Frame Prusa i3

I'll make the frame Prusa i3 in aluminum, but now I'm in doubt which frame to use, Prusa3ALU-FREZOVANY-v4 or Prusa3_SC10UU-v1. Someone can tell me the difference between the two and which is better?

Another question I have is if I use the plastic parts of Prusa i3 or Prusa i3 Rework, which is better?

The rework is better. I built a homemade one out of 1/4" ply but wanted the z more precise so i had Fate3d on ebay cut this one for me: [www.thingiverse.com]. It's EXCELLENT. Replaces the z mounts with much stronger and more precise wood etc etc. That's if it is laser cut. If it isnt id use the main frame components of that one and then spend time getting all the mounts VERY VERY precise. Ive also become a big fan of wood for repraps (i thought it was a stupid ida coming from metal machining) because it's fast and easy to modify and trivial to reinforce them. gluck whatever you do

I'm wondering why there doesn't seem to be a dibond version of the i3.

In the SW US Dibond (or ACP as it's called) is much more expensive than melamine an not too much less expensive than aluminum in full sheets at wholesale qty. It needs to be either milled/routed, high power laser or water jet cut. By the time all is said and done it's not that much less than getting a batch of AL cut. At retail I'd have to sell at 60 or so unfinished compared to 80 for AL. I've cut a proto on a Shopbot but for the money I think melamine is a better value. The cutting time on something like a CNC router reduces the yield per hour compared to either laser cut wood or water jet cut AL. Using an sgraber style wood or melamine frame makes the build very sturdy.

Maybe I'll do the Prusa i3 Rework to be better.

I bought a sheet of aluminum, but do not know which type is aluminum. Now I need to send some companies to make the budget of cut, which file I use: Prusa3ALU-FREZOVANY-v4 or Prusa3_SC10UU-v1?

go with the winged backed version. The single aluminium frame version you will end up having to brace the machine which im in the process of doing now

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Check my rubbish blog for my prusa i3

up and running
[3dimetech.blogspot.co.uk]

Use the freznovany file for a single plate. I've built and used several single plate AL machines and did not need rear support. I've also built several wood frames at this point and those did need rear support.

Well funny that I have a single plate version and have to print low speed due to the vibration I'd like too know how your keeping yours from vibrations

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Check my rubbish blog for my prusa i3

up and running
[3dimetech.blogspot.co.uk]

They are ridiculously easy to reinforce. Protip though and i have NO CLUE why it isn't standard. Cut a piece of 1/2" plywood and mount your reprap on it. Add "wings " to the back and this should pretty much eliminate vibration totally. Heck i ran out of m3 screws (got some coming from china heh) so it's missing more than a couple and i have no problems with that (with everything else.. yes). And theres no reason if you have an al frame you cant mount it to and/or reinforce it with wood.

If you get aluminum i would strongly suggest 6061 or 7075 if you can. They are extraordinarily strong, machinable etc. They are pretty much THE al's used in machining by hobbyists.

Yes there are upgrades and yes some prob dont have issues i dont see any issues at 25mm/s but soon im testing a new extruder and what to print between 150 mm/s - 250 mm/s and i know that my frame will definatly shake

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Check my rubbish blog for my prusa i3

up and running
[3dimetech.blogspot.co.uk]

The design of the single plate i3 is 60 to 80 mm/s and using it faster is more than the machine could handle reliably. Even with wings/fins there are other potential issues with an i3 due to other parts of the design or the extruder. For example low cost bearings and rods can contribute significantly to vibration in the machine. That said I think the weakest part of the single plate design is the connection to the frame. For higher speeds I use a Mendelmax 2 design though in production the higher speeds don't necessarily add to the print speed for a few reasons, one being the shape or nature of the object. Some shapes just take longer to print. With an extruded frame machine it's possible to get a more solid frame.

In terms of frame design and material with regards to flex, material thickness has more of an impact than material hardness or alloy composition. For example I cut frames from 6061T6 but as much for the quality and availability of the material. Not all alloys are available in all sheet sizes or thicknesses. The force on the AL frame regardless of the alloy is far lower than the limits of the material. The choke point for the i3 single plate is due to the attachment method not the alloy composition of the AL. I've also tested ACP and now 10 ga steel. For my money the sgraber type melamine or wooden frame will provide the support of a winged metal frame at a much lower price. Once it's tied together it's pretty solid.

You are absolutely right about the designs weakness.. you're wrong about the alloy though. It isnt hardness or tensile or compression it's the combination. For instance pure aluminum would dampen vibration.. it would do it because it is extraordinarily soft and is actually low strength. It is "doughy". 7075 is basically 6061 with some copper if i remember right. This makes it a bit stronger i believe but , importantly it radically changes how it handles stress and it's machinability. 6061 is indeed "hard" but in comparison to metals like steel it is butter.. the point of it's hardness is machinability and form retention. Ideally you should do all of the above. MOSTLY you should change the structure to a box. I have 12" or so long 1/2" ply walls connected to the wings and the entire thing is fastened down to a 1/2" sheet of ply. Ive run a lot around 90mm and vibration has never been a problem. My only problems have been with the hotend and bed levelling

Having said that the biggest improvement would be to get rid of the plastic on the base of the machine entirely and replace it with milled 6061. And machine flats into the threaded rod at precise positions with machined holes (not done on a drill press) so that the alignment is always correct. Imho this is the next big standard change in the i3 especially.

