I was considering ordering a Shapeoko 4 but I discovered something that bothered me. I want the 4 because I wanted to be able to deal with larger materials. I currently have a small CNC engraver that I use to create circuit boards. My current CNC has 800 steps/per mm. I see that the Shapeoko 4 has 40 steps/mm.
Does this mean I can no longer do PCBs with this?
Just being curious, does one actually need 800 steps/mm for PCB engraving ?
I have seen a number of PCBs being milled on both Shapeokos and Nomads, and never thought the stepper resolution would be a significant concern (mechanical precision, backlash, etc…yes)
Have you seen the cool PCB scratch milling work from @Debreuil ?
I would say yes it matters. On some of my high power PCBs, no, but on the small trace precision boards it matters. Even with the 800s/mm it can be difficult. (is it because of belt drive instead of ball screws that the resolution is so low?) Also it is worth noting that height mapping is VERY important for the precision boards.
As I noted, the Nomad is better for PCBs than the Shapeoko because of the smaller steps/mm, and is able to cut a finer trace than the Shapeoko.
Yes, the belt drive necessitates the step size due to the need to balance the pulley size/number of teeth against the motor torque and the need for the machine to move more quickly. While there are ways to work around this (replacing the motors w/ 0.9 degree ones, larger pulley, reduction gearing), they are necessarily compromises, and are not supported.
For the PCB Z-level the usual technique is to probe the surface of the PCB, then map the cutting to that surface — bCNC supports that.
Yes I do surface mapping in Candel for height mapping when I do PCBs. It looks like the Shapeoko 4 will not work for me. (and I don’t have a friend with one for me to review) Oh well, back to the research for a CNC I can use. (while avoiding Chinese CNC)
You may be right about the accuracy. The table support on a 3018 varies with y position. Stupid design, but they all have that. The linear rails should be on the moving table with fixed linear bearings. The support would be constant regardless of y position. Thanks for your post. I will research it some more. I really like the hybrid table on the Shapeoko 4! BTW, I also have my PCBs made, but the router PCB is for prototyping. Get it right, then order it.
My ballscrew Nomad runs at 400 steps per mm and is incredibly accurate. Also if you are worried that much about accuracy…probably shouldn’t be using a trim router unless you are well versed in measuring and adjusting runnout constantly.
I am not sure I know what you mean by a trim router. My current spindle is a 300w brushed. I made a video to control the motor. https://youtu.be/svj7zPuYvos
When you say trim router, you mean consumer routers? (Makita,Dewalt) Is their runout too much?
It seems obvious that Jim thinks his 3018 is more accurate than a Shapeoko or Nomad. The folks here on the forum believe that c3d machines are great and evangelize them, myself included. If people want to bash thier head against the wall let them. If getting a headache does not stop them you telling them to not do it is wasted effort. Since it is Jims money he can spend it anyway he wants. If he can find a machine that is better than c3d makes then great for him.
I think you mischaracterize my points. I do not want to order something I will be disappointed with. I pointed out how bad the design was for the small engraver. I am looking for a better larger machine. I am seeking answers and information. This is supposed to be a civilized forum. Perhaps you don’t belong.
so the shapeoko’s have a stepsize of something like 0.025mm
(just looking at the number of steps is only half the story, you obviously need to multiply that by the distance at the actual router bit for a full revolution).
If that’s not accurate enough then … yeah not the right machine for your needs.
However there are other areas to also look at. How accurate is the diameter of your bit? What is the runout? Accuracy has many aspects and you need to look at all of them to find the real limit…
@jelanier maybe you could just say what you’re looking for?
Are you looking for a machine with a huge work area that’s also suitable for milling PCBs?
Put simply, Carbide 3D doesn’t have one. The Shapeoko can do it but that’s not really its thing. It’s a router, it cuts shapes out of stuff. You need to look for a screw-driven machine like this one but to get one that’s as “batteries included” as Carbide 3D’s machines is going to cost you a fair bit.
That said, some folks on the forum have had luck putting ballscrews on the Shapeoko, with which you can get the oodles of precision you’re after. 1604 ballscrews + stepper + 8x microstepping = ~0.0025mm positioning.
“But microstepping isn’t accurate” you might say and on a mill hogging metal I’d agree with you but milling PCBs doesnt involve a whole lot of cutting force so I don’t think it’s a major concern here.