1 Attachment(s)
Rebuilding terribly engineered laser cutter
I need help.
I am no engineer, tinkerer with penchant for cnc/electronics/rc more like, but this thing that i bought threw even me.
I am at a point where i'm willing to just angle grinder the interior out and put in a proper XY
in place of dogs breakfast equivalent i have here.
I can deal with electronics and control, but i've never done linear motion (just fixed/diagnosed some).
What i have here is a big'ish laser cutter (80W, 600x900mm bed) which is driven by 2 steppers, one for gantry (Y) and one for head (X). Both NEMA17 sized.
Head X motion is fairly ok, runs on block bearing, tensioner/idler fork needs replaced though.
The Y is the dogs breakfast i mentioned. Dual-shaft motor runs shafts to sides of ONE round linear bearing, 12mm round chrome rail and one of whatever the hell that is - just a plastic wheel running on flat side of angled aluminium extrusion. Both are pulled by timing belts, by non-coplanar pulleys, because dual-shaft motor is mounted off centre and coupled with spiral cut flexible aluminium couplings. Motor cant be moved or adjusted because some bright spark decided to weld the bracket into case, by also not leaving space for work table subframe to fully rise.
The machine will do engraving just fine, at speeds of up to 400mm/s in X axis. But as soon as Y motion is engaged in any way(besides moving a scan line down) everything goes to **** - terrible resonance, repeatably bad cuts, i suspect due to windup because of couplings, etc. It cannot cut/draw a straight circle at 25mm/s. Waving cuts all over the place at certain travel angles irrespective of speed (10-200mm/s). Trying to draw anything over 250mm/s stalls the motor, probably due to windup induced racking. Which excludes any small detail work where lots of stops and direction changes are present.
Machine is absolutely useless outside of scan engraving. Angle grinder came to mind.
What i need to figure out is how to lay out and plan for parts, LEARNING about the parts needed, how to square things with no reference points, etc, etc.
I have tons of photos of extraordinary, fairly expensive cheapness to show off if anyone interested.
What i want to do is fit the motion with one bigger motor (nema23?) for Y and plain old NEMA17 for X, remove all the Y motion nonsense and fit something like a block track/bearings on both sides, driven by single shaft, that is driven by belted transmission (nema23 to Y drive shaft) behind it.
I'd appreciate any pointers on where to start.
Re: Rebuilding terribly engineered laser cutter
Quote:
Originally Posted by
threedee
I need help.
I am no engineer, tinkerer with penchant for cnc/electronics/rc more like, but this thing that i bought threw even me.
I am at a point where i'm willing to just angle grinder the interior out and put in a proper XY
in place of dogs breakfast equivalent i have here.
I can deal with electronics and control, but i've never done linear motion (just fixed/diagnosed some).
What i have here is a big'ish laser cutter (80W, 600x900mm bed) which is driven by 2 steppers, one for gantry (Y) and one for head (X). Both NEMA17 sized.
Head X motion is fairly ok, runs on block bearing, tensioner/idler fork needs replaced though.
The Y is the dogs breakfast i mentioned. Dual-shaft motor runs shafts to sides of ONE round linear bearing, 12mm round chrome rail and one of whatever the hell that is - just a plastic wheel running on flat side of angled aluminium extrusion. Both are pulled by timing belts, by non-coplanar pulleys, because dual-shaft motor is mounted off centre and coupled with spiral cut flexible aluminium couplings. Motor cant be moved or adjusted because some bright spark decided to weld the bracket into case, by also not leaving space for work table subframe to fully rise.
The machine will do engraving just fine, at speeds of up to 400mm/s in X axis. But as soon as Y motion is engaged in any way(besides moving a scan line down) everything goes to **** - terrible resonance, repeatably bad cuts, i suspect due to windup because of couplings, etc. It cannot cut/draw a straight circle at 25mm/s. Waving cuts all over the place at certain travel angles irrespective of speed (10-200mm/s). Trying to draw anything over 250mm/s stalls the motor, probably due to windup induced racking. Which excludes any small detail work where lots of stops and direction changes are present.
Machine is absolutely useless outside of scan engraving. Angle grinder came to mind.
