I was doing a quick project on the CNC tonight and was deeply disturbed by how badly the spoil board is gouged up. I can understand a little bit of press-through when machining all the way through your work piece, but C’mon… is there any excuse for the 12" long gouge that goes 90% of the way through the spoil board???
Supposedly we’re all trained and all capable of using the equipment safely and effectively. Maybe we start charging a stupid tax if you damage the equipment… doesn’t have to be crazy, just something to remind people that if they screw up, they should do something nice for the rest of us that have to live with their idiocy.
For example, if you nick into the spoil board more than a few thousandths, but less than 1/4" you drop a buck for every foot you cut. If you’re over 1/4" deep, you drop a buck an inch. Again, nothing crazy, but it would remind people to tighten the collets and not be idiots.
The resulting question is always “Was the damage because the floor was not set or because the collet nut was not tight?”
In the former case a responsible person would, at a minimum, be willing to babysit the machine when a new wasteboard is prepared. (In my opinion that would be more effective than a “stupid tax”.)
In the later case we need to get a (long handle) torque wrench to ensure the collet nut is correctly tightened and remind users to remove sawdust from the collet, collet nut, and endmill before and after using the machine.
So I’ll ask a stoopidnoob question:
once you’ve started your cut, and the chips are resting in the groove as the router moves away so you can see the cut, what is the preferred method to figure out if the whole thing is cutting through too far? I have my ideas, but would like to hear from the more experienced what really works…
(This is to avoid such things as the deep “circle” that’s currently cut in the spoilboard…)
Use the feeds & speeds built into the tool bits, I often add an extra Z cut layer just to be sure I get an idea of how much dust / chips it’ll throw on each pass.
If a bit slips, it’s not usually on the first few inches, and on the second pass of that layer, the channel is usually cleared (If not, your bit is too big to begin with). If the bit has slipped a little, you should see it as you pass the first cut as the bottoms won’t be even… that’s a good time to stop.
Also, WATCH how much the Z axis travels, if it looks like it’s going down further than you expect, hit pause, grab the vacuum and clean out the channel to check. The Pause button works wonders because it’s exceptionally good at resuming from the current position. We get in the habit of guarding the E-stop button on the first pass (and rightly so) but after that, just keep watching with your finger over the pause button.
Finally, like driving, DON’T SIT THERE ON YOUR PHONE, pay attention to what’s happening.
It can be impossible to tell. With a smallish endmill (e.g. 1/8 in) and thickish stock (e.g. 18 mm) the angle can be too steep to see the bottom of the cut.
Or, when using a downcut endmill chips tend to get packed into the bottom of the cut. The packed chips can cover the bottom portion of a cut.
If the endmill slipped the user may not know the cut is too deep until the entire file is finished.
In any case, the solution to the problem is trivial: 1. Remove sawdust from the collet and everything touching it; 2. Get the nut tight (torqued); 3. Set the floor.
Doesn’t spoilboard dust look significantly different than most of the things people are putting on the machine? I’m sure some people are working with MDF, but aren’t most people working in wood?
what gets me is why does this expensive spindle keeps slipping bits.I cut brass, wood, aluminum on mine and have never had this problem at 1/10th the cost. maybe the collets are just shot.
I would recommend a different ER25 nut also. The one that is in use now is always more difficult to tighten than one that uses a spanner wrench like this one:
Maybe we can put a Z bend in the regular wrench part to get the closer together. I know that’s usually my gripe when loosening: that the two wrenches are too far apart to easily squeeze together.
I’m not recommending this method mind you, BUT a fellow that helped train me with some cutting (not at DMS), pretty much followed all the suggested rules of good protocol except he used a vacuum behind cutter to remove chips while cutting to check his depth. He told me that if a spoil board gets gouged, it’s usually neglect by the operator. Either by not caring and HAing it or being unexperienced enough to know better of what to do.
If the vacuum collection is working correctly, the user does not see the chips.
That’s the crux of the problem. The folks who cut into the wasteboard don’t discuss (report) what went wrong. There is no way to know if “this expensive spindle keeps slipping bits”.
Having said that, I am aware of it occurring twice. (Easily identified by the fact that the cut keeps getting deeper with no Z movement.)
Getting the nut tight can be awkward (at my six feet the angle is steep; I nearly always bloody a knuckle) or difficult (@John_Marlow has said she does not believe she has the strength with the tools we have). I suspect fine sawdust is essentially a lubricant in this context. A bit of sawdust certainly makes the endmill feel slippery in the collet. In addition, it is certainly within the realm of possibility that a user could simply forget to tighten the nut (just last week I forgot to tighten the chuck on the Sherline; oddly the part came out perfect; I will never do that again). Added together I can certainly understand how an endmill might slip.
My thoughts…
• Keep the collet nuts and wrenches we have.
• Make a wooden jig for the collet wrench so it does not have to be touched when tightening / loosening
• Get a (longish) handle torque wrench that fits the spindle
With that setup I won’t have to deal with awkward angles, @John_Marlow will have leverage, and the nut can be precisely torqued.
If you’re referring to having to push outward with the wrench to adjust the tightness, and then banging your knuckles on the sharp metal corners nearby, there’s a way to hold the tools to where you can always push them inward, rather than outward, so you don’t hurt yourself like that. I’ve been meaning to make a sign about this as a reminder, but it involves which tool you have on top whether you’re tightening or loosening (sorry I don’t remember off-hand).
I’ve also had times when the bits were tightened so hard that I had to ask anyone around for help getting them loose. That’s always a pride-swallowing occasion.
Probably because it’s usually presented as a user error issue rather than a spindle/collet issue. I had a bit slip on me and the more-experienced woodshop user who helped me made sure I knew it was because I hadn’t tightened the collet enough. Not because the collets may be crap.
I’ve been looking at this a long time. A few observations with respect to spoilboard damage:
The most common cause, is failing to fully set the tool height after every single bit change. I have verified this with video. Typically, the user forgets both, or forgets to set maxZ.
Second most common, is setting the Z heights backwards (typically produces the really deep cut-throughs.) This is usually hitting the controller key for set MinZ (surface) twice.
It’s rarely the bit slipping. I does happen, but not often. It can be mostly eliminated by blowing all the dust out of the collect and nut, and cleaning any pine resin with blade cleaner or Simple Green. It does NOT require superhuman strength to tighten the nut effectively, and too much torque may damage the collet, nut, or (eek) the spindle itself. Cleaning must happen EVERY single time the nut is removed, without exception.
Alex and I have been separately working on re-vamping the training for the multicam. I envision this ultimately as a Moodle, a lab on vCarve, and 2-hour lab at the machine for hands-on training and q&A. I’ve been working on the Machine Lab, and have a syllabus ready now. If my screwed up back will permit me, I may add this to the schedule soon.
