Disadvantages of acrylic frames

I see a lot of Prusa (and probably other) kits with acrylic frames. No doubt they are lower cost, but what is the tradeoff?

The acrylic frame is cheap and easy to be cutted of. Otherhand, it don't weight a lot. So it has everything a company needs to save on building and shipping costs. It looks nice too, it's a good marketing point. Otherwise, it's maybe one of the worst material for any machine building. It's not stiff, it's fragile, it's not stable under heat... Some chinese kits propose 8mm acrylic frame. Which is better than my 5.75mm one, but still not good enough. To match a 5mm aluminium frame or even a 6mm wood frame, it should be at last 12-15mm thick. Flee acrylic frames, all is wrong about it on a printer, except maybe for the electronics case.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

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Zavashier
Otherwise, it's maybe one of the worst material for any machine building. It's not stiff, it's fragile, it's not stable under heat...

I'd disagree depending on what you are using it for. For something like the Prusa i3 where the acrylic is for the gantry support, the forces that the acrylic are acted upon are in such a way that the rigidity of the sheet isn't necessary. It also isn't subject a significant amount of heat as a gantry.

A better material imho is dibond. It's thinner, stiffer, lighter, and easier to machine. It also can be cheaper if you look around and find a good source particularly if they have cutoffs.

I own an acrylic frame. The frame bends like a piece of paper with the movement of the carriages. I could not print over 40mm without issues. I had to clamp reinforcement everywhere, and fix the whole frame to a heavy base. I will upgrade that frame as soon as possible ! Dibond is used on the new Ultimaker. It's ways better than acrylic indeed. IMHO, machine frames needs stiffness and mass at the same time, even for a small 3d printer. Except if you need to move with your printer, heavy materials are a better choice. In the closest fablab, there's a try with fibred concrete pannels, it don't shake even at high speed. Good stuff !

Edited 1 time(s). Last edit at 03/30/2015 12:52PM by Zavashier.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

I see that some Prusa kits have the option for acrylic, aluminum, and steel.

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RRuser
I see that some Prusa kits have the option for acrylic, aluminum, and steel.

3mm steel is a perfect material for a Prusa i3 frame, way better than wood, acrylic, aluminum (sheet or profile), dibond or MDF.

[reprap.org]

I concur, my prusa i3 is acrylic frame and it is like cardboard, I can get some decent prints off it but you only get what you put into it, I like the square all aluminum extrusion frames, they seem to be the most sturdy out there but they are pricey. You get what you pay for, I am however glad I bought a prusa i3 with acrylic frame as a good starting point to learn what I want from a 3d printer platform so if you are new to printing, get one that is a kit, assemble and figure out the in's and out's of 3d printing then if it is not too much for you get a better one once you can answer the question for yourself from experience gained from the i3. Just my two cents ;-) good luck!

Weld the acrylic together. I have 2 prusa i3's acrylic. After I assembled them i put acetone in a blunt syringe and squirted all the connections. Now they're sturdy (sturdier). Feel nice and solid.

My acrylic frame is just fine. I mounted to a piece of particle board, with zip ties holding down the frame to the board and zip ties holding the threaded rods of the build plate frame. I've had NO problems. My longest print is 13hours and no skips, misaligned layers or artifacts.

What about heat, long term?

Anyone converted from acrylic to steel.
I,m thinking of getting the P3steel frame off ebay to convert my Migbot. Looks like it uses the same mountings and will just be a straight swap.

The weakest point of the acrylic frames is the heatbed-subframe. When you print ABS , it can start to warp from radiated heat.
Even with a cardboard insulation underneath, the heat creeps throught the springs/screws and start melting the flimsy arms of the subframe.
-Olaf

Makes sense. Acrylic and heat don't mix, certainly not long term. Would love black metal options for all the i3 printers.

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RRuser
Makes sense. Acrylic and heat don't mix, certainly not long term. Would love black metal options for all the i3 printers.

