newbie from bristol soon to be up and running

[uppy121]

hi everyone

i am new to cnc. i live in bristol started to build my own machine in jan 13 just a few more bits to get and i will be up and running. if i can i will post some pics

85798580

[Jonathan]

What are you planning on cutting with it and what bearings have you used on the ballscrews?

[Ricardoco]

hi everyone
i am new to cnc. i live in bristol started to build my own machine in jan 13 just a few more bits to get and i will be up and running. if i can i will post some pic s85798580

Well welcome to the forum and you get a thumbs up from me because its in your house!! looks like your almost there, i look forward to seeing your pictures and your progress, And again welcome.

Rick

[uppy121]

i will be cutting ply ,mdf, softwood, and yes it is in my front room good job i live on my own

[Jonathan]

i will be cutting ply ,mdf, softwood

That's good, since the machine will just be able to cut those, but nothing harder. I asked because there are a couple concerning things about your current design:

The unsupported rails on two of the axes will significantly reduce the rigidity of the machine, see here (http://www.mycncuk.com/forums/faqs-problems-solutions/4356-why-not-use-unsupported-rails-2.html) for a detailed explanation as to why. To start with you might as well try the machine with them, but I'll be surprised if you don't swap them for supported rails in a few months.

It looks like you haven't put any angular contact bearings on one end of the leadscrew and that you're possibly using the motors to resist axial forces on the screw? If so you need to change this before running on the machine, as standard 'deep groove' bearings are not designed to work with axial forces, so they will quickly fail in addition to adding end-float to the screw. If you use a pair of angular contact bearings that wont be a problem. Look up the standard end-machining for ballscrews and it should be fairly obvious how to proceed.

What pitch screws have you used on the longest axis and how long are they? The critical speed/whipping might be a problem.

[blackburn mark]

Splendid stuff :)
nice and warm inside

looking at you Y axis, the rails look unsupported which may lead to some problems over such a large distance
they will be like guitar strings when you get going (maybe bass guitar strings :culpability:)
If it turns into a problem it looks like a supported rails would fit right in there without to much heart ache

EDIT: oops, Jonathan beat me to it

[Swarfing]

Welcome local chap...

shooting him down in flames already? Don't listen to them, you got this far without em. It would cost you thousands in training to learn what you have so far. Just get on and enjoy what your doing and keep on learning :welcoming:

[GEOFFREY]

Hi, wellcome. Built in your living room - thats great. At least you wont have any rust problems. Reminds me a bit of a WI competition that my wife entered a few years ago. In answer to the question "what is the most useful item in your kitchen" she put " my husbands bandsaw". I had a machine for several years, unsupported rails, rack and pinion drive etc., but it worked well for me as I only cut mdf and ply. As Swarfing said just enjoy it. G.

[uppy121]

thank you i will be building a second machine and i will take in your advice on the bars so all advice welcome all i have to do is sell a few woodworking machines and i will start buying some more parts thank you all very much:friendly_wink:

[kingcreaky]

shooting him down in flames already? Don't listen to them :stung:

Excellant work uppy. You'll have great fun learning, much the same as I am at the moment. Make sure you keep us posted with your build photos!

[uppy121]

list of items left to get

400w psu 36v power supply
cnc micro switch
end cap 75x75mm
plus
sbr 20 x 900 supported rail kit

[Ricardoco]

list of items left to get

400w psu 36v power supply
cnc micro switch
end cap 75x75mm
plus
sbr 20 x 900 supported rail kit

Hi there, it looks like you are going to get the supported rail then. It is best, but i managed for a while with unsupported, by the way i think you may be hitting the +Post New Thread button Rather than the +Reply To Thread button, Im sure one of the mods will put them all as one when they notice it.

Rick

[Jonathan]

Presumably you've got the stepper drivers already, since they're not on your list, but which ones did you get? It looks like you have the common 3Nm motors. They work best with a lot more than 36V - ideally 70V. The reason is the inductance of the motor limits how fast the current can rise, so at high speeds the current can't reach the rated value, hence the motors don't output as much torque. However, by increasing the voltage you increase the rate at which the current rises, so that gets higher torque at higher speeds. If the drivers you've got will accept 50V, then you might as well get a 50V PSU instead of 36V. It will make a big difference.


by the way i think you may be hitting the +Post New Thread button Rather than the +Reply To Thread button, Im sure one of the mods will put them all as one when they notice it.

Already did it once...

[uppy121]

5 axis breakout board
4 x drivers m542
400 w power supply
and yes 4 x 3 nm stepper motors

[GEOFFREY]

Machine building in living room, second machine being planned before the first is finished. It seems to me you are a natural for this site. Well done. G.

[Swarfing]

Sure is :toot:

I must remember to shift that milling table out of the Utility room before the kids trip over it .....lol!

[martin54]

Welcome to the forum, if you still need to buy a power supply for those drivers then as Jonathan has said you would be better off with a higher voltage, think those will run up to 50v unless your buying a second power supply because the one you have won't be enough for all the motors.

Have a read through some of the build logs before you start buying new parts for the next build, it will give you a good idea of what will suit your needs best for the new machine.

Best of luck with it.