Line Boring Efficiency and CNC Equipment Speeds

      Is a faster or heavier machine really worth it for boring lots of holes? February 19, 2013

Question
I have moved from a heavier platform (Routech) to a moderate platform (Omnitech) over time. Manufacturers are telling me that lighter and lighter frames are producing quality cut and good speeds, for nbm of 19mm melamine panels. For those who are using the lighter frames would you be able to comment on your quality of cut and overall speeds?

Additionally, I am seeing a few routers with spindles only (with static tool changers and no boring block) that are very fast and using router bits to line bore (5mm) and router bits for construction boring (8mm). This technique of boring might actually provide less blow-out than a drill block. User thoughts and comments are certainly appreciated.

Forum Responses
(CNC Forum)
From contributor M:
I have used a MultiCam MG (circa 1998), an Omnitech Selexx Pal and a Holz-Her 7120 (current machine). These happen to be in the three categories you mentioned. Each of these machines has its strong and weak points. I can say though that cut quality and accuracy on each machine in a nesting application is not a problem. I am not going to get into the drawbacks of each machine, but every machine out there has them. Each of these machines is at a different price point and have different capabilities, so direct comparisons are difficult and unfair.

Of the three machines the Omnitech was the best dedicated nester. It had a 5x5 drill block and an eight tool changer. Many nice features including auto tool touch off. The MultiCam had a very nice controller and is far more robust than most people give it credit for. Mine was a lot slower but they are a fair amount quicker now I understand, closer to 2000 IPM cut speeds, fine for three flute tooling. That machine has been in constant use since 1998 and runs as well today as when it was new, normal repairs being made.

The Holz-Her is most versatile. It has the capability of using pods over a flat table, a nice feature at times, pendulum processing (two working zones). It is large, heavily built, and generally more solid than the others and carries an 11x7 drill bank, a saw aggregate onboard and 12 tool changer. Also the ability to incorporate spindle aggregates, a slightly larger z axis range saw aggregate, and etc.

I have achieved very good results boring with a drill bank over a spoilboard, occasionally utilizing a secondary operation when drilling all the way through a divider with common line bore depending on the material. No problem with the construction bores though. It is a rarity that a construction bore routine will drop more than two bits at once. A line bore drops more on average. Although I have gamed my 11x7 drill with 7 and 5mm bits for best advantage and some less frequently used drills at the end, I would lose very little by populating the drill bank with all 5mm and drilling the construction bores with the spindle. That being said the best bang for the buck may well be a 5x5 populated with all 5mm drills especially if the router is faster. The downside is it presses you for more open tool holders.

It is worth mentioning that top speed is nowhere near as important as acceleration for nesting cabinet parts. The Holz-Her machine can achieve 1600 IPM cutting or more, but in practical terms even if it is programmed to it never operates at the speed due to the fact it takes 24 plus inches of travel to get there and the same to decelerate again. You see the problem on a 4x8 table, right? The tradeoff is power and durability. A smaller lighter machine will often accelerate more quickly, and therefore finish a cycle faster even if top speed is never reached. The relationship between the power of the drives and the weight of the gantry is key. In my personal experience the Omnitech can be tweaked to get up to speed really fast.



From contributor J:
The moderate router platforms have certainly come down in cost, and have noted quality improvements over the past years making them an option (even upgrades) for those who have owned heavier machines in the past, as well as those considering their first CNC.

As noted in a previous post, many of the machines are able to move quite quickly. Simple, reliable, and easy to maintain fixed tool changers are also a viable option on some offerings in this class with high rapids speeds, as they can get in and out of tool changes quickly. Sometimes as fast as other machines with ride along tool changers. Some take the position that rapids is an overstated performance criteria, while others note it as a determining factor regarding the overall build quality of the router platform.

Those machines that can stop and start the gantry at high rates of speed without compromising the integrity of the frame may note a higher build quality than another machine (of a similar build year) noting slower rapids speed. Many also make a case that the controller and linear motion package required to achieve these speeds will be superior. These industrial components provide some of the machines in this class the ability to accelerate/decelerate quickly and reach/run programmed feed speeds and maintain them for longer periods of time.

As far as drilling, we usually see drill blocks requested/specified for line boring applications, but the spindle quantity has come down based upon the ability of the machines to quickly get to the next position and drop the block again. For construction boring, it is possible to chuck up a drill bit in a tool holder and use the main spindle to drill as long as the spindle can be set to the proper RPM, although tool change positions will be used for drill storage.

The vacuum system is also a large contributor to what can be achieved for cut quality, feed speeds and cycle times for machines in this class. You will note a lot of variance in vacuum systems in this market segment.



From contributor L:
The problem with line boring with one tool no matter how fast the machine is the distance from hole to hole is so short the machine never reaches full speed. With a 5 or 7 row of bits in very little more time you get that many holes instead of one. It probably doesn't much matter for construction 8mm holes. How much those really fast accelerations shorten the life on the drive systems depends on how much mass needs to be moved and how beefy the drive components are. More can probably be gained in material handling than in traverse speeds.


From contributor Y:
Overall machine speed is way overrated for case production. I ran a plant with Komo and Northwood machines, fast to be sure. The rest of the flow of the parts was big batch, not very lean, and labor intensive (by the process not for lack of quality equipment), handling parts multiple times. I run an older (mush slower and lighter and less money) CNT 4x8 machine, single spindle on drill block.

In my whole system I can produce as many finished cabinets in a day with one man as I could with two and a half men there. My operator edgebands parts from the previous sheet, and will start hardware/assembly if still waiting on the machine. Cycle times are almost irrelevant in this scenario. The cycle times only have to be faster than what an operator can band and assemble. Our parts are generally grouped by cabinet and spread out over only a few sheets, not the entire batch (so I may burn up an extra sheet of melamine or pw on a kitchen, but save hours of labor). I could duplicate this little cell for about $100k in 1000sqft to get whatever volume of parts I need. It would also increase my flexibility and ability to process multiple different color jobs simultaneously.

All that said, I notice you have closets on your site. This is a little slow for a large volume of closets. For more than the occasional closet you probably need a drill head, and the more spindles the better (depending on how you build your closet, and again, a well thought out process may still make a single spindle work, but I have not fooled around with enough closets to invest the time to do that.)



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