Run Time

[twiles]

I am trying to calculate the actual run-time for a 4 x 8 sheet of 3/4” particle board, cutting out 8 – 22” diameter circles from the sheet. I have a customer that may be interested in about 500 – 1000 pcs. over the next couple of months and is asking me for a price. Since I do not have my machine yet, I need to try to figure this pretty close with those quantities. Can I interest anyone in running a quick program on their machine for this and telling me how long it takes the SB to run through it???
Hope to order my machine next week, so thanks for helping me out with this before I get it!!!!

Thanks,

Terry

[rgengrave@aol.com]

I cut some old scrap I had and cut a 22" 3/4 in 2 minutes 14 seconds.

I set my speed to .25 and got a good smooth cut.

Hope this helps you Terry.

Ron

[Gerald D]

Ron, which bit?

[twiles]

Maybe I am reading your E-mail wrong, but it took you that long to cut ONE circle? Or, was the program for all 8 circles 2min. 14sec.????? I thought the machine could cut this stuff at about 100 inches per minute?? At that speed I have been figuring about 7.5 minutes for the whole program of 8 parts.

TW

[Gerald D]

Terry, during your figuring of cutting 100 inches per minute in 3/4" particle board, what cutting tool did you have in mind? Router and bit, water-jet, sabre-saw, etc.?

Remember that Shopbot will push a tool of your supply at 100 inches per minute, provided that the pushing force required is under 80 lbs, and provided that the PC supplied by you is fast enough.

Ron V's practical test done for your benefit is probably based on a router & bit situation, and the .25 inch/second (15 inches/minute) that he mentioned is very typical. However, I can't figure how he cut the circumference of a 22" circle (70" total), at 15" per minute, in just over 2 minutes?

[twiles]

I will be using the Porter Cable 3 1/4HP Router with either a 3/8" or 1/2" solid carbide compression spiral bit (two flute) cutting standard Particle Board. The PC that I have lined up for the machine is a 300 MHZ pentium with windows 95 and 130MB of RAM. Please tell me I can run at least 80 or so IPM?!?

[rgengrave@aol.com]

I used a 1/4 straight bit, the time I got was from a program I use to tell me how long it will take to cut any file, I think you can find this in Vector too?.

Ron

[danhamm@abccom.bc.ca]

Terry I don't know if this will help you or not,
I cut picture frames from 5/8 mdf at 2 in. sec or 120 in. min 1st cut is a profile cut at .35 next cut is 1/8 bit cutting .625 I get 52 pic frames
from 1-4/8 sheet 1 hr. and 22 min.
What will happen if you force the cut is you will
get run out, a climbing action from the bit,your cut where it starts and finishes won't match up its not as bad in particle board as it is with grained wood "but" hope this helps..

[Gerald D]

Ron, thanks for the bit info.

Terry, the issues of time and speed have always worried me on this forum, because we often see "data" that makes no sense. The only reliable measure of time is a stopwatch, and for speed a tape measure and stopwatch. The speed setting on ShopBot is accurate only if your PC allows the higher speeds. I am wary of people reporting more than 1 inch/second and would encourage a test against a stopwatch. (A PC running Windows 95 may be a disadvantage - ShopBot runs in DOS and you don't want to distract your PC by having to run Windows in the background)

Regarding the capability of routers and bits, this subject is distinctly seperate from ShopBot and can be tested in isolation. Suggest you borrow/hire/purchase a router and bit of your choice and then do some practical tests this weekend. Whatever speeds and quality of finishes that you can achieve by hand, will be replicated by ShopBot - except that ShopBot will not want all the breaks for drinks!

[birdsofplay]

Very intereresting discussion here .

Actuall testing is always more accurate IMHO.

With the "very nice" SB Ramping function it is always going to be difficult to calculate actual machine time even IF you know the total travel and the Jog and Cut speeds.

If you're like me you HATE accounting, and ...

I realize that total Machine time costing is difficult as well. It's depends on several issues ...

1. Your amortization of "some" machine life span
2. Consumables used
3. Whether it requires constant operator attention.
4. Overhead, etc.

A simple bit of division isnt reality, however ...
$5000 machine / 1000 hrs of use is only $5/hr

Since the whole machine doesnt wear out this simplicity falls apart quickly.
a. Router rebuild costs and
b. bit usage
c. maintenance hourly rate for rebuild
d. operator rate for load/unload

Finish and cleanup is another issue, kinda.

