Help me with an initial project spec

Hi guys,

This is my first post on here, though I have been trolling for a while.

Background: I started thinking about building a CNC router/aluminium mill back when I had a large garage/workshop. This was to help me build some speakers, and the enclosures for DIY HiFi components. I am fortunate enough to work in Tier 1 Automotive and as such have access to large numbers of scrap/decommissioned machines. As such I have a useful collection of linear bearings and aluminium extrusion T slot sections.

Recently, as often happens, splitting up with my fiancée and moving in with a less disturbed significant other has meant my only work space is a spare room I am slowly converting to a man/cave/office/reluctant spare room. This has meant my plans have had to change. I wanted to build an all in one Cartesian machine that could 3D print, cut aluminium, plastic and wood and perhaps be accurate enough to cut custom PCB's. Ehilst speccing this machine I realise that the most successful 3D printers, have very low moving mass and move a lot faster than the required speeds for cutting and milling, with a lot less torque. On reflection it seems unlikely that I could build a machine that is capable of the high accuracy and speed as well as being strong and stiff enough to be a useful CNC machine.

This has leant me toward Delta 3D printers for purely printing work and a separate, more beefy (and therefore expensive) Cartesian machine.

I have been lucky enough to score 6 AMT linear bearings with 15mm by 700mm rails. The bearing blocks are numbered: MSA15E-N, a 15mm pillow type. The rails are 700mm long and have the part number MSA15R-N. These look perfect for a Delta printer. I have got my hands on a few off cuts fo aluminium that can easily be turned into a 'head' and have a load of 40 by 40 t slot extrusion.

I am writing this to get some billy basics from you guys:

Examples of existing metal framed/linear bearing delta printers
Which control electronics, steppers, heated beds, etc work well for Delta prints.
Where is a good source of light, strong and high precision turnbuckles/ball joints?
Is the bowden system this type of printer uses a pain in the arse?
etc etc.

I am currently sat in front of AutoCAD designing up ideas and am wondering about the mechanics of the design. How do I effectively choose the length of the turn-buckles? What soze should I aim for my print platform (therefore volume)? What are the pro's and cons of long turrnbuckles vs short ones.. Etc etc etc..

Your input and help is greatly appreciated.

Kind regards,

Jai Stanley

Edited 1 time(s). Last edit at 10/27/2014 08:53AM by jaistanley.

I built mine as a frankenstein rostock derivative. I used nema17's sourced cheap on e-bay and a ramps 1.4 with discount lcd. I hear you have to stay away from the full graphics controller on deltas as the arduino does not have enough hp to run it and the delta.

If you take a look at my blog, I went through the build process, still refining the design. I will be using some high precision joints in the near future as I upgrade this thing slowly. I am going through a move at the moment, and the delta is waiting on a new hot end. So I will be quiet for a bit of time. I am also gearing up to make it heated.

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My Personal Blog. Build blog.
[engineerd3d.ddns.net]

Modicum V1 sold on e-bay user jaguarking11

Hi Jai,

You will really need to explore this entire website. Really.

I am completing a large format delta.
- I recommend getting 32 bit electronics if you can - like a Smoothyboard. See here and here.
- Info on steppers here. Almost all repraps use Nema 17s. I used much higher torque, double precision Nema 23 steppers from here for the three towers and the direct drive extruder. I recommend making your motor brackets very heavy, as they will be quieter.
- Heated bed - depends on the size and shape you choose. The bed does not have to be round. By making the arms a bit longer the bed can become more triangular. My printer is an example. You may have to make your heated bed if the size is not a set size like round or square 10", 12" etc.
- Turnbuckles/ball joints - I didn't use them as I made magnetic joints. These have there own issues.
- The bowden system is a must for a delta. Some of the issues are being addressed in firmware such as algorithms for pressure control in the dev version of Repetier, and I think Marlin has it also. BTW, a little oil on a cloth wire-tied around the filament just before the extruder both cleans the filament, and lightly lubricates it. For PLA this may be a must as it is stiffer and rougher than ABS. I use it for ABS too and it works fine for me.

I spent a year in research and design, and about 6 months building as I started from scratch on every part. It would be much faster to use an existing design, but it's fun not to.

Good luck on your build.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

Hi guys,

Do, after a bit of tinkering on AutoCAD and scouting though the parts I've collected over the last few months I put together the start of my frame. I'm still in the designing phase (can attach drawings for those that are interested) but actually putting things together with what I have has helped no-end with understanding what the requirements are. Obviously, with so many bits being constrained by what I actually have, rather than what I would design from scratch I am constrained slightly: but the results so far are extremely promising!

I spent Friday afternoon mocking it up as seen. It was like playing grown-ups mechano as I have loads of bits of hardware I have saved from the scrap pile over the years.



Please bear in mind that I have had to do ZERO machining so far, as long as you don't count saw cuts as machining.

It's VERY large! I knew that a delta design will usually take up a larger space for the same given print space, but this thing is HUGE! I love it.

I hope to get 3mm stainless brackets laser cut for the stepper motors, and to hold/constrain the upper and lower spars at 120 degrees to each other.

I have the proximity sensors on l brackets that will hopefully act as both physical end stops (the bracket itself) and adjustable limit switches. I haven't yet worked out how you drive these, but an engineer at work tells me they are 24v pnp. I'll have to look into that and may end up using micro switches to start with. I also have a couple of smaller Balluf proximity sensors that I hope to use for automatic bed leveling on the indefector.

Speaking of which, I intend on getting the indefector and the carriage plates cut by a friend at work in 3mm carbon fibre sheet. He has an open-builds CNC router he recently built and loves. Hopefully the CF will be dimensionally stable, and very light. I want to mount the extruder/extruders on the indefector directly so I can print flexi/hybrid parts too. I can see a real use for these parts as flexi joints or dampers.

