Extrusion Stiffening Upgrade... Epoxy?

Ive been thinking of a way to stiffen the extrusions on my 500mm x carve. I know the deflection on the 500mm model is not as bad as it is on the 1000mm model. However i think stiffer rails will still improve my ability to cut harder woods, aluminum while reduceing the amount of chatter and noise i get from my machine

Now what I was thinking was to maybe fill the extrusions with epoxy hoping to increase the rigidity and reduce vibrations. However im no expert when it comes to thermoset plastics and epoxys so i was hoping someone may be able to advise me on if its worth it. will it warp or deform the extrusion? Dont really want to risk it on my machine yet.

I did the steel mod on my 500mm, but am switching to 40x40 v rail. I could sell you mine - it’s like a rock.

I also have a 1000mm with the steel mod (but tapped for 6mm screws).

There is a special type of epoxy, called steel reinforced cold weld epoxy that I have been experimenting with which has a tensile strength of around 4000 PSI. So far its been pretty amazing on everything I’ve used it on.

Stiffness depends on a few things:

  • The side surface of the beam PLUS the side surface multiplied with the square of the distance between the beam center and the center of gravity of the combined beam, so two standard makerslides with a resistance of 1,3 will result in a horizontal strength of 2,6 but if you bolt them together you have to add 1.6*1.2^2 = 2.3 for each makerslide so the total is 7.2 So bolting the makerslide profile together with a strip if 4mm makes them 3 times stronger. The choice for steel or aluminum has hardly a difference in horizontal direction as the strip is in the center of gravity.
  • The E value of the material used, steel is 3 times more rigid as a material than aluminum. Bolting them together does not change anything in vertical direction for the makerslides. The strip itself, being vertical does add strength so a steel strip is stronger than an aluminum.

As I use the NEMA17 motors I decided to use aluminum above steel for weight reasons.

I tested the deflection of the spindle plate before the mod and measured 0.55mm deflection at a pull of 10kg, after the mod it was only 0.17mm

If you can find the E value of the epoxy you can calculate how much it contributes. Normally plastics do not add anything in strenght unless they are glass reinforced.


Would adding additional stringers to the 60 minute mod have any effect? While putting a span in between the two maker slides has been shown to work, would adding spans to the outside of the makerslides (3 total spans) be an exercise in futility? Like the old saying goes, if one is good…

Just thinking about the concept. I can see problems with crushing the makerslides if too much tension is placed on them when tightening. But, is the theory reasonable?

If you would add a 4x40 mm strip on the outside of the makerslide it would add some strength and a lot if you still bolt everything together, One aluminum strip weights 260 grams and with the NEMA17 I did not want to add too much weight.
The 60 minute mod seems to work pretty good, the big advantage is that you do not have to take your machine apart. I agree to your concern and came up with the following.
Step one, drill 5mm holes in the 4x40mm strip
Step two, fix it to the inside of the makerslide and use it as a drill jig, drill from the inside

Note one of the makerslides is upside down

Put the 10mm bolts and slide nuts on the strip and slide the package together

This is the best pickture I have, nothing to be crushed here

NOTE: the strip should be 4.4mm so in my case I had to adapt the spacers
During assembly I did the wheel alignment first before trightning these bolts


I never considered that method for mounting. I guess those slots can be used for things other than what the instructions say! Thanks for pointing it out!

A strip of 4mm fibreglass or carbon fiber(keeping cost in mind) is also a good idea as the weight is lot less