What could couse this problem.

**madeinwood** · 05-10-2017, 05:52 PM

What is causing this problem (see attached picture)? Brand new CNC. Have tried different cutters/bits. Have changed different speeds, plunge rates, pass depth,... Have cut first rough and then full finish cut (with offsets). Still same problem. Same problem in all inner corners if cutting shapes not circles.
Second questions: If I make circle 10cm diameter and using correct bit I get 10.050cm circle, is that difference ok for high price precision CNC?

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**ger21** · 05-10-2017, 06:00 PM

Machine deflection while plunging.
Ramp into the cut, rather than plunging.

If I make circle 10cm diameter and using correct bit I get 10.050cm circle, is that difference ok for high price precision CNC?

It might be for some, but not for others. Try cutting slower, or in the opposite direction

**madeinwood** · 05-10-2017, 06:05 PM

Originally Posted by ger21

Machine deflection while plunging.
Ramp into the cut, rather than plunging.

I have CNC-Step S-1000/T. Could it be that they have made it with bad structure? Looks/ feels very solid and they guaranty high precision (of course on paper). Could it be spindle problem? When it runs in corners z axis is not moving (see attached picture)

**madeinwood** · 05-10-2017, 06:12 PM

To understand better another picture. It is making those burns/cuts only in last pass when leaving tabs to hold part down.

p.s: Thank You for replay. Sorry for double post.

**ger21** · 05-10-2017, 06:21 PM

Any time the machine stops to change direction, you're going to get marks like that, due to tool or machine deflection.

If you must use tabs, use a 3D ramped tab, so the machine does not have to stop at the tab.

Inside corners are always an issue,as the tool wants to pull into the corner when changing direction.

**shadowvoice** · 05-22-2017, 08:19 AM

Case is solved.
1. Madeinwood used wrong Post which caused wrong dimensions of parts (constant 0.20mm error) - suggested to use different post. Dimensions went into norm.
2. Exact stop mode in Mach was set. Plus wrong acceleration/braking ramps - fixed.
3. Vertical plunge in material - suggested to awoid that.
4. Tool/material deflection plus chances to acheve reliable measuring results on wooden parts explained.
5. Test cut (pocket) showed dimensional deviation within -0.02-0.04mm.

**madeinwood** · 05-22-2017, 08:26 AM

Originally Posted by shadowvoice

Case is solved.
1. Madeinwood used wrong Post which caused wrong dimensions of parts (constant 0.20mm error) - suggested to use different post. Dimensions went into norm.
2. Exact stop mode in Mach was set. Plus wrong acceleration/braking ramps - fixed.
3. Vertical plunge in material - suggested to awoid that.
4. Tool/material deflection plus chances to acheve reliable measuring results on wooden parts explained.
5. Test cut (pocket) showed dimensional deviation within -0.02-0.04mm.

Post is approved by me. Everyone involved is CNC Step was more then helpfull to solve any issues.

**bzen** · 02-15-2018, 01:34 PM

so im cutting 6mm plywood cirlcles(4x4") and im using the poor mans compression bit trick, im using a double fluted down cut bit to get through the top half and then a double fluted upcut to finish and im getting hairs in the middle of my cuts and dont know how to solve this problem