That is my understanding, Serge used Nema 23's on the X and Y with my plates and everything works fine.
[email protected]

 

And using a NEMA 17 for the Z-axis. I'll have specs and such in the build details of "myOX" ... probably during the train ride Monday.

 

I'm relatively new to motion control and have some math questions.

It seems to me that when the 20 tooth, GT2 pulley rotates exactly 360 degrees, the GT2 belt moves exactly 20 teeth. That means the "effective" circumference of the GT2 pulley is 40mm. I assume the belt stretches with use, so the the distance between teeth will be slightly more than 2mm and the belt moves slightly more than 40mm...but for now, I'm neglecting belt stretch.

Taking it a little further, the basic step size is 0.2mm (40mm/200steps) or 0.0079". Using divide-by-8 micro-steps, yields a 0.025mm (0.00098") per micro-step size.

Are my assumptions correct?

Chaz

 

I just got the same parts for another build; I've hard-coded in 40mm/0.2mm for the pulley, yeah. I don't use microsteps yet so I can't say for sure, but math-wise, presumably 1/8th steps would indeed be 0.025mm.

Mark or someone with older belt may want to jump in here, but I'm assuming the fibreglass interior prevents stretching. Though perhaps that's only achievable with a continuous steel cable, so the belt may stretch a little over time as the strands settle.

I'd actually be interested to know the answer to that myself, since it may be a factor in my current build too.

 

@JustinTime, LoL not sure if serious.
For everyone else, here is a link to the awesome calculators by Josef Prusa. These should solve most of your steps per millimeter problems. Even if you were sleeping in Math class.
http://calculator.josefprusa.cz/

 

If you use Mach3, you don't have to do the calculations as you can calibrate your axis by measuring the actual movement.

 

Thanks. Josef Prusa's calculator verified what was running around in my head. I new it had been done about a million times before...and I now know what a micron is.

I have a 12" (300mm) electronic ruler that I will use to measure the actual travel.



I also have the serial port cable that connects to the ruler, so I can make lots and lots of automated measurements...eventually.

Chaz

 

Hello all!

I'm new to the forums but not new to the site... if that makes sense! This question doesn't have anything to do with the current discussion, so I apologize for butting in, but I have a bit of a quandary.

I'm planning on starting my OX Build here very soon, but can't figure out a way to CNC the plates. You see, I have an Oliver Intellicarve 13x18 CNC machine, but I cannot figure out an accurate way to mill the plates. For those of you that don't know, it uses a program called ipicture to generate gcode. You upload a photo, set the size parameters and save the gcode to a USB...plug it into the machine, set the origin and hit start. Not much control over any project settings really... (hence why I'm planning on building a machine!) I could save a jpg of the plates and attempt to load it in this way, but I'm afraid that if I don't get the LxW of the jpg set correctly (because you have to factor the white borders of the jpg) the end result won't be correct! Anyone have any suggestions?

Thank-you in advance!

Adam

 

If you just need the g-code on a USB stick won't the g-code files from sketchucam placed on the stick be the same?
What format is the file on the stick ?
Normal text file?
.nc ?

 

I wondered that as well... But the format of the files that go on the USB are extension .GEE

I also believe the area of travel from the sketchucam file is larger than my 13x18 area... ?

 

The biggest part in the plate set can be milled with a 12x12 milling area.
.GEE ? Hmmm

Maybe this will help
http://file.downloadatoz.com/gee-file-extension/

 

It was about 10 hours (!) of train, not counting about 1h30 of car for door to door travel when it normally takes me only 8 hours by car. WiFi on board, train allows me to work a bit especially when seat next to me is empty. This time the train was packed, the internet about as slow as the train and ... I slept through most of it. I just can't drive by myself for that long any more for same reason. ;(

 

It would be double work, but, you cold buy the elecronics for the ox and hook it up to the intelicarve. Assuming that the intellicarve has standard steppers.

