Jumping into 3D printing from CNC

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JNOV
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Joined: Thu Feb 01, 2018 2:53 pm

Jumping into 3D printing from CNC

Post by JNOV » Wed Feb 07, 2018 5:34 pm

Hi --I've a fair a mount of experience machining parts with a heavy duty CNC machine. I want to/need to get a 3D printer to augment my capabilities but am at the bottom of the learning curve. I think I've settled on a filament-based, rather than resin-based, machine. I've done some research on the FFF contenders, and I like what I've read and watched regarding the M3 independent dual-extruder model. One question I have about the M3 machine is why doesn't it have an enclosure? It seems like it should be relatively simple to fabricate one, but if that's true, why doesn't it just come with one? From what I've read, it seems that warping can be a problem (at least with some materials) if an enclosure isn't used. Is that right?

I'd really appreciate any insights you can give me on this point. Thanks so much!

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insta
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Re: Jumping into 3D printing from CNC

Post by insta » Wed Feb 07, 2018 7:19 pm

Warping can be a problem, and enclosures aren't shipped because nobody needs the exact same thing, and they're easy enough to set up on your own. I've upturned a moving box over a printer before, and it worked fine. I normally leave them open, as I'm usually printing PLA or PETG.

There are a few things to wrap your mind around going to FDM printing from CNC:
  • tolerances drop by an order of magnitude at least (depending on your CNC)
  • speed for deep parts will increase substantially, but FDM will not compete with laser cutters or single-pass cuts at all
  • material waste will drop to hilariously low levels
Custom 3D printing for you or your business -- quote [at] pingring.org

Phil
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Re: Jumping into 3D printing from CNC

Post by Phil » Wed Feb 07, 2018 8:26 pm

An enclosure would add significant expense with a limited gain. You can print most things with most any material without an enclosure; some designs using certain filaments will require an enclosure to print well. The cardboard box over the printer can suffice in those, (usually rare), situations.
I have an M2 with dual extruders. Having the extruders move independently, as in the M3, is a big step up, probably worth the added expense. I bought the dual with certain ideas in mind for it, but those ideas mostly evaporated. If you can do your printing with a single extruder, you will be much better off to buy the less expensive, less complicated machine. I use S3D as my slicing software, and it leave lots to be desired for dual printing.
I also own a Markforged Mark II. It is totally specialized with the choice of one and a half materials: nylon and CF-filled nylon. It has no flexibility, whereas the MakerGear is phenomenally flexible and resilient. The Markforged's advantage is having the capability to include continuous fiber in the X-Y plane of the print, making prints stronger and more rigid. If you want to make jigs for a machine shop, you really should review the Markforged line.
All-in-all, I highly recommend buying a MakerGear printer. Use this forum to enhance what you can do with it.

JNOV
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Re: Jumping into 3D printing from CNC

Post by JNOV » Thu Feb 08, 2018 2:18 am

Thanks, guys. The main reason I'm interested in the dual extruder design is to print with support materials. Are there limitations on which main materials work with particular support materials?. E.g., Can I use PLA with ABS, nylon, or C.F. filament?

jferguson
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Re: Jumping into 3D printing from CNC

Post by jferguson » Thu Feb 08, 2018 2:03 pm

Assuming you are designing your projects yourself, and you are pretty swift with the cad software, you'll be blown away by the reduction in cycle time for projects. I may be less adept at CNC milling than a lot of other people, but i find that 80 % of my time in a cnc job is spent dealing with fixtures and contortions to cut the piece without cutting the mill or the clamps AND maintaining some sort of precise relationship among the various milled surfaces. And then sometimes 90% of the actual time on the machine is making fixtures, not the thing itself. And for one part, the burden of the time spent making the fixture to hang onto the workpiece seems disproportionate.

this pretty much goes away with 3d printing. You do need to think a bit about which end of part goes on the bed, and how or if part extensions (cantilevers) will be supported, and where the nice finish needs to be, but this takes minutes not hours. And best of all, you turn the printer loose, go upstairs, pour your beer or ?? and relax. I've found CNC better done by being present and definietely no alcohol.

I needed wing-assembly fixutres for r/c airplanes. Initially I was going to cnc route them from acetal, but they needed to be 1 1/2 inch thick which would have required a lot of material for the number I needed - $$$. The benefit of acetal is that spilled CA clue wouldn't have stuck to it. But the material cost was too much. So I printed them from PLA, and just rpelace the ones which are messed up with spilled glue.

