Budget 5'x10' 3axis router for wood/soft metals.

[GlennW038]

Hi everyone, I am about to get started with this build but I would like to get anyone's opinions on my so call "plan" for this build.

To start off, I am a electrical engineer working a desk job and I have been researching how to build a cnc machine for awhile, having access to Autodesk inventor 2015 CAM software, all axis's are available to me to generate gcode for. But knowing that I need to walk before I can run, lets start with a 3 axis machine. a 5' by 10' machine. (who says you have to learn to walk slow? )

I am not really going off of a design plan, since trying that and modelling everything has gotten me through 3 totally different designed that i still was not confident in easy or rigid the machine will be.
Going for broke, i plan on spending close to $3500 USD on this machine. I have had good luck with Aliexpress in the past for linear parts so ill be using them as well as ebay supplies for building this machine.

The frame was made using Superstruts at home depot. And now before you go off about how there is twist and flex with using these, I will be trying to correct for that during this build to ensure its a strong enough frame.



Cost of the metal so far to build was under $350 USD, including all the brackets and bolts/nuts. Had to go to 3 home depots to get all the brackets....
I am doing my best to keep them accurate to the lengths I need. using a jig holding the steel while cutting and then angle griding the final dimensions.
Since this is all bolt together, i figured it would be easy to make any adjustments down the road should i need further alignment.
I am going to be adding some further reinforcement (tack welds or more brackets/steel) to this as the 3 walled box frame doesn't hold its endpoints that well.

The next step after this was to gather the required linear components for the machine as well as the drive system.

For this large machine, I will be using some good quality components that keep me within my budget.

First up, I decided on using helical rack and pinion to drive the Y axis, one on each side, left and right helical to correct for axial loads on the motor. (I think i will still require some thrust bearings to compensate further but I am not sure).
The X axis will most likely be rack and pinion as well since 5ft ballscrew will show signs of whip and I don't have a machine to make a rotating ballnut carriage to correct this...
The Z axis is a plain 600mm ballscrew 2010.

They will all be using 25mm Linear guides (not expensive brands, but should be within the tolerances i need)

The price I got was from Annie Tian:

6pcs : 1500mm length, 25mm guide width, Linear rail guide
2pcs: 600mm length, 25mm guide width, linear rail guide
12pcs: Matching guide blocks (HGH25CA)
1set(BK15+BF15)
1set(ballscrew L600 SFU2010 including ballnut (end machined for BK15/BF15)
Total price including shipping to MA, USA = $993.92 USD

I will be butting the linear rails together to form the full Y axis.

For the rack and pinion, I was thinking something like this:

High precision Helical gear and rack , Left helical and right helical gear rack, gear and rack Length 1400mm/pc-in Linear Guides from Industry & Business on Aliexpress.com | Alibaba Group

For the X axis, What opinions does the masters on this forum think i should use? (helical rack and pinion, or ballscrew)

The motors and drives to pull this beast were selected to be closed loop steppers, Nema 34, with 10.5NM holding torque. I will be getting 4 of these:

NEMA34 10.5NM Closed Loop Stepper Motor Drive Kit 2PH 20 70VAC/30~100VDC 86mm CNC Engraving-in Motor Driver from Industry & Business on Aliexpress.com | Alibaba Group
~$940 USD

For powering these massive motors, I will be using 96V ~17A, connecting 4 of these together:

MW High Quality 48V 8 3A 400W DC Regulated Switching Power Supply CNC 400W | eBay(MW High Quality 48V 8.3A 400W DC Regulated Switching Power Supply CNC 400W)
~$180 USD

I wasn't sure if this would be enough amps, but given that the drivers can use 20-70VAC or 30-100 VDC, and that the total amps for all the motors divided by them usually using less (2/3rds or so) gives me
7.5A * 4 = 30A *.67 = 20.1A

Which is higher than the 17A that the supply will give, but I don't think i will be running this machine at max power (unless someone can give better alternatives to power this workhorse. )

The controller is the one portion of this that I did minimal research with, I was thinking of making my own controller but do not feel that I can take that dive just yet. For the controller I was thinking of using something compatible with linuxCNC as I found that the differences between them were minimal and that if you knew linux, linuxCNC would be a good choice for penny pinching.

