Direction change lines issue milling hardwood

[scottp55]

Yes. an Onsrud 37-23

Now that I have the Tiny .25mm radius TBN, I expect similar detail results as the .01" flat Onsrud...but faster as 2 Flute.
And looking forward to topos..also bought the .25" shank version with 3" length:)

Here's another one cut against the grain in Curly Sugar Maple with same bit and no roughing.
I used 20% stepover on THIS one, and on very steepest angles, I could notice VERY shallow lines where the flat hit the 30 degree angle...it's why I did 10% stepover on most.

Tried a thinned 50/50 Tung gently placed on the ponds to help contrast...BUT it just ran off and got absorbed. 100% Tung just sat there for an hour, and did improve contrast a little

Gerry is right that your Z is huge! Going to provide a lot of leverage on your machine, and accentuate vibration I think. Lighter cuts? Cut WITH gantry direction maybe? Maybe a thick block of something to place material on to reduce the leverage at full Z extension?
Other know WAY more than me about machines, as I've only had this one model with now 5.5" Z.
Can't help with any Mach 3 settings..sorry:(

scott

OH...That particular one of Narrow Pond in Maine, was made for Bob who owns Allagash Camps. He LOVED the detail,as he flies into most of those ponds...
and tries to avoid the hills:)
Certainly I would NEVER imply that Bob is a little "rough around the edges" and "Slightly Cracked".....Nah...NEVER!!

[marbles]

Why is the gantry and Z axis so tall?

It been designed for carving large blocks of foam in 3 and 4 axis.

Generally, the only reason you would need to lower acceleration is due to a lack of rigidity. Higher acceleration **should** make the machine smoother, and more accurate, unless the machine is flexing.

I'm going to go through motor tuning again today to understand the machines limits and and reset accordingly.

[marbles]

Now that I have the Tiny .25mm radius TBN, I expect similar detail results as the .01" flat Onsrud...but faster as 2 Flute.
And looking forward to topos..also bought the .25" shank version with 3" length:)

These are looking great the detail is very good! "Something to aim for" as Bob from Allagash Camps might say flying in

[martin54]

I didn't comment on the machine but ger21 said what I was thinking, if the machine has been designed for a specific purpose then it may be that your not going to be able to obtain the detail you require on a small hardwood peice with this machine.
You could try raising your work peice so it is closer to the gantry, that would reduce your z travel, also experiment with speed, feed & DOC

[marbles]

I didn't comment on the machine but ger21 said what I was thinking, if the machine has been designed for a specific purpose then it may be that your not going to be able to obtain the detail you require on a small hardwood peice with this machine.
You could try raising your work peice so it is closer to the gantry, that would reduce your z travel, also experiment with speed, feed & DOC

Lets be clear here! The issue is extremely small, we are talking about a stepover of less that 0.18mm and after a few tweaks and advice from yourselves the issue will be resolved to my satisfaction. In terms of the bigger pciture for a machine designed to use a 8-20mm diameter ballend cutters on blocks of foam its remarkable its getting this close on a first run in hardwood at that scale. I'm keeping the long Z!!

[martin54]

I didn't comment on the machine but ger21 said what I was thinking, if the machine has been designed for a specific purpose then it may be that your not going to be able to obtain the detail you require on a small hardwood peice with this machine.
You could try raising your work peice so it is closer to the gantry, that would reduce your z travel, also experiment with speed, feed & DOC

Lets be clear here! The issue is extremely small, we are talking about a stepover of less that 0.18mm and after a few tweaks and advice from yourselves the issue will be resolved to my satisfaction. In terms of the bigger pciture for a machine designed to use a 8-20mm diameter ballend cutters on blocks of foam its remarkable its getting this close on a first run in hardwood at that scale. I'm keeping the long Z!!

