Not so square squares

  1. Did you buy everything from here? yes

  2. Are you using end stops? no

  3. Mac or PC? PC
    OK so my squares aren’t square and my circles are egg shaped but only on one corner of the cnc… so the first thing I checked was to make sure every thing was square and it is, X and Y are perpendicular and corner to diagonal corner is dead on so i am at a loss. what do i check next? the pics below are of the not so square squares and the egg shaped circled and some good ones cut on the opposite corner.

How far out are you hanging on the z axis? How fast are you cutting? How big is your cutter, what kind of cutter? How big is that square, how far off is it? I can’t tell much from that pic, it actually looks square to me.

I using a 1/4" end mill the square is a outer profile of an one inch square. the square was 1" in the Y and almost a full 1/8" shy in the X. and as far as the Z axis it was only about 2" down.

A few more questions in there. Speed, doc, flutes?

A picture of your MPCNC and the Estlcam screen might help the diagnosis.

2 flutes doc 1mm in the pic and 3/4" in the birch plywood I ruined before I noticed the problem. speed where 50 ipm at 75%.

Asking a million questions makes helping take forever. What kind of cutter, I have a feeling you are using a router bit.

You are using twice the recommended size cutter cutting full width at 21mm/s which is about 4 times more load than normal if not more.

Have a look at some of my videos for a more realistic starting speed and an idea of the proper tools.

I am using an end mill not a router bit I get them from a local distributor (Steel Sales). the speed was more like 15ish mm/s if you consider I was only running at 75% speed. Maybe i am going to fast ill watch your videos but forgive me but i do not understand how that would make me cut wrong in only one part of the machine? would that not affect the entire cnc?

Picture of the bit would be much more useful than the business card. The speed could be okay but you’re using a bit that’s very large. The issue you’re having as you’re putting too much torque on the machine and it’s flexing and things are moving while you’re trying to cut. I’m trying to help figure out exactly what the issue is but there’s a lot of things wrong here. I think the best way for you to see what a good cut looks like is emulate one of my videos same bit same speed and see what it sounds like and looks like when it’s cutting properly.

ok watched one of your videos here is my cut

You are absolutely killing me with the units. you gave the measurements in inches then used the calipers in mm.

So from what I see in plywood you are less that .5mm off over 4", from an unknown z axis length?

No need to measure the cutoffs, unless that was your tool path?

Lots of conversions going on but I still am not seeing a problem?

So what was I supposed to be seeing in that video? Have you measured your bit?

You didn’t show if it was square or not.

I’m done for the day I’ll check back monday.

I dont know why but the video cut off these photos. no it was not square, that is the problem, that was the point of the video. But again I dont understand how im only having this problem in one corner of my machine and the rest of the machine cuts true. thats what in trying to get help with, I do understand that speeds and feeds and bit size can all affect your cuts but that would affect the whole cnc not just one corner. ive got almost 100 dog holes to cut in my new waist board but i cant change it out till i get this problem figured out. Im sorry if im being a pain im just under the gun here i got a show coming up really soon and i have a ton of work to do between now and then. I do thank you for your help!

ok been wracking my brain all day trying to figure this out… and then just by chance I found it! Dont ask me how but somehow BOTH set screws on the X axis back side stepper gear where missing… quick trip to the Home Depot and I am back in action! So if anyone ever has a problem like this again make sure they check those set screws. Thank you for all the help

Heh. That makes sense. I used blue loctite on mine, so far, none have fallen out.

Instead of loctite, you can use a second screw to put behing the first one. It is easier to take apart in case you need to. Loctite makes it hard to unscrew after, which can be problematic because these tiny little Allen keys cannot handle too much torque

Loctite can be loosened with a little heat (all except green).

I use a heat gun or even my soldering iron to heat up the part with the screw in it. After a few seconds the screw comes right out.

Unfortunately, I didn’t learn this trick until after I drilled and re-tapped a screw that had red loctite on it one time :confused:

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