In my experience, you would be better off sending the company you found the dxf. It is a pretty common file type for these applications.

 

I think you are right but i'm always afraid that they will cut wrongly.

About the gantry plates having 5mm instead of 6mm. Could it be a problem in the end?

 

Thanks Rick. I think i'll continue my search for the ox gantry plates with 6mm...

 

Thanks GrayUK.

I already contacted Mr Robert but i live in Portugal and in the end i will end up paying about 500 dollars or more for the kit because of customs. It's a deal breaker to me.

 

5mm should be fine

Ty !
I'm cutting sets as I wait for the wheels, they are a day out

 

Thanks guys for all the help. I'm a little lost in CNC World but i'll make it. I'll try to find some plates with 6mm but if not i will use the 5mm ones and then i'll probably make the new ones.

Last question for today.

Is there dxf files with other parts in mm? threaded rod plate, and others?

 

No one?

 

I found the files and i installed sketchup. in sketchup i saw that i can export to 2d graphics. but they are in inches..how can i convert them to mm without mistakes in meaures?

 

It's a chicken or egg problem, is it not... what was first, a CNC machine or gantry plates?

 

Hi Jonathan,

Have you considered Chris? I believe it is 150 dallar with shipment in the US + a bit more for Europe, perhaps 200. You will not pay 300 dollar to customs...

There is also the openbuilds shop in the UK who make them, but they are more expensive I think.

Frederic

 

How do you measure it?

Frederic

 

If the "Inches" is grayed out, you will need to change the format to "Decimal" to change be able to change units to anything else.

"Architectural", "Engineering" and "Fractional" all default to imperial units ("Engineering" = Feet, others = Inches).

 

If someone share a picture of a PCB millied by OX, we can see how much backlash is there.

In my first V-slot machine, with gt2 2mm, I did this:

I Did some movement testing through the arrows of UniversalGcodeSender, making some squares, with each line always moving every 5mm.
Unable to accurately measure the size of the gaps, but they are much visible.


I'm finishing a new machine with gt3 belt now. With a Dial, I mensured 0,2mm in backlash. This is too much to make PCB.

 

Even more important than the difference between 5mm and 6mm is the type of aluminum.
Tempering can make the aluminum over 200% stronger.
I use T6/T651, 6.6mm thick aluminum to make the gantry plates.
Chris ([email protected])

From wikipedia..."
Mechanical properties[edit]
The mechanical properties of 6061 depend greatly on the temper, or heat treatment, of the material.[2]Young's Modulus is 10×106 psi (69 GPa) regardless of temper.[3]
6061-O[edit]
Annealed 6061 (6061-O temper) has maximum tensile strength no more than 18,000 psi (125 MPa), and maximum yield strength no more than 8,000 psi (55 MPa). The material has elongation (stretch before ultimate failure) of 25–30%.
6061-T4[edit]
T4 temper 6061 has an ultimate tensile strength of at least 30,000 psi (207 MPa) and yield strength of at least 16,000 psi (110 MPa). It has elongation of 16%.
6061-T6[edit]
T6 temper 6061 has an ultimate tensile strength of at least 42,000 psi (300 MPa) and yield strength of at least 35,000 psi (241 MPa). More typical values are 45,000 psi (310 MPa) and 40,000 psi (275 MPa), respectively.[4] In thicknesses of 0.250 inch (6.35 mm) or less, it has elongation of 8% or more; in thicker sections, it has elongation of 10%. T651 temper has similar mechanical properties.

 

I suspect you will find a difference in the stiffness of annealed 1/4" aluminum (6061-O) verses tempered 1/4" aluminum (6061-T6/T651)

 

Rick 2.0 posted a pretty clear explanation of the difference between the strength and stiffness characteristic.

Generally speaking Aluminium of any grade 2024, 5083, 6061 etc etc, although they can have widely varying strength have a similar "modulus of elasticity" to within a few points. An interesting point to note; 2024-O is generally regarded as a "general purpose" Alloy with a low yield strength (~76Mpa) has a Modulus of elasticity of 73.1 GPa, 6061-T6 generally regarded as a high strength material (and it is) has a yield strength of 276Mpa and it's Modulus of elasticity is 68.9MPa. (Refer to http://asm.matweb.com/)

What I am trying to say is if you had two identical sets of plates, one made from 2024-O and one from 6061-T6, under the same load conditions (and assuming you stay withing the stress limit of the 2024). The 2024 plates will deflect less.

So anyone making plates from Aluminium, the biggest factor that affects performance is the plate thickness more that it's strength properties. On these types of machines I would find it highly unlikely we would ever reach the stress limit of even the lowest strength Aluminium.

For what it's worth Kram242 made his OX with Fiberglass plates and it works perfectly fine.

 

Even at 5mm your plates would be more rigid than the original fiberglass plates used on the Original OX. If that's all you can get, or will save you significant money then go for it.

There is a DXF of the plates in a thread I posted (Waterjet Gantry plates) in the Forums

 

This video show my try to mensure the backlash.

https://www.dropbox.com/s/7hn9wzjz2kmmfvm/Backlash V-slot GT2-3mm.avi?dl=0

I tryed a lot of things. Played with microstepping, all Grbl configurations, very tight and very loose belts. I put regular m3 in the pulley to get a very tighten pulley/shaft.

No load. I'm assuming that the backlash in gt3 belts is not too much, but, the direct belt/motor setup adopted that "amplifies" the stepper angles error.
I start to think 26.67 steps/mm (1/8 micro) is to low. In full-step this is about 3.33.

I can achieve some about 20000 mm/min, with 5000 mm/s^2 without lose steps. Only for test, of course. With a milling machine I don't need this. I'm comfortable with 2,000mm/min and up to 200 mm/s^2.

I will try a reduction system. But is hard to find gt2 3mm pulley with few and lot of teeth. I will start with 16/40 gt2 2mm that I found in RobotDigg, but I will need a lathe to make the shaft, because the pulley's bore are in different size.

I will appreciate if someone can do a similar test. Just some engraving square/circles in the spoilboard with very little depth, to clearly show the junction point of the square or circle, for example.

Unfortunately, neither here, neither shapeoko forum, I found practical information about mesured backlash with our direct driven gt2 2mm or 3mm. Should I start a new post in this forum, to get more visibility to this issue?

I already finish the new (prototype) Z axis, with chinese ballscrews. This one have about 0.01-0.02mm backlash. Same motor/driver/arduino.

 

" 6061-T6 generally regarded as a high strength material (and it is) has a yield strength of 276Mpa and it's Modulus of elasticity is 68.9MPa. "

On a project I was working on a couple years ago I found out the hard way that 6061-T6 is much harder to bend than Annealed 6061 (6061-O)

I designed and machined this mold to make boy scout clips out of 1/16" aluminum. I made the first couple out of 6061-O, and they were perfect... easy to bend and adjust, but when I ordered the material from McMaster-Carr to make 200 of them I bought tempered aluminum (6061-T6) because it was a little cheaper than 6061-O at the time. It was a lot harder to bend and adjust. I even tried putting it in our annealing oven to make it softer to no avail... getting the temperatures, and times at the various temperatures, and cool down rates just right to do it turned out a lot harder than I thought it would be.

 

Thanks for the help guys, very nice explanations.

Yesterday i spent all day searching for someone that could make the plates in the cities nearby. Well i found a company that make the plates with 6mm 5754 aluminium. I think it will work great. .

I saw that they had V-Track instead of V-slot... what are the diferences...?