[jxdxwx]

Rounded corners in Mach3 appears to have been a topic of many discussions on this forum.

I'm only trying to make a good 2D rectangular cutout. Have tried many different feed and
speed combinations and cutting very shallow pockets in an attempt to get fairly nice and
consistent internal corners without a wonky looking radius. By wonky I mean inconsistent
and misshapen. (even tried multiple passes on a 1/16th deep pocket)

Any external square corners that I cut appear to be coming out very nice, square and sharp
even without slowing down. Interpolated holes are fairly round. +/- .003 on 1" diameter.

Running Mach3, ESS SmoothStepper, PMDX-126, Machine is tight with linear guides, ballscrews &
AC servos. Material I'm cutting is 6mm cast acrylic.

Is there a combination of 'LOOK AHEAD' and 'CV' settings that I should be using as a good
starting point?

[RCaffin]

Wonky INTERNAL corners with good external corners suggests that the abrupt change in cutter loading at the internal corners is deflecting the machine a bit. This could mean there is still some backlash somewhere, or maybe the head is just not rigid.

Cheers
Roger

[daniellyall]

have a slow acceleration can have some very funky things happen in M3 with going around corner`s.

have a tuned acceleration can help. you run a big file on one axis at a time and checking the start and end spot is in the same place, if not changing the acceleration can help bring it into line.

having look ahead at 200 seems to help it does on my Ahole of a machine

but making sure it`s not a mechanical problem first helps, like what roger says about deflection, backlash or not being rigid enough for the speed you are going.

there are a lot of thing that can make what you are seeing happen.

[ger21]

What are your acceleration settings, and what is your feedrate?
Can you post a picture?

In most cases, you want ALL CV options turned off except "Stop CV on Angles >"

[awerby]

Internal corners are inherently tricky to cut with rotary tools. When the cutter suddenly has to engage not only from the side but from the front, bad things can happen, as RCaffin points out. Sophisticated CAM programs deal with these corners in a special way, approaching them carefully and making an extra move to avoid that sudden transition. A setup that's less than perfectly rigid can make things worse, especially if one just plows into it.

[daniellyall]

the HSM fusion tool paths are very good at going around corners, a lot better that what Vcarve pro does, it`s keeping a constant load that help`s and it slows down a bit when it goes around a corner what helps to. the reason why it just works better is over my head but it does. gerry or awerby probably know why

[jxdxwx]

Ger21,

Tried taking pictures with what I have and nothing illustrates what I was seeing very well.
I'm beginning the process of setting up a video camera to do the crosshair zeroing and
will be able to use it for screen grabs as it appears more clear than my phones camera.

My cut speed/feed was 15k and the .1875 is at .003/.004 chip load while the .078 is .001/.002

UPDATE: I did have LOOKAHEAD set at 30 (now at 200) and tried with various settings
for CV turned ON then tried with them OFF. But do still have CONSTANT VELOCITY
checked instead of EXACT STOP. I added the CV ANGLE setting to 89 as most on here
have done. Also I changed my ACCELERATION in motor tuning. It was at 100 and I've
changed that to 50. Velocity is still set at 1200.

Should I also change my CONSTANT VELOCITY to EXACT STOP?

Did spend some time measuring my machine for backlash today. Happy to report that I
see no mechanical backlash to speak of. X, Y & Z have ZERO, My A axis (second table)
looks to have close to .0005".

Attached is something similar, but less typical of what I will be doing with my machine.
It has a little larger corner radius then I have been practicing with as I do not currently
have the correct tools to practice the smaller corner radius. The parallel lines of the thru
pocket and c'bore made the wonky corner radius much more glaring. Also attached is 3D
model/drawing if anyone wants to compare their results.

What I have looks better, but not 100% sure how good until I'm able to run another part and
measure it.

[jxdxwx]

run a big file on one axis at a time and checking the start and end spot is in the same place, if not changing the acceleration can help bring it into line.

I am interested to do this. Could you please elaborate with more detail on what I need to do and how to measure?

[RCaffin]

Hi jxdxwx

You can reduce the wonky corner effect to some extent by using a smaller cutter and arcing the corners, rather that doing an abrupt 90 degrees.
If necessary, use a big cutter to hog out the midddle while carefully avoiding any sharp corners, then finish to dimension with a small cutter. The arc radius must be bigger than the cutter radius.

Worth a try?