Just trying to help, not suggesting for one minute you make alterations to the machins since it was built for a specific purpose. All I was saying was that some way of moving the work piece closer to the bottom of the gantry might help give better results & faster machining times with jobs like this. Something like a box giving a second table hieght would probably be enough
I know guys that have custom built machines with adjustable table hieghts but these are built in at the design stage which you are clearly well past

[scottp55]

These are looking great the detail is very good! "Something to aim for" as Bob from Allagash Camps might say flying in

Yep...Forgot to mention what happened when Dad gave it to him that first night.
MOST people look at it for a bit, puzzled until the orientation "Clicks", but seaplane pilots seem to recognize it immediately like Bob did, as they fly over it at 500 to 5,000 feet.
After Bob gawked at it for a minute, he ran around the camp shutting off ALL the gas lamps...placed it in the center of the table...lit a candle and examined the shadows Minutely!
THEN with candle, cigar smoke, and a flashlight beam...proceeded to show Dad and his friend all his favorite fishing holes/canoe stashes/and with smoke simulating winds, demonstrated some of his
harriest landings and take offs from his pond for an hour
He EVEN got out a magnifying glass!!

IF I hadn't had the detail in there he would have been disappointed.
But instead it has a Prime place in the main cabin, and guests can't touch it unless they wash their hands and ASK

Anybody who would commission a job like this, will most likely be VERY familiar with the area, and best detail pretty much a must to get top dollar.

Oh, here's another early Cherry one. It would have benefited from a roughing pass/thinned finish/ and NOT increasing feed like I tried.
I did it without a Roughing, and spent a bit of time with the Foredom and 400G Radial Bristle discs and 600G Abranet(especially on the sapwood...Heartwood was pretty good)

Don't know what your finish will be, but maybe a thinned de-waxed shellac would be good to penetrate face grain with a .02" machining allowance?
That would allow almost any finish to be used.

Those Engraving bits are also VERY good at fine detailed models when you go for Tiny size:)

I! Wouldn't give up the Z either if hardwood topos weren't my main concern.
I LIKE Martin's idea of a tall "Box" (maybe located near one end of the gantry in an area not used much?) for detailed hardwood work?

Here's some interesting reading on my machine, refitted with a TALL retrofit Z axis;
http://www.talkshopbot.com/forum/showth ... pgrade-kit

http://www.talkshopbot.com/forum/showth ... dification

Good luck with experimenting...It's the best way to learn YOUR machine
scott

OH! I have best luck(least tearout) using a Downcut bit for roughing toolpath.
Especially like This .125" for small stuff..It SAYS plastic, BUT if that's the case, then Bloodwood,Ebony,Teak,Rosewood, etc. are plastic ;
https://www.ebay.ca/itm/5-1-8-1250-CARB ... rk:21:pf:0

[adze_cnc]

My first thoughts are I would be using 8% stepover but that might not be the major cause of the visible lines (only a contributor).

Maybe I'm being thick but how would using a 63/10000 of an inch (0.16mm) stepover be that much better than a 71/1000 of an inch (0.18mm) stepover for a 2mm diameter cutter?

When you get into the realm of much less than the diameter of a human hair quoting a percent stepover change from 9% to 8% seems much larger than it is in absolute values.

[mtylerfl]

I dunno - I can always tell the difference between 8% and 10%.

Maybe 9% is a good compromise!

No worries.

[marbles]

I didn't comment on the machine but ger21 said what I was thinking, if the machine has been designed for a specific purpose then it may be that your not going to be able to obtain the detail you require on a small hardwood peice with this machine.
You could try raising your work peice so it is closer to the gantry, that would reduce your z travel, also experiment with speed, feed & DOC

No problemo squire You caught me in the Monday morning moment
Work piece is raised, see pic. Ran more tests. Works much better

[marbles]

He EVEN got out a magnifying glass!! IF I hadn't had the detail in there he would have been disappointed.
But instead it has a Prime place in the main cabin, and guests can't touch it unless they wash their hands and ASK
Anybody who would commission a job like this, will most likely be VERY familiar with the area, and best detail pretty much a must to get top dollar.

Totally agree. Landscapes are personal and people are really going to covet something that they have an emotional attachment to. Saying all that it would be great if everyone would just like the same terrain file cut out would make my life a lot easier

I! Wouldn't give up the Z either if hardwood topos weren't my main concern.
I LIKE Martin's idea of a tall "Box" (maybe located near one end of the gantry in an area not used much?) for detailed hardwood work?

It wasnt clear from the conversation but I had it set up ok before. the bed can be raised and lowered and i'd already done what Martin suggested.

