Tim

   Whiplash might be unusual 😀   .. but threaded screws can certainly suffer from backlash ...

  The threaded screws can also suffer from being curved or bent.

In the common 'home' 3D printers, the threaded screw is used for the z-axis, where gravity tends to apply a convenient downward force that helps to minimise the effects of any 'slack' between the thread and the bearing. 

Optionally, there are a variety of modified bearings, often consisting of two parts, which combined with a spring, attempt to remove the slack from the system.

The belts used in the 3d printers are usually stiffened to minimise stretching, typically with glassfibre, although other belts have steel. My limited reading suggests glassfibre is more suitable for the small pulleys usually found in small 3D printers, as steel does not bend enough. It also seems plausible that the quality of belts on the market varies widely, typically with the cheaper ones being more susceptible to stretching.

Of course,  it is important to tension any belts correctly.

All of these points are offered in good faith, but I cannot independently check the details, so one or more may be rumours rather than facts.

Best wishes, Dave

Really ? I've never had a T8 with whiplash !

Not so Ron.

Lead screws and ball screws have problems, expensive and above a certain length suffer whiplash.

Top commercial stops use rack and pinion - rock solid but with a bit of backlash. Easily corrected.

Cheap to good use timing belt. It's reliable but of course it is a spring so can give a different length depending on length+load.

  The list of forums is at https://forum.dronebotworkshop.com/

Have a look down the list and start a new thread in the one you think is most appropriate. At a quick glance, you might choose between Project Corner and High Tech Hobbies. Recommend you copy over the details which are still part of the main discussion and build in any new items.

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As a side comment, my only vaguely comparable experience is with a small commercial 3D printer, with the x belt moving the print head over about 25 cm maximum (and the bed similarly in the y direction), typically over a 15 cm range during a print, as few objects completely span the bed, which is only a quarter or less, of your 1 metre span. However, to make a reasonable print, this involves continual back & forth motions with a repeatability to hit the 'same spot' to 1/10 of a mm, and I suspect it usually much better than 1/10 of a mm.

So, whilst there may be software tricks to compensate for backlash effects, maybe the first place is to try to identify the true cause of the problem. Is the machine structure stiff enough, belt tension correct and so on?

Also note, the 3D printers, and I think your machine, do not step at a constant rate, but rather accelerate and decelerate. I notice your code has an acceleration parameter, but I don't know if the value to appropriate. Have you tried slowing the acceleration and step speed, to see if it reduces the backlash effect?

Also note, the 3D printers often use simple microswitches to determine a 'homing position', at power on, but after that they rely on absolute counting of steps. For X and Y, the small uncertainity in the microswitch operating position is of no importance. In the Z direction, they are moving to higher resolution, aiming towards 1/100th mm. It maybe worth trying a microswitch first, as it might meet your requirements.  

Good luck, Dave

Speed( fast );

Stepto( target + 10 );

Speed( slow );

Stepto( target );

Another common new user mistake is not clicking the Reply link at the bottom right. That way a @xxxxx tag gets inserted automatically into your replay and I get an email telling me IF I am subscribed.

Don't be confused by the fact I live in Canada but don't really know metric, I am an old-timer and a lot of stuff here is still Imperial. I can handle temperature, speed, less so length, no knowledge of weights or volumes although I know a Litre and Quart are close.

Check out my other replies to you.

You said

I have built a measuring device (fence?) for my miter saw 

In my country, the fence on a Mitre saw is at 90 degrees to the saw blade unless it is rotated to do say a 45-degree cut. The fence on that saw does not move. A tablesaw however does have a fence that moves to allow ripping wood to a specific width. Can you show a picture of the saw?

As Ron (@zander) has said, there'll always be some play in a belt; furthermore, it'll probably get worse as the belt ages and gets stretched from being pulled back and forth.

Using a screw to perform the move can reduce the backlash considerably. I have successfully used a T8 (8mm Acme threaded rod) with an anti backlash nut such as (remove quotes and change ".ca" to your country's code)

"https://www.amazon.ca/gp/product/B074JYFW6B/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1"

I'd recommend against the single part brass nuts that usually come with these rods, I find them very sloppy and not good for precise work. The addition of the second threaded section and spring to keep both threaded sections in compression is very good for reducing backlash.

You'd need to rotate the stepper 90 degrees and buy an adapter to connect the stepper shaft to the 8mm threaded rod.