Router Shuddering

Does anyone know how to prevent the router from shuddering back and forth? I first noticed that a shudder had developed when I was milling some aluminum. I was about half way through my cut which was basically a series of circles when I noticed that when the gantry was pushing forward or pulling back the entire mount that the 611 is on was shuddering back and forth. I then raised the bit and had it do the cut again this time in the air and sure enough every time it is at the left or right side of the circle where it is pulling or pushing the most it shudders. I would like to clarify that it isnt the entire gantry that shudders only the 611 is. Its not a big shudder so when I cut things like acrylic it doesn’t really make a difference but when Im milling aluminum it causes a ton of problems and is basically preventing me from even finishing a single pass before the bit jams its self up and the cut goes all erratic.

1 Like

Check the set screws on you pulleys.

The issue you’re experiencing is likely due to deflection of the cutting bit in the y-direction. When your bit is trying to cut in the y-direction your mount is encountering more resistance than it can handle, so the bit/mount is deflecting; when it deflects, the depth of cut is increased (the edge of the bit digs into the surface when the bit is angled from vertical). This increase in the depth of cut causes the bit to be pushed against where it wants to go, causing chatter or shuddering.

You’ll experience this more noticeably in the 1000mm XCarve, and also if you haven’t stiffened your x-axis. I would pay close attention to the tightness of your v-wheels on your z-axis as well.

I figured it was a problem with the v-wheels on the z so I checked them and in doing so found that in order for the wheels to be tight enough to prevent the spindle from deflecting the z-axis can no longer go up or down. I have two questions.

  1. is it possible that the eccentric nuts on the v wheels are pulling the spindle to far out of alignment because the holes have become misshapen from adjustment over time?

  2. Is it possible that the lead screw is bent because when I do jog the z-axis it looks like it isn’t going smoothly?

I think the amount of wear from adjusting the eccentric nuts will be negligible. It is possible your lead screw is bent. Mine was, and it seems a lot of others received theirs bent as well. You can contact Inventables to see if they’ll replace it, if it is causing the issue, or you can hammer the lead screw with a mallet on a flat surface to lessen the bend.

ok I will see if I can straighten it. I was hoping not to have to take the z_axis apart but I guess I dont have a choice.

After talking to the customer support, they will not replace it because according to them that is just the way they are. They said to just crank up the current going to the z axis which I didnt want to do seeing as how my enclosure is to small and doesnt fit my arduino and gshield in it to properly cool them. Any tips on cooling the shield if its just sitting on the table?

Since you apparently have already made adjustment to all the mechanical aspects that could cause your issue then you really need to set the current going to ALL of your axis on the GRBL shield. It is easy to do and can go a long way to stop the jerky movement. When cutting aluminum, depth of cut and feed rate are very important and will take lots of time testing variations of both to get right.

Setting your current won’t necessarily cause over heating of your GRBL unless you turn it up too high, in which case your stepper motors will heat up or get even more jerky.

The factory setting on the GRBL should NOT be accepted as the proper setting. There are lots of posts on this forum on setting them but in a nut shell do this:

1. Jog your Y axis all the way to the front of the machine. Issue a command to send the Y axis as far as possible in the opposite direction. While it is moving turn the power down to the Y axis until it stutters and then turn it back up until it is running smoothly. You may have to repeat the jogging a couple of times until you get it set.

2. Using a sharpie, put a dot on the trim pot that you adjusted. This will be the lowest possible setting (and likely be too low for actual carving especially in aluminum).

3. Repeat Steps one and two only thins time turning the power up until it starts to stutter and then back down until it runs smooth.

4. Put another dot on the trim pow with a sharpie which will identify the upper limit.

5. Adjust the trim pot to positon that is between the two dots (upper and lower limits).

6. Repeat this process for the X and Z axis.

7. Once you have all three axis adjusted let the machine set idle with the power ON for 10 minutes or so and then check the stepper motors for heat. If they are heating up while sitting still then turn the power down. If they are cool or slightly warm to touch then do a test carve on something. If you find that there is still some stuttering on one of the axis then turn up the power on that particular axis just a little bit at a time, testing after each adjustment.

