[BillParticipant]

I would like to hear some pro and cons about using acrylic, instead of masonite, for the gantry system. Obviously, the cost would go up (way up?). It would also be heavier, but I’m not sure that’s a bad thing. Would it make the gantry stronger? More stable? Any thoughts?

[ChrisKeymaster]

We actually built a first-gen version of this machine out of 1/2″ acrylic. It looked amazing, but the acrylic did present a few issues.

Acrylic is much heavier, harder and more brittle than masonite. This does not necessarily make for a stronger gantry; my guess is that the strongest material for this design would be a high-quality 1/4″ plywood (steel or aluminum plate would be even stronger, but that calls for a different jointing method and more $$).

The weight might add some extra stability, especially to the attachment points where the gantry sits on the Y-rails. Here we use an advanced gravitational joining technique (the gantry sits on the rails, held on by its own weight).

The motors do get fairly hot–we measured them at about 130F–which could be an issue as far as bending (acrylic likes to bend when heated).

Since all the tab slots in the CAD files are 0.24″, this may be an issue as not all 1/4″ acrylic is actually 1/4″ thick so you may then need to adjust the CAD files accordingly.

[BillParticipant]

I’m having trouble finding 1/4″ masonite. My local Home Depot and Lowes do not stock it. I want to look into alternatives. Plywood sounds good, but they’re thickness is generally thinner than advertised.

[JRdezignsParticipant]

What are your opinions on 1/4″ MDF.I ran into the same problem at the local home depot and Lowes…

-James-

[GunnarITParticipant]

I’m also having troubles finding Masonite where I live.

Can anyone shed some light on what the difference between Masonit and MDF are ?

I can’t get any precise answers on this subject. Most carpenters reply “It’s mostly the same”.

[SchweppesParticipant]

http://en.wikipedia.org/wiki/Medium-density_fibreboard

http://en.wikipedia.org/wiki/Masonite

[Open Form ArchitectureParticipant]

@ Chris:

So what is your and Taylor’s final opinion about using MDF 1/4″ (0.25) instead of Masonite 1/4″ (0.22-0.24)? It seems that we’re having difficulties finding the right Masonite (in multiple regions) and a substitute option could be helpful. Ideally we don’t need to re-draw all the holes, etc. given that we’re not entirely familiar with the components.

From my experience MDF is a more robust material (at it’s edges) and less susceptible to chipping and peeling. I have a 1/4″ MDF panel right beside me and it feels fairly light but I have had a harm time finding links to a comparative analysis of Density (Weight:Volume ratio) and whether MDF is much heavier than the Masonite. My fear is that MDF might be heavier and cause increased strain on the motors.

From Wikipedia – “MDF”:

“MDF has a typical density of 600-800 kg/m³ or .022-.029 lbs/in3″

From Wikipedia – “Hardboard” :

“Consequently, the density of hardboard is 31 lbs. or more per cubic foot (500 kg/m³)[1] and is usually about 50-65 lbs. per cubic foot (800-1040 kg/m³)”

But I don’t know if we can go by this.

Darrel

[BillParticipant]

I was not able to find a supplier for the Masonite and just wasn’t comfortable with using MDF, so I ended up getting 6mm Baltic Birch Plywood. It’s not as cheap as Masonite or MDF, but was still pretty inexpensive. I’m planning on starting to laser cut the parts this weekend and will report back how it goes.

[TaylorKeymaster]

@OFA,

I think you’d be hard-pressed to find a material crappier than Masonite. We used it to keep things cheap, and to demonstrate that some keen engineering choices can make up for basic materials.

When it comes to weight, you’re in luck. Initially, we found that the behavior of the gantry actually improved when bearing more weight. That particular issue has since been solved with longer Y bearing assemblies (for improved contact with the rail), but it demonstrated that a heavier panel material shouldn’t hamper the movement of the device. Further, we built gen. 1.0 with 1/2″ acrylic, a material that’s sure to outweigh the MDF and plywood options you listed.

