DeWalt mount flex

I have noticed, in my opinion, excessive flex with the DeWalt mount flexing. There is enough flex to deflect a center drill when spot drilling.
Any way to stiffen this up? It hangs out from the gantry far enough to generate quite a bit of leverage.
I have had several issues with the small XC and it is taking a lot of fussing to tweak it in.

Where is the mount flexing at? I haven’t noticed any mount issues, although the X and Y axes could both use some stiffening for something like the Dewalt.

Which stiffening mods have you performed?

What size is your machine? (Assuming 500mm)

What is your Z feedrate while drilling?

Are you drilling straight through or peck drilling?

Can you describe how your machine is “flexing”? I assume the flex happens between the makerslide and the spindle mount. Is this correct?

There is some north and south but also east and west. All wheels are tight as are the belts but even a center drill will push it off a bit.
If I mount an indicator in the spindle to level it there is way too much flex to get it tight.
I get .015 easily just by rotating the spindle.
I am going to see if I can move the spindle in toward the X bar. That should take some of it out, as it is the spindle is far enough out to exert lots of torque.
The with the addition of a dust shoe it is really noticeable. Not too bad with easy to mill wood but with aluminum (light cuts or just drilling) it is hard to hold a good tolerance.
That said, I am enjoying this CNC a lot, it gets close enough that it gives me parts that would be quite hard otherwise.

In addition I have not done any stiffing mods as yet. That may be next.

Definitely perform the stiffening mods first, especially on the X axis. I chose the Aluminum Tee available through McMaster-Carr to stiffen my X, but if you check the forum you will find several alternative methods. This should help some.

In my opinion, there is more slop in the Z axis on the stock machine then there should be unless just using a Laser. I will be upgrading the Z in the near future bc of its instabilities. I will be performing this one of two ways.

1: replace the Entire Z axis with linear bearings instead of the V-wheels and Makerslide. These are available on Amazon and several other websites.


2: replace the Z makerslide with one a little longer, replace the Acme rod with a longer one and alter it so that the top and bottom of the rod is captured by a Bearing. The bearing at the bottom can be secured by duplicating the set up on the top of the Z minus the stepper motor. This will also allow for a Limit switch to be installed on the bottom of the Z. Also by adding a second Delrin nut closer to the bottom of the spindle mount this will help stabilize the entire Z.

Option 2 is cheaper than option 1.

After observing the Z axis on my machine I have come to the conclusion that trapping the Acme Rod on the bottom as well, will help stabilize the Z axis. Especially if adding a second Delrin nut. I can grab the bottom of my spindle (DWP611) and flex it forward and back. When doing this, I see the Acme Rod move out at the bottom, thus not allowing the Acme Rod to stay parellel with the Z makerslide. If the Rod was trapped at the bottom this movement would not happen. The stock configuration is ok for light work IMO but adding the larger 611 spindle and more power requires a little modification. There is just too much “flex” that can come from the V-wheels and makerslide without the bottom of the Rod secured. The second Delrin nut helps distribute the forces as well along the acme Rod. This should secure the spindle enough so that the V-wheels can only slide up and down removing any forward/back motion or atleast reducing the amount. This upgrade should reduce any “flex” in the Z.

This issue is why I do not have a spindle mounted dust shoe. There is already too much flex, this will only compound it IMO.

This should do it for you but please keep in mind that I have not performed the mod yet. So I am doing a slight amount of speculation.

I don’t have all my info in front of me but to my calculations a 275mm makerslide on the Z is about the max workable length. With the bottom just barely past the bottom of the Xcarriage. The extra extension of makerslide above the carriage is not as critical bc the spindle is barely used all of the way up, mainly tool changes. The majority of the contact of the v wheels during cutting should be at the same height of the Xcarriage, or just slightly below. This will pretty much guarantee very little flex of the Z makerslide during the milling cycle and only showing flex under excess stress. Reducing feedrate in those situations will help with this.

The real Key will come with the second Delrin nut further down on the spindle mount and acme Rod. I am thinking about mounting the spindle mount to a 1/4" piece of aluminum plate to help facilitate the second Delrin nut but this is still in the planning stages. I am also tossing around the idea of using thicker piece of aluminum (1/2"-3/4") and just milling out the center area where the Delrin Nut This will allow me to do away with the aluminum spacers.

If I add this plate, I can gain around an inch of extra of travel by allowing the spindle mount to hang below the plate. This will allow me to raise the Xaxis in some fashion or another to give extra cutting capacity on the Z. Almost 6" (maybe 5.5") if I remember correctly and if my calculations are correct.

I studied my machine for about 10 minutes tonight. My observations show that the Slop is around the Bearings and V-wheels. By trapping the Rod on both sides this removes nearly all of the flex that will come from the Rod. The second Delrin nut will couple the Rod and mount together stiffening up the Z.

It will be hard pressed to really stiffen up the Z much more other than replace the V-wheels with Linear Slides. Which is basically a hole new design with no need of the makerslide.

Now with all of this said, this still may not remove all of the flex. The rest of the flex will come from the Xcarriage V-wheels and Bearings. Not the X axis itself but the Xcarriage is where the most prominent flex will show up next. Still contemplating how to reduce this flex. Considering using a single bolt all of the way through each set of VWheels but I also remember seeing someone use threaded connectors to couple each set of Vwheels together. By coupling the Xcarriage VWheels together this should reduce some of the rotational flex of the Xcarriage.

Hopefully I will be able to perform this update in the near future. But I am needed elsewhere. My shop time in the next six months will be drastically reduced almost to zero. So we will have to see. looking forward to see how your machine will turn out as well.

There’s observable flex in the V wheel screws. If you try to twist the router towards you, the endmill will deflect anything between 1 and 2mm (at least in my case)
Ill try and upload a video of this.

EDIT: i just remembered i did a stiffening mod for this exact reason and i cant get it to flex anymore.

With the dewalt a stuffing mod is a must.
Just the weight of the router is enough to cause the gantry to twist. I was amazed at the difference it made.

Unfortunately I have noticed that even with the mod the 1000mm gantry will still flex some when under a heavy cut load. But this can be avoided by tuning your cut settings.
(From what I can tell depth of cut seems to have as much if not more of a impact on this than feed rate.)

Also, for beastly cuts, keep them close to one side of the machine rather than dead middle. Cutting off to one side eliminates a lot of the twist, with or without the stiffening mod (but you should do the mod as well).

Good point! I need to try this.

I have installed a stiffener. An easy one but it seems to work well.
I used 1/2X1/8 aluminum bard and 8-32 machine screws. Drilled and tapped 8-32 holes in the bottom bar with thru holes in the top. No disassembly required and it seems to have made a real difference.
The router still sticks out a good bit from the maker slide. Not sure how I can snug it in about an inch or so.
Have some interference between the DeWalt and the stepper motor mount that required spacing it out more than I like.

Maybe some heavy duty ball bearing drawer slides in place of the V wheels.

Linear rails would be the step up for the Z axis.