3D Feeds

[Bob Savage]

Hey peeps. It's been a while... my day job has kept me very busy, which is a good thing. I'm getting back to doing some woodworking and recently did some 3D cutting and wanted to ask what may be a somewhat vague question, nonetheless.

I understand every machine is different, etc., so I'm just looking for some averages from those of you who do 3D work.

What speeds do you all generally use for X, Y and Z when doing 3D cutting?

For example, is an average of 60 IPM for X and Y and 50-55 for Z a slow rate, "normal or fast? How about 75 for X/Y and 70 for Z? Is that a reasonable rate to expect from a Shopbot, Camaster, etc?

This question is mostly geared towards machine/motor reliability (i.e. where does your machine start losing steps, particularly on the Z axis, if ever), but I'm interested in cutting quality too.

Thanks

[Joseph B. Chritz]

That’s a tough one to answer. I think your feed rates are about right for starting out.

Let’s consider the machine with no cutting forces. Acceleration and deceleration are often user adjustable and can be set up for each machine. The power of the drive motors, the mass you are moving, and the resistance of the guide ways all affect the settings. If they are set too high a stepper motor could lose steps and a servo could overshoot or otherwise cause problems. This is sometimes the limiting factor for feed rate. Because of the acceleration and deceleration time the machine seldom if ever reaches maximum feed rate. Response time also affects good results. That’s the time it takes for the machine to do what it’s told. Take a light cut along one axis then the other, like a letter L. A light cut will reduce the cutting forces that also affect good results. Increase the feed rate and the sharp corner will probably become rounded.

Now consider the tooling. Remember when you put the new chain on your chain saw. Every thing was the same except the cutting tool and you could cut a lot faster and easier. A sharp tool cuts with less force than a dull tool. You have to look pretty close to see a dull tool, but a good check is to gently draw the cutting edge against the surface of a finger nail. A sharp tool will try to cut the nail and a dull tool will glide across the surface. Remember that dull is a relative term and although the tool may not be as sharp as a new tool it may still work fine, just with a little more effort.

The material you are cutting and the depth you are cutting have an influence on acceptable feed rate. When doing 3d work the depth of cut can vary so you have to be careful with the roughing and finishing passes. Even if you’re very careful you can be surprised by some small detail you’ve overlooked. This is a lesson I keep learning over and over again.

I'm sure I've forgotten a few important things to consider, but the best thing to do is start with a safe feed rate that you are comfortable with and adjust as you see fit.

[michael turner]

Hey peeps. It's been a while... my day job has kept me very busy, which is a good thing. I'm getting back to doing some woodworking and recently did some 3D cutting and wanted to ask what may be a somewhat vague question, nonetheless.

I understand every machine is different, etc., so I'm just looking for some averages from those of you who do 3D work.

What speeds do you all generally use for X, Y and Z when doing 3D cutting?

For example, is an average of 60 IPM for X and Y and 50-55 for Z a slow rate, "normal or fast? How about 75 for X/Y and 70 for Z? Is that a reasonable rate to expect from a Shopbot, Camaster, etc?

This question is mostly geared towards machine/motor reliability (i.e. where does your machine start losing steps, particularly on the Z axis, if ever), but I'm interested in cutting quality too.

Thanks

Bob as already explained, lots of things can influence the final feedrate. Are you talking roughing or finishing? Most roughing cuts will be deeper than your finishing cut and therefore need to be a little slower, unless the machine and spindle have the needed power to push through without problems.

I carve lots of full 3d, 4 axis in the round products, and the specie of wood can also determine feedrate. My bits are never sharp so I have to take that into consideration as well!

Mike

[Bob Savage]

Thanks for the info guys. I'm really just trying to gain some perspective because I've had issues with my Z0 reference being lost on 3D and some vcarving basically since I received the machine almost a year ago. Camaster has been helpful and on one occasion went above and beyond to help get this fixed but in the end I was effectively told that I'm expecting too much from the stepper motors. I have no real reason to doubt this is true but I'm still struggling with the concept that it's so easy to push the machine to failure (i.e. scrapping the part because it begins cutting too deeply), and it's really affected my confidence in the machine.

I also want to state that I am in no way attempting to bring negative attention to Camaster (I've actually remained quit for almost a year), but being told my only real option is to move to servo motors, I need to put this out there so I can ensure that my expectations are indeed too high and the only way to do it is compare my results with those of others. If I need to run vcarving and 3D jobs at 45-50 IPS then I will, but I need validation that I'm just asking too much of the steppers.

