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Sled test 2... better but strange veering in bottom left segment

So, slowly getting going. I cut the first sled but somehow calibration was out so I recalibrated and recut the sled. Dimensions were pretty close on the new cut, ~ 1/8 of an inch in the y dimension, but I had this strange veering off in the second sled at the bottom left segment of the circle. Any tips? I didn’t see the sled or chains bind and the path was consistently cut in this manner. See pics below (pic of two circles is the first attempt on the right and the void left by the second attempt is on the left). My thought is to use this new sled to more accurately cut another - the index holes for the ring and router appear to be accurate which I believe are the critical dimensions. My first one was made by hand per the instructions but i’m not confident in how well i have the ring aligned to the router.

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Hi @mybludrunsorange,

Great job on getting going! And welcome to the community!

I see what you are saying about the sled being a little weird in that bottom area. I assume you are using a drawing provided to you and not one you drew yourself.

What was your workflow from the drawing through the CAM?

When you say “consistently cut”, are you referring to it cutting the same path on multiple step down cuts? Or did you try to cut it again and get the same results? To my eye, the two cuts pictured do not show the same deviation at the bottom, and the right one looks more oval, with a vertical long axis, but perhaps that is an artifact of the picture.

It looks like you are using a bottom feed sprocket configuration (the chain to the sled comes from the bottom of the sprocket). Are you using any means of preventing chain skip? I am wondering if it missed a tooth as the cut came around at the bottom. Which direction did the router travel around the sled? Also, were the alignment holes cut first and the outline later?

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I second the Welcome!
Is that an illusion or does the centre have the same ‘veering’?

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I think you are correct. Good catch.

That makes my question about chain skip moot. And now I don’t have any working hypotheses on what might be causing it.

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Depending on CAD/CAM i was thinking about a misguided lead-in/lead-out, but could be totally off here.

  • file used
  • CAD/CAM workflow
  • video of a circle in that area

will clarify

I’ve usually found lead in/out to be the same length regardless of the rest of the cut, so would seem odd to have it magnified on the larger circle. An interesting thought, though.

I’d be interested to see a bulls eye pattern cut on the machine to see if all the circles are cut the same way. Probably easier and more useful to just start with a single circle in a new file specifically created to test only a circle. That might help to determine if the original file is at fault, or if there is a systemic problem with cutting circles on the machine.

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It’s a bit pointy for a machine setting. I guess 1 bearing is holding on to a spot to long. Observation or video would show that.

A simple circle and a video please @mybludrunsorange :slight_smile:

Edit: Post the .nc file also, that shows fast if CAD/CAM or mechanical issue.
Although, zooming in with GroundControl you would notice that point if it was from the software side.

Hi, I had to take 4-5 tries to get my first sled. I found many problems but there were me and not the Maslow. Set screws fell out of the “Z” connection That took care of two of them. Found the set screws in the saw dust. Whoops. It is a learning process. The last cut I miss calculated and the circles overlapped. And no straps this time. It was getting late so I set it up for just the straps.
All was going great until I turned on the light so I could see and had a power surge. Yup, It stopped. I shut it all down and went it the house and fell asleep in front of the TV. :slight_smile:
I now know I have too many little issues. I need to go over the whole thing ans see what else I missed.
It is a learning process for me. My back ground is computers. Most of things going wrong are the process and not the hardware. Well, the power server I didn’t see coming.

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It’s the small steps, stone by stone, that let you cross the river MaslowCNC.
Sometime you have to go 2 steps back to get forward.
Do not attempt to jump. (Dalai Lama)

Idea of moral support this way stolen from here:

Always credit the designer. (Abraham Lincoln)

Edit: Figured my english has messed up a word that i interpreted wrong.
Mental was maybe more what i was looking for. Feel free to take like away again. Standard feature.

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I agree the problem is likely me. I think the 2nd sled is a huge improvement over the 1st cut attempt.

Yes, the issue occurred in both the small inner circle and outer circle. I used the files here without any updates. There was a pre-configured gcode file. All looked good in Ground Control.

I can’t provide a video at this time - perhaps tonight - but it is possible one of the ring bearings is holding on too long. I didn’t sand the inner edge of the ring to knock back the irregular surfaces, so I’ll do that tonight and re-cut a sled. The strange thing is that the 1st egg shaped cut didn’t have this strange irregularity. If the ring were the cause I’d have expected it to occur there as well. I guess it’s possible some sawdust or something is on the ring or in the groove on one of the bearings.

