Go to main site 3dtek.xyz

Variation in depth when carving and some build pics


#1

Hi Guys,

I’ve finally finished the build and have successfully carved a few items, a couple where super intricate and took ~3 hours. The xyz took it like a champ. It’s nice to finally see some success after a few months of headaches (not xyz related; I had to get my garage ready, build a new table and working on it almost daily for a few hours at a time (sometimes late into the night)

Anyway, I am super happy with the results thus far with the exception of some variation in the depth of cut. On most of my pieces there is usually one side where the depth is slightly shallower than the other side. Its most prevalent in the X direction but the Y also suffers (although no as much).

I have checked for square and it is a little off to the order of 2mm across the 1500mm bed. I figured, 1-2mm across 1500mm is really not going to be noticeable especially considering most of my work pieces are going to be in the order of 3-500mm at most. For all intents and purposes, my straight edge looks spot on. The only way I can tell is by measuring with a 0.5mm gradation ruler at each extremity.

I have also noticed that there is a little slack in the z-axis. This one was the most difficult to get square but it is. There just seems to be some play in the axis more than I would like.

I have uploaded some shots of my electronics box and the problem carves.

Any ideas? Do i need to surface my waste board?

I am using Vectric Aspire for CAD/CAM and UGCS to upload the gcode. I am using a 60deg 6mm v-bit and my depth of cut is 0.7mm. I ave tried a simple fusion 360 generated gcode piece as well as a sample shapeoko test pattern and I have the same issue.

I can provide more info re GRBL settings and cut speeds but I don’t think they are relevant here?

Pics here

Some differences (my machine)

  • I have stiffened the X-axis using MattWheeler’s method using 10 bolts evenly spaced across the 1500mm length.
  • I have a 1500mm bed in both x and Y directions
  • my wasteboard is 16mm laminated MDF (cant find bare MDF at the right size which is 1500x1500!)
  • the wasteboard is supported by 4 (not 3) shorter extrusions (see pic) - and a $&# load of threaded inserts which were punched, drilled, countersunk and threaded!
  • I have a customised electronics box that houses my AIO and power supply. It has a top mounted IEC connector with fused switch and emrgency stop button and top mounted SUNON 240V fan blowing out. I also have a 40mm fan blowing in in addition to the 40mm fan blowing on the AIO (I dont think this affects it but just in case the info is here)

I still have a bit of cleanup to do but so far I’m pretty happy with the results. Let me know if you want some more pics of the build and ill create a dedicated post.

Thanks in advance


#2

I’ve been thinking about this a little more. Considering the variations happen within 10-20mm of each other I doubt it is a baseboard issue. I am starting to think it is related to flex in one of the rails. I don’t have any dial indicators so it is hard to measure.

For the purposes of keeping track of what it is I’ll list the potential issues here (in order of probability).

  1. Flex in Z-axis towards Y axis
  2. Flex in Z-axis towards X axis
  3. Uneven baseboard (and/or sag in wasteboard)
  4. Y-axis misalignment with wasteboard
  5. Torque induced creep (from axis direction changes)
  6. Flex in X or Y axis

I can’t really sell a product until this is all sorted.

Please let me know what you think or if there is a way to test each of the above easily.


#3

Had a look at your pics, and what stood out to me was that each individual cut seemed to be consistent in depth, but the depth varied between cuts, not within a single path.

If there was slack in the Z axis, you might see the depth of cut increasing within each cut, as the spindle wiggles down, or the bit pulls it’s way into the work.

If the work surface was not parallel with the base/rail/whatever, you might see a general increase or decrease in cut depth across the whole work.

This looks like either missed steps on the Z axis, or a sticky/binding spot on the Z axis.
It looks like in each individual cut, it thinks it has the right depth, and holds it, but next time it doesn’t get to where it thinks it should be, but holds that depth for the duration of that cut.

Maybe try some long cuts parallel to the axes, some long cuts where depth varies along the cut (sawtooth pattern, and look closely at what happens when Z changes direction), and some parallel cuts at the same depth.

Cheers,
Andrew


#4

the waste-board MDF flexes like a gym junkie, so keep an eye on that for starters. the easiest method i used for keeping near perfect level waste-board is this: just use the xyz to actually carve (level) out the wasteboard once your done anything you place on the wasteboard is now always going to be level according to the machine, works perfectly … except when you get radical temp changes and the wasteboard naturally flexes and warpes.
hope it helps.
your electronics look VERY tidy i like, i actually run in temps of 38-40 degree days out in a shed with crappy ventilation, my AIO board has heatsinks top AND bottom with fans top and bottom, purrs all day long no matter the temp… have NOT exceeded 40degrees … and will not. but running in high temp environment s is possible.

cheers Dale


#5

I make removable waste boards out of marine ply. They stay flat and stable.
I make signs out of 19 mm thick timber and screw the timber to the board and then clamp this to the machine. Stops the bristles getting caught in the clamps.


#6

G’day,
I was having a similar problem to this with my Z axis, I reduced my Z axis Acceleration down from 300 to 150 and it seemed to settle down, I think that I was losing steps due to the mass of the spindle motor and associated brackets etc etc was too much for the expected acceleration figures, so give it a try it may just sort things out.