Any input from this group is appreciated.

[Bob Savage]

I carve lots of full 3d, 4 axis in the round products, and the specie of wood can also determine feedrate. My bits are never sharp so I have to take that into consideration as well!

Mike

I've had this issue with both Vcarving and 3D finishing. I don't recall having the issue with roughing.

[Nicholas Bukky]

Bob
I have a router running steppers and when I set it to run at high feed rates say 300ipm while doing 3d it never reaches much above 60 because of it trying to accel/decel to points. I have had minimal loss in z height on occasion but nothing that was to bad. I was typically able to sand the part to make it ok.

How much loss are you having that you have to scrap parts?? Got pics??

Thanks,
Nick

[Gene Crain]

I've had this issue with both Vcarving and 3D finishing. I don't recall having the issue with roughing.

...did at any time Camaster ask you if you painted the machine blue?

[Bob Savage]

Bob
I have a router running steppers and when I set it to run at high feed rates say 300ipm while doing 3d it never reaches much above 60 because of it trying to accel/decel to points. I have had minimal loss in z height on occasion but nothing that was to bad. I was typically able to sand the part to make it ok.

How much loss are you having that you have to scrap parts?? Got pics??

Thanks,
Nick

I've kept the speeds down (was using above 100 at one time) so the drop has been much less than previously (last nights was maybe .04" or so but still enough to cause me pain), but I've had drops up to .25". I do have some pics of projects from a few months back. I'll make them smaller so I can upload... actually, I may not be able to because my contributor status changed. Anyway, I'll get some up so you can see.

[Bob Savage]

...did at any time Camaster ask you if you painted the machine blue?

LOL... no, but I would be lying if I didn't say there have been times of frustration that I wished it was blue.

[Bob Savage]

How much loss are you having that you have to scrap parts?? Got pics??

Thanks,
Nick

Let's see if this works. If it does, there are two pics attached. One is of a sailfish. You can see starting from the right where the 3D finishing has occured then towards the middle there's a substantial drop (that fish is about 10" tall). The one of the dog has smaller drops, but you can see multiple lines where the axis dropped multiple times.

[Gene Crain]

LOL... no, but I would be lying if I didn't say there have been times of frustration that I wished it was blue.

with wincnc does the computer actually run the machine/file?....maybe you need a newer computer with enough RAM for the speeds you are looking for...with the bot I have i got a new desktop with dual core processor and I can run/jog as fast as the software will allow for my antique ....have you looked into the computer?

[james mcgrew]

bob, about two weeks ago i asked joey if he had heard from you, had not seen you on the camheads forum in a good while, last we spoke you were pretty busy at work. i will be going to calhoun to meet with some other camaster owners and the owners of Wincnc, the purpose is to better learn the tuning of the machines and to better figure how to teach the use of the ini file and the relation to the machines in operation (this is my goal) we will be meeting this friday if you could make it i would encourage you to do so. i will be back on saturday and have been working on training a high school shop teacher how to use the machine. your machine, his and mine as well as many others are the same configuration. it does not take much of a config alteration to cause step problems yet once tuned well they just keep on tickin!! once i get back i am hoping you can make time for me to work with you on this. i have never recieved enough info to be of any real assistance in helping you obtain your goals but i am willing!!

i will make time this weekend to get to the root of what your needs are and how we can get there, i have had carves last 36 hours and have a 5x5 seal due soon i expect 48 hours (in sections)

you have a large community of camaster machine owners having a pretty good time with these things, we certainly will not leave you behind in all the fun!! welcome back

here is some recent work the seals take 4-10 hours for some fine detail

[james mcgrew]

LOL... no, but I would be lying if I didn't say there have been times of frustration that I wished it was blue.

i sometimes have thoughts while riding down the road that i soon regret, thank god for forgiveness!!

[Bob Savage]

i sometimes have thoughts while riding down the road that i soon regret, thank god for forgiveness!!

Talked to Joey last night. I'm both hopeful and confident that eventually, my blue thoughts will diminish. Next steps are in place.

By the way, smoking carvings in your previous post.

[michael turner]

Bob I know nothing Wincnc or camaster, but if your photo of the sail fish shows what I think it shows, it could possibly be noise as well, though on my antique Digital Tool machine, if I get noise it just stops, but then again I am running Mach software.

What type, size steppers, drives etc. does the machine have? Are you running screws, belt or rack?

Mike