What are the current limitations to machining speed and quality?

LowRider CNC Hardware Development
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Our LowRider kit is out for delivery, and we’re squealing with excitement! In the coming days we will order the tubes, and print and machine the parts. I am extremely fortunate to have access to a laser cutter, shop bot, waterjet, FormLabs Form 2, MarkForged Mark Two (with continuous strand CF), and many other fun toys. (Although since MIT just shut down we’ll see if I have access to any of it. :open_mouth: )

My goal is not to build the world’s best LowRider, I’ve seen the quality of the work on this forum and my meager skills don’t hold a candle. However, I feel like I can help push back the darkness a little bit by exploring ideas which would be too costly to do without such easy access.

So far, I’ve understood that the challenges are weight, cost, availability, and high-tolerance jobs. (Which I think really shows the genius of V1Engineering, which has done a superb job of eliminating the hardest problems: design, calibration, and successful build completions.)

I’d like to have more insight into each of these four groups, to take a stab at seeing if the 80/20 rule (80 % of the gains come from 20% of the efforts) still applies here.

For instance, the weight of the endplates could be halved by making a tileboard/foam/tileboard sandwich, 4x8 sheets of which can be found for $10-20 at your local home improvement store. Making this accurately is challenging and time-consuming, unless you have a laser cutter doing the hard work. Then it becomes as easy as assembling legos.

Likewise, the MarkForged Mark Two prints using Onyx, a special Nylon/chopped strand CF filament, and can embed continuous strand CF into part layers. It’s way too expensive for doing the entire build, but if we knew that critical parts were the bottlenecks then this could provide a relatively inexpensive (5-$20) upgrade path.

I’d love to hear from you guys about your challenges before I click print.

Thoughts?

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I was looking into this… it’s also possible to get aluminum/plastic or foam/aluminum sandwich material that is available from sign shops in thin format sometimes as offcuts you could double up but if you want the thicker stuff it’s mostly used as building cladding then you have to buy huge quantities but that might be ideal.

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I have printed carbon fiber and while being very rigid it’s also very brittle… I think the first time you have an issue where the carriage drops on one side (happens more than you might think) it would crack.

I reprinted my top clamps in PC+ filament and I was able to tighten them to the point the pipes don’t slip which I couldn’t do with PLA. Also I reprinted the rest of the parts with 100% infill PLA and it helped noticeably with rigidity.

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Cool to know about PC+. (I was today years old when I learned you could print in polycarbonate.) MarkForged’s onyx is a nylon filament. My experience with in diverse sectors it is that it’s very tough without being brittle.

Which tubes were slipping? I’m surprised that any of the forces are high enough. Was it a dramatic slip or were the tubes slowly working their way forward inside of the clamps?

That’s a good data point. Could you elaborate on it some? Specifically, in which parts did it help? Was it a visible flexing when you pushed on it, or was it something you could observe in the finished part?

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Good point… I just checked and I was using CF PLA. That was super rigid, the nylon might help with that. I found I had to go to a 0.6 nozzle to avoid the fibers clogging.

When assembling I tightened until just barely to the point I couldn’t twist the horizontal pipes in the clamps… eventually the PLA failed after a couple months. Another alternative might be to put some masking tape on the pipes to give them traction and tighten less. PC is more flexy than PLA so everything is a tradeoff.

I had some sagging in my carriage … when I disassembled it there was some warping in the PLA pieces the roller wheels attach to. The Y plates also were twisting at the ‘dog ears’ where they attached. I reprinted those as well as the bottom clamps at 100% infill and it helped. I also recut my Y plates out of baltic birch but still had some twisting think something more rigid or bigger ears would help.

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That’s amazing. I like how you are thinking about this. My own understanding is that all these parts are like compliant mechanisms. You stress one thing, the strain gets transferred to another part that might not be able to compensate. I will be interested in your results with the Onyx, even though I wouldn’t be able to replicate. It would be one more datum for the calculations.

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Or, if you had hand-cut the initial pieces from cheap/scrap ply, perhaps a handy CNC machine that could mill the parts for you? :smiley:

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Ideally, all the parts are designed to be equally “just strong enough” like the Deacon’s Masterpiece. 8^)

I used NylonX carbon infused filament in my Lowrider. This is definitely not as rigid as PLA, but is also much less brittle and much “tougher”. Most of the 3d prints I make are functional parts, and I like everything about this filament except the cost.

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I originally started out with a MPCNC that i printed up in PETG. While I do perfer to print with PETG mostly, it had too much flex for my liking. I printer all my LR2 parts in PLA at 55% infill. I have not broke or cracked any 3D printed parts so far. I think a lot of people tend to overthink the build by looking at it initially. Also wood is very forgiving provided that you don’t try to run too fast with this build. :beers: :sunglasses:

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