nothing super sophisticated that would have to cost big buck.

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 02, 2017, 01:35:26 pm
content: Quote from: janoc on July 02, 2017, 09:33:47 amsad it can only print around 10cm x 10cm x 10cm... i wish there is bigger version at cheap price... well the mini has to be that cheap in order to compete with other 8bit avr printer that can print bigger... for eg this prusahttp://www.ebay.com.my/itm/DIY-Self-Assembly-Auto-Leveling-3D-Printer-High-Precision-Acrylic-Frame-Prusa-i3-/152522573436?hash=item23830dc67c:g:l5AAAOSw32lYnX6l... (it was twice the price when i bought mine without a monitor) to be fair though, those oshw china version are not that sturdy, some part are made from abs 3d printed themselves they are not heat resistance, modification/replacement is needed soon, so some mechanical design skill will be needed (i can see some improvement on the latest design). for capable tinkerers alike, this still a bless because both hardware and firmware are modifiable, not sure if we can hack monoprice fw (or hw) to make it print bigger.. anyway this is personal preferences, i can also find some issues with monoprice mini printer in the net as well... ymmv..

author: janoc
author_rank: Super Contributor
timestamp: July 02, 2017, 02:47:40 pm
content: Quote from: Mechatrommer on July 02, 2017, 01:35:26 pmThe Mini has print volume of about 12x12x12cm, so it is actually slightly bigger.However, the Mini is not really competition to the various printer kits like that crappy plastic Prusa but more to the appliance type printers where the user wants to plug it in and use it without having to spend a week assembling and making it work first.I am actually pretty sorry for anyone who buys one of those Prusa kits today - even if the kit is of good quality (not all are), the basic mechanical Prusa i3 design has some "features" that make it very hard to tram the machine and to keep it square over time (like the fixing of the Y axis to the frame or the ensuring the squareness of the Z axis vs the X-Y plane). That is why I have actually bought Nophead's Mendel90 kit back in the day instead of a cheaper Prusa kit. Mendel90 is basically the same design as Prusa - but done right, so the machine is easy to align and it stays in tram. It is also a lot more rigid (no "z wobble/banding" and similar nonsense).So it is cool that you get larger build volume for the same price, but if the frame twists and sags in various ways while the machine is running or is not square, then what good is it? Also while the print volume is theoretically 20x20x20cm, very few of these machines can actually print that large - mostly because the object won't stick to the bed or will warp (it doesn't heat uniformly and the corners are cold). I think the only one that I have actually seen doing that has been the new PRUSA I3 MK2S which uses much more advanced print bed. But that's a 1000€ class printer and uses a $170 Rambo controller board with Mega2560.These kits almost universally produce crappy printers unless you are willing to spend huge amount of time maintaining the machine and replacing parts with better ones. Some people love that but many just want to use the machine and not to be constantly repairing it. My time is worth more than that.A more fair comparison would be something like DaVinci Mini - 15x15x15cm build volume, DRM-ed filament, non-standard proprietary software and costs $300. Or one of the Printrbots which are in the same category. For 99% of work people use these things for the print volume is sufficient.