3D carving question.

[david_gardner]

I an cutting one of the mantel files from VectorArt 3D using the 1/4, 1/8 and 1/16 ballnose bit set from Gary Beckwith. Artcam says the 1/4 bit is going to take about an hour, the 1/8 bit about 3 hours and the 1/16 bit a whopping 7 hours using the feeds and stepover recommended by Gary. I have run the 1/4 bit with good results. I ran the 1/8 bit file with good results but it was apparent that it wasn't really cutting hardly anything in most areas and just a tiny bit where the 1/4 couldn't reach. Before I run the 1/16 file for the next 7 hours I'm wondering if there isn't a way to speed this up. It seem s like an awfully long time to cut nearly nothing. I'm a new botter and this is my first 3D attempt but even to me this seems crazy. I'm hoping you guys can hep me out with this. Any ideas?

[carlosgmarroquin]

I remember that there is a way to use the simulation from the 1/4 bit and generate a toolpath for the 1/8 only where the 1/4 bit didn't enter. It's called rest machining. You could check the options in the toolpath section.

Hope it helps

[david_gardner]

I tried following the directions for that and I think it worked but it wants to machine the entire relief. It honestly looks like the entire relief needs to be machined to get the detail. I'm just wondering if I can't run it at a significantly higher speed since it's basically removing only a miniscule amount of material.

[carlosgmarroquin]

what you get from that operation is a set of vectors in the areas where you have to machine with the next smaller bit. So you have to generate a 3d toolpath with those vectors selected. Did you try that?

[bleeth]

You should be able to run at a higher speed but with 3-d files the ramping pretty much ends up holding your speed down. You didn't mention what material you are cutting or what size your relief is. 1/16 bits are pretty tender. It will be cutting the entire relief. I have had pretty good results from doing the larger bit as a roughing pass and then a 1/8 with 7% step in hardwood and mdf. Cleaning that up with sandpaper beat going to smaller bit and stepover. To me the 1/16 bit is for small reliefs. Just think-If you were doing a piece of jewelry a couple of inches square cutting time would be 6-8 hours minimum!

[david_gardner]

Carlos - It returns the same original vector which I took to mean that it thinks it needs to macine the entire relief again and I agree with it.

Dave - I'm cutting pine and the relief is 24" wide 6" high and .5" deep. The level of detail in this file really requires the 1/16 bit to get into all the nooks and crannies, I could never get all of that with sandpaper. I've read some of Brady's ramping info and may attempt to play with that.

[carlosgmarroquin]

I remember having that same problem. When you select rest machining, you have the choice to generate the simulation or use the one that you have already generated. I always had to rerun the simulation in order to work. Let me check that, and I get back to you.

[david_gardner]

Thanks for your help.

[garyb]

Hey David, give me a call and I will walk you through it. You are just missing the correct settings for the toolpath strategy

[carlosgmarroquin]

Gray: Do you agree that the rest machining strategy is the way to go in this case?

[david_gardner]

Gary - Is it okay if I call you at work tomorrow? The cruise director is about to pull the plug on bot time for this evening if you know what I mean.

[garyb]

No problem David, give me a call at your leisure.
Yes Carlos, I would use the machine rest in this case expecially if the previous cutter didn't get the full detail of the model.

[jamesgilliam]

I just finished this plaque today, 24" X 10" in walnut. I am running an older PRT. Rough cut was 4 hours with a 1/4" bit, finish cut was 16 1/2 hours with the 1/16" bit, using a 8% stepover. The detail is fantastic, and barely needs any sanding.

6905

[ljdm]

James -
What were your move speeds for that? Lot of detail in that carving. Just want to compare to my PR/PRT.

[jamesgilliam]

Lou, Move speed was 1.5ips for all axis. If I go over 1.75 with the old board it starts to loose steps.

[myxpykalix]

James that looks great but 16.5 hours? whew...did you just put it on and come back the next day?

[rb99]

Does anyone know the cost per hour to run the bots?

RB

[khalid]

Once you generate the Vectors for rest machining, you can machine those areas with the same Previous tools too.. However few areas will still be left again...

[jhicks]

Expensive dinner.
Cost per hour? HMMM? Lets say its an employee at $6.50/ hr. not quite viable for cost/resale/profit.
If you use it as a mold base and pour copies it makes sense and there are some cool materials to pour that look a lot like wood mold including color and grain textures from original.
make one... Its the most expensive one you will ever make.
Make a mold and pour many.... Ammortization suddenly makes money IF you can generate the volume.
Nice finished mold master.

[benchmark]

Jerry,

If the model of the last supper is from VectorArt3D I think their license agreement excludes their use a mould for replication.

Paul

[jamesgilliam]

Jack, Yes 16.5 hours and I let the machine run overnight. I am just glad the router waited until the next morning to act up.

