OK, I'm an idiot. Where do I find the length of 20x60 V-slot for the Z axis. Since my build is bigger, I have to specifically cut this to whatever length it is supposed to be. Where is this model I keep hearing about? The Sketchup I see doesn't have V-slot lengths that I can find. Anybody? Buehler?

 

Your question isn't really clear Alberto - what are you trying to measure?

And if you're not happy working in mm, work in inches - your CAM app should work in both.

What is 'giving me a 26.66 mm'? Giving you 26.66mm of what?

The easiest way to work out your calibration is to accurately measure a known g-code distance. So zero your machine and then mark the point your tool is at, then tell it to move a set distance away and measure again (start with a smallish distance to begin with - like 6 inches). Keep increasing your distance, measuring and updating your accuracy until you are travelling the entire distance of your axis.

 

Thanks Rick. I said I was an idiot! I have been in the parts list about a million times and didn't see that.

I have that skp file, but don't see how to find measurements for the Z piece. New to sketchup.

 

@DiggerJ Tools > Dimensions

I added a key ('D') in the options so I just hit D and it changes to dimensions. You can also use the T key and look at the figure from the Tape Measure tool.

 

The original design uses a piece of 20x40 leftover from an other piece given that OX's overall dimensions. I forget which ...

If you did like me, modify the overall dimensions, I had to get an extra piece of 20x60 (1000mm being shortest). I made a longer Z (to ~ 10") and the rest is ... spare. In the case of myOX, the spare piece might become an extra long Z to go down bottomless table to work larger pieces IF the precision stays acceptable going that far with down.

It has definitely been a worthwhile learning experience at my end so far.

 

Thanks guys. I got it now. When I get a little time, I need to go through some Sketchup tutorials. I was able to measure from you directions.

I bought extra 20x40 and 20x60, as I will be using it for the vertical alignment and clamping for the dovetail cutting process. Now I just need some metric measurin' stuff.

I am having a blast with this build!

 

Bottomless table? Tell me more.

 

Sorry not to be clear I'm asking about the steps per unit in the configuration of the softwatre. As I used to used on the old small machines for the screw I used 32000 steps but when using the calculator it give me 26.66 steps for the belt. This is right?

Thanks again,

Alberto

 

Well the fiber OX parts are coming out how I was hoping, so that's a good thing
It's a lot of work but the end results should be worth it.
Here you can see the finish before cleaning and buff, the idea was to get the marble look of the fiber board to show when the light hits it.
Think I achieved that part

More to come

 

Without knowing what screw/belt, what steppers (and their configuration) and what software - and the units you are using, I am sorry I can't give you a definitive answer.

But... your screw or belt will have a specific pitch, etc., so it should be possible to work out some generic figures.

For a screw, the calculation is: mm Per Min = (Frequency * 60) / (Turns Per mm * Steps Per Rotation * Microsteps)

So, say your stepper is a 1.8deg/step unit, configured for 1/8th step, that means there are 200 (360deg / 1.8deg per step) *8 steps (1/8 step divisor) per rotation - or 1600 steps per rotation.

The Openbuilds parts store screw gives 8mm/revolution. So using a 'stock' 1.8deg stepper at 1:1, to move 1mm, you need to move 200/8 steps - or 25 steps - or 45 degrees.

Using that, we can work out that the distance you move with one step at 1:1 is 0.04mm
At 1/2 that is 0.02mm, at 1/4 is it 0.01mm, at 1/8 it is 0.001mm, etc. Invert that to work out how many steps per mm - so at 1/8 stepping, you need 1/.001, or 1000 steps per mm.

To work the same sort of calculation out for a belt is similar.

Using the GT3 belt, it has a pitch of 3mm and typically you are using a 20-tooth pulley. So divide one rotation (360 deg) by 20 teeth and you get 18deg/tooth. Each 18 degrees represents 3mm of travel, so each degree represents .16667mm (3mm/18deg).

A typical stepper rated at 1.8 degrees will move the GT3 belt .3mm per step at 1:1 using a 20-tooth pulley (.16667mm/deg * 1.8deg = 0.3000006mm)

Now, depending on how 'fine' you have set your stepper will determine the progression per step.

1/2 = 0.15mm
1/4 = 0.075mm
1/8 = 0.0375mm
1/16 = 0.01875mm
1/32 = 0.009375mm

 

@Alberto Boria just as an example, I have a screw that has a progression much lower than that of the OpenBuilds screw and a stepper that is rated at .9, so my figures for my z-axis are quite different. But, I have GT3 belt with 20 tooth pulleys and 1.8deg NEMA23 steppers, so my belt axes figures are the same as for above.

 

Here http://www.openbuilds.com/threads/belt-rack-and-pinion.275/ and here

 

thanks for the help. I will be using a 1/2"-10 screw for the Z axis with an open builds nema 23 but all other motors are xylotex 269.

I will try with this numbers and let you know how it goes.

Thanks

 

The short version : go check out the "myOX" build.