If you have the 1000 mm x-carve, you really need to modify your x axis to stiffen it. Especially if you plan to mill aluminum. That will be the single biggest improvement you can make to the X-Carve. That is especially true since you have the Dewalt on board (which is another major improvement).

For cooling your GRBLE, you might try finding a computer repair store. They typically have computer cooling fans laying around. You could connect it to your computer to power it and mount it above your GRBL.

If the problem you are having is caused by something else then this will not fix it but it will make sure your machine is delivering the proper power to your steppers. From what I have read in your original post, this is what I believe will solve your problem.

Best of luck my friend and happy carving.


It sounds like it could be “Chatter”
I ran into this when I switched from MDF to white oak just this weekend.

When moving “side to side” the router would shudder and make this rough “scalped” cut.

This is caused when the cut is putting too much of a load on the system causing things to flex and snap back.
“Load” is determined by several different factors so there are lots always you can adjust your system to eliminate this.
Some of the factors include, RPM, Feed Speed, Depth of cut, Type of material (Hardness) Type of bit, Type of cutting strategy (Climb vs conventional), How much if the bit is sticking out of the spindle, how much flex does your machine have.
The easiest ones to play with are RPM, feed speed and depth of cut.
In my case I turned down the RPM as low as it would go and it helps a lot but did not eliminate it.
Later I ran at a significantly lower feed rate and had no issue. The trick is to find the combo of settings that will give the best quality to cut time.
For aluminum you have the added problem of heat build up if you cut too slow. So just “slowing down” could cause other problems.
I have heard people say that cutting fast with very shallow depth of cut works best. (If you look there should be several posts on cutting aluminum that will cover this better)

In my case the “Shudder” issue shows that I have my XC tuned pretty well. Because before when I would put too much load on the system it would slip or stall and get knocked out of alignment. Now it just keeps dragging the bit along as it flexes and skitters across the material.

1 Like

Thanks for everyone’s help however the problem still isn’t solved.

Heres an update. I cranked up the current to all my motors and tightened all the v wheels so it is much stiffer and I am no longer have the issue with the z axis not being able to move. I also went out to home depot and got some steel and stiffened the x axis following chaleys guide so now the x axis is much stiffer however I am still having my original problem but now it is only when the x axis is pushing forwards so thats some improvement. Im not sure where the deflection is coming from now that the x axis is stiffened I would think that it should be possible to at least get one pass to work properly but so far I haven’t managed it.

this is the endmill im using

as far as feed rate and depth I have been trying everything and every single pass is the same no matter how fast I go or how deep.I run the 611 on 2 or a bit over that.

Do you know if you are using climb or conventional milling?

I dont know what that means but if it helps for these cuts im just using easel.

After googling climb milling my answer is no. and I should explain all im trying to do is get the endmill to make a small circle just to see if it ends up at the same point it started, so far it hasn’t even made a complete one.

What kind of feedrate and depth of cut are you using?

I’m not using one because I was having so much of an issue I would change them every cut. I will say now I turned the depth to be really shallow im not sure exactly bit not veru deep and the feed rate to about 12 because if I go any faster its a mess.

When the router touches the surface of the material should I be able to see it deflect at all. Right now I can see the whole router tip backwards as soon as the endmill touches the material it is cutting, I checked my vwheels and they are all extreamly tight some of them are even set to as tight as they can go and there is still movent of the router but I can’t pinpoint where the movement is coming from.I thought it was the x axis because I hadn’t stiffened it yet and it did help now that it is stiffened like I said the router still deflects backwards when it touches the materials surface.

What material and depth of cut does this happen in?

Do you have a range of DoC that you have tried? I stay between 0.005" and 0.010" for my DoC with 6061 Aluminum.

Are you able to post a video? That would help a lot to determine what’s going on.

I have deffinetly tryed a cut in that depth with the same result. I can certainly shoot a video but what is the best way to post it.

I think you can upload it directly into your post from your computer. Youtube is a nice choice if you are already familiar with that, too.