I'm working on an MDF version of the OX. MDF has great dimensional stability but on a small scale it lacks the hardness of Aluminum, Steel and Garolite. Forces on the parts will cause the holes to deform which results in sloppy linear motion over time. To make up for this in the design, I'm going to pass all of the 'axles' for the V-Wheels through a torsion box structure. This gives them two support points at least 20mm apart. It will act as if the the part was a 1" thick solid block of MDF but it will be made from 1/4" MDF sheets you can get at Home Depot and cut on a 50W laser. The belts will all run outside the aluminum rail so it will be possible to use 9mm x 3mm GT3 belts. The X rails are secured to the vertical torsion box members as well as the outside plate. They are spaced further apart than in the OX design so that the V-Wheels contact centers form a square when viewed from the side. I'm also planning for a taller Z and spaced the Z wheels out further. These two changes combined should give us a very rigid Z-axis.



I'm still finishing up the X/Z axis core. I realize that there needs to be some play to align the X rails to be parallel and match the final width of carriage. Making something thats rigid, long lasting, easy to assemble and easy to adjust (you have to reach all of those eccentric spacers!) is a difficult challenge in wood. But its fun to try

 

Interesting approach Gareth and it certainly looks promising. I look forward to seeing the finished result.

Tweakie.

 

Mark thanks for posting up this design. I recently built a 2x4' shapeoko and I'm not entirely happy with how it scaled up. I setup mine with a 4' X gantry for easier use in the garage. Unfortunately this X gantry twists easily even after adding an addition 20x40 and bolting them together. I'm going to be converting it over to a OX with a 2' X axis and I'm currently in the CAD phase and have a couple questions.

I use Mach3 and I've noticed it would be incredibly helpful to have a Z home switch. My CAM software ends up each job moving the Z to machine zero and then to Y zero. It's really easy to forget to manually move Z up to before ref all home making it really easy to run into fixtures. Has anyone figured out a good way to put a limit switch on the Z axis?

The Z access threaded rod plates have a recess of 16mm for a 5x16x5 bearing and a lock collar is used to keep it in place. Unfortunately the only 8mm lock collars I can find all have a 16mm OD. This will cause the collar to rub against the outer shoulder of the bearing instead of spin freely with the threaded rod. I'm currently planning on using two thin 8mm hex nuts instead of the lock collar. Snug up the bearing with the first and then tighten another nut against it. Doing this on both axis. Anyone see issues with this?

What type of garolite are people using and where are they sourcing it in the US? McMaster has several different grades and I'm not sure which is most appropriate in this use case. Since I have the shapeoko or access to a 4x8 showboat if necessary, I should be able to go slow and either do 1/4" aluminum or garolite. Should I just go straight to the aluminum?

 

A friend of mine built a cnc with MDF and had issues with the wood chipping/wearing at the wheel bolts so he cut new parts and sprayed them with a hard laqur finish to harden.
He said it worked for him, maybe something you might want to try

 

@Gadroc
I would go with aluminum as you may find its cheaper then Garolite
http://www.onlinemetalsupply.com/6061-t6-aluminum-plate-250-x-12-x-24.html
Just my 5 cents

 

Gareth- Sounds like a great idea. I had an idea a while back of stacking laser cut thin plywood to create a part. If you have a laser you could cut several layers of say baltic birch plywood instead of mdf. If you are worried about the wheel shafts deforming the mdf you could add bronze bearings or even drill bushings. I don't know how long you want it to last long enough to mill out some better ones. I use baltic birch a lot for jigs and fixtures. It is hard and stable and relatively easy to find. You can often find it very thin that is used in making model airplanes. Keep us posted with how you make out. Best Bill

 

@Robert Hummel Thanks for the link. The sites I was looking at had the same for about $55. Looks like I'll be ordering some aluminum. Any recommendations on bit to pick up for working on this?

One other question around tolerances. The standard v-slot build plates have clearance between wheel holes of v-slot thickness + 20.64. The OX plates had 1-2 millimeters additional. Was this intentional or just sketch up inaccuracies? I'm in the middle of converting the drawings into another cad system which support arcs / circles and can push back up some DXF without the sketch up off by partial millimeters problems.

 

@JustinTime Sketch up does not (at least last time I used it) handle circles as arcs. Cut a hole in something and it's immediately a set of line segments and when exporting it converts arcs to line segments as well. This can be seen in Mark's DXF files. This leads to several small inaccuracies in the resulting files and potential problems with CAM / machining if you have to many segments per arc.

I'd highly recommend anyone using sketch up for mechanical parts look at Autodesk Fusion 360. It has parametric features more suited to designing things like this and has a free hobby license level and built in community design features. SketchUp is free as in beer, but not open source so there is not really a philosophical reason to stay with it.

