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Okay, after having a cnc for three years now, I am seeing how much more I could do in a shift if I didn't have to unload, clean, and reload to get the next cycle going. I've been amazed at how much time it takes to deal with all of this in between cycles. I've read through all the recent threads on this subject and have two basic questions: 1. If I had only one option, what is the real timesaver - the ability to offload? Or do you have to go the full enchilada (with the onload) for all of it to make sense? In other words, if I don't need the onload feature to help save time, why would I pay for it? 2. I cut plywood almost exclusively - very rarely get into melamine or pb core material. If I got the onload feature, how do you make sure each sheet is sufficiently sucked down before cycling? I'm used to doing a quick check before hitting that start button to make sure I don't have any flipped corners that could cause problems and occasionally I have to flip a sheet over for better vacuum holding. That could negate the efficiency of the onload if I still have to check each piece. How do you guys deal with your onload when you are cutting plywood?
I had a standard flat table for 5 yea4 and have been running a full auto load/unload machine for almost 2 years. I found that the time to unload was pretty equal to the time it took to run the sheet. A sheet that might take 8 minutes to run had lots of parts and would take a while to unload, sometime as much as 10 minutes per sheet. The auto load feature takes up some space, and if I didnt have room I could still load pretty quick with a scissor lift. I believe you will still have much more efficiency with just auto unload and manually loading your sheets. Additionally with you runn8ng lots of plywood, (we have never run any on new machine) depending on part size and material quality you might want to check every sheet for hold down. Even with melami ne, sometimes we get a corner lift that with a little hand pressure will suck down tight.
The offload table is by far the best way to increase your efficiency. Even if Derrek's assessment is correct and it takes as long to unload the offload table as it does to run the program the key is there is a panel running while the operator is unloading the offload table. You also have the added advantage of not blowing dust into the air when cleaning the table. It seems a little high to estimate equal time to offload parts as it takes to run them but if you are labeling the parts or there are large quantities of differing parts that require a lot of sorting I could see that being the case. There is automatic labeling available on some machines that prelabel the parts on the panel prior to it being machined. That can speed the process up as well.
It's fair to estimate 20 to 30 seconds to push off the parts while sweeping the table. This is much faster then an operator can accomplish the same task. If you add automatic loading the cycle time will likely be 45-60 seconds. This is once again going to be more efficient for the machine to load/offload and sweep the table then for the operator to do those same tasks.
I work on all brands but I do sell the Giben by Anderson brand. The Giben machine can also be set up to run in fully automatic mode. What that means is you can load a folder with let's say 15 programs, hit cycle start and the machine will run all 15 programs without hitting cycle start again. This allows the operator to simply unload parts from the offload table and perform a secondary task since they are not babysitting the machine.
This allows for consistent estimating and the best efficiency you can obtain from your CNC.
Rob, you bring up a really good point about table cleaning as the offloading is occurring. I do not want to have to blow off the table before loading a new sheet. The point, in my thinking, is to have the machine deal with all of that to keep the cycles going efficiently and eliminate downtime. From some of the threads I read, it sounds like that is a real hit and miss with machines. Are there any machines that can sufficiently clean without having to worry about extra vacuuming/blowing? That is one area I do not want to have to worry about. I really wanted to go to IWF and check out all of this first hand but we had a family crises and I couldn't make it work. So, I missed out...As far as onload goes, I could see a real benefit to having the parts pre-labeled so that the time spent during the cycle could be used for edgebanding and doweling. I'm not sure how much the onloading end would cost, so, not sure if I could make the numbers work - especially if I am having to interrupt each sheet to make sure everything is sucked down tight.
The auto load on my machine cleans the table very well until the spoilboard get down and gets a gap if more than 10mm. We devised the simple spacer to lower it and we can run the spoilboard down another 6mm.
Derrek, what kind of machine do you have? Do you pre-make your material stacks for each job with the appropriate interior/exterior sheets? Or, do you just use your onloader for cabinet liner material and load the finished material by hand?
I have a Biesse RoverS with 4x8 table.
Thanks, Derrek, that would be really helpful!
In addition to our MDF spoil board we use two (2) removable MDF waste boards. A waste board is placed on top of the spoil board and the material being machined is placed on top of the waste board.
At the end of a cycle the entire sheet of parts and the waste board is dragged onto a shop-made rolling cart, that the operator walks through the center of. See pic.
After a quick blow off of the (mostly clean) spoil board, the second waste board is loaded, along with a new sheet of material, and the machine goes back to work. While the second sheet is being machined, the parts from the first sheet are labeled and stacked, and the first waste board is cleaned.
With a little practice (and hustle), most operators can do a sheet change in under 60 seconds, and for most sheets, all clean-up is performed while the machine is working on the next sheet.
Waste boards are machined on two faces and to the same thickness. When one side gets worn, we flip the waste board and continue. We start with 3/8" waste boards and machine them down again and again, until they're too flimsy to do the job.