I think the main issue will be sizing the tab holes to match a variety of material thicknesses. If there’s interest, I can look at creating a parametric version of the file (the easiest way for me to do this is through Illustrator/symbols). If we do go this route, what programs do you all have access to? What would be the most useful file format?

[ChrisKeymaster]

@OFA,

ditto what Taylor says. There’s a little more info in this post about adapting the slots and tabs for different material thicknesses.

[Open Form ArchitectureParticipant]

@ Taylor:

I am looking at doing the panels with 1/4″ MDF, which seems to me the most logical option. However I still fell like I don’t have a clear answer from you about the material. If I understand: MDF is good, even if it is slightly heavier. As you say it (might be) is more expensive -but likely not hugely different.

The major issue seems to be then, that the MDF is not between the 0.21″ to 0.22″ as shown in the other post: http://diylilcnc.org/forum/topic/before-you-get-panels-cut-read-this-post and that we will in ALL cases need to adjust the holes (and tabs) to fit. I measured a piece of 1/4″ MDF here at the studio, and it was exactly 0.25″ = too big for the holes.

* Concerning the drawing set, I did have problems with the extra (missing) panels you added. The updated driver case boxes were SPlines, and caused problems to the Laser cutting machine. I therefore had to redraw the updated parts. I just wanted to let you know. I will look at AutoCAD and the feasibility of redoing (by block) the tab holes so that they can be updated to different thicknesses. I work with AutoCAD 2007 files.

Darrel

[Open Form ArchitectureParticipant]

@ Taylor – Continued:

I forgot to mention, that working from Illustrator > to AutoCAD makes all of the holes individual blocks. This of course means that in AutoCAD I cannot do a quick update of all the blocks. If I redo all the holes as one block, then this should (ideally) be fed to others.

Also: I assume that all the holes for the tabs should be centred according to the centre hole? And if I’m going to redo all the blocks, I guess I have the choice of still doing the masonite, because I’m going to resize everything anyhow. In this case, do you think Masonite is still better than MDF?

[TaylorKeymaster]

@OFA – Sorry for the confusion! To clarify:

MDF should be fine, or even better than Masonite (as it’s less likely to peel). I don’t think, without having tested it personally, that the added weight should be an issue.

Our laser runs straight from Illustrator, just like a conventional printer. That’s why our working files are in AI format. Initially, when we completed the design, we had an AI file with symbols that represented the slots throughout the gantry. We stripped out the parametric nature of the symbols in an attempt to make a PDF file that was universally accessible (or as close as possible).

It sounds like we need to collect examples of workflow from the community, then respond to commonalities in future releases of our CAD files. I’ll post a little demo file in the downloads section of an AI file containing two instances of the same symbol. Try importing this into AutoCAD and see if you can get the symbols to read as blocks. If you can, we can look at releasing a symbol-based version of our AI file.

[Open Form ArchitectureParticipant]

@ Taylor:

Thanks for doing the “Demo File” – I’ve had a chance to test it, and what happens is that Illustrator (when I export from Illustrator to either DWG or DXF) is that Illustrator creates a series of blocks within blocks, none of which are parametric.

I tried to edit the “symbol definition” in Illustrator CS4 and it seems to update without too much problems. I was also planning to go slightly bigger with the holes – from 0.24″ to 0.26″ instead -in the case of 1/4″ MDF (with a real uniform thickness of 0.25″). This way the holes won’t be too snug.

Perhaps send me the Illustrator file to test, or I will just do it from scratch in the AutoCAD file I’ve already modified… It’s probably as quick.

[TaylorKeymaster]

@OFA

Cool! I’ll work on cleaning up the AI file – it’s not ready to release directly without some housekeeping. This will take a couple days, so don’t hold back if you think it’s just as easy to work straight from AutoCAD.

To answer a questions I forgot earlier – do go ahead and keep all slots centered when you change their size.

[Author]

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