Newbie question on Drilling

[bstern]

Has anyone used a "gang drilling' spindle to drill 32mm system holes. I will be doing closets with long runs of 32mm dilling. Up to 3 rows per 8' to 10' side panel. As I am not cutting yet, I have run some simulations and the time to drill is 80% of the process time. I have seen some spindles that have 3 to 9 drills in a row. Seems this would cut my time considerable. Of course it would be used on a 2nd Z and only in one axis.

Can this be done?

Thanks,
Bob

[henrik_o]

This is not the answer you were looking for, but IMO if you run an operation where cycle time per sheet is an important factor and you can standardize on a certain drill picture for shelf holes, you really should look into obtaining a line borer for the shelf holes.

We currently do all our boring on a 25-spindle Bilek, and I will say that I look very much forward to putting it into semi-retirement as our PRS Alpha arrives.

The problem with a line borer is setup time. Doing all boring on it kills efficiency, because there's so much time lost in changing drill bits and aligning fences/stops and holddowns. Once it is set up, it can however not be beat for cycle time. It's wicked fast.

With the Alpha, we'll be doing all construction boring on-sheet. However, for production runs, shelf hole drilling will be done on the line borer, and that's all that this machine will do, eliminating the setup time.

Now, I already have a line borer: if I did not my plan might be different since the machine itself comes at a cost.

That said, I do not know what the used market looks like in your area, but here in Sweden used line borers can be picked up for pennies. They're too special for the hobbyists/small shops to drive prices up, and the larger shops want relatively new specimens. The machine dealers routinely auction out older machines for $300-$800: they just want somone to take them off their hands. I know people who have contacted machine dealers when the latter had just bought up a set of machines from a bankruptcy (spelling?) and been told "you can have it for free if you come and pick it up so we don't have to". (This is of course a good tip in general, not specific to just this type of machine. They almost never want all the machines, but under the terms of their purchase they have to remove all of it, and they sell some for scrap iron at a loss. Offer to take it off their hands and you can get some absolutely amazing deals.)

Ok, I'm rambling. Sorry about that.

[bstern]

Hendrik

Thanks for your responce. In my situation I still would like to know if it can be done.

Thanks,
Bob

[henrik_o]

Anyway, to redeem my rambling with some concrete numbers, I digged up the time sheet for a job we did some time ago. This involved 25 kitchen-sized cabinets.

Time to stack from table saw and transport to line borer was 10 minutes. This included parts not pertinent to this calculation, but it's a ballpark.

Time to set up for shelf hole drilling was 20 minutes, including two test runs with adjustments.

Time to run the shelf hole pictures, two cycles per part, was roughly 30 minutes. This includes post-cycle stacking.

Total time in operation, 60 minutes. For 2,500 holes, that comes down to 0.7 completed holes every second.

If we dedicate the machine to just producing shelf holes, and as such calculate 5 minutes for setup, which is probably very generous, then --ceteris paribus-- we're at a total time of 45 minutes and a cycle time/hole of about 1 second.

Shopbot owners who do cabinets for a living would have to provide their numbers, I can't give them, but it would surprise me if cycle time per hole without calculating handling times is not at least five times larger, and possible as much as an order of magnitude bigger if we figure in machine jogs and handling.

Of course, using a line borer requires a human operator in all cycles, while the Shopbot does not. If you can keep the person operating the 'bot productive all the time it's machining, that's almost pure machine time. This is probably not realistical, but anyway, the labour cost should be significantly lower. On the flip side, however, the drastically increased machining time could easily cause bottlenecks for human labour if we're talking volume production, which is not nearly as big a problem with a line borer set up for a single operation, so you need to figure that in as well -- you can probably avoid it, but it will demand very precise production planning.

Aight, in parting, this might seem like an inane hunt for seconds to many woodworkers, and it probably is. But if you're in a production scenario where adding a multi-spindle head to the shopbot is at least worth considering, then I think the above qualifies for discussion. Take it for what it is, some free thoughts (hopefully without too egregious errors) for further exploration.

[henrik_o]

Bob,

Didn't see your reply until I had already posted. For what it's worth, I am also interested in anything to do with specialty spindle units, so if anyone has the goods on items like asked for, please inform us.

That said, Bob, if you don't mind it would be interesting to me to know what it is about your situation that makes this a compelling alternative to either the vanilla air drill head on the Shopbot or a dedicated line borer. Please don't take offense at my curiosity, it's just that I'm looking at pretty much the same issues and would like to know how fellow woodworkers reason.

[bstern]

Henrik,

First I am a brand new shop and have not even started cutting with my bot. I will only be making custom closets. I would like to do as much as I can automated and on as few machines as posible. (Ready the fewer employees the better) Ideally I would load sheets of melamine on the bot. from there to the edgebander, then to install of rafix fitting next to the trailer for install. I think my dream machine would have 2Zs with a 5 to 7 drilling head on one Z and a tool changer on the other. The drilling head could reduce panel processing time form upwards of 30 min to about 10 or less so that is what I am exploring first.

I am new to the whole thing, so this is just my analysis and not based on any experience what so ever.



Bob

[jhicks]

Bob, For whats worth I think its somewhat related to consistency in set up and volumes planned. I believe a case can be made for either the line borer or the bot depending on the actual design variations, jigs/fixtures, and machine run time/volume demands.
IF one has sufficient business to run the bot full time cutting then a person on the line borer makes sense. Especially if they all have same spacing or quick allignment jigs can be devised to eliminate set up.
If you are starting out, the bot can get you to a point where you see too much machine time in drilling which is holding up your output quantities. Then its time to look further into a line borer.
Of course I agree the used market may have many great used machines for few dollars. In that case I think the borer would be very desireable near the bot to unload, fence up, and drill as the bot cuts parts. Kinda of like the edgebander as far as a secondary process but what if you were hand ironing on edge band?. It would be a no brainer IF you have volume to justify one.

In the end, its about tools you have, tools you want, time you have, people you have, ORDERS you have, $ you have, space you have or don't have.

I always like to walk before I run so the most important thing is CUSTOMERS with profitable orders. When I can't accomplish volumes I want or need to its time to increase the prices, add tools, or whatever is necessary to increase volume throughput at lowest possible cost and highest competitive margins. So calculating costs and time are fine until you have a lot of spare time and nothing to run. giving up a low margin order is the right idea IF you have more profitable business to replace it. If NOT...
How much does that cost to have an empty shop making no $?

Rather know there is something going through the shop and labor is active making some profit $ vs sitting on their hands as you/they need to get paid either way so anything contributing to overhead is a plus unless and until it interferes with more profitable business.
Good luck

[bstern]

I appreciate all the input.
I am really just trying to analyze how to set the shop up the right the first time. After starting up a few manufacturing business I have found it more expensive and time consuming to change your plans after start up. I tend to research things to death and try to look outside conventional methods. That how I ended up with the bot and not a panel saw and such.

I was really just looking to see if anyone has had any experience with this type of specialty spindle. Gather some info and make a decision to drop it or continue researching.

Not worried about business and marketing, that part of the plan is taken care of.

[henrik_o]

On revisiting the thread;

Have you got a brand name or link for the spindle systems you've seen? The capability and price of the systems in question would be crucial for evaluating whether they're interesting for any machining operation.

Also, how much of a bottleneck is the time lost if going with the vanilla air drill attachment? What's your expected volume (sheets/day)? Will you be working alone or with employees (how many)?

Re-reading the thread, I now notice you mentioned boring up to three shelf hole arrays per part. This would be a problem with a line borer since it involves re-setting another axis in every run.