Does anyone wish to offer their estimations for machine time costing calculations ?

Anyo info welcome, thanx

[twiles]

Bob, thanks for the input. I have taken all of these factors into account and compared them to what the local market if for this type of work. My preliminary numbers are about $65 / Hr. I put together a handy Excel spreadsheet that calculates the final cost by just entering the number of pieces per sheet, the number of inches to be cut per piece and the IPM. It has a bunch of other variables that can be adjusted too and incluedes material costing. If anyone would like a copy, just E-mail me.
Gerald, in my past 6 years of working with CNC machines I have become aware of the amount of trial and error involved with getting the right bit combination. I also know that in all of the software that I have seen and used, there has never been one that is accurate in calculating run-time. At my day job, we just purchased, and I just finished setting up, a machine that was almost $225K. Our standard feed rate for 3/4" melamine and PB is 1000 IPM and it will not estimate run-time even close. It is typically off by about 60%. The smallest machine that I have ever worked on is a $175K Komo. Now that I am looking for a toy to put in my garage, I am just trying to get an idea of what to expect from it.

What my original question was.....if someone could create a program that would cut out 8 - 22" circles from a single 4X8 sheet and basically "dry run" the program on their shop-bot (not cutting material. I am curious how long this machine takes to "go through the motions" for all 8 parts at 80IPM. You don't need to cut any materials and the cutting tool is not important as I know that I will need to fine-tune the tooling, feeds and speeds to get the best cut.

[bill.young]

Terry,

I aircut your file ( eight 22" circles on a 4x8) and it took 9 minutes and 19 secs, timed with my watch. I set my xy move speed at 1.3 ips, and xy jog speed at 2 ips. There was a 0.8" plunge at the beginning of each piece at a z-axis move speed of .2 and z-axis jog speed of .4

This is actually very close to what the calculated time is. I figured 52.6 sec/circle ( 70" perimeter at 1.3 in/sec ), 16' of jog distance at 2 ips, and 48 sec of up-and-down time. That works out to a total of 9 min and 24 sec.

FYI, my ShopBot is a early rack-and-pinion tool and is connected to a pentium 133.

Hope this helps,
Bill

[birdsofplay]

Given the machine speed and the Micro capability inside the SB box, I'm not sure that PC speed is going to be much of a factor above 100Mhz.

Usually faster is better but the bottle neck is the machine, in this case IMHO

It's kinda like corporate america ...
The Whippings will continue until Morale is improved ! NOT !

[Gerald D]

Terry, sorry for misinterpretting your first post and underestimating your experience with CNC routing. Your request for the actual ShopBot run time, during an "air" cut is quite valid, since we have seen the discrepancies that can creep in. When I get back to our shop on Monday, I will certainly try to get a stop-watch time. However, I am using a 486 PC and I know that I cannot reach the (jog) speeds advertised by ShopBot.

It would be interesting to see the results from a couple of guys, telling us which PC's they use. Just to level the playing field, I assume that the cut program would start at a corner of the 8x4 sheet, each 22" circle would be cut 24" apart (centres on square grid), move speed set to 80"/min, jog speed set to maximum, plunge depth 1", and tool returning back to start corner for a full cycle.

[Gerald D]

Dang, In the time I typed my last post, two other guys beat me to it!

[twiles]

Bob, Thanks for the test run!! If I plug 100IPM in my Excel calculator for this project, it comes up with 9.6 minutes per sheet, so I must be pretty close (except that I only have 100 inches of travel included because I did not count the "return trip" to the home position. Obviously when cutting forces are applied and the ramping feature is in force, there will be a little bit extra, but this is a great start.
Gerald, if you run the same type of program on your machine with a sub-pentium PC, that should give us a pretty good idea between the two, for all that are wondering.

Sorry my original question was a little vague, I guess I assumed that most everyone that had a shop-bot used it primarily with a router. I met with two people this afternoon and both of them asked me if I was going to get into doing laser work with the machine. What kind of $$$$ does it take to get a laser attachment??? I would not even know where to begin.....

[jorgy.tucson@worldnet.att.net]

Terry, just for fun I programmed and ran a program cutting 4, 22" circles. Elapsed time 3 min, 33 sec. MS @ 1.33"/sec. For eight circles should be right at 7 min. run time. Total cycle time I would estimate 10 min. or about $2/circle NIC sheet stock. The computer that runs my sb is a 386, 33mhz, no hard drive. I programmed continuous arcs, no time consumming up & down jogs. The object is to make money as fast as possible. Have fun.

