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Discussion in 'CNC Mills/Routers' started by John foale, Nov 7, 2014.
Great bit of kit time will tell if it is up to the job
John foale published a new build:
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Nice build. We'll be waiting to see some of the projects it produces.
Great build! What extrusions are you running for the gantry at that length? Any problems with deflection?
Deflection on X is a problem, not a huge problem I had some defection on the Z axis this was due to the inferior Spindle clamp supplied,
I purchased a aftermarket heavier duty one and that cured that problem.
Having said that we have not really pushed the machine due to belt slip once we have upgraded the belts then it might be more of a problem.
In this case I will look at ways of stiffening the gantry or if need be shortening it
Consider using a Belt on a Belt, Rack and Pinion style. It seems to be far more reliable stopping stretch and slips.
I will keep that in mind, thanks
what is a Belt on a Belt, Rack and Pinion style
I do know the belt drive design on the ox machines is flawed, it can slip to easily, also there is too much movement on the z and x axis(width in my case)
Basically, a belt is fixed within the actual slot of the rail, teeth facing upwards. Then, the next belt is fitted as usual with teeth facing downwards, therefore meshing, with the first fixed belt. With the wheels of the gantry pressing the two belts together. It does seem to be a logical step to take.
There are several threads describing these methods in detail on this forum. Just do a search on "Belts", and many will appear.
I now know what belt on belt is, not sure i can see an advantage other than dealing with slack, is that correct GrayUK
Well yes, it does deal with the slack, and stops stretching over the length. This is the main problem with belt drive.
It helps with the repetitive consistency factor, which is what CNC is all about.
As i have a problem with the long axis jumping now and again, I guess this is concidered a good mod.
Also i will need to mod the short axis as there is too much flex when drilling downwards.
I have already replaced the z axis with a pre made one from cnc4you, that was a massive improvement, the rack and pinion is nt really an easy option for me as i have a dual plate on the long axis
I want to build the ox in this size to for my sign shop as well. What kinda of belt are you using? I am thinking of using the GT3 belt which is thicker than GT2. For motor I want to use nema 23 1.26Nm 2.8A which fit my budget but I am not sure it is strong enough for this size.
GT3 belts are the minimum spec I would go for, the machine uses GT2 at the moment but I believe it is being upgraded along with idlers for the X axis and strengthening the X span.
What about motor spec?
23 NEMA 1 on X & 2 on Y and 17NEMA on Z, I don't have the exact motor specs to hand
I have the GT2 3mm belts, my machine is 1400mm x 700mm and the belts are not really good enough for routing out guitars, they jump teeth, I am upgrading my machine completely with supported rails and ball screws or lead screws, i have had enough of the poor design problems with these would be cnc machines, that are really only good enough as 3d printers or laser printers.
I have to agree with you, we were sold the machine with the job in mind as a criteria, it has not lived up to it in many ways, the cost swayed the purchaser
Thank you for sharing, I will keep these factors in mind before building anything. I just want to cut thin 3-5mm plastic sheet with my machine.
You should be okay then with thin Plastic sheet
one thing to look out for with the OX, make sure there is an idler pulley either side of the gear on the Nema motor, this will help to stop the belt slipping.
Piccyman can you explain to me what you mean? The ox plate design have 4 solid v wheel on the top and 3 at the bottom. Do you mean changing the 2 middle ones on top to pulley or adding 2 edition pulley to it?
Sounds like Piccyman was talking about this: http://www.openbuilds.com/threads/longest-x-axis.868/#post-10332
This is from Colin at Robocutters, my machine didn't have this mod so the belt kept slipping.
I have now completely removed the short axis, and rebuilding it with 2 50x50x5mm ally square sections, supported rail and a ballscrew. The long axis, i am not sure about yet, but have 2 1400mm balls crews on their way.
I see what you mean now, I guess its kinda catch 22, need a machine running first before you can cut a mod plate. I think I may do a double belt trick with 5mm GT3 first and see.
Well it has been months since we purchased the machine and still not one Guitar off the machine! the supplier has been very slow in help to find solutions to our problems, we need a belt upgrade, idler pulleys etc, personally I don't see why we should pay for these "upgrades" as the machine will not do the job it was purchased for in good faith and on good advice
I agree, I have now almost rebuilt my machine, on the plus side i now know how to build a strong machine cheaply.
to make it worse, before i bought the machine i asked if it was strong enough to build guitars, and was told it would do it easily, not even close :-(, at best these are only good enough as a 3d printer