First Build Suggestions for Semi-skilled Newbie?

I am currently in machinist school. I have some experience with drafting, mechanical engineering, electronics, and Arduino. I want to build a 3-D printer for my final project. Budget is not a big issue, but I don't think I could spend more than 300 hours on it and graduate in time. The printer build would need to show several machining techniques. Also my instructor will be teaching me G-Codes or M-Code next year, so I would prefer it operated on that. (I don't know if they all do.) I don't really have any expectations for what type of parts I will be able to print in the end, but I would prefer to use the cheapest plastic medium possible so I can make whatever I want with it later on and not feel foolish for making a $1 toothbrush that costs me $10. What would be a good printer to build with these parameters in mind, please?

Edited 1 time(s). Last edit at 01/09/2015 03:02AM by repraprip.

A popular one is Prusa i3 but if you don't care about build size I myself would make a Mendel Max (don't know why but I always liked that machine). You can either buy a complete kit or source all the parts on your own and just buy a plastic kit. If you buy a full kit I think you would be hard pressed to spend 300 hours on one, probably more like half that if you take your time. If you built stuff like this before maybe even a long weekend. However if you need to engineer something (for a class) then a kit may not work as it's mostly just bolting things together then wiring and adjusting and testing.

As for plastics, the 2 most popular are ABS and PLA and the price is about the same for both (a toothbrush sized item might cost you $0.50 to $0.75). A 3D printer is one of those things you did not know you needed until you have one then you can't imagine living without one.

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tmorris9
A 3D printer is one of those things you did not know you needed until you have one then you can't imagine living without one.

QFT!

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If you bought a Prusa i3 kit then it would probably take less than 20 hours for someone with engineering and electronic skills to build.
There are various parts that you could then machine yourself as upgrades once you have worked with it a bit.
Perhaps machining an all metal hotend? A metal extruder gear? A lighter carriage?
However I think a Delta printer would give more ways to play with machining skills so perhaps a Kossel would be more suitable.

What about a CoreXY? Frame is pretty straightford, then you could machine the hot end and extruder as mentioned as well as an intricate case.

I really appreciate the advice. It totally got me started. Thanks, everybody! I have to build the frame myself (no kits allowed), and hopefully I will have time to build the extruder head as well. After researching your suggestions I think I'll go with threaded rod design as my experience with belts hasn't been great. I was wondering if any of you know if the heated table stays on for the whole process or if it is just necessary in the beginning? Also if I put bigger motors will the software still work the same?

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repraprip
I have to build the frame myself (no kits allowed), and hopefully I will have time to build the extruder head as well.

There are kits that are essentially materials only, all the nuts, bolts, screws, etc. So it's not so much a kit ready to assembly, but just a kit of parts already collected. Typically plastic parts are printed but if you have to machine them, I'd double check the design of all the parts to see how conducive they are for subtractive manufacturing. Sometimes there's pockets and channels that may be difficult or impossible to machine.

Also, I'd really recommend using a commercial extruder. Consider it similar to a stepper motor...you don't have to make that from raw materials, do you? You'll save yourself a ton of heartache as a extruder can make or break a printer.

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After researching your suggestions I think I'll go with threaded rod design as my experience with belts hasn't been great.

Threaded rod is SLOW compared to belt unless you have a high lead, but then you lose resolution. Having a slow z-axis isn't usually a problem as it's only moving a fraction at a time, but in the X and Y axis it'll really slow down your printing time. Belts aren't that hard to work with, and some designs don't even use belts. They use fishing line or similar materials instead.

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I was wondering if any of you know if the heated table stays on for the whole process or if it is just necessary in the beginning?

Varies with the printer, what's the object is that is being printed, and the material type. Different materials have different characteristics and peeling, warping, delaminating, initial adhesion, etc all are issues that can happen. The slicing software usually has parameters that control what the desired temperature is for the first layer as well as second and higher layers.

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Also if I put bigger motors will the software still work the same?

Yes. Bigger motors usually require more power and you may have problems with your stepper drivers supplying enough current without overheating. You may also need to adjust your speeds depending on the characteristic of your motor but the software itself, whether you're referring to the slicer or the firmware, will work the same either way.

Standard threaded rod is horrible compared to belts. You get awful backlash, cyclic errors and extremely slow speeds.
Multistart ACME with zero backlash nuts are great, but things start to get expensive.

There is nothing inherently wrong with belts, its just that most implementations suck. If you actually read the engineering documents on designing linear belt systems they explain you need substantial tension for maximum performance. We are talking 10-30lb per axis, even with small GT2 belts. I bet 99% of existing printers would fold in half if you applied the recommended tension.

There are enormous CNC routers that use wide steel reinforced belts under extreme tension and can hold <0.001" no problem.

Edited 1 time(s). Last edit at 01/14/2015 01:14PM by 691175002.