Feel free to feedback on things you think I could do better/a different way/an easier way.

Currently I think I will take the 6 corner brackets I have and have an idler on each, with skate bearings and the belt strung between them. The steppers would then mount to the frame at the bottom and link to the axle of the bottom idler with a belt/pulley system. This would be so that I could experiment with different reduction ratios without having to rely on micro stepping. Do you think this is a good idea? I am keen on getting very high precision with a lesser risk of missing steps etc.

Many thanks for any input:

Jai Stanley

Edited 1 time(s). Last edit at 11/26/2014 02:31PM by jaistanley.

@ Paul

Hi Paul,

Thanks for the reply. I was in two minds about which stepper to use: I haven't done any calculations or anything, but was concerned that my setup will be heavier than the smaller systems thus have more intertia and require more torque from the steppers. For the price of them, I may as well go for the Nema 24. Which ones though? I'm not yet fluent in this. Which of these: Zapp would you recommend? I am aware that the maximum current of many of the drivers seems to be limited to 2.5a so perhaps some of the 2.1a Nema 24 bipolar motors? Will these be OK running on the typical drivers found in all in one boards such as smoothie or the azteeg x5?

I am hoping to use a smaller, geared stepper for the extruder as I'd really like to use a direct setup, hopefully a dual extruder at at a later date to make hybrid flexi/abs parts. I know this adds weight to the indefector, but hope that strong motors and frame, as well as weight saving elsewhere will make up for this somewhat. I'll have a search through the forum to see what the general concencus is.

From what I have been reading, I have already been considering using a 32 bit board. Lots of reports of the 8 bit boards struggling with the delta maths and large lcd screens lead me down this route. My only concern is that as a new-comer I was hoping to use the many online tutorials/youtube videos about firmware such as repetier host or marlin to get me started. Do the 32bit boards have the firmware compatibility? Is the smoothie firmware as easy to use/configure/comparrible to the others?

Thanks again for the feedback.

Jai

Jai,
I'm considering upgrading to the Azteeg x5 myself which is a Smothie derivative, and uses the smoothie firmware, as it has the drivers I want that use higher voltage. From what I've read, I think the ease of settings will be at least as good, as well as the features. You are supposed to be able to install new firmware by just putting it on memory card. Those that have it could comment from experience.

You can use Nema 23 motors that have a higher current rating than the drivers. You will not be able to get the maximum torque the motors could provide (since the drivers only put out so much), but they will still be very strong. Make sure you install good heat syncs on the driver and use a good fan or you will get thermal shutdowns.

I do not recommend mounting the extruder stepper on the effector, and here's why. When your printer is doing infill, that print head is moving back and forth rapidly and rhythmically, at different frequencies depending on print speed and part width. Your printer will find a resonant peak there, and if the acceleration is high enough, the resonance will be enough to cause it to miss steps, even with Nema 23s. A heavy effector will make this much worse. You can mitigate this somewhat by lowering accelerations, and there is also a "frequency" setting in Slic3r (that I haven't tried yet) that may also help.

Off the top of my head, there are actually at least four important variables - two in firmware: acceleration (for moves and printing),and jerk (determines starting velocity (1/2 jerk) and max velocity change before acceleration is used.), Print speed and "frequency" are set in Slic3r. These all will need to be tuned so you can print as fast as possible and do not miss steps. This can make things tricky at the beginning, as the defaults that come with the firmware are bogus - they were put in there by the last person that tested the firmware - someone who has a completely different printer than yours. Also some settings like Jerk and Acceleration affect each other. There needs to be better guides for tuning them! At the beginning you will want to lower print speed to between 30 and 60 mm/sec, lower accelerations drastically, and then test printing repeatedly, (first calibrating your extruder) printing many small but tall test pieces to determine how fast it can print and accelerate without shifting. Change only one thing at a time. Depending on your motor torque, the jerk setting can most likely be left at the default, and possibly even raised. When you start testing I recommend posting about the issues you are having and include your configuration.h.

With my printer I can print a vase using a spiral path at 200mm/sec with no problem, but if I try to do infill at over 90mm/sec it will shift - because of the resonance. I'm still working on that, and I'm sure I'll resolve it. I'm working on lightening things up also.

Regards
-Paul

Edited 1 time(s). Last edit at 11/28/2014 04:39AM by Paul Wanamaker.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

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jaistanley
From what I have been reading, I have already been considering using a 32 bit board. Lots of reports of the 8 bit boards struggling with the delta maths and large lcd screens lead me down this route.

Smoothie not only does the math faster in lots of areas, but it also does it more correctly ( in 8-bit electronics with deltas the speeds you reach are not actually the ones you requested ).

Quote
jaistanley
My only concern is that as a new-comer I was hoping to use the many online tutorials/youtube videos about firmware such as repetier host or marlin to get me started.

Smoothie ( at least when using the Smoothieboard, the Azteeg X5 does not have the same level of documentation ) is very well documented in the Smoothie wiki.
We even have guides : [smoothieware.org]

Quote
jaistanley
Do the 32bit boards have the firmware compatibility?

No, they use a new firmware ( the Smoothie firmware ) that was coded to take better advantage of the 32bits platform, and be easier to use/configure, amongst other things.

Quote
jaistanley
Is the smoothie firmware as easy to use/configure/comparrible to the others?

It's actually much easier. Instead of having to open the Arduino IDE, edit code, compile, and flash the board each time, with Smoothie all you need to do is plug the board in, edit a text file, and you are done.
There are also example configuration files for different machine types ( for example deltas ), and documentation of the configuration options on the wiki.
We hear from quite a few people that are surprised/happy how much easier it is to configure/use.

Cheers.