Well I bit the bullet and ordered the Orballo Printing P3steel frame. Link below. Just hope now all my Migbot parts fit it without too much messing about.
Looks the dogs, 3mm black powder coated frame. Only problem, no lcd mount. The Migbot is incorporated in the acrylic top rail. I'll have to print a housing up for it.
Orballo P3Steel

Looks like they have a kit too...
[orballoprinting.com]

[A little OT]
It seems, there is no maker in the world, who offers a "mixed material" frame kit, where each component is made from the best stuff for the job.
I highly doubt, that the y-table has to be made from 3mm steel?! 3mm carbon fibre would work better, right?

I will replace parts of my acrylic frame, when they are sold separately.
-Olaf

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o_lampe
I highly doubt, that the y-table has to be made from 3mm steel?! 3mm carbon fibre would work better, right?
...

If you have ever tried to cut or CNC a carbon fiber sheet (2 or 3mm thick) then you would immediately understand why nobody sells or has ever used such a part in any 3D printer. It's just not practical or economical to manufacture. Also there is no real requirement to make the Y carriage that light and rigid, as you gain next to nothing in terms of print speed and probably nothing at all in print quality.

Carbon fiber is a great material and it can be used in RepRap printers (for example for the rods in a linear delta), but you have to understand how it can be used and what gains it brings to the table.

Carbon fibre is light enough to be used without all the fancy weightsaving holes and cutoffs. Just a plain 22x22cm plate, made from prepreg carbon.
Then put it in the oven and drill a few holes.

Carbon is just an example, but IMHO a lot of materials would be better for the y-bed, than 3mm steel.
Probably a steel frame wouldn´t need these full-height triangles, that are mounted perpendicular to the frame? They could be made shorter, so they could be made from the material, that is now used to make the y-bed?

[OT
]In the delta forum I asked about using CF as heatbed material, too. Carbon/graphite is conductive and we would have the lightest, stiffest printbed.
-Olaf

I replaced the Y carriage/ bearing holder with this aluminum frame [www.amazon.com]

The rest of the acrylic parts are fine as far as I can tell. I was going mad trying to level the bed - even slight spring tensions would cause warpage of the acrylic. This aluminum one is much stiffer and the bearing hole cut outs and tie wrap mountings are perfect. More consistent prints!

Valerie

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o_lampe
Carbon fibre is light enough to be used without all the fancy weightsaving holes and cutoffs. Just a plain 22x22cm plate, made from prepreg carbon.
Then put it in the oven and drill a few holes.

Carbon is just an example, but IMHO a lot of materials would be better for the y-bed, than 3mm steel.
Probably a steel frame wouldn´t need these full-height triangles, that are mounted perpendicular to the frame? They could be made shorter, so they could be made from the material, that is now used to make the y-bed?

[OT
]In the delta forum I asked about using CF as heatbed material, too. Carbon/graphite is conductive and we would have the lightest, stiffest printbed.
-Olaf

Olaf,
Either you don't read my posts, or you failed to understand what I wrote above. Carbon fiber is not shipped from manufacturers in 22x22cm sheets, if you want a 22x22cm Y carriage made from 2mm or 3mm thick CF, you have to cut that part from a larger sheet. That requires special tools (because CF is so hard to cut and abrasive) and a special dust disposal setup, because CF dust is extremely dangerous if inhaled. So any industrial or DIY process to manufacture a 22x22cm Y carriage out of CF is going to be extremely expensive, and for what? Nothing... If you think the 200g weight gain on the Y-carriage by swapping 3mm steel for 2mm CF is going to improve the performance (print quality and/or print speed) of a Prusa i3, you are seriously deluding yourself.

If you still fail to understand the message I am trying to convey here, I invite you to design you own Prusa i3 variant made out of CF or a mix of materials of your choice, with the shape that you want, and whatever "fancy weightsaving holes and cutoffs" you feel are needed, then show to the world how you have achieved a "better" 3D printer than the original Prusa i3, whatever "better" means for you.

Andrew,
have you ever worked with prepreg CF? I guess not, because prepreg CF can be cut with "household-scissors" before it gets tempered.
It is soft as vinyl tiles. See youtube video.

