Randomly I noticed my engraving bits were making weird finishes and I looked and noticed this issue. Looks like the bit is either sitting crooked in the collet which makes the point actually make tiny little circles, or the entire router mount is tilted a bit. I’ve tried loosening the screws and pulling the compact router out and putting it back in but it doesn’t seem to improve the problem. I end up just taking the bit out and putting it back in over and over until eventually I get it to sit “good enough.”
The next leveling issue i have is that the entire X axis is inaccurate slightly. Y axis is fine, but i have the carbide corner square and so my pieces sit square to the machine, but if I engrave a thin line along the x axis, it slowly moves and at the start the line is 20mm from the x axis 0 point and by the time it makes its way 18" to the right its 21mm from the x axis 0 point. Is my entire cross beam that the router is on tilted at a slight angle? I assume I could jog the machine all the way forward and see if theres equal space between the front plates. If there’s not, how do I correct that and how do I stop it from twisting like that in the future?
I had a similar issue where it was making a tiny circle at the bottom of corners with V-Cuts. I fixed this by taking the collet apart and cleaning the sawdust out completely with air hose and an awl where compacted. This fixed the issue.
Your second issue is caused by your gantry not being square to the y rails. Run the gantry to the front, and measure the distance between the gantry and the Y rail end caps. Power down your shapeoko, and make both ends equal.
Also, have you checked your Y belts tension lately? Uequal tension will cause the X gantry to skew a little when it travels from back to front.
So I’ve always been confused about the belt tensioning with the bike app and all that. At one part it mentions sticking blocks under your marked spots then it says to use a 1/4 shank bit on each marked spot… wouldn’t big blocks vs a tiny bit create completely different frequencies? Wouldn’t it also depends where you placed these? It kinda just tells you to pick a random distance, how is that going to get me to the perfect frequency when all those variables would alter the tone? If I stick a 1/4 inch bit under my spots then tang it, it just slaps like a fish on a rock. If I put a 3/4" high block under it makes a twang. I’m confused how the variance of the tests tells me what the frequency should be?
If this is telling me how to make the tension on the 2 belts the same, okay, but what’s the tension supposed to be in the first place? I’m not machining microchips here, I just need it “pretty damn good”
Like if I pull on the belt, what should the distance between the beam and the belt be? Wouldn’t that be a much simpler and quicker way of getting people routers to a decent spot?
If at 1/4" height, your flapping like a fish, I would say your belts are to loose.
I’ve made two marks on my Y rails, 11" apart, 12" from the front of the machine. Using a sound frequency app on my phone, I tuned the two belts have an equal frequency. I just now checked and they are around 90 hz. Pretty sure they were around 115 hz when I first tuned them, but they are still pretty close to equal tension.
I use two 1/4" hex drive screw driver bits to raise the belt.
Sorry if that was confusing, I’ll try to answer each below;
It will be a little different yes, but if you stay away from the ends of the axis keeping the angle created on the belt shallow there is only a very small change in tension with the block height, but stick to about 1/4" and you should be good, I used blocks of about 10mm, the frequency difference is small.
I left the block height at ‘small’ to avoid people thinking they had to hunt for a specific size, perhaps “6-10mm” or similar would have been a more useful suggestion.
The distance between the blocks is the key parameter, I gave tables for 280mm and 500mm length of belt between the blocks because the longer axes on the XL and XXL let you use a longer run and that makes it a bit easier on the larger machines.
So long as you don’t create a steep angle between belt on a block and a belt clip or V wheel the ends of the belt outside the raised section you’re twanging don’t really matter.
I suggest putting the raised section approximately in the middle of the axis, the key is consistency between your Y axes, measure them up for the same spacing and positioning.
As Steve.Mc says, if you can’t get no twang on 1/4" blocks then that’s too loose and wants enough tension to twang at least. Flapping around like a fish is way too loose.
The 3/4" block is creating enough angle at the ends to lengthen the belt and bring it into tension.
Equal tension on the two Y belts is important to keep things square.
I’d look for 100-130Hz over 280mm for a short axis and 70-90Hz over 500mm for a long axis, tight enough is all you need, extra tension above that just prematurely wears things out for no benefit.
The problem with that is we don’t know how hard you’re pulling…
In the video I did try the method where you pull with a specified force and measure. I didn’t like it and didn’t get consistent results. The distances are small and hard to measure, especially when you are trying to pull with a specific force at the same time. I found the twang and listen method much easier.
Once you get the tension OK and hear the note the twang is meant to make you may well never use the frequency app again.
I just check the machine by ear now, I know what sort of note I expect, I can twang left and right Y axes and hear if they’re about the same tone. I only get the phone out to set it up after changing belts.