42?

is a 42cm^3 build volume doable/practical at all with a mendel90? you know, just because? sort of like an amp that goes to 11.

Do you really mean 42cm³? As in 3.5cm x 3.5cm x 3.43cm? Well, sure!

Now, 8,000cm³ (20x20x20cm) might be more challenging.

42cm x 42cm x 42cm

16.5354" x 16.5354" x 16.5354" :/

The main issues are the weight of the bed will be 4.4 times bigger, so either it will accelerate four times slower, or you need a motor with more torque. Also the machine will be twice as deep as the bed.

You might be better with a moving head / stationary bed machine.

Edited 1 time(s). Last edit at 04/25/2015 03:34PM by nophead.

---

[www.hydraraptor.blogspot.com]

Quote
nophead
The main issues are the weight of the bed will be 4.4 times bigger, so either it will accelerate four times slower, or you need a motor with more torque. Also the machine will be twice as deep as the bed.

You might be better with a moving head / stationary bed machine.

so, in your expert opinion, what might be the largest practical build size?

Well any size will work if you have room for it and scale up the size of the rods and motors, etc, appropriately. At larger sizes moving head has better performance over cost ratio. All large CNC machines have stationary beds but smaller ones have moving beds to simply the design and keep the cost down. At 200x200 the mass of the bed and a non-Bowden extruder are similar, which is why a lot of RepRap designs are like Mendel90.

Edited 1 time(s). Last edit at 04/25/2015 07:30PM by nophead.

---

[www.hydraraptor.blogspot.com]

thank you so much for the insight.

Another thing is the power requirements if you are going to have a heated bed. A much larger bed requires much more power. You're looking at minimum at some type of external power control and either much higher current, higher voltage and current, or switching to mains power if you want things to heat up in a reasonable period of time.