View Full Version : CNC Novice, Looking to build, little help? Design, Sourcing and General Help
28-02-2012, 10:48 PM
Been lurking here for a while now, I think it maybe time, within the next 2-3 months to build my own CNC! I have had limited contact with CNC machines so not a complete noob! I am really after some help with a build from those who know! I have got a very good friend who can cut all the aluminium parts I need hopefully.
Firstly I will want to cut mainly aluminium, wood, plastic and foam. I was thinking that a X 500 x Y 500 x Z 250mm but depends on costs. I was looking at using a water-cooled 2.2 or 3kw spindle and vfd. I would like to have fairly high accuracy and use aluminium profile to construct where possible as i have access to misumi.
I need some help with what parts i need, so need to construct a shopping list.
Is there anyone who would be able to mockup a solid works model with my work considered?
Anything else I have overlooked? I massively appreciate any help and hopefully can pass on the knowledge I learn now to others here in the future.
29-02-2012, 12:32 PM
I'll help anyway I can.
First regards Machine design and materials.!! The materials you want to cut and the travels on the Z axis conflict slightly.?
Aluminuium needs a really strong Z axis with miniumum flex, Often this achieved with short as possible Z axis. When cutting Ali it's usually thinner material so short travel it's not a problem.
Wood,plastics etc you often need travel due to larger materials so large Z travel and because softer materials can get away with longer Z axis.
So Basicly your in conflict and what you wanting is to have your cake and eat it.!!!! . . . . . . WELL YOU CAN. .:dance:. . . . You just have to design in a way to do it.?
Either build a massively over engineered Z axis (Not practicle or cheap) or build a moving bed that lifts to the material to the cutter.!!. . . .This is how I do it and it works great.
Regards motors, drives, screws etc then I recommend you DONT BUY A THING untill you have the machine design fully done and know the materials it's to be built from and therefore the mass you need to move. Having a accurate design helps selecting the right components so much easier, which saves money and stress.
Don't try rushing it just wastes money and time so just take little steps and start with the design. . . . Heres some tips:
Decide if you want moving gantry or moving bed.?
Moving bed requires more room (roughly twice length of moving gantry) but gives strong machine, it also removes the lifting table option or makes it very much more difficult.
On moving gantry try to keep gantry sides low as possible.
Tall sides can sway/flex, closer to the bearings the gantry sits the stronger the machine will be. Lifting the sides and rails up gives clearence and allows both.
For MAX strength use twin ballscrews on the moving gantry Axis.
Use only supported linear round rail or better still profiled linear rail thou much more expensive. Avoid at all cost's unsupported round rail.!
When designing Z axis put the linear rail on the front plate and bearings on the rear plate to give the strongest possible Z axis.
Don't use thin material for the front plate, 19-20mm is ideal. Just remember the Z axis is the sharpe end taking all the strain and if this flexs no matter how strong the rest of the machine the tool will deflect resulting in a shit work.
Don't be afraid of weight and dont skimp on design to keep it low, Mass helps greatly with cutting esp with harder materials like ALi. Down side is depending on how much Mass it can increase cost's slightly due to larger motors/drive/PSU required.
Hope this helps and just take it slow.! . . . .Bit like eating an Elephant.!!. . . . small bites at a time.
Edit: Here's a few models of a machine I'm working on now that shows most of what I mention, it use's steel for frame but could easily be profile.
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