What i need to figure out is how to lay out and plan for parts, LEARNING about the parts needed, how to square things with no reference points, etc, etc.
I have tons of photos of extraordinary, fairly expensive cheapness to show off if anyone interested.
What i want to do is fit the motion with one bigger motor (nema23?) for Y and plain old NEMA17 for X, remove all the Y motion nonsense and fit something like a block track/bearings on both sides, driven by single shaft, that is driven by belted transmission (nema23 to Y drive shaft) behind it.
I'd appreciate any pointers on where to start.
Re: Rebuilding terribly engineered laser cutter
I don’t have one so can’t help but maybe posting some internal pictures will get you some ideas
Re: Rebuilding terribly engineered laser cutter
Quote:
Originally Posted by
routercnc
I don’t have one so can’t help but maybe posting some internal pictures will get you some ideas
Yes, it will be great to see the marvels of the Chinese engineering.. I am waiting for it.
I doubt it will be too difficult to upgrade it. Open its insides and find the drives for the motor, find the power supply for the drives. Hopefully separate drives , not integrated in some stupid board..
I doubt nema 17 could achieve proper laser speeds, only if its servo.
You can use square chinese rails 12 or 15 size for the system, not all of them are bad, i can point you to good ones for cheap, which i have tested, not once. Steel and so.
3 Attachment(s)
Re: Rebuilding terribly engineered laser cutter
Electronics are not the problem - Controller+front display panel (RDC6442S), 2x stepper drivers (0.09-1.13A M415DRV), 24V psu, laser tube HV psu (MYJG100W), 2x nema17 sized motors (cant identify by marks). Motors/drivers can be replaced if needed. For now it works.
The motion is another matter. If anyone is familliar with K40 laser construction, mine is that scaled way up past reasonable limits. K40 is 3020 bed, mine is 9060, runs on same XY essentially. Which is BS.
Problem is there is so little space and no continuous plane to put down reinforced rail on right side.
There are bed lift bearings located in the floor of 70mm wide space could have been used for rail. Same 70mm space houses drive belt, drag chain and said lift upper bearing blocks.
Any way to put down reindorced rails are to raise them off the deck somehow.
Re: Rebuilding terribly engineered laser cutter
I think you should stick with the small steppers, you don't need power you need speed and at 200 full steps/rev those little motors are quite zippy.
Re: Rebuilding terribly engineered laser cutter
Obviously this gantry is racking.
There is enough space to fit 20x20 aluminum profile and on top of it 12 or 15 size bearings. or if not, , size 20 rail in the air with no support and 1 bearing block. It will be way better than it is
Re: Rebuilding terribly engineered laser cutter
I'm sure they are. My problem with them is i cannot be sure of their specs. Model/serial numbers do not exist on "Smooth" manufacturer website. Nor anywhere on t'intertubes for that matter, aside from what I'VE posted...
Drivers came preset to 0.5A which suggests weak motors. Looked about the net for replacements, seeing nema17 sized motors up to 2A, 1A being more or less norm. So why 0.5A on mine ?
Right side is completely unsupported. The only things holding in "in position" are one plastic wheel pulled by gravity and drive belt. I can lift the gantry off the "rail" by 5mm. Right side motion is effectively restrined only on the left rail. So yeah, racking. But not to the point of stalling. I'm getting oscillations in straight and curved cuts. Resonance wave. Changes angle from speed to speed, but always present.
Re: Rebuilding terribly engineered laser cutter
Maybe armed with a plastic glue gun and pieces of plastic if needed, you can fix all on place and there will be no real need to do anything more? I have done that to flimsy 3d friends printer and the "upgraded version" was like 10 times better than the original
Re: Rebuilding terribly engineered laser cutter
Quote:
Originally Posted by
threedee
Right side is completely unsupported. The only things holding in "in position" are one plastic wheel pulled by gravity and drive belt. I can lift the gantry off the "rail" by 5mm.
The engineering issues there are the poor rail and bearings and the belts not being synchronised properly, the plastic wheel is a good engineering solution if the rest were adequate.
I think you should get someone to look at this for you as you are considering changes which, at best, may not help whilst not addressing the primary issues.