The smoothstepper (ESS) was one I was looking into, but it says it also requires a breakoutboard, I thought this was the breakout board so I am a bit confused here. What is the purpose of this card then as I have seen this mentioned lots of times in the build logs. Should I get a breakout board like this to go with it?
http://www.ebay.com/itm/5-Axis-USB-C...-/261479889613

I have not designed the X axis or Z axis, but I will be doing that as I go. (probably not a smart idea, however i've seen many build logs, and the lengths seem to be unchanged once the axis size is set)

I will be trying to keep this more of a bolt together machine. But it will be a slow build and I hope to get some good advice from some experts in the forum so it won't end up being disasterous. (I havn't bought anything but the framing material which can be adjusted and cut again. so any improvements that will save some headache, please let me know.)

I will be documenting everything about this build too.

Regards,
Glenn Williams

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[wizard]

What do you intend to machine with this, balsa wood perhaps?

Seriously those struts are awfully light weight for a machine this size. How well it will work does depend upon your expectations but the lack of effective bracing and gusseting in the current picture has me worried that it won't meet your expectations.

[ger21]

The Smoothstepper is a motion controller, which accepts low level commands from Mach3 and generates step and direction pulses. The Smoothstepper has 3 "ports" worth of I/O, accessible directly through it's pins, or using breakout boards.

The "breakout board" you linked to is actually also a motion controller, with probably one port worth of I/O, and screw terminals to access them.
The two boards are not compatible, and are for Mach3 use only. They won't work with LinuxCNC.

Generally, when people start their builds by buying parts, then asking questions, they tend to end up starting over. Right now your on your way to a machine that won't be very good at much of anything.

[GlennW038]

@Wizard,

I did mention that its only a start, I will be adding more bracing, and welding to ensure its a solid frame. I am also planning on having this steel support structure be just a skeleton, getting some mdf to solidify the base, back and sides.
Its not going to be that deep of a cut as imaged from the picture. The picture was just the only one I remembered to take
There will be Cedar 2x4s along the base creating a tension box around that skeleton structure. I expect to only make the Z axis 8 or so inches.
Depending on if I can get a professional welder in my area, I may decide to go with steel tubing. Its a work in progress, and I have not bought anything beside those struts. 80% of it is returnable, gotta love buying local.

@ger21

Thank you for the input on the controller. I was a bit confused. So I gather that there are some control boards and some breakout boards. Would you recommend anything for LinuxCNC? I only require something that can control the spindle and the drivers (up to 5) I wasn't quite sure if there was a standard that everyone goes with, I couldn't find many control board threads here...And I agree that if you go in buying parts without reason or fail safes, then getting overwhelmed is completely foreseeable. However, I am going in under the assumption that this machine will be 5'x10', and usually that size Nema 34 motors are a good amount of torque for whatever need. HGR rails are in the top tier for linear components, 2 for each axis. If anything I would be wasting time not getting these essentials in order before I build the machine. So I figured work on the first part of this project, the frame first. Then order all these components. then work on how they will fit to the frame. I hope having a thread here will invite some good assistance in ideas.

[asuratman]

Hello Glenn,
Do you have any experience with those motors and drives? Those are cheap. Do you know about their helical gear and how to calculate for motor tuning?

[GlennW038]

After doing extensive research on frame design, ill be using 2"x2"x3/16" steel tubing for a smaller 2'x4' box gantry design. I am also going to be using ball screws instead and eventually make a bigger v2.0 later. Will make new thread as I know I'll have questions for the experts down the line.

@asuratman,
No, I don't have experience but based on the driver's pdf (from china) its shouldn't be so difficult. I have a oscilloscope to check the signal to the motor if needed. But besides that I decided to go with an easier approach and use steppers, closed loop. Just deciding which brand. Favoring the automationtechnologies nema 34 closed loop DSP based stepper.


@someadmin
Please close this thread, I will be making a new one, if possible remove thread completely as now i consider this a bad approach.

[victorofga]

have you checked places about used pallet racks...
compared with you showing on pictures I think pallet racks were more rigid than this setup

Buy Used Pallet Racks Online | Warehouse Used Pallet Racks | Beams & Uprights | Got-Rack of Florida

144" Long x 6" High Pallet Rack Beam | eBay

these are only two example.. very possible you can find within driving distance some..

[jannos]

Hi.
You can use simple power transformer for stepper driver(20-70v AC). Connecting two swiching power supply to get 96v is not good idea, and you do not need dc voltage. I got transformer from old 2kw UPS. Only had to remove some of the windings to get the correct output voltage.