Milling a 44mm hole with a 12mm HSS 3 flute through a 1" steel plate, cutting down hill.

Told it to 'drill' 26mm deep to make sure it went through. The software did it in 14 steps of 1.857mm so the last cut was a a bit lighter.

All went well until the last cut when it decided to cut all the way up the side of the hole. My fine chips became needles and it went oversize with a bulge at 10 o'clock.

It then did exactly the same on the second hole.

It's okay because I was going to clean it up with a boring head anyway and I can make the bushing that goes in it oversize if necessary.

My guess is that the tool was bending towards the center all the way down then flexed out when there was no more metal underneath it.

Is there a work around for this, or is it something else :confused:

What was the cutter path followed?

Did you program it to drill the center out, then work outwards, or did you program it to drill close/at the perimeter?

I've found that the specific cutter path you follow has a large effect on the quality and time of milled holes.

John

The software decided to do it with a centre plunge and then two cuts. 27.7mm diam, then 43.4mm leaving me 0.6mm to clean out with the boring head.

I tried the next plate cutting up hill and it went egg shaped with a lip at the bottom where the last cut went undersized. It has to be tool drag and flex somehere in the system.

Nobody mentioned drag from the cutting action bending the mill out of shape, time to get out the DTI and then lean on it a bit :D

going from 27 to 43 is a big step, reduce your cutter overlap
take it it did this at full depth
think your strategy was all wrong
what software you using?
mike

think your strategy was all wrong
what software you using?

Hi Mike

I'm using g-simple very badly, I should have included a finishing cut that would have spiraled down in to the hole with minimal tool drag and made it all perfect.

g-simple draws a series of paralel tool paths across the billet and then starts cutting them from bottom left in a series of passes at ever increasing depth. If it hits an outline it follows it with a clean up allowance if you asked for one. It then goes back to the paralel paths to remove any metal left standing outside the ouline(s).

Having cut the outline(s) it then does any pockets one after the other in a similar fashion. Round holes it cuts as 360 degree arcs.

Sounds primitive but it is a darned sight better than my home brewed software which spiralled in to size at full depth. I wrote that before I found this here site and got eddjukated, may need to revisit it, but it isn't easy to come up with reasonable tool paths for every circumstance. I have a notion to break the part into a myriad of tiny squares and remember how deep each one is and how deep it can go. That would allow for a lot of whittling before I went for the final shape.

Understanding the problem is halfway to a solution, now I know that I have to allow for the machine bending out of shape due to cutting drag I can do something about it. I don't want to spend thousands on software, I'd rather spend it on more tangible assets :D

best regards

Robin

The demo version of Mach 3 is free and comes with a bunch of wizards
that can be used to create your g-code for you.
Including Cut Circle and Circle Pocket that could help.
Check it out here (http://www.machsupport.com/).
Hoss

try cambam too best of all its free
ace converter's also free

mike

Hi Robin,

CNC machining is a bit like computers. Went you first get involved you are paranoid about the hardware then, after a while it suddenly dawns on you that really what counts is the software. You've just reached that point, congratulations.

Good software is one of the most important asset you will buy for your CNC machine and it doesn't need to cost so much.

Regards
Phil

PS: I remember many years ago developing my own computer program that would perform calculates based on an input/output matrix table. After 3 months of effort somebody showed me a new, commercially available piece of software called a Spread Sheet.

Understanding the problem is halfway to a solution, now I know that I have to allow for the machine bending out of shape due to cutting drag I can do something about it. I don't want to spend thousands on software, I'd rather spend it on more tangible assets :D

best regards

Robin

can't argue with that
good software makes a big difference
try dolphin :)

Good software is one of the most important asset you will buy for your CNC machine and it doesn't need to cost so much.

Unfortunately I blew $13k on a Baker rifle so I now have to wait until her indoors wants something equivalent before it's my turn again.

I don't need software to do the actual machine control, I just need to convert dxf to tool paths and G codes.

I have downloaded Cambam instantly plummetting to the botttom of the learning curve, doubtless I shall still be using gsimple for the forseeable future :D

The wizards in the free demo version of MACH3 will do what you need with virtually a horizontal learning curve.

If you have never used Wizards you should at least have a look. I think they will fit you needs perfectly.