 

The iPicture output files (with .GEE file extension) are normal GCode text files. If you use SketchUp or any other software to create a GCode file then, if necessary (not sure it is), just change the file extension to .GEE and it should load from your stick as normal.

Tweakie.

 

I would if I could! My dad and I have started some sign making/lithophanes as a side business in the back of my coffee shop, and he is quite the stickler on warranties and doing things that void them... Chances of sliding that by him.... Not likely!

 

Sounds like it just might work! I'll play around with that this evening and see if it will work! Thanks!

 

I think I've found a small error in the parts list for the OX build.

The link for the GT2 pulley points to the GT3 pulley. I placed my order based on the links so.......

I'm sure it will be fixed shortly but thought I would put a heads up here in case anyone places an order in the next few days.

 

Actually, I think the NEMA 23 steppers have 1/4" (6.35mm) shafts and the GT2 2mm pulleys OB sells all have a 5mm bore. The GT2 3mm pulleys have a 1/4" (6.32mm) bore so they are actually the correct thing.

If you were using NEMA 17 steppers then you'd want the 5mm bore.

EDIT:

Just to clarify, the 2mm and 3mm are BOTH called GT2, the difference is the tooth pitch. The OB store incorrectly has (had?) a designation of GT3 on the 3mm pitch parts to reduce confusion I think. You can get GT2 2mm, GT2 3mm, and GT2 5mm as far as I can find online.

EDIT:

Last, edit, I promise.

The GT2 actually refers to the tooth profile, not the pitch. The company that created these profiles DOES have a GT3 profile, but it's a little different.

 

Thanks.
So to use the NEMA23's I need the GT3 Pulleys. Hence I need to order GT3 belt.
So there is an error with the parts list for the OX build which currently lists GT2 belt and pulley?

 

No, the part list is correct and links to the correct item in the store. The name of the item in the store is technically wrong. They are GT2 3mm parts, not GT3 parts.

In any case, the parts linked to from the parts list are what you need.

 

PowerGrip GT2 belts are currently available in 2 mm, 3 mm, 5 mm, 8 mm and 14 mm pitches.
Specific advantages of the PowerGrip GT2 system can be summarized as follows:
•
Longer belt life
The strong fiberglass tensile cords wrapped in a durable neoprene body provide the flexibility
needed for increased service life. The deep tooth profile provides superior load-carrying
strength and greatly reduces ratcheting when used with pulleys provided by a licensed supplier.
•
Precision registration
PowerGrip GT2 belts provide timing and synchronization accuracy that make for flawless
registration, with no loss of torque carrying capacity.
•
Increased load-carrying capacity
Load capacities far exceed HTD and trapezoidal belt capabilities making PowerGrip GT2 belts
the choice for accurate registration, heavy loads and small pulleys.
•
Quieter operation
The PowerGrip GT2 belt's specially engineered teeth mesh cleanly with pulley grooves to
reduce noise and vibration. Clean meshing and reduced belt width result in significant noise
reduction when compared to Trapezoidal and HTD belts.
•
Precise positioning
PowerGrip GT2 belts are specifically designed for applications where precision is critical, such
as computer printers and plotters, laboratory equipment and machine tools.

 

Exactly.
On the store:
GT2 = GT2 2mm
GT3 = GT2 3mm

 

Quick question for you guys I am planning on building this CNC lay out and was wondering has anyone every added another z axis for a hot wire cutter to cut out foam core wings and such. My freind and I are gonna build this one and wanna make sure that this can be done.

 

I wonder if you could incorporate the y axis that is already installed for the ox and just add the hot wire steppers on the upper part of the extended rails.

 

The belt & pinion system used on the Ox would allow multiple Z carriages on the Y beam. Not sure what controller setup would work well with that and not cause problems though.

 

I am thinking something along the line like what Mark said or maybe something like this as well where it is removalable and such.

 

Also does any one know who has the plans for the ox's gantry plates. I need them to cut the plates out.