What a few of us have done is incorporate physical hard stops at one end of the table which are square to the axis you’re worried about. As long as you dock the gantry with the wheels butted up against the stops you’ll be all set as once you power up the cnc each stepper is locked in step. If you haven’t built yours up yet this will make more sense when you see it in person. I head scratched about this for a while with mine too trying to understand how it would track without any limits on it’s wandering.
I did run into these problems myself and certainly over a longer cut 4-5ft it presents more of an issue than over a smaller area as you’d imagine so chickened out and I’ve used a small strip of rails to solve it. Since incorporating the track/rails it’s been problem free.
I was thinking of a hard stop that incorporated some type of guide as well to keep the wheels square [edit: centered on rail] as well like below… do you have a picture of what you are saying?
Here’s a shot that may help, my stops are just quarter circle stops. what you’re suggesting in the drawing would work great too and so yes we’re on the same page.
Thanks for the picture. I had to stare at it for quite a while to figure out what you did because the lighting/shading caused an optical illusion (at least to me) and made it look like you had two narrow pieces of wood (maybe 1x3) installed vertically running the length of the table that the wheels rode on… but then I couldn’t reconcile what I saw at the top right and finally was able to see what you really did (two ~3" wide pieces of wood sitting atop the table that keeps the wheels from shifting).
Thats a great looking machine! Have you shared that here before? I think people would love to see the different fixtures, and links to the STLs for them. Huge control box too, eh?
Found it:
I guess I have a short memory. Because I already had a like on that topic!
Ha ha yeah it’s been around before. The control box isn’t what it appears like in the photo, it’s just a bunch of dangling bits. I still haven’t figured out a great way to put that all together in a sensible way, some ideas were hatched but not followed through on.
The end stops are super simple blocks to mimic the arc of the wheels with a hole or two for screws to fasten them. Nothing fancy.
I’m exploring ideas for a new table and had been considering going to some angle iron with V groove wheels. I think this would be a simple mod, if the wheels are easy enough to come by.
I think the arc is not needed and probably would be better as a wall/straight edge. The reason being as you probably imagined is that you can wheel up the ramp and be slightly out side to side where at least with a wall you can be sure they’re stopped the same way.
This is a very minor part to me, it seems like a bigger problem than it is, I’ve found the cuts to be extremely consistent pass to pass with very little attention to the squaring on my part. The place where you’d run into issues really is if you’re trying to maximize a workpiece and are planning to cut every millimeter of the edge and you don’t get the piece situated perfectly parallel to that axis.
I’m always working with wiggle room for instances like that with a cm-ish to spare to avoid this exact problem.
So here you can see my board wasn’t parallel but the cuts were totally fine. Not sure if that makes sense but I’ve reduced my concern over this significantly since starting to cut and use my lr2.
Thanks, that makes sense. I’m certainly not trying to use every mm of the board… I just want to make sure I have precision so that when I make 3-5 passes to cut through some plywood, each cut is in the same spot and a straight line comes out as a straight line. Looks like from your picture and what I’ve read, it does a good job at it.
Always will, the only issue we ever deal with is parallelograms, and an off plane z (for carves).
Once the machine is one and moving it is locked. If you use the first pass to outline your entire project in the air (1 min tops), you will have no surprises like starting at a funky angle or hitting clamps.
Thanks, I have a lot of experience with the Maslow CNC (I’ve been using and developing software for it for two years) and understand the challenges. The Maslow is a great machine with really great precision, but accuracy error is more like parabolas rather than parallelograms.
But for me, I need to move the Maslow outside my shed because it has to be in the middle of the shed to clear the ceiling (vertically oriented CNC inside a shed with a very low roof… darn home owner association rules). So I’m working on an outdoor frame for it. But, I still want something I can use regardless of the weather, use as a horizontal work space when not cutting, and preferably something that doesn’t have the accuracy ‘challenges’ the current Maslow has… Seems that lowrider fits that. I’m hoping my plan for ‘infinitely-adjustable’ rails pans out… will see.
You won’t have issues, just judging on how much thought you’re putting into it and how well these work once the initial tweaks are started out.
Here’s one of the bigger pieces I’ve cut, it’s 3/4" spruce ply and a little over 4ft tall for my little ones. The sequential cuts line up extremely well as I said and Ryan suggested. I was really thrilled with the outcome for this. Also for the finishing pass you can do a full depth pass which will hide any tiny steps too.
I was out cutting a bit more and grabbed a better picture of the stops for you.
The kids will get a kick out of the possibilities. I call the 3d printer dad’s toy maker and I think as they get older their imagination will give us all some projects.
That is how I do it. The Z rail hits the belt stop, to really square the machine I use layers of tape on the belt stop to shim it as perfect as I can get it.
Hey, I’m bit off topic here, I’m thinking about lr2 and I’m wondering how to change the spoil board after it becomes damaged? Do you have to take the machine off the table or is there a way around?