As for parts: ideally we should definitely be using drill rod. I'm thinking we should be using pillow blocks.. not ultraquality but not cheap, on the bed. I honestly think the biggest problem with precision and backlash is the cheap belt setup. We should be using wider, higher quality belt setups. My cnc mill uses some delrin and some al gears etc from [www.sdp-si.com] and the difference is shocking. Their trumotion etc (square tooth) belts are a HUGE upgrade. As ramps prices come down and theres more competition for parts kits hopefully we can spend a little more on quality motion components and save the money elsewhere. For instance.. theres no real reason to use laser cut frames and that can be 20% of the cost of an i3

Edited 1 time(s). Last edit at 07/03/2014 02:55PM by cdreid9999.

With the upgrades suggested the price would be four to five times the cost do an i3. The i3 is a low cost machine aimed at the DIY set. For less than what was outlined one could build a Mendelmax 2. Fwiw zinc is added to AL to get 7075. For an i3 frame one could use 5052 or even 10 ga a569 steel and be fine.

As for the frame cost, in my experience starting with batches of ten and now getting batches of one hundred the cost of the labor to cut and tap a plate is more than the material cost. My split right now is about 60/40 labor-cutting to material. Each set takes about 22 mins on a Flow Mach 2. The steel doesn't really take any less time. Steel though has the advantage of being able to be cut using CNC air plasma for a lower cost than water jet. Expect to pay up to $3 a minute for water jet small batch but in production quantity is can be quite a bit less. Machining them in the US I haven't found cost effective for the yield. I could,get them machined in Asia dirt cheap but after freight and uncertain material quality I don't see the value.

Laser cut wood is dirt cheap comparatively. With that the labor/cost ratio is is significantly inverted to about a 20/80 with the bulk of the cost handling and cutting the material to fit in the machine. CO2 laser is readily accessible at local hackerspaces and low end machines can be had for as low a a couple grand. You can't cut metal with them but they will cut many types of material and engrave and etch those plus metals. A full set takes about 17 mins to cut using a ULS V 4.60. Here's a shot of one of our runs...

Who owns a single aluminium i3 here cos i do own one for two years and i know for a fact that theres vibrations in the frame does not matter what grade of aluminium you use theres still vibrations due to the design of the i3 the only thing thats keeping the frame vertical is m10 threaded bar and nuts, so the frame has to be braced to eliminate that

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Check my rubbish blog for my prusa i3

up and running
[3dimetech.blogspot.co.uk]

check out this frame style
[www.reprap.org]

the prusa i3 is a great little printer, but has it`s flaws.

improve it by using this brace:

[www.thingiverse.com]

and this set of "insulators" to get rid of any z-wobble:

[www.thingiverse.com]

also using way bigger washers helps considerably! mine have a 10mm inner hole diameter and 30mm! outer Dia.


If you use longer threaded rods on the Y-sub-frame you could easily connect the printers very top edge to the poutsides of the threaded rods via some printed parts and increase stability to the level of at least a old prusa i2 if not more, because it still has the brace, the aluminum frame and those rods on there

Alex

I assume i'm wrong about the 7075. i was experimenting with some melted down 6061 scrap and reading up on alloys etc and noted a very strong alloy that includes copper so i tossed some in.. i could definitely tell the difference (though i RARELY machine castings).

On the aluminum frame vibrating of course it does.. the flaw is in the Design not the materials. stronger materials MAY decrease vibration (or increase it) but the flaw is the design. Try this on an i3. cut 2 sections of 1/2" 5ply plywood as tall as your printer and 18" or so long. Mount them on the "wing" supports and to the front. wood screws and/or wood glue. Now mount the whole thing on a piece of the same plywood base and glue/bolt the wood together and fasten the threaded rod down. I'll guarantee you lose pretty much all vibration. But no if you want an ultralight portable "foldarap" type of machine you cannot be vibration free.

Vegasloski i was specifically talking about substituting steel for laser cutting because aluminum is very hard to laser cut. The plain truth is there is ZERO reason to laser cut prusa frames. You'd be better off hand cutting 2 frames, mounting one where you want the x axis and the other at the printers front then connecting them with supports and very precisely alighing your z axes but noones going to make a profit off that and it's not going to be "cool looking". Note all the prosumer level printers now have box frames. There's a reason for that.

Alexander i love that brace and i have VERY large washers on my i3. I plan on redesigning the entire bottom end of my printer though. It's overly complex, too imprecise.. 100 other problems. I plan on designing an even cheaper sturdier version of the i3 that makes the whole thing more idiotproof as far as squaring it, much sturdier x/z connection and that keeps the dual z but ties them together with belts for uniform movement (why this wasnt done boggles the mind)