[jreuck]

Hello everyone!

First off, I"m not an engineer, however I do sometimes wish that was my major instead of photography, though I love art, so I'm torn! this new build will be the ultimate marriage for me in combining the two major interests in my life a balance if you will, one aiding the other!


I'm looking to build a CNC in the next couple of months (router and Plasma)Both for personal work as well as some side business to help pay for the Art I'd like to create with it! Currently I'm hung up on motors to drive each Axis.. Originally I began with the idea of steppers, then decided for their advantages such as high continuous torque while maintaining higher IPM and of course the closed loop system to switch to servo motors. I'm no engineer, but thought this would be the best place to ask questions!


I've added these to my BOM ( Motiontek | AC Servo Motor Driver | CNC KIT Router Mill Plasma Canada USA ) Have spoken them on the phone for a quote of 4 motors and seems to be a good size and option for my machine with a 10:1 or 5:1 Gearbox. After finding these, as per norm, I kept shopping and came across these ( http://www.automationtechnologiesinc...motor-750w-set ) /Polish according to rep from Automation technologies./

And finally for servo's I found the Deltas again at Automation ( http://www.automationtechnologiesinc...-and-driver-1k )

These are the three I've narrowed down to.. if anyone has suggestions, feel free


anyone have suggestion for a smooth stepper for Servo? I thought I knew I wanted the PMDX 424 for sure, but that was with using Stepper motors. I'm still learning about AC Servo's and perhaps I need a specialized Board?


My machine will be 11' x 5' working area.
Steel build
Rack and pinion for X and Y
Ballscrew for Z
2.2kw Spindle
Hypertherm powermax 65 Plasma
Water table.


Planning this began 3 months ago when I knew nothing about CNC machines besides that I knew I always wanted one for my shop. Ideas, and plans have changed several times as more knowledge has been gained through research and phone calls. I am hopeful that I'm in the final leg of design and creating a parts list and budget.

I've included a sketch up rendering as an example, ideas have changed since, including servo's vs steppers, and the Plasma is not included.

This build has helped me along the way in making decisions such as using Epoxy for planes and such. ( http://www.cnczone.com/forums/cnc-wo...948-cnc-6.html )

If anyone has any sources they've used for their parts, I've scoured the internet for moderately priced hardware, however I'm always open to new resources!
Thank you so much for any advice you can give an ignorant person!

[RCaffin]

Personally, I think your Y-axis rails should be much further apart - say, double that spacing.
Cheers
Roger

[jreuck]

ok, so I had thought about splitting that Y axis into two smaller rectangular tubes. Would this have a positive or negative effect on the torsional rigidity? How big would each one need to be?



Thanks!

[RCaffin]

If you do split the Y axis beam into two tubes, I suggest you have them welded together on both sides for the full length. The forces from the Z axis going up and down and the spindle spinning up and down will be significant. Better get the design right at this stage.

Cheers
Roger

[ger21]

Don't split the beam!
One large beam is better than two small ones.

What size is the current beam?
It looks like you can spread the rails another inch on the current beam, which would be better than nothing.

Have you priced zero backlash gearboxes that will fit those servos? They can easily cost more than the servos. And honestly, I think those servos are way overkill for a plasma, where a simple stepper motor/rack and pinion setup would be half the price and still give very good performance.

I think you're going to find that changing from router to plasma well be a huge pita, especially with a water table and a machine that large.

I'd really recommend separate machines if you have the room.

You could build a plasma machine based on something like a mechmate for probably half the price of what you're spending there, and get nearly identical cuts.

Also, I think a much better e-chain design would be to lift the tray so you don't have that double bend. Have it come out the backside horizontally and have one single 180° bend. That's how it's always done on commercial machines.

[awerby]

I wouldn't worry about the motors and drivers until I had the frame built. There are lots of changes you could make between now and then which would affect your choices. Servos are nice, but you have to gear them down a lot. Gearheads are expensive, though - you might consider doing it with timing belts and pulleys. If you want to use this with plasma, be aware that the arc will tend to influence the low-level signals that come from the encoders (and not in a good way). It can be done, but it will require some shielding.

I've seen people use the same mechanicals for routing and plasma by setting up a plasma table next to the router and attaching an arm to the Z axis that reaches over to the plasma table and holds the torch. This seems like a better idea than trying to cut metal on the same table as you're using for wood.

[jreuck]

After playing with the idea, and looking at pros and cons, I think I'll stick with a solid beam. mostly because aligning two would be much more difficult than just one larger. in the mock-up, its a 4"x6" beam. I've since then changed it to a 6"x8" with 1/4 wall.

I have had some troubles finding a good gearbox that doesn't break the bank, but so far I've not had much luck other than Automation Technologies. http://www.automationtechnologiesinc...earbox-4000rpm but not sure if I should be looking at 5:1 or 10:1

The E-Chain was the last thing I've added here. raising that up wont be an issue, and probably will do so.

As for the water table, I know I've got it pictured sliding off the end and a solid table. I haven't decided if I'll split that in half for two separate water tables when only needing half the work surface. plus, much more manageable at that size. I suppose they will have mounted bearings to roll off onto stand.

I have seriously debated on two machines, however space just won't allow for it at the time I'm afraid... Which is a bummer since I will eventually get tired of moving that water table contraption every time. I suppose if I could find a plasma table or build one resulting a substantially cheaper overall cost, I'd go that route. I should add, this project is intended to make some extra money and (hopefully in the near future) replace my full time, in supplementing a part time, full time work from home! Ideally starting with customer orders of signs, special gifts and such to, own product lines, and prototyping for individuals with product/project ideas.


Thanks!

[jreuck]

I've seen people use the same mechanicals for routing and plasma by setting up a plasma table next to the router and attaching an arm to the Z axis that reaches over to the plasma table and holds the torch. This seems like a better idea than trying to cut metal on the same table as you're using for wood.

I just saw this, Great idea! I'll be sure to look into that!

thanks!