Imperfect circles

[Explant (Nadeem Sheikh)]

I repeatedly observe that circles do not come out as a ‘true’ circle; there’s either a flat spot or/in addition a jagged edge as if the bit got jogged. Anyone experiencing the same. Does not matter the size of circle OR hos small bit I use (down to 1/16"). I have a Shapeko 5Pro with a spindle

[gdon_2003 (Guy Donham)]

The most likely problem is a mechanical one. Depending on your machine type the SO3/4 can have loose belts or loose set screws on the stepper motor pulley or loose v-wheels. If you have an SO4 Pro check that your rails are properly lubricated. A dry linear rail will cause small loss of steps and make your circles ovals or as you described the bit moved over and out of the intended path. The same is true for the SO5 about keeping the rails lubricated. Some SO5 users have had loose bolts on the ball screw bearings.

Do mechanical checks first. After that check connections are tight and no connectors are pushed out. that symptom can be found by feeling the connectors and some are hot indicating a loose connection causing high resistance and produce heat.

So check everything out mechanically first. If all mechanics check out you can run a calibration and change the stepper motor steps but that is a last resort and is not likely since you said the bit moved out of the intended path. Calibration of the stepper motor should only be done if your circles are ovals and cuts consistently not round. The bit moving is likely a mechanical problem.

[WillAdams (William Adams (Carbide 3D))]

As @gdon_2003 noted, this is most likely a mechanical issue.

Please write in to support@carbide3d.com — we have an SO5 Pro motion guide checklist which we will review with you.

If it’s very small, then the problem could be one of toolpaths and the tool being pulled into a cut due to the cutting forces — where possible avoid slotting and add geometry and cut as a pocket

Making vacuum hose adapters

While cutting up vacuum extension wands for this is expedient, it’s a bit problematic given that Shop Vac recently filed for bankruptcy, was bought at the last minute, and production hasn’t caught up. I need a receptacle for the Sweepy 2.0 dust fitting — one option would be to purchase one from Woodcraft, but Carbide 3D sells blocks of HDPE: which looks to be just barely big enough for things to fit. Measuring the hose fitting I get a diameter of ~63.5mm — offsetting that twice we arrive at…

and/or

Adding geometry to cut as a pocket with a finishing pass

One technique which is often suggested to avoid slotting is to add geometry around a part which one wishes to cut out and cut as a pocket down to tab depth — here’s one technique for that. In this case, the project is a bevel gauge which will be cut out of 0.0625" (~1.5mm) thick aluminum: [bevelgauge] Due to the narrowness of the angles, an 0.03125" endmill has to be used, so after importing and scaling the file (we will be cutting out one which is 3") we select the perimeter and offset it tw…

and consider leaving a roughing clearance and taking a finishing pass.

Best Bit for full cut through

One which has a cutting flute length equal to or greater than the thickness of the stock — pretty much any tool should work. Big thing is the toolpaths — if cutting out, rather than just cutting a slot: [image] Offset to the outside by endmill diameter plus 10% or so: [image] [image] [image] Then cut as a pocket: [image] down to tab height or the penultimate pass: [image] then move the contour down to below the pocket and start cutting at the bottom of the pocket: [image] and…