Here's some interesting reading on my machine, refitted with a TALL retrofit Z axis;
http://www.talkshopbot.com/forum/showth ... pgrade-kit

[marbles]

My first thoughts are I would be using 8% stepover but that might not be the major cause of the visible lines (only a contributor).

Maybe I'm being thick but how would using a 63/10000 of an inch (0.16mm) stepover be that much better than a 71/1000 of an inch (0.18mm) stepover for a 2mm diameter cutter?

When you get into the realm of much less than the diameter of a human hair quoting a percent stepover change from 9% to 8% seems much larger than it is in absolute values.

I've just run two different files with a 2mm ballend to contrast. Its not unfortunetly a rigorous scientific analysis as one was an offset cut (9% stepover) and the other raster (6% step over) BUT the 6% stepover had no visible stepover marks. The much bigger ballends like the 20mm diameter cutters I use seem to give a smoother finish comparitively but would be good to read an article which resolved the questions I still have also around this area. Stepover = time = money

[martin54]

Right so now we are on the same page I'm not sure with your main concern being large foam blocks that a fixed area that was raised is the best way to go. Last thing you want to do is restrict the machines movement when your carving your foam blocks
A secondary torrsion box type table that can be removed would probably be what I would look at doing. I would think about what other projects you might like to do as well as toppos & make it large enough to do those as well but not so large that it is a struggle to put on & off your main table. You could also build some clamping arrangements into the top as well, threaded holes, T track, that sort of thing. The closer to the bottom of the gantry the better as this will reduce the amount of z travel below the gantry
Trial & error is the only way you are going to be able to work out what is best for your toppos, Scotts are brilliant but look at his machining times Finding a compromise that works well for you is probably going to be your biggest problem
As well as experimenting with different settings I would also look at experimenting with different hardwoods, some machine better than others & you may find you can reduce machining times but still retain the quality you desire.

Best of luck with it, least you know your heading in the right direction, just need to do some tweaking

Oh I meant to say I use to ski in the Cairngorms many years ago when I had 2 legs that worked properly

[Adrian]

Stepover = time = money

Which is why I gave up the idea of doing anything that requires a 3D toolpath commercially a long time ago. In the time it takes to produce a single 3D object I can make enough 2D objects that would make the price of the 3D object astronomical. All the time I have enough 2D work to occupy the machines 3D will have to wait until I retire (again)!

[scottp55]

Much better!!
You're getting a handle on it:)
The .5mm TBN will help a lot with details, and eliminate the 2mmBN Radius marks.
You have some serious vertical faces there though...I'll be interested to see the TBN cut:)

Oh, the 9.5" Z , is not my set-up...we went the Shopbot 5.5" Z retrofit kit as we had to do both of our Desktops...Max and Lauri are acquaintances that let us visit their shop when we were deciding on a machine and set-up. Wonderful Luthiers, and Lauri's MOP inlays are beautiful!

Yep Martin....Long cut times because of the single Flute Engraving bit, and max rpm of 18K...but most of these were for myself or gifts. HATE saying "I could have done better, but I was in a hurry"
I like to sign and date my stuff, but won't if I'm not proud of the piece.

Oh, Marbles...DID do 2 offset test cut's in Cherry with no Roughing toolpath with the Chinese .125" shank .25mm TBNs on a Lion model with a lot of detail.
One at a typical speed feeds for very dense hardwoods like Cocobolo,Bloodwood,Ebony, etc., and then Sped up and increased all parameters...,
And VERY difficult to tell the difference!

Perhaps the comparison will give you a better starting point, and then gradually bump up feeds/speeds/pass depth/stepover until YOUR best finish is found.
This is a new tower, and the file is on control computer as I was winging the test cut...I THINK the cut times were about 25 minutes for the faster one..I'll check and post if much different.
Oh, Offset/Conventional toolpath works very well(and fairly fast) in dense woods when the model is round or sometimes oval IF the file doesn't JUMP from area to area...PREVIEW!
The 2 Cubes are Beech, and even at 1,1,18K were 25 minutes each with the .25mmR TBNs.

My next topos should be MUCH faster Martin!