Cheers
Roger

[daniellyall]

hay roger that does work with fusion I don't use i or j in the post processor it`s just a R move and the corners come out very nices inside or out. it makes it a little bit slower but quality goes up so that`s a win.

jxdxwx you will need a way to measure the movement that is very accurate like a DTI or a set of calipers that you can attach to a axis, so it does not change position, or have it fix in a spot that is safe for the measuring device`s, like how you would calibrate a axis.

what I do is run a file that has 1000 moves or there about in all 3 axis, I run it one axis at a time with the other 2 turned off, it is a Vcarve file so it has a lot of short and long movements with a lot of speed change.
I take a measurement at the start zero out the calipers run the file then at the end if it is out in positive or negative I add +10 to the acceleration then run the file again if it comes up negative again or positive I take off 20 from the acceleration then if it's the same I remove another 10, if it has gone the other way I add 5 back to the acceleration then I just add or take away to it comes back to + or - 0.001. it takes a bit of time sometime I can do it in a couple of run`s sometimes hours. all it is finding the sweet spot where M3 is happy with the acceleration on my Ahole of a machine.

but before I did this I replaced all the stepper motors, replaced the Z axis ballscrew, nut and bearing`s that was a $1000. made sure all the wiring was in good shape no ground loops replaced some of the wiring with shielded wire separated the high and low current, and had them on there own star point side by side.
earthed out the dust extractor piping. tested the machine running as the only thing powered up in the shed no light`s nothing this was to make sure no other 3 phase machine was making the machine go wonky or the lighting.
I did everything to make sure there was no mechanical or electrical problems with the machine I spent 4 years on it, to I worked out a formula that made the machine run well.

this is just this machine it is a chinese copy of a copy made very badly with mislabeled stepper motor`s all sorts of problems. other will say they never have a problem with M3 what is very true I have another small router that is a dream to use, not one problem since the day I changed it over to M3 even with M4 it`s fine but can't run it at the moment it`s computer died.

this may not work at all for you it could be a simple problem like your going to fast not enough acceleration something like that, you need to make sure it is nothing mechanical that is wrong with it first otherwise you will be going in circles. like I did for 2 years. then I decided to listen to the experienced members and I found one mechanical problem after the other then when that was all was sorted, made sure the electrics was good fixed all those problems.

now i have a machine that I services 4 times a year and that's all. it has a limited speed but I know how to fix that and what`s wrong but that means spending more money on quality parts so it has to weight to after March 4 Cv settings are done.

[jxdxwx]

I have another small router that is a dream to use, not one problem since the day I changed it over to M3 even with M4 it`s fine but can't run it at the moment it`s computer died.

Hey daniellyall,

What make & model is your reliable, dream to use machine?
Steppers or servos? What type of guides?

[jxdxwx]

You can reduce the wonky corner effect to some extent by using a smaller cutter and arcing the corners,
rather that doing an abrupt 90 degrees. If necessary, use a big cutter to hog out the midddle while carefully
avoiding any sharp corners, then finish to dimension with a small cutter. The arc radius must be bigger
than the cutter radius.

Roger,

Thank you. I do seem to know stuff like that when I'm out in the shop, but for some reason I drop IQ points
and forget little details like that when I am in here on the computer. The radius that concerns me most is an
.03". Although I've found good tools for cutting cast acrylic, They are in larger sizes. LMT Onsrud does carry
.062" for an .03R, but I would like to use the method you suggest. With maybe a 1.5mm.

Would you happen to know a good source for metric router bits for a quality finish when cutting cast acrylic?

~jxdxwx

[daniellyall]

A emco

[RCaffin]

Hi jxdxwx

a good source for metric router bits for a quality finish when cutting cast acrylic

Sorry, no idea about router bits per se. Mine is not a router.
Standard milling cutters I have some experience with.

I have used a fair bit from carbidechiu on ebay. Yeah, sure, Chinese ebay, but so far his stuff is giving me good service. Note that most Chinese stuff is all (mostly) metric. You will need metric collets.

I have little experience with his HRC40 stuff.
I have some happy experience with his HRC45 stuff, and would buy it again.
Ditto for his HRC55 stuff - I have been cutting some steels with that, with no visible effect on the cutter.
The HRC65 stuff he sells is not cheap, but it goes through steel rather well. However, for acrylic it would be superfluous.
He also has some Al&Cu stuff which is wicked sharp, but only a limited range of sizes.

Also, carbidechiu has made custom cutters for me at a fair price. He had some 1.0 mm ball end mills and 1.2 mm ball end mills, but I wanted 1.1 mm ball end mills. He had the factory make up 5 (coated) for me.

I have also bought HSS from CTC.biz. He is on eBay, but going direct is cheaper per item but you pay postage. Balance what you want.

For really small stuff you could try Precise Bits in the USA. One of our regulars here is an agent for them.

Must go - dinner.
Cheers
Roger

[bhurts]

I buy all my micro to medium sized tools from drillman1 on eBay. Located in Texas and made in the USA. All solid carbide at amazing prices for small cutters.

Carbide Endmills, BARGAIN BIN items in CARBIDE PLUS store on eBay!

Link is to his eBay store.

Ben

[daniellyall]

toolstoday and lakeshore carbide free shipping and good services

[jxdxwx]

I buy all my micro to medium sized tools from drillman1 on eBay. Located in Texas and made in the USA. All solid carbide at amazing prices for small cutters.

Carbide Endmills, BARGAIN BIN items in CARBIDE PLUS store on eBay!

Link is to his eBay store.

Ben

Yeah, looks good on pricing and selection. And I'm also in Texas so I went ahead and ordered some tools from him.

Thanks Ben.