I agree, that CF dust is dangerous, but all we need is drilling a few holes in it. When it is soooo extremely dangerous, why do they use it in race cars ( formula 1 ) as breakpad? Have you ever seen a tyre change in F1? All that dust spreading...all the mechanics and the driver must have lung cancer by now...
I think you are over reacting, but why?

200gr. weight difference is a world when you consider acceleration and inertia issues. ( But I doubt it would be such a big weight difference? )
-Olaf

Edited 2 time(s). Last edit at 07/10/2015 05:05AM by o_lampe.

"I was going mad trying to level the bed - even slight spring tensions would cause warpage of the acrylic"

You mean that you could see the Y acrylic warp, just from adjusting the bed?

Yes, the acrylic was so flexible that any appreciable tension on the springs would not only tighten the spring down it would also flex the acrylic up. Kind of defeats having the springs for adjustment. So, I tried keeping the tension very light on the springs but found I was always releveling the bed. I'm happy with the new aluminum carriage.

Valerie

You can observe the same flex as Valerie observed in the acrylic Y carriage, if you make it from plywood or even thin aluminum. Also MDF frames have issues with temperature and humidity changes.

Maybe there is a minimum thickness that solves most acrylic problems. Aren't printers using 8 mm now?

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RRuser
Maybe there is a minimum thickness that solves most acrylic problems. Aren't printers using 8 mm now?

See Zavashier's post above. 8mm acrylic is still no good, and as you increase thickness it becomes much more difficult to laser cut. The long and short of the matter is that acrylic is just not a good material for 3D printer frames.

Melamine works well particularly for the cost. The laminate makes it far less susceptible to issues with other engineered wood products. I've got some here with heavy duty cycles for more than a year and still going strong. ACP (Dibond's generic name) is outstanding. The drawback being you have to use a CNC router or waterjet to cut it. If you are handy you could hand cut it but like even cutting a wooden frame you'd still need some power tools and mad hand cutting skills. another potential drawback of ACP in the US is local availability compared to more traditional materials like aluminum or steel. By the time I get enough ACP to me in big enough sheets I could have bought twice as much steel or almost that much aluminum.

The dance, if you will, of getting a good DIY frame is the cost and availability of the material combined with the ease and access to tooling in which to cut them. If you don't mind the extra cost aluminum extrusions are absolutely rock solid in the proper design. I've still got a couple of Mendelmax 2s and have built MM3s for clients. If you are getting good motion parts and want a robust, accurate machine it's going to cost somewhat more.

Would you say iron is as good as aluminum?

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RRuser
Would you say iron is as good as aluminum?

You probably mean laser cut 3mm steel vs 6mm aluminum. I doubt anybody is going to build a 3D printer frame out of cast iron...
And yes, for this specific purpose, steel is a little bit better than aluminum (and much cheaper too).

I cut some 10 ga steel single plate frames last year. A 10 ga thickness is about 1/8", just a shade thicker. Over here steel that thin is sized in gauge. It's still a bit heavy compared to aluminum, particularly the bed but not too heavy to use. I used a CNC plasma for the steel. It's quick and cheap. About the same cycle time cost per minute as CO2 laser on engineered wood product or poly carbonate or acrylic but cut quicker. The material at wholesale is about 20% of what 1/4" 6061-T6 AL but a bit more than twice what melamine costs. Unless you use hi-def plasma or waterjet the holes at 2.5 mm aren't precise enough to be tapped but the acrylic frames tap poorly as well and you can't tap engineered wood reliably. Mounting printed parts with bolt through holes is not an issue though the builder may need to tweak the alignment a bit.

In the testing I didn't see a functional advantage to a single plate steel from over a melamine Graber LC type frame (single plate with rear uprights) in terms of vibration or suitability of use. Aesthetically steel is able to be powder coated with some great finishes as is the AL. I've done neons, metallic pearls, glossy blacks and whites. Really fantastic looking parts with a good contrast color of the printed parts. Based on the tests I didn't cut any Graber LC based steel frames as I didn't see it adding to the performance of the machine compared to the cost and weight.