You'll also find yourself just making something that you might otherwise have tried to figure out how to convert from something bought at hiome depot.

And alhtough it's also true of cnc work to some degree, the pressure to get it right the first time is much less, because except for the time spent printing the cost of not having something exactly right on the first pass is much less. I find that most things I do iterate 4 or 5 times while I fix my mistakes and implement the improvements which are never obvious until you're holding the thing in your hand.

I don't have an enclosure and print, so far, only in PLA and PETG. i do have some warping problems of part corners pulling up from the bed, but this is usually fixed by adjusting bed temperature.

maybe 30 years ago there was a great cartoon in New Yorker. Two women are standing in a kitchen where there are dozens of large bowls full of chooped food. "Cuisinart over-run" one woman says to the other. I found exactly seme thing at our place. If it has to be aluminum, then it's a cnc project, Or to higher tolerance, then I cnc nylon or delrin, but otherwise I print. the house is full of little 3drint boxes, electronic enclousres, sensor enclosure, battery cases, raspberry pi cases, on and on.
Last edited by jferguson on Thu Feb 08, 2018 6:35 pm, edited 1 time in total.

JNOV
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Re: Jumping into 3D printing from CNC

Post by JNOV » Thu Feb 08, 2018 3:13 pm

Thanks. Have you had occasion to CNC mill 3D printed parts? For example, if you need a part with a cylindrical extension that needs to be close to exactly 1/2" in diameter to fit a bearing, would you try to 3D print it at exactly 1/2", hoping that the print tolerance would be good enough, or would you print it at 1/2" + some small excess and then CNC mill the slighly over-dimensioned part to 1/2" diameter?

I'm also really curious about whether folks feel that the ability to print support materials is a big deal (and whether there are any limitations on which primary materials, e.g., ABS, nylon, carbon fiber filament, can be used with support materials). To me, it seems that printing soluble support structure would be extremely helpful for printing arbitrary geometries, but I don't have any experience, so perhaps support structures are not as ubiquitously necessary as it seems to me they must be and perhaps physically removing supports printed out of the primary print material is not as painful and messy as I'm imagining.

Thanks again for your insights.

Phil
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Re: Jumping into 3D printing from CNC

Post by Phil » Thu Feb 08, 2018 3:45 pm

JNOV wrote:Thanks, guys. The main reason I'm interested in the dual extruder design is to print with support materials. Are there limitations on which main materials work with particular support materials?. E.g., Can I use PLA with ABS, nylon, or C.F. filament?
PLA and ABS do not stick, so it depends on how the support functions. It is very problematic to use PLA support between layers of ABS.
I printed a test part with ABS and Ninjaflex. I found you can print Ninjaflex on top of ABS, but not ABS on top of Ninjaflex. You probably need to test those other materials together.

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insta
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Re: Jumping into 3D printing from CNC

Post by insta » Thu Feb 08, 2018 4:50 pm

JNOV wrote:Thanks. Have you had occasion to CNC mill 3D printed parts? For example, if you need a part with a cylindrical extension that needs to be close to exactly 1/2" in diameter to fit a bearing, would you try to 3D print it at exactly 1/2", hoping that the print tolerance would be good enough, or would you print it at 1/2" + some small excess and then CNC mill the slighly over-dimensioned part to 1/2" diameter?

Thanks again for your insights.
For bearing pockets, I print them slightly smaller (like .05mm-ish) and just hammer the bearing in. It's just plastic.

Also, dual-material support is a pain in the butt. Don't approach the process anticipating you'll use it successfully. It is far, far better to print multiple pieces and assemble them afterwards.
Custom 3D printing for you or your business -- quote [at] pingring.org

jferguson
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Re: Jumping into 3D printing from CNC

Post by jferguson » Thu Feb 08, 2018 6:39 pm

I haven't milled any 3d prints but I did have to do some fitting on a cover which worked quite well with a mill-file.

JNOV
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Joined: Thu Feb 01, 2018 2:53 pm

Re: Jumping into 3D printing from CNC

Post by JNOV » Thu Feb 08, 2018 7:19 pm

Also, dual-material support is a pain in the butt. Don't approach the process anticipating you'll use it successfully. It is far, far better to print multiple pieces and assemble them afterwards.
That's very helpful information -- thanks. Dual-printing with support materials was the main considerations (aside from the cost, hassle, and limitations of working with resin) that pushed me toward FFF and away from SLA.

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