Richard the subject of what it costs to run the machine has many sides. I have tracked the KW usage on both my router and electronics for the bot. At the current rate my power company charges per KWH it costs me about five cents an hour. The real cost is in tooling in so far as how many hours will the "average" tool last. I have run some that will last about 12 hours before the finished edge on plywood is starting to be below the standard that I want, and I have others that I use in Corafoam or Sintra that have lasted for years. As Jerry pointed out, consider also the cost of an employee, or better yet, what is the bot freeing you up to do while it works away? If you say your time is worth $25 an hour, and say the bot is an employee at $6.50, the cost there is now $31.50 an hour with no margin for profit figured in. We could go on with this subject for a while, but I will stop for now. Hope this helps.

James

[the_doctor]

Looks great! Man, my loaded shop rate is $85ph. $1750 plus materials and programing time. It would be a tough sell for me.

[jamesgilliam]

Carl, I did this for a fundraiser for a school at an area church. My normal rate would put it about $1500, a tough sell indeed.

[the_doctor]

James, I not sure if you’re doing these projects on the side or for profit. Everybody has their view on how to calculate a rate. In business an hourly rate is not calculated on what your worth, it’s on fixed and variable costs. Example; the kw cost for a business here in Philly is double that of resident charges. The cost of the cement the machine sits on (about $10 sq foot) plus taxes. The cost of the tooling, replacement tooling, motors, wires, upgraded software, heating on the twenty hours it took to make the project, programming, design, and the time I'm spending typing this reply. Not to mention payroll at $20 ph plus taxes and benefits for somewhat skilled labors. Yes I said labors. Very few skilled millwrights out there. Alright I stop but there are more expenses I didn’t cover. Have a great day Carl P.S. I know I should be in the shop but I’m loafing this morning.

[the_doctor]

James, I was on a rant. Got your reply,and checked were your from. Much cheaper to operate down there.

[khalid]

Why not optimize your Gcode?.. Why not you people getting benefits from your high-end CNC's..

My First preference for such 3D work is to optimize the Gcode generation process in CAM and then optimizing the Mechanical side (My Machine )..

[ljdm]

James - I'm running the older PRT board on my PR, and run 2.5 or 3ips X,Y and 1.5 or 2ips Z, never lose steps. That's on the roughing and finish passes, in oak, 1/8" endmill and ballnose and 1/16" ballnose. Usually leave .06 for the finish pass. Any idea why you are losing steps, is that X znd Y, or Z also? We are using the same board (I believe), curious about why you are losing steps.
Lou

[scottbot]

What's this 'rest machining'?
I get the concept but I've never seen anything that could be selected in Partworks 3D or Aspire called rest machining.
Sounds like something I could use.

James,
Beautiful plaque. I really like your choice of wood.

Scott

[carlosgmarroquin]

As long as I understand it, Artcam or any other program with this algorithm will compare your model against the result of a toolpath and if there are places that doesn't match (meaning, the tool could not go further) it will generate a vector delimiting that area.
So you could generate antoher toolpath inside that vector with a smaller tool

[khalid]

Carlos.. You can use the same tool again to machine those areas.. Just try it


The difficult part is that the toolchange must be in precise way otherwise the whole part can look shabby

[jamesgilliam]

Carl, I would have replied sooner but the wife went in the hospital, nothing too serious, but I just got home. Don't worry about the ranting. Right now the machine sits idle most of the time as I am building our house next to the shop. I don't have a fixed rate, I go job by job, and being a one man shop lets me do that quite well. I will only take on a project that interests me. Some at the end, after all costs were figured only made around $35/hr, others have made over $150/hr. I guess being, as I like to say, self-unemployed, makes all the difference.

Lou, I believe we are running the same board, but I am still using the old DOS based control software. I started to switch to the windows based one, but about that time I was seeing alot of posts of everyone having issues with it, so I used the old rule, "If it ain't broke, don't fix it.

[ljdm]

James - My 2 cents - switch to the windows version. DOS version limits part file editing to 65k lines. Not sure how the different versions could affect losing steps though, but like I said, I run SB ver 3.4.26 and cut 3ips with no problems, DOS I cut 1.5ips. Once I got used to the differences from DOS to Windows, haven't had any of the problems others have had. Again...my 2 cents.
Lou

[dmidkiff]

James,
I was also hesitant to change because of all the trouble, but kept up with the forum and it seemed that all the bugs were worked out. I made the plunge. I still do not keep the latest versions because of the bugs but am running the windows version and it made a huge difference in performance.
Dave

[jamesgilliam]

Lou and Dave, Well I may have to take the plunge and see if I can get my speed up and time down. Dave, what version are you running?
James

[dmidkiff]

James,
Sorry, I don't know where to look for the version that I am running. The best that I could find is sb3. If someone could give me a clue where to look, I would post better info.
Dave

[ljdm]

Dave - go to (H)elp, then help (A)bout, it will show software version.

[dmidkiff]

Thanks Lou I have version 3.4.27
Dave

[jon]

Are any of you guys running RhinoCAM? I could have done the part in less time for sure, I use this software for both modelling, and machining. It has rest machining, and a great simulation rendering engine. I also just recently started using a 1/32" ball cutter (from Garr tooling) and it hasn't broken yet! The detail is amazing.