I'm wanting to build an OX but with a bit of a larger working space... I would like to be able to work on a 4ft x 4ft square material with a machine approx 5ft x 5ft I was planning on going with the standard OX design but with longer struts for the X and Y axis. Any advice on this? Will this design be scale-able for this? Anything I should consider as I move forward with my build? Thanks for any advice!
Having no firsthand experience with the ox extrusions but i still voice my opinion. To simply lenghten the machine would not be a big problem but lenghening the y- bar might. Not only the weels and their axles might bend under the now much greater load ( especially if your router is in the center) but also the y-beam itself will bend downwards (think of a long rope held between two humans) and might "Wobble" (for lack of better english) back and forward with accelleration and hard stops. So it should be stiffended not only vertically but maybe more importantly horizontally too. Otherwise you might have holes drilld not rectangular to the surface (vertical stiffness) or overshoot and racking etc. giving you no exact parts (horizontal stiffness) with no repeatable accuracy in case youd have to go multible passes. Milling aluminum would be and example here. The wobble could be minimised by going with slow accelleration but than i simply asume youd want a fast machine for the fact that you want a big one ( and big parts beeing milled therefor). It can be done thought have a look here (giant shapeoko 2 mutant): good luck greets flo
Thank you for your input! It looks like in the video they used thicker aluminum for the X-beam*.. perhaps I can increase the size of the v-strut from 2 sandwiched 20x60mm to 20x80mm this would increase the strength but also increase the weight of the bar as well... The other idea I had was in regards to the sandwich 20x60mm strut on the X axis*... if this was one piece - say a 40mm x 60mm solid beam rather than two sandwitched beams it seems that would greatly increase the stability of the X beam* and allow me to simply expand the original design. This "sandwitch" seems to be the weakness... I wonder what the possibility of getting a 40mm x 60mm x 1500mm v-strut is possible or if it would work for this. **corrected y vs X axis error
http://www.8020.net/t-slot-5.asp#20 Series What about doing it on a 40mm x 40mm design.. do you think I would still have the same bowing effect? Another idea.. what about instead using qty 3 20x40mm like this: | | --- or a 40mm x 40mm and a 20mm x 40mm [ ] --- might make for a stronger rail...
ngoodfellow and Flo. Firstly, just to be pedantic, can I draw your attention to:- http://www.openbuilds.com/threads/cnc-axis-reference.951/ Simply, as a beginner, it will help to keep confusion to a minimum, from any further help passed your way. Assuming we are talking about the X axis now, the problem to consider, is that with the various possible strengthening techniques available, and there many, you will leave yourself with the need to generate a whole new set of Gantry plates at the out set. Have a look around the Forum at all the various machines built, and being built. There should be one almost right for you. Then you will probably find a suitable set of gantry plates to match. If you haven't yet, then read, read, and read. There is loads and loads of information available. I'm sure, many here, will admit that they came here with one idea, and went away with a whole different one!! Welcome to the world of CNC. Cheers Gray
thanks for the info and I have corrected my previous post I agree with the different gantry plate design as I did consider this... I will search the forum to see if I can find a build similar to what I have in mind! Main reason for a build of this size is to be able to work with a piece of 8ft x 4ft plywood (from Home Depot) without having to do alot of cutting (one cut down the middle to split it in half) in order to have the best material working area.
Haha, so here on openbuilds we use a standard which is absolutely uncommon in the world of cnc? the origin of the axes comes from the so called "right hands rule" and actually is used all around the world since the beginning of indurstrialisation. Every machinist / miller / turner / mechanic or nowadays cnc or cad guy knows it. It is even taught in apretenceship (spellign?) or even school when visiting a techical inclined school (opposed to arts/ language ...school) Not that i would mind.... all parts i milled the last couple of years turned out nicely even beeing obviously wrong way round LOL greets flo
I knew you would bite on that one Flo! This is how it was before I got here. There has been many a discussion about this matter in the past. But now, when you read about X and Y on this Forum, you know what we mean. Cheers Gray
I don't believe the issue is so much that it is non standard but that incorrect assumptions being made about where the front of the machine is. When you work from the front of the machine rather than the side it all makes sense.
Yes, once I decided that the orientation was the front, and 0,0,0 was the front left corner, the right hand rule made sense. I plan on adding labels to the axis's, so my son (6) understands what is going on.
OK guys quick question... what do you think about running a threaded steel rod as reinforcement through the center of the V-Strut in order to strengthen the design... any thoughts? (Before this turns into an XYZ argument lol)
I thought about scaling the design up to a 20mm standard instead of 10mm standard but then I will have to return my steppers for ones with a longer post... The motors I purchased only extrude about 20mm so it should work with the 10mm V-strut but if I scale to a large v-strut I may have issues.. I really want to be able to cut 4ft by 4ft! Also another noob questions... what gauge aluminum should I be using to cut out my plates? How thick will it need to be for standard OX design? I couldn't seem to find this in the specs