A bit longer, I tend to look too far ahead and myOX will try the impossible : go deep ! The concept is quite simple : allow for a longer Z axis, have the bottom of the table (on usual OX) not be there, and use work bench beneath such that it also has an opening. From there, the workbench opening could become a 4th axis or just a plain old adjustable height shelf to hold the work piece.

Yes, I know, the precision might get way way off as the tool end goes further down. Also, the volume (body) of the Z axis and router/spindle can get in the way of the work piece. I thought about those aspects, thinking being something I do too much of.

In my case, I'll be taking steps towards the long neck OX . First, the usual 2.5D work - engraving and a bit of light cutting. Then work on thicker blocks of (soft) material. Then the bottom comes off and the fun begins inch by inch until, maybe one day, I hit the floor. That ain't no OX, it's a Giraffe !

 

Hello!

I need some newbie assistance please! I'm building one of these terrific Ox Routers and I've just begun assembling the components. I have a question about the "Solid Wheel Kits". I looked at the video several times and I didn't see the answer, so I'm asking here...

The Wheel Kit (see photo) includes a "precision shim". In the video, they show assembling the gantry sides using *completed* wheel assemblies-- so my question is, does the "precision shim" go INSIDE the wheel (like, between the bearing races) or does it go OUTSIDE the wheel, between the bearing race and the spacer-- OR, are there TWO shims, one Inside and one Outside?

This is unclear to me and I don't want to assemble all this stuff just to have to pull it apart again later ;-)

Thanks

John Whitten

BTW-- This Ox Router looks awesome! I can hardly wait to get mine built and cranked-up!!!

 

The 1 mm goes inside the wheel between the bearings and 1/4 spacer is used outside

 

There is a shim between the wheel bearings and if you watch part one of the assembly video, you will also see one or 2 shims between the 1/4" spacer and eccentrics. The video shows the shims external to the wheel and their positions, and there is also one in the wheels between the bearings.

 

Yeah, that's what I figured you were gonna say! ;-) Now I've got some wheel assemblies to reassemble...

But- hey, it gives me something to keep me busy!

Thanks for the answers, I appreciate the help


John

 

Looking Good Robert! really nice and I like the color. What exactly is the material if I might ask(spec)?

 

Ty
It is a ceramic fiber board used in electrical switch gear to isolate buss bar and phases

Extremely strong

 

Ain't delayed gratification a wonderful thing! LOL

 

So your 1/2"-10 screw has a pitch of .1" (progresses 1" in 10 turns). If we divide that by 200 for the 1.8deg OpenBuilds steppers,that gives us 0.0005"/step at 1:1

1: 0.0127mm = 0.0005"
1/2: 0.00635mm = 0.00025"
1/4: 0.003175mm = 0.000125"
1/8: 0.0015875mm = 0.0000625"
1/16:0.00079375mm = 0.00003125"

 

John, the wheel kit consists of a 'tyre', two bearings, a spacer, a washer and a screw. The washer goes between the bearings. There is an additional washer (or more)required, depending on where in the structure you are putting your wheel. The videos are pretty awful from a 'best way to assemble' perspective, especially the X/Z-axis assembly - very ham-fisted approach. Look in the 'tips' section of the forum for a much easier assembly.

 

Phenolic?

 

Thanks again

Alberto

 

Heh. Well, it wasn't so bad. I've already gotten all the ones for the gantry redone, and I'm working on the Z-axis now. I can't move forward though on my Y axis until I get my next order. I messed up the last time and ordered an extra 20x60 instead of a 20x80. But that's okay. Now I will just have to build myself a 3D printer to use up the extra v-slot rail... ;-)

 

If I may pick up on just one section here. I also use TinyG because I think it's the better of the 2, not because of the lack of a parallel port. If you want to use Mach3 & don't have a parallel port, why not add one? There are a few add on cards available on eBay that look like they will do the job & they are very cheap. I haven't tried them for this purpose, but have used one in the past, to add a much loved scanner. I stand to be corrected, of course, but I can see no reason why it would not work. Typical example for under US$10 http://www.ebay.com.au/itm/Parallel...70642649?pt=AU_Components&hash=item5b01b4afd9 I don't know if they are suitable for a Mac, but I have read this reason a few times for PC, so took the chance to bring the option up.

 

Thanks SlyClockWerkz for the DXF in inches! My background is electronics, not mechanical. I imported the original file into SketchUp and eMachines and one of them had the width at 180 inches and the other was 180 feet.

 

Here are some photos of my progress thus far. I've gotten the two side gantry pieces built, and the Z-axis built, minus the X-axis motor. My Nema 17 motor didn't fit so I stole the X-axis motor to drive the Z-axis and I'll order another motor to use for X. The only difficulty I've encountered, apart from my mixup with the shims is that the screw nut should have been attached with 10mm screws if you're using a 1/4-inch aluminum plate. I ended up drilling out the holes a bit so the screws could "countersink" into the holes enough to get a bite. As soon as I receive my other "Y" axis leg, I'll start bolting the frame together and mounting the carriage assemblies.


John