Hi, I haven't been on here for a few years due to a marriage split and then cancer. I originally built an Ox CNC way back which I had to sell due to the above issues. A couple of years later in my madness I purchased a pre-built machine from Ebay to speed up my desire to turn some of my old designs into reality. The picture is not my actual machine but other than that it is identical. From the day I received it I had nothing but issues. Extremely noisy steppers, poor cut quality, Stepper motors failing one after the other, power supply failing, MB failing etc etc. I have since replaced almost every electrical component, and now I notice that the lead screw has warped. I went to fire it up the other day and it is not responding to X and Y commands. I did complain to Ebay with no joy what so ever a while back. So, now I am at the point where I want to salvage what I can by using Openbuild replacement parts. The Gantry is way way too heavy which I believe is behind the lead screw warping, the MB has a KK01breakout board which can be purchased for £25 (uuugh), it has nema 34 steppers which sound like they are crushing walnuts as they move. The CNC is truly horrible. The size of the bed is 150x100cm/5x3ft although the actual cutting area is a lot less and it weighs a ton (two men can barely move it. I paid nearly £4000 for this 4 years ago and as yet it has not produced anything of note. Yes I know, I have been walking about with MUG on my forehead ever since. I am interested to know how any of you would go about turning this useless ugly duckling into a CNC that will actually produce something. I do have my own ideas but most of you out there are far more knowledgeable than me and i suspect will come up with something much better. Just don't suggest binning it, not just yet anyway. Thanks for reading.
I would start with disconnecting all the steppers from the machine and run them with no load and see what they do and/or how they sound and take it form there. It may be a stepper driver that is bad or too much/not enough amps settings. The X axis lead screw may not be bent, just the normal whip in this length. Changing the bearing to thrust bearings may elevate this problem. That's just for starters. Once this is done, other problems can be checked and solved. The X axis, for example, is way too flimsy with the two (20x20?) rails. Should be at least 60x20 or bigger.
Thanks for that JustinTime, Yes I agree that the steppers need to be checked. I failed to mention in my first post that the spot weld had broken apart on the gantry and I had to have it re welded. This just makes me think that the whole gantry is far too heavy. I am toying with the idea of totally re making the gantry with lighter material ie Vslot and then using a lighter spindle, plus I want to jointly use it for laser engraver but I am not sure if Vslot will bow over that width.
Checkout How to calculate V-Slot® deflection - or base your redesign on our proven machines: OPENBUILDS MACHINES | OpenBuilds (or even sell off the old machine, put the proceeds toward a kit). The proven aspect of the kit way ensures success without additional school fees
In relation to this, if I do decide to rebuild I will purchase the Openbuilds Blackbox as it offers a much simpler setup solution as electronics are not my strongest asset. I have a feeling that my current Nema 34 steppers are not compatible with the Blackbox as they are only rated at 2 amp. Can anyone confirm this?. Spec highlighted in yellow. Many thanks
You can run 1.7A -> 3.2A motors with BlackBox: See docs:blackbox:currentadjustment [OpenBuilds Documentation] They won't fit our standard plates though, so maybe set them aside for now unless you really want to make adapter plates etc They will have more torque (which you don't need) but accelerate slower than our motors
Billy, first let me say that those steppers are MASSIVE! LOL. I have two NEMA 34 steppers on my Y axis but they are more like the first one on your list and they are pleeeenty strong. Keep the spindle. It's not that heavy. Change the Z stepper to a way smaller NEMA 23 stepper and you'll save just there 1.5kg. The Z axis doesn't need THAT much power to lift the spindle and the weight of it helps on the down movement.
