After prototyping and establishing toolpaths and progression, I set up for a production run and got skunked. After the 1st hole of a series (set to 22mm depth) started at zero but stopped at 12.5mm and there was a ‘skipping/stepping’ sound. Subsequent holes ‘started’ 10mm or so above the workpiece and down to the 12.5mm depth. This happened multiple times after many resets, new files, etc. I could not seem to get much deeper than the 12.5mm after trying lower start depths and end depths.
I had a similar issue a week ago with a 1/16" end mill but not a 1/4" end mill on the same piece. Also today, with surfacing bit I had to 'fake the starting z height to make it surface properly. Prior to today, I do not recall having this kind of an issue.
As a newbie to the forum I’ll try to search for the answer, but if someone can help me cut to the chase, I’d appreciate it. TIA
Belt tension — the Z-axis should be guitar string tight (but careful not to bend the motor shaft): http://docs.carbide3d.com/assembly/shapeoko/xxl/step-5-belting/ on deep cuts it may help to remove one spring from the Z-axis temporarily, esp. if one hasn’t added a spoilboard on top of the wasteboard — it also helps to install the router as low as possible (installing the Makita adapter upside down will help). Some folks have found it helps to remove bolts which won’t stay tensioned (M4 Z-axis tension bolt, various V wheels with eccentric nuts), apply a thin bead of threadlock along the length of the threads, then reinstalling. See the video at: https://www.youtube.com/watch?v=_lIIb_PdziA Note that the X-axis motor is held in place on standoffs and if those bolts are loose this can cause belt tension issues.
It is also important to be sure that the collet is correctly tightened, the endmill fits correctly and doesn’t slip, and the router is mounted securely in the mount, and that the mount doesn’t shift. Note than endmill pullout can happen gradually, especially when profiling against tall walls.[4]
Are you sure you weren’t hitting the bottom of travel? Not hitting the collet on the top of the workpiece? 22mm deep… how much stickout on the endmill? This sounds a bit like there isn’t very much of the endmill in the collet - which won’t stand up to high end forces if that’s the case and may slip up into the collet under force.
Skipping/stepping sounds implies…well, skipped steps. Belt slipping, skipped steps, both sound alike. Getting the Z belt tension right can be a little challenging, and the pulleys behind the z axis plate have been known to come loose, making that worse.
Endmills are not great drills, and don’t clear chips vertically very well off the bottom surface - if the feed/plunge is too fast, that can induce skipped steps, which is also what this could be.
Thanks for the responses and narrowing the focus. I’ll weed through the links and go through the processes to deal with correcting this as I can. Bummer, I was trying to get something done not find more problems to deal with…
I double checked the ‘Z’ setting after this happened a couple times and the zero was where it should be. The collett had plenty of clearance and was tight. The lowest point was above the wasteboard level that endmill had just handled fine.
On the drilling front, I’ll try slowing the plunge/feed. I was wondering, but since I was doing the same basic drilling I had done over the past week, it seemed like something else was afoot. I have an endmill that lifts chips I might try, too. What is the best option for drilling? Smaller than 1/4" for 5/16" holes for one? This may turn into a major need.
I think unless you have special collets that’ll accommodate those sizes that I’d try a end mill smaller than the hole size and pocket out the hole in small depth increments.
The advice someone gave about marking deep holes and then using a real drill was pretty good advice.
(Though super tedious, it definitely would have been less of a PITA if I had used the drill press yesterday!)
The basic premise behind the purchase of the CNC was to repeat the drilling of a LOT of accurately located holes and not use a drill press. As noted above, It seemed to work fine previously, but likely added stress to the machine. I suppose I could lessen the depth of (2) of the holes per item and possibly flip the workpiece and drill (1) hole half through on each side.
Regarding multiple passes, that seems like a good option to consider. Unless there is an issue of drilling inside of the same holes multiple times.
Aside from drilling potential, the marking, carving, setting zero and other capabilities of this bit seems like it’s a ‘must have’ bit. On first searches, where can this be found for $14? So far I’ve closer to twice that for pricing.
Can the Shapeoko (or any CNC) be set/controlled to only move up and down without rotating for a contour? I thought (with at least Carbide Create) the holes had to be cut with a circular motion so you needed a bit with a diameter less than the hole diameter. It seems like it would be an easy option to add ‘vertical drill’ to toolpaths. Or is there a trick/workaround or setting I’m not seeing?
need a drill bit rated for trim router speeds (RPM) — IME, these are unusual and pricey when available
need a CAM tool which supports a drill operation (ideally peck drilling) — Carbide Motion doesn’t
Usually getting an endmill which is close to, but at least 10% narrower than the hole and milling as a pocket with a suitable toolpath and depth per pass setting works pretty well from an efficiency standpoint.
on a gcode level it can most certainly be done, the question is how to get a tool to generate the gcode for you if you don’t want to do this by hand
I suspect that in carbide create you can make an extremely tiny circle or even a very very short line segment, say 0.1 mm, and then tell it to contour that… and you get close enough
