Wheels on gantry

The wheels on my gantry are quite tight even with the eccentric nuts adjusted fully loose. This is due to hole misplacement on the gantry, a manufacturing defect or too wide a hole location tolerance which should be looked into. What is the life expectancy of these wheels? Would it be a good idea to have spares?

Is that on all axes or just the y-gantries?

Hello Chris, It’s the y gantries (both). Of the four eccentric nuts only one adjusts properly. I would suggest you spec these holes to be center drilled first and then drilled if not already. The fact that one adjusts properly suggests this (assuming the aluminum rails are produced with the necessary tolerances). Otherwise you guys have designed a very nice & robust tabletop CNC. I just wish you made a 22x30 instead of the 12x30!


Chris, on the subject of model size, can you order longer rails and screws so I can convert my 12x30 to a 22x30? I don’t want to have to modify the rail myself from a 30x30. Also, what are we looking at for costs?

Ah, I see. The Y-gantry plates had their holes positioned a little more closely together than they should’ve been (on the design side, though we didn’t catch it until it until later on), requiring the eccentric nuts to be nearly at their most open state when assembling the y-axes. Thank goodness for the adjustability of the eccentric nuts :upside_down_face:. If they’re all the way open and you’re still having tightness issues, then it may help to remove the paint from the inside of the eccentric nut hole to allow for a slightly larger wheel spacing. .

The irregularity in spacing is a bit odd to hear, but it may be a small burr somewhere or irregularity in the paint because the steel plates are actually laser-cut on a industrial machine :slightly_smiling_face: I’m curious why you’re interested in 22x30" in particular?

I didn’t know they were laser cut. Sizewise the 30x30 is too large to place on my shop table where a 22x30 will fit nicely and large enough to do the intended work. I was so occupied looking at various tabletop mills and figuring out the software requirements that I didn’t think other things thru. Fortunately your CNC design is easily modified. Just to be clear 22x30 is the work/cutting area. So, can you work on my request and provide an estimate?

Mostly it’s just the aluminum angle and the ACME rod that would change to make the machine bigger or smaller. For woodworkers a machine sized to fit on 60" by 60" Baltic Birch plywood would likely provide 50 inches or more of capacity.That would allow 1/2 sheet capacity for plywood/MDF projects. This would likely be popular IMHO.

I completely see where your coming from with that CRD. For now with how the machine is selling and how well its going its hard to change gears and make something bigger.

To make these machines bigger they would need a complete rework of the power supply and the control board to handle bigger stepper motors. Even bigger diameter acme screws and angle . Its way more work than it would appear. Its a complete redesign and rebuild from the ground up. I had this discussion multiple times this weekend at the wood show in Toronto.

Gregs, are you saying the 30x30 model has larger stepper motors and ACME screws than the 12x30 model? I want to enlarge my 12x30 model just 10 inches on the Y axis only which as your aware utilizes two motors, not the one motor as is on the X axis. I need to know this as I plan on buying 30x30 parts, namely the angle and ACME screws then cutting them to length. So, will this work?

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No they have the same motors but if you wanted to renovate the 30 X 30 you would need bigger motors screws ect. So you are safe to do that. What I am referring too is only if you wanted to make the 30 X 30 bigger.

Sorry for the confusion.

You would need larger diameter ACME screws to avoid wiping at faster speeds but everything else should work as is. More powerful motors would be nice but not necessary. More powerful motors could be had in the NEMA 23 size so the mechanicals would need only minor changes. Stronger motors would likely require a bigger power supply and drivers but the rest of the electronics should be fine.

What is “wiping”. I’m still studying getting ready for spring so I haven’t put my 12x30 to work yet.

I think he meant “whipping”

Yes, of course, I meant whipping. SDS, whipping is the wobbling action from rapidly turning screws that are not perfectly straight and/or well balanced. These screws, by nature, must be unsupported (except at the motor and the opposite end) to give the gantry unobstructed travel. Ball screws can exhibit the same problem. Belts can overcome this problem but may provide less positional accuracy. Rack and pinion drives can very good to overcome the whipping issue on larger machines as long as back lash is well managed to provide good positional accuracy.
As you can see there are many options, none of them perfect.

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