@Vince.Fab Thanks for the info! Is the tensioning guideline for the steel belts still ‘guitar string’ tight? Or maybe a little under that?
Do you happen to remember where you bought your current steel core belts from?
I’ve got over a year on my steel belts, and have never calibrated GRBL or adjusted belts. I have had to do some minor tweaks over time in fusion to account for what I’d assume is minimal stretching, has worked fine for what I do. I design everything to size, then use compensation to tune fitment. Most apparent on small adaptive and boring operations. Plan is to adjust and calibrate everything this week while swapping some things on the machine.
1 Like
I’ve got about 9 months, including some abusive testing on my kevlar cored belts which seem to be a less brittle alternative to the steel core whilst doing less stretching than the fibreglass varieties. ( from reprap.nl )
1 Like
@LiamN I received 5 meters of the Kevlar from reprap as well (back in March), but I am hesitant to put that on because of the stretching @mikep experienced with his, and that occurrence seems to be typical for aramid/kevlar reinforced belting:
…However, it’s important to note that while Kevlar has excellent dimensional stability in dry and stable environments, wet environments, or those with fluctuating humidity levels, can be detrimental to Kevlar-reinforced belts. This is because Kevlar cords (and cords made of other aramid materials) experience a change in length as they absorb and release moisture. This length instability can affect the belt’s performance — altering the engagement between belt and sprocket teeth, or affecting the tension of a V-belt, for example.
Although Kevlar is suitable for a wide range of temperatures, it has a negative thermal coefficient of expansion, meaning that it shrinks as the temperature rises and lengthens as it cools. Since this behavior is the opposite of most other machine components (especially those made of metal) — which expand as temperature increases and contract as temperature decreases — Kevlar-reinforced belts may not be suitable in environments with significant temperature fluctuations.
My SO3 is in a location that has temp swings of ~10-15 degF over the course of the year (August max to February min), and humidity fluctuations of ~35% relative humidity in the winter to ~60% in the summer…
1 Like
Yep,
It’s swings and roundabouts, mine is in a shed which regularly changes 15C every day, I periodically re-check the tension with the phone app and re-check the steps/mm when I have to re-set the tension.
I’ve only had to re-tension and recalibrate after some particularly violent abuse involving a fractured cutter in Aluminium making the whole machine shake.
EDIT - Swings and Roundabouts = Snakes and Ladders / Benefits and Problems for the non English 
1 Like
I think I also mentioned that as an alternative to fiberglass and steel I really liked the kevlar, and have moved all belts on my machine to kevlar. The fiberglass stretches a lot more, and the steel has fatigue problems I don’t like. Kevlar is better. They all have tradeoffs.
3 Likes
One purely better option over the generic fiberglass belts is to get actual Gates-branded belts — quality/consistency seems much better, as does lifespan — I’m still on the set I put on my Y-axis when I did a 9mm belt upgrade on my machine a while before before upgrading to XL.
3 Likes
Yes, I should have put that in my reply, that kevlar was your preference, sorry about that…
I have all 3 to try so I will start with the steel and see how that goes. I am still wary about the kevlar as my setup isn’t well controlled for humidity (or temp, but more so for humidity)…
1 Like
Indeed.
I’ve tried ‘em all over the past 4 years.
In my experience steel have “failed” (distort, tell me to change them out) most quickly. Especially at “guitar string tight”. I’m not an engineer nor a machinist, I have no way to quantify, just my practical experience.
I’m progressing into year two on Kevlar belts, Not too tight, not too loose.
Now, if I could just keep the rails clean under the v-wheels!
3 Likes
Did you try measuring the tension the phone app?
2 Likes
Yes and no. That brilliant piece of work was subsequent to my abandonment of steel belts. BUT, I stopped striving for “guitar string tight” belts upon breaking a stepper motor shaft a while back.
The steel belts I tried were never that tight.
4 Likes
Great,
I find that a periodic check of the twang frequency quickly tells me if the belts have started to stretch and go slack. The only time I’ve seen this so far on the kevlar belts is after some abuse though…
3 Likes
Same here. If the belts seem a bit stretched but appear un damaged I use this:
2 Likes
This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.