Phil


I have downloaded Cambam instantly plummetting to the botttom of the learning curve, doubtless I shall still be using gsimple for the forseeable future :D

Unfortunately I blew $13k on a Baker rifle so I now have to wait until her indoors wants something equivalent before it's my turn again.

I don't need software to do the actual machine control, I just need to convert dxf to tool paths and G codes.

I have downloaded Cambam instantly plummetting to the botttom of the learning curve, doubtless I shall still be using gsimple for the forseeable future :D

If you've got £85 to spend then I can highly recommend SheetCAM for 2.5D stuff - check out www.sheetcam.com

Cheers.

Well, Cambam got the big heaveho when it wouldn't let me select all the lines from my dxf. Even my crummy attempt at a converter stitched the parts together automatically, it ain't hard.

Couldn't see a demo Mach 3, tried loading Mach 2 but it was enormous and all consuming. There were no wizards so that quickly got the boot to.

G Simple is starting to look pretty good, at least that works :D

If you've got £85 to spend then I can highly recommend SheetCAM for 2.5D stuff - check out www.sheetcam.com (http://www.sheetcam.com/)

Cheers.

I also use Sheetcam. Excellent 2.5d software for the price!

Mach3 will run as a demo. It is limited to I think 500 lines of G-code.
Mach is a excellent controller. I don't use the wizards very often since I have sheetcam.

Steve

Well, Cambam got the big heaveho when it wouldn't let me select all the lines from my dxf. Even my crummy attempt at a converter stitched the parts together automatically, it ain't hard.
Hello Robin,

I'm sorry CamBam didn't work out for you, but thanks for giving it a go. :)

If it's not too much trouble could you please provide me with a bit more information where it is going wrong. I am about to put out a new release soon and have been trying to resolve as many bugs and annoyances as time will allow.

I have fixed a bug with the polyline joining routines which may have caused the problems you experienced. If you are up for another go, I can provide you with a development release to see if this improves things.

Thanks for your time

Regards

Andy (10bulls)

If it's not too much trouble could you please provide me with a bit more information where it is going wrong.

Hi Andy

Oops! Didn't know you were here, bad day, angst, humble apologies etc :eek:

I was trying to do the plate nearest the camera in the piccy. I put the two outlines in to a dxf and opened it with Cambam.

It let me select the parts for one outline but when I tried to add the next outline it let me select them but only accepted the bits top left, ignoring bottom right. I floundered about for a bit breaking it apart, reimporting it, but no luck :confused:

Perhaps I didn't understand, love to try again. I like to saw off the excess but that means a lot of g-code editing because G-simple only works with rectangular blocks. I sawed and edited this plate from eight hours down to two and a half.

best regards

Robin

Hi Andy
Oops! Didn't know you were here, bad day, angst, humble apologies etc :eek:

Crikey! I dread to think what someone with a 13k baker rifle would do to unwind after a 'bad day'. :)

I'm keen to hear of all the bugs and problems at the moment. I'm trying to clear off as many of these as possible for the next release so now is a good time to shout them out.

I use CamBam for all my CAM and CAD now (warts and all), as a penance to make me get on and fix all the crappy bits.

I think I know the problem you are having. (chair)

I'm afraid there is an 'intermitent' bug in this release where some drawing objects aren't 'accepted' by the machine operations. Saving the drawing, closing CamBam and reopening the file usually fixes this. It is proving a little elusive to track down. I do apologise.

If it's not that, then please feel free to send me any drawings to test.
@ 10bulls at gmail dot com

As to your original question regarding out of round.

In cambam you can spiral mill a hole by adding a drill operation based on a point. Tell it cutter diameter, hole diameter, and set type to spiral mill (cw/ccw). The horizontal and plunge feedrates control the pitch of the spiral.
I use this a lot. On the last pass it does a circle so this *may* result in a sort of finishing pass as the cutter 'springs' back into the stock as you pointed out. Just a thought.

:rainfro:

Andy,
I know you have your own forum for cambam on cnczone, but I just want to say here that after looking at it last night I am very very impressed!

I am going to try it out and thank you very much for putting in that kind of effort and allowing other cnc enthusiasts to use it for free!!

Steve