Hey reprappers, I'm scheming to put together a Darwin style repstrap. I'm looking at getting parts laser cut by a local supplier [www.lasercut.net.au] ( Perth, Western Australia). Now the plywood design seems to have been superseded by the bits from bytes acrylic design. I have reservations in using acrylic as it has a nasty tendency to crack and fatigue. Does anybody see any issues with using the same pattern and making it out of 5mm MDF board? https://reprap.org/forum/read.php?4,16349,16349#msg-16349 Thu, 13 Aug 2026 20:39:34 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?4,16349,16444#msg-16444 https://reprap.org/forum/read.php?4,16349,16444#msg-16444
I had a closer look at the deign and realized that some of the parts have partial cuts rather than full depth.

This morning lo a behold the laser cutting place emails me back with a big WTF is with these designs?

hehe.

you are correct , I think I will get out my (t)rusty protractor and compass and look into working on (http://reprap.org/bin/view/Main/PlywoodRepRaps) the slot-A into tab-B design to work with.

Vik informs me that his work has stopped on the plywood design, however I think I will grab it and start hacking away.

The idea of the reprap has grabbed my brain and won't let go...

On another note, rep-rappers beware PIC micros do NOT like 12V unregulated through them

ERK :P


Simon]]> zignig Reprappers Tue, 02 Sep 2008 07:15:33 -0400 https://reprap.org/forum/read.php?4,16349,16385#msg-16385 https://reprap.org/forum/read.php?4,16349,16385#msg-16385 Ian Adkins Reprappers Mon, 01 Sep 2008 03:37:42 -0400 https://reprap.org/forum/read.php?4,16349,16359#msg-16359 https://reprap.org/forum/read.php?4,16349,16359#msg-16359
I shall go for acrylic.....

Now I need to get a quote for the laser cutting.

:)

Cheers.]]> zignig Reprappers Sun, 31 Aug 2008 08:37:38 -0400 https://reprap.org/forum/read.php?4,16349,16356#msg-16356 https://reprap.org/forum/read.php?4,16349,16356#msg-16356
From what I've been able to find it looks like acrylic takes almost 2,000 times more load to break than MDF while still being as stiff. The parts I broke most often were the corner blocks; MDF's higher co-efficient of friction should result in less force being required to hold the rods, but I doubt it's enough less to reduce the danger of over tightening.

Acrylic is also easier to put back together after breaking a part than MDF.

Ply is a much stronger alternative with a closer max load, although it is over twice as stiff. The biggest problem with it is that 5 mm Ply doesn't necessarily mean the board will be 5 mm thick it could be 4.5->5 mm. The only parts, I can remember, where this is significant are the X carriage and the X motor mount plates. So to use ply these would need to be altered to take into account whatever size the ply actually is.

The numbers I found are:

Acrylic
3.2 GPa young's modulus
72.3 MPa modulus of rupture

MDF
3.8 GPa young's modulus
32.8 KPa modulus of rupture

PLY (marine ply of unspecified wood)
7.5 GPa young's modulus
4 Mpa modulus of rupture

The difference between the modulus of Rupture of MDF and Acrylic seems very high so if anyone could check them that would be appreciated.]]> peteredworthy Reprappers Sun, 31 Aug 2008 06:51:20 -0400 https://reprap.org/forum/read.php?4,16349,16349#msg-16349 https://reprap.org/forum/read.php?4,16349,16349#msg-16349
I'm scheming to put together a Darwin style repstrap.

I'm looking at getting parts laser cut by a local supplier [www.lasercut.net.au] ( Perth, Western Australia).

Now the plywood design seems to have been superseded by the bits from bytes acrylic design.

I have reservations in using acrylic as it has a nasty tendency to crack and fatigue. Does anybody see any issues with using the same pattern and making it out of 5mm MDF board?]]> zignig Reprappers Sun, 31 Aug 2008 04:17:00 -0400