XYZ

XYZ Table Development Log

Here is a log of XYZ table development. The background: build an XYZ torch table for producing the metal components of a CEB Machine. See here for CEB machine fabrication.

Arnar Mar Sig, Iceland Fab Team

Power, Speed, Accuracy

I was thinking about using steel for the main support frame welded together at the joints, but it would be easy to change that part to bolt together type. The Y and Z axes would be made from aluminium bolted together. The reason for the steel frame is to get maximum support and stability if the axes are moving fast.

You can post it and get input as you want, Its opne souce;)

The reason for linear bearings and screws on the X axes is so i dont have to move a big and vibrating motor with the axe. This is propably the biggest motor on the table. Also using the design that torchmate uses then we need 2 motors on both sides.

The most expensive part of the controller board are the power transistors. If one didin't need the 30-50V 6A output then we can change to smaller transistors. Also i have dedicated stepper motor IC's to control the critical timing so its a bit more expensive then using a generial purpuse microcontroller like most designs use, but thous designs can't step really fast. Also many other "open" router table designs still relay on proprietary controllers.

I will most likley use Olimex (www.olimex.com) to fab the PCB it costs 30euro to fab 1x 100x160mm board. I can do single sides boards at my shop but this board has to be double sides.

The controller board has a small 8-Bit AVR to communicat with the dedicated IC's and a computer. I haven't started the code but its really simple and written in C and small parts in assembly. The controller will communicat thru RS232 or Ethernet (if we add that option, and it would be really nice to have). The controller will be able to take in simple commands like "Move this axe to position X at Y speed", so it will be able to work standalone without Smari's routing software.

I haven't found any open source controller that has the power, speed and accuracy i want, thats why i'm doing this design.

Basic electronics specs

When building the router you should be able to use almost any Bipolar stepper motor that has the power to drive the mechanics. I'm designing the motor driver now, the specs are: Support for 3x Bipolar steppers, 30-50V max 6A (200-250W) Input for 3x incremental encoder for step verification and currection. Max step freq of 20kHz RS232 port for programing (Maybe USB)

The board will probably cost between 300-400$us to make.

If you have any input on the design or the machanics then please tell.

Capacities

I just started drawing the CNC rouer in SolidWorks yesterday. The basic version will have 3 axes with an changeable head. The head can be a cutting head, plastic extrude, acetylene/plasma cutter. (The head could also add another axe for 4-5 axe version). I was also thinking about adding fittings to be able to add a rotating spindle to do CNC lathe work.

I've started the design of the motor drivers as you know Smari and I can probable finish the design and send the pcb out to fabrication this weekend.

Casting aluminium isin't so hard. Making the molds is also simple and cheep, just expanded polystyren and plaster. Molds can also be created in sand, but its not as good. Casting carbon fiber is almost like doing fibreglass, you can do it at home buts is messy.

Project Budget and Goals

Arnar,

I like the one motor design. I think the Torchmate drive system is more complicated, such as the one motor on each side.

Tell me more about the power transistors. What is the particular transistor you're using? Can you redesign to simply use a larger number of smaller transistors, or is that ineffective?

So look at the budget:

1. Structural steel - $400

2. Control board - $400

2a. Encoder - $100 for each axis - if needed

3. Control software - free

4. Stepper motors - $100, main

5. Stepper motors - $100, 2 smaller ones - from Xylotex

6. Ball screws - 13 feet total plus 3 ball sets - $300?

7. Linear bearnings and shafts: 26 feet - $300?

I just sent for a quote to Nook Industries for the parts in the XYZ-table diagram, http://openfarmtech.org/index.php?title=Torch_Table .

Those last two are my guesses, but that's about $1600 - 1900 total?

What kind of accuracy are you aiming for? The ball lead screws from Nook Industries are down to +-.0004 inch. I would need only .01 for the purposes of CEB. Have you considered simple threaded rod? It's $23 for 10 feet of 1/2" rod, part 98935A632 at http://www.mcmaster.com/ . Or, $40 for precision threaded rod, 6 feet of 1/2". The precision rod is down to .009 inch accuracy per foot of travel. That would do for me.

Then again, if one attached 2 nuts to a simple threaded rod, the backlash (play) would decrease. That may be another route for the cheap way.

What do you do professionally? Are you an electrical engineer?

Are you looking to neo-commercialize (see http://www.p2pfoundation.net/Neocommercialization ) the XYZ table? Are your goals similar to mine, like the open franchising of the CEB press - http://openfarmtech.org/index.php?title=CEB_Press ?

Marcin

Encoders, electronics component prices

I took together the parts needed and checked the prices. The full controller with all features will cost about 307$us (ordering components for just a single unit). By removing the Incremental Encoder support (and also decreasing accuracy), the unit can be build for 232$us. After checking the prices i found that the transistors aren't that expensive. You can cut the number of transistors used to 12 and then only having max 3A output, but the price is only 17.76$us lower.