Thanks for the tips. I’ll take a look at these possible solutions.

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Good luck! You will figure it out.

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The more I think about this… my first cut was on the right side of the substrate. If there is something hanging due to a rough ring, the bearings may not have been hitting it on the first cut that turned out oblong. I’m definitely going to sand the ring tonight.

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run a finger over it first to see if you feel anything. If for no other reason than to double check the difference before and after.

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So, moving everything to the new “bad” sled instead of my handmade one and sanding the ring appears to have fixed the issue. I’m not sure which did the trick but both needed to be done. While the bad sled had the messed up segment, the hole dimensions were much more accurate than what my handmade sled had.

I now appear to be out less than an 8th of an inch which is reasonable to me but I’d like to get down around 1/32 or less if possible. I plan on making some small furniture pieces so this seems like a reasonable target. I have some nicer plywood I’m going to cut a 3rd sled from that has a much nicer/smoother surface and should slide across the backer board better.

Outside of that, other opportunities to improve calibration include adding the bungie cord to remove z-axis slop, add a chain tensioner at the gear to improve engagement.

Any other recommendations on dialing the machine in? Are there specific numbers in the settings that can be tweaked to dial things in a more granular way as related to being off in the x, y axis dimensions? One thought that occurred to me was to simply apply a distortion factor to my files in the amount that my Maslow’s off. Has anyone attempted such a thing? It seems like it might be a great feature to have. I have some experience in printing and distortion factors are something used regularly there when compensating for plates being wrapped around cylinders. Seems like it could apply here even though we’re talking about a flat surface.

Great to hear!

if you are planning to cut furniture, I would probably look into an alternative z-axis. I have been very happy with a c-beam setup, and the increase in z-axis speed is a very nice bonus, but the avoidance of all the stock z-axis headaches is what really sold me on it. Here is a good thread to look at for alternative z-axis set ups (that link goes to my posting about my setup, but the whole thread is useful. Also, I list out all the parts I bought a couple posts later).

This is what works for me, and is super simple and cheap to implement. It is simply a long m4 machine screw with a nylon standoff over top of it. I can’t remember if the standoff was one that came with my maslow kit that I repurposed, or one from a parts bin, but either way, a big box store would have both the screw and standoff. I think I used a 1 inch standoff and a 30mm long screw.

do a search for calibration. There is a ton of information on the forum about how to dial in your machine.

if you follow the above advice, this should not be necessary. I think the “Holey Calibration” thread may be of interest to you.

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Many thanks for the responses and insight. This will likely save me a few hours of digging through forums. I saw the Z axis upgrades others were doing and it’s definitely on the list.

Last question, the list of parts is a complete BOM for your Z axis? Did you 3D print the clamp/mount or did you cut it yourself on the Maslow?

Yes and no… it is a complete listing of mechanical parts I ordered, but does not include misc. screws, aluminum plate, and delrin plate that I used. I ended up cutting the mount/clamp out of delrin by hand, literally for the rounded portion. I don’t recommend this, and had I been thinking I would have routed it using a template. I may re-cut it using the maslow, but for now it is working well, and I am considering switching to a dc spindle, which would require a redesign anyway.

As for the rest of the design, you will likely need other parts that I did not need, such as brackets to support the c-beam on the sled (mine is made of 1/8" steel, so I was able to screw the c-beam directly to it), and you will need to figure out a way to mount the axis motor to the back of the c-beam. I used one of the original l-brackets and attached that to a piece of plate aluminum that I could screw into t-nuts set into the channels on the back of the c-beam. This allowed me to adjust the motor up or down so that the gears were aligned. It sounds like a lot of tinkering, but I think I only put about an hour or two into it.

There are some good examples of others that have attached c-beams to their wooden sleds in that z-axis consolidation thread.

no need for it to be the last question… in fact I hope it’s not your last question :wink: I think it won’t be long before your questions are to clarify problems that others are asking for help with. Glad to have you aboard and making great progress!

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I like this. We need a whole section of MaslowCNC wisdom falsely attributed to famous people.

“Always wear hearing protection.” - Wittgenstein

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