Mentioned elsewhere, I talked about the inherent pros and cons of different linear mechanisms.
It seems like a hidden cost of making a printer is just establishing good, smooth, precise linear motion. You can:
go expensive with commerical linear slides,
go squircle with plastic bushings (and zero maintenance or lubrication)
-go Sk8r Boi with lots (and lots) of rolling carriages a la quadrap
-go linear bearing and have lubrication goo marking up your hands when fiddling about with the hot-end…and they’re not entirely silent.
-go bronze bushing…
-go ???
So I’m a little light on bronze bushing experience, I’d imagine they’d have similar lubrication requirements as linear bearings.
What am I missing? Are we overlooking the out-side-the-box solution to all our problems? (Fluorelastomer over black iron pipe will be the new-hotness)
What’s the ultimate Venn Diagram solution that’s cheap, precise, and maintenance free?
Plastic bushings can be accurate, you’ve just gotta have the right press-in fit for them. LM8UUs and the like are far from silent because we’re under-loading them. It’s not enough to even have the balls circulate. I’m sure you’ve noticed that if you press on your bed with LM8UUs installed, they become near silent. Personally, I like the Delrin V-wheel on T-slot myself. But I haven’t found a method that I particularly like for an overhead gantry.
I have good luck with the sintered bronze bushings. They require no lubrication. basically zero maintenance. They have oils baked in during manufacturing.
Wheels on V-slot is my current favorite as well, just wish I could make them a little more compact sometimes. I’ve been meaning to try the expensive linear slides, though they are, as mentioned, expensive.
I like the linear rectangular rails. They’re overkill but they give me considerable satisfaction. I’ve been buying used ones though. Apparently new ones aren’t expensive if you can buy them in bulk, not sure how to work that into a DIY design.
I like the wheels on extrusion solutions, my only gripe is that there’s an awful lot of exposed moving things. All the more better to grab the hair of an over-curious observer. If a fully enclosed device is a goal, carriages on extrusions add a lot of complexity when they were originally used to reduce it.
More to the point, there’s cost in the frame (a well designed sheet steel frame will be cheap and stiff, but us hobbiests are pretty much stuck with bolting sticks together)…the brain, the guides, the extruder…all are costs that could benefit from further cost savings. The simple metal hits a target for cost BECAUSE Brook has access to the tools to create a precision cut and bent steel frame. If the hobbiest wants to duplicate that envelope and doesn’t have access to laser cut plywood, well, they might as well make it larger, because they won’t make it cheaper.
You need both rigid frame and high tolerance components. It’s only as strong as the weakest link. If you self source it could be around a grand in just parts for a 200 sq/mm bed. I agree that using engineered wood frames isn’t ideal for a higher end machine but they’ve got their place on low end machines.
I’d be curious to see specific examples of delaminating wood and heat damage. I don’t use them except for entry level machines but there are a few of our entry level i3 units in the farm. I’ve got one here now about 10 months old with cycle time per machine usually 8-10 hours a day many days up to 14, six days a week depending on the job. There is no appreciable heat build up in the frame or bed @ 200 hot end, 60 bed as measured with an IR pyrometer. Until the low cost printers start being made by stamped frames and injection molded parts the lower cost materials like engineered wood products will offer the best value at the low end.
@Mike_Miller That’s a great point and the difference between DIY and a finished consumer good. Reaching critical mass to have machines stamped isn’t too difficult and more are doing it. You have to be able to ship enough and have the numbers to justify it. It’s faster and cheaper but you need to commit to larger quanities. There are plenty of places in the US or even Mexico to get finished parts. Type A uses a stamping plant in Nor Cal.
I have now gained some experience with v-slot extrusion with metal wheels. Though wheels and carriages are my own design, that wouldn’t make difference.
Metal wheels wears out the aluminum pretty fast when they are tightened to correct backlash. When most of prints happen in the middle of bed, rails are worn to sloppy in there(horrible sound when wheels resonate). And on the sides they are almost too tight. So if you want to use v-slot and metal wheels, there should be spring loaded tensioner for it. Or use plastic wheels.
Since I’m trying to build rigid, solid and accurate printer which will last, these v-slot rails aren’t my choise. I’m moving to 12mm chromed rail, but not sure which kind of bearings. My printer is now H-Bot but I’m going to change it to Core-xy. Therefore it’s important to have good quality bearings on x-ends so it wouldn’t wobble around. Maybe the most interesting opinion is to machine out bronze bushings by myself. I could do them with very good fit, maybe with +0.03mm bore or something like that. Only negative thing in my mind is that they wouldn’t flex at all, so rails need to be absolutely straight!
I have read very little about bronze bushings, even many commercial printer uses that kind of linear bearings(makebot, xyz davinci etc…)
It would be nice to hear others thoughts!
I use printed plastic glider with 4mm ptfe tube spacers between plastic glider and glass towers(delta printer), lubricated with Wynn’s Winflon ptfe superlube - Cheap and easy to make.
After experimenting with most of the things you mention, I’ve gone back to LMs. Sure, they are noisy but I care less about noise and more about a cheap smooth linear motion platform that will scale.
I think your experience with wood depends GREATLY on the local micro-climate. In arid Colorado, you’d probably be fine, in Equatorial Asia with a MUCH higher humidity, your experiences might differ.
I started at University and haven’t had time to finish my build. I also have a lengthy commute every day to class that is doing its damage. There is also a ball screw version being built by a friend. I’ll update asap. Sorry guys for the delay.