[Bl@ckrat]

so ive had to sell my old machine boo hoo , and im missing it already (moving)

but this gives me the opportunity to build a new machine, better and FASTER ! even though it may be a few years before i get to start (or even if ever)
i have been looking at various other builds and the means and ways they are built

here in SA aluminium is crazy priced when compared with steel , so i have been playing around with some stress tests

i have the same profile of a ally ganty riser in 30mm thickness ... when a force of 100kg (1000N) is applied to the top of the riser it deflects by .4mm
the same profile in 6mm steel , but boxed with a 50mm space between only deflects .15mm with the same force ,

the weight difference is 4kgs (per riser)

my question is , why would i choose ally over steel ?

[Bl@ckrat]

http://www.blackratcomposites.com/fi...20Study-1.docx
http://www.blackratcomposites.com/fi...20Study-2.docx

[wizard]

so ive had to sell my old machine boo hoo , and im missing it already (moving)

but this gives me the opportunity to build a new machine, better and FASTER ! even though it may be a few years before i get to start (or even if ever)
i have been looking at various other builds and the means and ways they are built

here in SA aluminium is crazy priced when compared with steel , so i have been playing around with some stress tests

That right there is sound reasoning to choose steel.

i have the same profile of a ally ganty riser in 30mm thickness ... when a force of 100kg (1000N) is applied to the top of the riser it deflects by .4mm
the same profile in 6mm steel , but boxed with a 50mm space between only deflects .15mm with the same force ,

The problem here is that plate risers are probably a bad idea for most machine designs. For the same weight of materials you would get a much stronger riser with a box profile. That is steel or aluminum, square or rectangular tubing. If you want faster you either need to control weight or you need more power. As such designing with materials that are stiffer makes sense.

I say for most machines because how you expect to use the machine and how much space you have to build the machine are valid factors. The other thing to keep in mind here is the validity of you simulation, most gantry routers will have two such plates with the forces acting on both plates.

In the end, as the owner of the machine, you have to operating whatever you build within its mechanical abilities. What you have access to often dictates how a machine will come together.

the weight difference is 4kgs (per riser)

my question is , why would i choose ally over steel ?

In this case I'd choose neither and look for some tubing.

[Bl@ckrat]

one thing i completely overlooked on my old machine was the voltage , so simple, but yup ! was running on only 48v , whereas i could have doubled it !

my next machine will without a doubt be servo's with a step down pulley ... 700 watts ish per axis and on 220v so no power supplies needed.

http://www.cnczone.com/forums/diy-cn...1500x1000.html

also , hiwin/ thk rails and ground ballscrews ! 3kw spindle or more

this cnc is addictive eh !!

the design as you say depends on what you have available ... here laser cut mild steel isnt very pricey and its easy to work with ... my next frame i will have stress relieved and ground .....