Have I got this right? X axis friction

LowRider CNC Your Builds
1

I am creeping along here and have assembled it all today.

How much friction/rolling resistance should there be in the X axis on the two bars?

Here is a video of the thing in action.

If you push it … it stops pretty quickly. Real quick. I have loosened and tightened and fiddled with the bolts but it seems to be the same.

What do you all think/advise?

Cheers

Rob

2

Probably alright. As long as it’s not sticking anywhere. It will smooth itself out over time too.

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Thanks mate. Got the X belt in after much fiddling around yesterday, today is the Y sides and then see what happens

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My strategy is thus:

Set up belts, then do a long fast move on the axis at maybe F5000. Which is about twice as fast as you’d want to cut anything. Return to Zero. Make the belt as tight as you can, while still achieving a fast move with no slipping.

For example, here’s a workflow:

  • Nota bene: I define “X” as my long axis driven by the two parallel belts.

  1. Bring the gantry to X=0. As defined by some physical stop. Be certain that when in contact with the stops, both ends of the gantry are perfectly aligned with each other. This is your base physical starting point. Spend time making sure it is as perfect as you can make it.

  2. Sneak up on your belt tension. I use the console on CNCJs and just type in a move. For example, G0 X2200. No F parameter, just let the machine crawl along at the speed defined in your firmware. Return to Zero with G0 X-2200. Do the wheels come home and contact the stops precisely at the same time? There are lots of reasons if they don’t, but if your two belts are reasonably matched in tension then look to the squareness and stiffness of your gantry.

Do it again, and grab the long side of either X belt and tug on it. At some point, the machine will slip. This helps you get a “feel” for how tight your belt should be. When it slips, it’s too tight.

  1. Tighten both belts as evenly as you can, while successfully repeating the long X move. Get them as tight as possible, while still making accurate long moves.

** Nota bene: M84 is your friend. Release the steppers and move the gantry to zero by hand when things get cockeyed.

  1. Once you’ve got it dialled in, experiment with the F parameter:

G0 X2200 F3000

The F parameter increases the overall speed of the movement.

This is totally subjective. There’s some F parameter that’s just too high for your machine. If you’re happy with going slow, then so be it.

What I do is crank up my speed little by little, watching the gantry return to Zero, until if fails. Then I loosen the belts a bit and see if it will go faster. At some point, you will arrive at a happy medium of accuracy and speed, and then you go to bed.

Arriving at a maximum comfortable speed for your machine gives you a lot of flexibility in terms of feed/speed parameters. This process takes an evening (and a shorty of PBR), but you will learn a lot about your machine and put to rest your questions about belt tension.

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