[dan@burningimpressions.ca]

Terry, $$$$ for laser attachment? the only laser I know of being packed is Kern WWW.uslink.nkernet/1-kern Most use mirrors and run between 40 - 60 inches a second as Universal or Epilog. We took our laser apart and
tried to run it on a rotary engraver table 40/40
there were lots of problems weight,speed,lenses,
programming,excitation, we had fun though... I did see a video of a shopbot with a laser on it though..
A 250 watt tube on a shopbot would be nice..

[Gerald D]

This is the cutting plan:


4870

This is the ShopBot program (*.sbp) for 3/8" cutter diam.:
J3,0,0,0.1
J3,12,23.1875,0.1
CC,22.375,T,-1,360,0,-1
J3,12,24.8125,0.1
CC,22.375,T,-1,540,180,-1
J3,36,24.8125,0.1
CC,22.375,T,-1,540,180,-1
J3,36,23.1875,0.1
CC,22.375,T,-1,360,0,-1
J3,60,23.1875,0.1
CC,22.375,T,-1,360,0,-1
J3,60,24.8125,0.1
CC,22.375,T,-1,540,180,-1
J3,84,24.8125,0.1
CC,22.375,T,-1,540,180,-1
J3,84,23.1875,0.1
CC,22.375,T,-1,360,0,-1
J3,0,0,2

Speeds set similar Bill Young above. (My plunge 1" as opposed to his 0.8" - tiny difference)

Total run time, from hitting load button was 11 min 41 sec. (Shown on screen and confirmed with clock). Using a 486 PC.

Some observations:
1. The jog speed was about equal to the move speed - certainly not 2 inches/sec. The final return jog took about 90 seconds.
2. From hitting load command to start of actual cutting was about 30 seconds.
3. After every 2 circles, there is about a 5 second pause while the system calculates its next moves.
4. Our PRT 96 has the later "micro-stepping" software, this may be more demanding on the PC than the earlier software.
5. Originally our machine was even slower, while Windows was still running on the PC. Now we boot directly in DOS

Anybody else want to cut and paste the program to join the drag races?

[carol]

This circle cutting is fascinating and frustrating. I think it was 22" circles that was wanted. If the diameter in Gerald's program is specified at 22.375 True with a 3/8" cutter, then the hole is 22.1875 and the 'wheel' is 21.8125. Right? And is a circle a hole or a 'wheel'? Now you know why I find the command description so frustrating.

So, am I right about the size of the hole and the size of the wheel?

[bill.young]

Carol,

Remember that it's the center of the bit that's traveling along Gerald's 22 3/8" circle. So his 3/8" bit is cutting a groove that's 3/8" wide. As the bit goes around the circle, it will cut a "wheel" that's 3/16" smaller than it's true path ( half the bit diameter) and a hole that's 3/16" bigger than the bit's true path.

Don't forget, though, that the "wheel" is 3/16" smaller all the way around, as if you took a 22 3/8" disk and cut 3/16" off of it's outside edge all of the way around. This makes it a total of 3/8" smaller than the path that the center of the bit took; 22" in diameter.

Hope this helps,

Bill

[Gerald D]

Carol, I took the ,T, option in the CC command - this means that ShopBot does no compensation for the tool diameter.

[beacon14]

For what it's worth, we have a Pentium 120 with 16Megs RAM (bought it at MicroSeconds for $175), and our jog speed is accurate up to 4ips. We were having problems with the jog speed set higher, so I timed it at various speeds and found that everything works fine (for us) at jog speeds up to 4.0 (a 96" jog takes 24 seconds). We have a PR96 rack&pinion, but not the newest version (about 1 1/2 yrs old). We run Shopbot under Windows 95, but the computer won't let us do anything else while the machine is running.

[Gerald D]

This morning I tried Terry's circles with my new laptop (Acer 202T with 600MHz processor) and Windows ME. Run time 9min 26sec. This laptop will not be my permanent driver, because it is 20x the price of the current 486 driver and only 20% faster on a really high-speed job!

Windows ME caused absolutely no problems. Did follow the advice of "Prevent MS_DOS-based program from detecting windows" posted under another topic last week. Also made sure that I did not load ShopBot from the CD, but only from the stiffy supplied with our machine.