I poked around a bit and found the Zen Toolworks 7x7 machine is about right for price and size, and they've recently released a variant intended for 3D printing. It is the same as the standard 7x7, but has an extended height gantry that allows about 5 inches of table clearance.
I assembled the machine, but made the mistake of installing the Z axis plate the wrong way around, so that it hangs down into the workspace:
Oops. Obviously there isn't much table clearance here. It only takes a few minutes to remove and flip it.I also built some Linisteppers that I intended to run the machine (that's them at the lower right in the image above). Unfortunately Linisteppers won't run the 4 wire NEMA 17 motors that come with the machine. I have some Pololu drivers coming, but I didn't want to wait around to get the machine moving, so I pulled some old 6 wire steppers from the junkbox (the blue motors on the mill table in the image). These are NEMA 23 though, so I needed to adapt them to the machine.
Since I don't yet have a 3D printer that I could use to whip up some mounting and coupling adapters, I went with something lower tech:
The shaft coupler is made of 1/4" I.D. polyethylene tubing, with a smaller diameter piece over the smaller shaft. I went with polyethylene instead of vinyl because it is more ridged, but it's also more slippery, so there might be some potential for loss of position during sudden acceleration. It's all held down with little worm gear hose clamps.It's functional, but not nearly as pretty as the couplers supplied with the motor.
I'm putting off boxing up the drivers and moving the machine to it's home in the basement until I know what the final configuration will be. I want to compare the Pololu drivers to the Linisteppers before I decide what will be running the machine. The Pololu drivers will run the original motors, which from the specs appear to be about the same as these old salvage motors, and they are about a 10th the size of the Linisteppers, but the Linisteppers have some interesting points, and with the PIC MCU I have the option of doing some interesting things with them.
At this point I've got a Linistepper hooked up to an axis and I'm playing with driving it with an Arduino board. The Arduino has built-in USB, so I can send single-axis movement commands from the PC that the Arduino turns into step and direction commands to send to the Linistepper. Simple moves with no velocity ramping work nicely, and I can start at about 200 RPM (about 10IPM). That's actually not terrible, but I'm sure it can do a lot better with velocity ramping.
I'm writing some Arduino code to do velocity ramping based on the math from this EETimes article. Once I have that working for linear velocity ramps (fixed acceleration), I want to set it up with a table of acceleration values to see if a non-linear ramp (acceleration inversely proportional to velocity) improves the performance any more.
I had planned on running the machine with an old PC with a parallel port, but if I can get the Arduino working the way I want (2 axes per Arduino), and if I can get well coordinated motions with two Arduinos, I might just go with a USB controlled machine using 2 Arduinos as stepper driver drivers.
7 comments:
I really would like to get into the 3D printing scene and Zen Toolworks 3D printer kit seems to be reasonably priced, but I haven't been able to find anyone online that has successfully built a 3D printer using their kit. I know you have to purchase other stuff to get it to work, but knowing how much more money it would cost me to build a 3D printer using their kit would help me decide if I should pull the trigger whether I should purchase it or not. How is your build coming along?
I have the mill running, but I don't have an extruder for it yet. What I've found is that lead screws for the X and Y axis make it horribly slow compared to the usual 3D printer setup with belts.
I have some belts and some designs I did for converting the leadscrew design to belt driven, but I haven't gotten around to printing out the parts yet (with the RepRap at the local maker space).
Overall, I'd say that this is a workable solution, but I think it is more interesting in it's mill form than as a 3D printer.
For the money you would be much better off building a Darwin, which you can complete for around $350. With this you'd be $350 in and not even have electronics yet, and they are the most expensive part.
It think I probably will not end up converting this to printing. Instead I'll brace up the gantry to fix the rigidity problems and use it as a mill.
Wow, thanks for responding so quickly. I had looked into Reprap’s a long time ago, but from what I remember they looked difficult to build. But for $350, I think I better take another look at them. I did a quick Google search I came across three Darwin 3D printers, the Classic, RepStrap Darwin Clone and Non-clone RepStrap. Which one should I be able to build for $350, the Non-clone RepStrap? It would really be cool if I could purchase a kit of some sort, kind of like Zen Toolworks kits, do you know of any good places where I can purchase a complete kit? I only ask because you seem very knowledgeable about this stuff. Thanks in Advance.
I said 'Darwin' but what I meant was 'Prusa Mendel'. That's what we have at the maker space, it's probably the most popular rep rap at this time. Darwin is an old design that you won't want to build.
Try this link:
http://www.plansandprojects.com/My%20Machines/Prusa_Mendel1/
It's a decent project log of building a Prusa Mendel, which should give you a pretty good idea of the sort of problems you'll run into.
I'm not up on parts sources, but most of what you'll need that isn't 3D printed parts you can pick up at a hardware store. It's tedious to get them all if you're just buying what you need, so there are kits that have most or all of it collected together for you.
If you get a kit, look for one with linear bearings instead of bushings. They work better and are less hassle, for not that much more. Also plan on a heated bed, and I recommend buying a complete hot-end for about $75 to save yourself a lot of work.
You can spend a lot more than $350 on it of course, depending on how much you do yourself instead of buying, but if you make cost your first priority you can stay in that range.
Thanks for the information and the link looks to be a good starting point. I don't know how much I would be able to do myself, but you probably saved me a lot of time and money.
Have you made any advancements toward using the 7x7 3D as a printer or did you go ahead and convert it into a mill?
I went and got the 3D model thinking of using it the reprap controller (Sanguinololu) but can't get any of the settings write -_-
I haven't put much effort into getting it converted over. I have access to a 3D printer at the local hackerspace, so my motivation for getting it done has been pretty low.
I still plan to do the conversion at some point. Now that I have a process for getting parts made I'll be more likely to get done the motor brackets for converting it to belt drive.
I still need to build or obtain the extruder and hot end and all that though, so there's still a lot I'll need to do.
What sort of problems are you having with getting it working?
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