I was not referring to bit size, but type as for these plates you have to use 1/8th cutter since M5 holes < 6.35mm. Machining 6061 is it best with a straight flute, o-flute, downcut, uncut, etc… Any recommended or avoided coatings.

 

I used MArk's drawings as reference in my CAD program but I replaced all the holes with real circles...

Ill have to check out Autodesk Fusion 360.
My current favorite parametrics CAD tool is Moment of Inspiration: http://moi3d.com/
Made by the same dude that wrote Rhino. Outputs to OpenNURBS format and STL.

 

Had some more parts that came in today. Got some more done on the z axis. Just waiting for some extruded aluminum to come in

 

Wow. So cool Great job. Can't wait, my parts are shipped.

 

Fair enough, but I'd say the same to you

SketchUcam is not another CAD system, so the tangent is meaningless. I don't care that SketchUcam can back track SkethUp line-segments back to arcs for generating g-code. The CAD piece is important to me as I'm realigning some things to fit with other components I already have, and I already have more capable CAM software. Quite honestly DXF output from SketchUp is about as useful as STL for anyone trying to modify a design, which is to say crap. Circles/arc don't have dimensions or center points and I've never seen a SketchUp design that was dimensionally accurate. All dimensions are off by fractions of millimeters, which means they are a pain to align in an assembly, as hole patterns don't line up. You end up redrawing them dimensionally accurate and replacing all arcs with fitted arcs and then re-dimensioning them because the are always again fractions of a mm off. In my opinion SketchUp is a great free form design system, but rubbish for detailed mechanical parts or CNC work. To each their own.

 

Here's how I did my z limit+home switches http://www.openbuilds.com/builds/optical-limit-home-switches.512/

Instead of lock collars I used nuts and drilled+tapped a set screw to lock them in place. It allows me to pretension the threaded rod into place and then lock it there.... seems to help. My bearings are 608 so the nut only touches the inner race. I tried just the nut but it spun loose.

 

@JustinTime, It is and I understand why people use it… and people get passionate about their tools! I just do more than SketchUCam can do, which btw is AWESOME value. This means Sketchups anemic export capabilities (3D Surfaces or segmented 2d) becomes a major stumbling block. For wood and foam I would agree… but for something like building an OX I'm a little more careful. A small inaccuracy in a plate could lead to HOURS of frustration trying to square up or track down amplified inaccuracies at the cutting tool.

Back on topic. My first parts order arrived yesterday, thanks @kram242! I just need to finish up the CAD model to get my cut area where I want it and order the last bits of table support extrusion from misumi and cut the plates (one the aluminum for them arrives.)

@The Dude have you worked out how/where to mount the limits for the Z axis. It's tight fit to get things where the Z motion would trigger them.

 

I am really looking into building OX as I have been looking to build one router for a while now. The plan is to bild with Aluminium, BUT shipping cost from US is a kill.
Anybody knows if V-Slot is available in Europe?

 

I am intresting too building OX and I am also from Eurepe . But I would like to know the cost for the OX 2*4 complete kit with the plates. and an estimation for the shipping will be good.....
Indeed it looks awesome machine.

 

There's a guy in England that is a distributor he is called Robo-Cutter Uk. Go to the openbuild store and check the news that is where the announcement of distributors it. Good luck in your builds!

 

Good morning Thanks guys. I will look right away. !!

 

Just a short note to write that my VPS server is down, the host company (GoDaddy) are onto it but I did not want anybody to think that the website was down for any other reason then the hosting company seems to be having problems with the server. The correct link is www.robocutters.co.uk (when its working again), thanks.

Colin.

 

Thanks for the info and yes, all working again now (phew!) and URL edited to go to the website as well...

 

Hey guys. Did anyone try ever to move the whole X axis up and down as Z axis , using two steppers but making the connection of the router more strong because it will stand only at X axis wheels ? Of course this increase the cost of the construction , but do we gain something of it ? More stability let say as more clearance of the height ?. I am asking you because I am going to order materials to construct my own machine and just I had that thought.

 

Very interesting idea.
I use Mach3 as my machine control software and this will only allow for 2 axes to be slaved (such as Y and A for the 2 motors driving the Y axis back and forth). Other machine control software may be different.

Check out this build http://openbuilds.com/builds/spunks-cam.522/

Tweakie.

 

Do you mean like this?
http://www.openbuilds.com/builds/spunks-cam.522/

 

My apologies Colin - I must have been editing my post to add the link at the same time you were making your post.

Tweakie.

 

no need to apologize we were both on the same track

 

Well since it was a snow day today (around 18" and counting). I got some more dont on my OX. This thing is really starting to impress me very fun build.

 

@JustinTime , trust me i cant wait. This V-slot is amazing its like an erector set for machines. The more i use it the more im impressed with it