That budget looks about right, the only thing missing are the incremental encoders if one wants to use them, they are about 50-100$us for low end 1024tick/rev, 3 are needed. I was hoping to build this for between 2-3k (a bit more expensive to build in iceland)

I want to be able to mill PCB boards with this router, so 0.1mm (.003") is the minimum accuracy i want, but having down to 0.0004" would be awesome. For most DIY people a simple threaded rod and bolt would do. I want this do be a "neo-commercialize" project. All the hardware, mechanical and software designs should be open source and everybody should be able to build the machine and use the parts they want (skipping encoders, using threaded rods.. etc) to get the accuracy the want, but I still want to be able to sell complete machines with the best accuracy we can get (hense everything is deisgned for maximum accuracy).

I do Software programing and electrical designs for Valka (www.valka.is). We make fish processing machines.

Guide Rails, Encoders

Just talked to Nook Industries. I was told that the linear bearings and shafts are about twice as expensive compared to profile guide rails, so I'll get a quote on that plus ball screws and pass it on. Just a data point.

We can redesign structure easily if needed, by just replacing the linear shafts with linear rails. The rails are supported on their whole length, as opposed to linear shafts, which are supported at the ends.

Their turnkey package for motors, controllers and encoders is under $5k. So looks like your work is Factor 10 Engineering (http://www.10xe.org/). I love it, because $500<$5k. In my language, that's 10 times more freedom.

Electronics, BOM

Hi Marcin

I buy most parts from Digikey, the TMC* parts i will probably buy from semiconductorstore.com or some other place if i find them.

I'm going to redesign the router to have at last the X and Y axes on profile guide rails and cut costs a bit.

Yes, its a Open Office spreadsheet. You can open it with OpenOffice on Mac, i find it a bit less of a crap then Microsoft office on mac, but it still sucks.

Your right, its simpler to driver a unipoler motor and most DIY projects choose to use them. Bipoler motor has one winding per phase while a unipoler has 2 winding per phase, but at any given moment there are only 2 windings in use. This makes a unipoler motor with the same torque as a bipoler motor bigger, heavier and more expensive then bipoler. You can also buy steppers that are hybrids and can be driven both ways.

The driver IC's i'm going to use take care of the motor driving so it dosen't matter much in the end except for cheeper and less heavy motors:)

Arnar,

Can you resend partlist.ods? I'm just getting a blank page.

Xylotex has 23 Nema motors at $50, http://www.xylotex.com/StepperMotor.htm, so that's cheap. Are those the type you plan on using? If it's got two phases, that makes the 6 amps you're talking about?

Have you considered power scaleability by attaching 2 (or more) double-shaft motors one behind the other? That would be a good feature for high power, such as lathing, or even adopting a similar design to milling. Is your controller capable of being paralleled, such as using 2 (or more) controllers to drive the additional motors, so we can scale the power completely? That would be a useful feature from the standpoint of scaleability. This would be quite exotic to have, and I always aim for such. For example, the Boundary Layer Turbine is absolutely power scaleable by virtue of adding disks: http://openfarmtech.org/index.php?title=Boundary_Layer_Turbine

So your strategy is to put the complexity into electronics and not into the motors, as electronics are cheaper, right? That's the same strategy as hybrid electric cars: rip out the transmission and replace it with electronic torque control such as PWM.

Marcin

Bill Swann

I talked to Bill Swan, product designer from Texas, after I saw an XYZ table that he made. http://www.hal-pc.org/~dsbswann4/ ; 7138271503; 8323383080(c). Dbswann4@yahooo.com.

He told me about Nook Industries. Basic design includes:

Shawn Kelly

<bluumax@yahoo.com> date Jan 23, 2008 4:43 PM

Hi Marcin. I would really suggest a Xylotex drive or other known professional drive. I use the Xylotex for my Taig mill. [1] They cost about $500 with motors, but you get $500 worth. I wouldn't trust many drives I see on ebay to run a "real" mill / router table. There is also the Linistepper kit for unipolar motors. I know these work. Cost is about $100 for 3 axis [2] CNC software will run standard G code that is output from CAM to the machine. G code is machine commands & machine coordinates. I use Corel draw to make the parts, save as .DXF & convert to g code using Lazy CAM, part of Mach3 Mach3 actually runs the mill table. [3]

The software (turbo CNC / mach3) reads the g code & feeds it to the Xylotex drive. I'm in a studio apt now so I can't build anything big. There's a lot of stuff on ebay & [4] is a really good place to look.

$50 for Torchmate 3 size stepper motors: [5]

Tom Lingafelter at Nook Industries

Thank you for your recent inquiry via our website. I would like to discuss your application further at your earliest convienence.

Tom Lingafelter

Lead Engineer - Precision Actuator Group

Nook Industries, Inc.

23300 Mercantile Road

Beachwood, OH 44122-5921

tlingafelter@nookind.com

216-378-9922 ext. 103

216-378-9923 Fax

440-487-8533 Cell

Nema 34 or 42 motor - Gearbox. Frame size of motor. Torque and speed -

Encoder receives feedback from motor regarding motor position. It's an optical disk with slits. Photoelectic sensor, emitter and receiver. Steppers are typically mechanically stable, so you don't need encoders.

Parts Sourcing and Specifications

1. Specifications of different size motors. NEMA 42 is the largest.