PDA

View Full Version : To CNC or not to CNC???



tillmann
04-17-2006, 05:48 PM
I am an owner of an audio business, which builds custom stainless steel/aluminum alloy racks for vintage studio recording equipment. Basically, we remove old audio mixer and console modules, repair them, and install them in industry standard, 19” stainless steel/aluminum chassis. We order the racks pre-cut as far as the external enclosure structure, however the aluminum alloy faceplate and rear plate have to be cut so that the various vintage modules can be inserted and audio and AC power connectors can be inserted and secured into the rear of the rack. Sometimes we do this painstakingly on our own by hand, and other times we contract it out to someone that has proven to be unreliable and caused major delays in our production in the past.

We have one of two options; finding someone local in New Orleans to do the machining and hope that they are quick and reliable- something very hard to find in New Orleans, or buying a small CNC machine and doing it ourselves, thereby being able to do it in-house and on demand. We only need a machine big enough to cut something 19 inches by 10-15 inches and to do engraving. I’ve been told by someone that do our own machining in-house would be a nightmare and would not be cost effective because of maintenance and upkeep costs of the machine, but I was not told this by a machinist. Basically, we need this thing to cut 100-300 racks per year, most of which will be flat aluminum alloy cutting and engraving. It was described to us that the machine would be “spitting out grease and oil mixed with metal shavings all over the place and the cost in bits, lubrication, and maintenance would not be worth it” and that we would have to have a separate container just to house the machine in order to catch all the lubricant and metal that it would expel.

We are already familiar with CAD programming as we had to give the machinist who did the cutting a CAD file in order to have the front and rear plates cut. We are not professional machinists but rather audio and electrical engineers. Below I’ve provided a few pics of what we do so that those of you that have trouble envisioning what we do can see what we are cutting. So tell me, are we biting off more than we can chew in investing $5,000-$10,000 in such a CNC milling machine?

Many thanks!

Millman
04-17-2006, 06:55 PM
Damn, you're lucky. I have worked on old audio and I think they have better overall tone than most new equipment. CNC would be the best way to go, but how can you get a good mill for 10,000? Personally don't care for CNC, in your case, you would be using thin stock; wouldn't create that much of a mess. I would go for it because you already have the necessary skills for programming. Need any fixturing made??

Evan
04-17-2006, 06:55 PM
You won't find anything new in a CNC mill with that size work envelope in that price range or even close to it. What you are describing is more appropriate for a CNC gantry router or a laser cutter. Have you looked into laser cutting services? They can do pre anodized aluminum plate including top quality engraving all in one setup. I have no idea who might have such equipment near you though.

jburstein
04-17-2006, 07:22 PM
You may want to look into getting a CNC router. Most mills with that kind of work envelope are very large and quite expensive. Since you're just cutting aluminum, and it's relatively thin stuff, a wood router would probably do the job for you pretty well.

-Justin

Mcgyver
04-17-2006, 07:44 PM
from a business perspective, cnc'ing the front panel is not strategic in that its not a core competency and there are 1000's of job shops that would do it for you, the only reason why you'd bring this in house is for costing...if your through put was so high that the all in cost would make it cheaper to do yourself. can't seen this being the case unless you have enough uses to keep the mill and machinist running 40 hours or more per week.

so out source it. of there are not reliable suppliers in your local, go to another city. you can email the cad file and still receive the part the next day.

now if what you really want is to start playing around with machine tools, well thats a whole different set of drivers...

TECHSHOP
04-17-2006, 08:00 PM
I would go with the CNC router, you should be able to find one that can handle that size work for about that price. You would need to have a dedicated place and some type of chip removal (venturi vac?) system. The thing will make a bit of a mess, but you could use it for other items (Al, plastic, wood), to spread your cost out. A "real" mill capable of working steel, would be "too" large, "too" expensive, and severly "underworked" for your application. The router will also (usually) run on 110v, for which your shop (usually) will not need to be "upgraded" to handle.

Mad Scientist
04-17-2006, 09:20 PM
Advertisement from Nuts & Volts (electronics magazine)

Front panels?
Download the free >Front Panel Designer<
To design your front panels in minutes.
Order your front panel online and receive them just in time.
www.frontpanelexpress.com

I know nothing about them but from their ad it looks like what you want.

Leigh
04-17-2006, 10:22 PM
I doubt that you would benefit from CNC. It's great if you're doing 1000 (or 10,000) of the same part. But you're doing one-offs (five-offs ??). You'll probably never do 100 of any one configuration, and certainly not all at once. The setup time, and spoilage from debugging the CNC program, will kill you.

Why does the vendor have to be in New Orleans? UPS still delivers there from just about anywhere in the country.

sid pileski
04-17-2006, 11:01 PM
I don't know, I bought a Prototrak k3 mill, that is ideal for this kind of work.
I've done it. The machine was 20k, maybe over your budget that you said, not to brag, but this is in my home shop. I do work for others (not looking for anymore) that has always justified my equipment. Seems if you are already providing the cad file, half way there. And, look at the other possibilities open to you. For me it was always the chicken and the egg. I couldn't take on more complicated work because I didn't have the machine and vice versa. So, I bit the bullet, and invested. I do not regret.

tillmann
04-18-2006, 01:23 AM
many thanks for all the helpful responses! just to clarify, we do have several different sizes and form factors that we would need to cut, however the parameters of the different cuts and engraving do not vary too drastically. It's all flat and all around the same size and structure.

do any of you have experience with this machine?

http://www.microkinetics.com/cncdmill.htm


The big reason for the on-site machine is to save time and hopefully a little bit of money in the long run- but time is the major issue. We need something to minimize the amount of time spent drilling, measuring, punching and cutting manually and also waiting for cuts to be made when we subcontract it out, which JUST FOR THE FRONT FACEPLATE CUT and NOT the engraving we were getting charged nearly $30 per rack, not including the rear which we did manually. Basically two rectangular cuts were $30. Additionally, it's hard not to be put on the low priority list by the companies we outsource it to, because of the comparitively low volume we contract, and to do it properly we need a very quick turn around time of 2-3 days.

Last thing to clarify, the largest size that we have had to cut to date is 17.5 x 7 inches (a rack cannot be CUT any more than 17.5 inches but can be engraved at the full 19). If the y-axis at 15 inches makes a large difference in the price of a machine, we could rather easily state that there would be a wait on racks of 7 inches or greater width. That would NOT throw a monkey wrench in our operation all all.

Could a smaller machine be set up to do one half of the front plate at a time as far as engraving is concerned?

Cheers!

Leigh
04-18-2006, 01:44 AM
Perhaps a stupid question, but why are you putting the long dimension on the Y axis? Machines typically have a greater travel on the X axis. One standard rack panel size is 19" x 7". This would be easily accommodated on most machines with the 19" dimension on the X axis. And most machines would do 19" x 10.5" panels similarly.

HTRN
04-18-2006, 02:49 AM
Mr Tillman, as somebody who has been employed in both production and job shops, I'd like you to consider a bunch of questions.

1) How complicated is the part? - is it typically a straight forward manual operation( drilling holes, slots etc), or is it tapped holes, large complex geometries, etc.

2) How many jobs, how many parts per job? The more jobs, and the more parts per job the better the choice is for CNC. How much "runtime" per day do you expect the CNC mill to have? You mentioned it's $30/part, but if you only need 1 per day, a $20K machine would take two and a half years to justify the cost of the machine alone, not counting power, labor, material or tooling.

3) What kind of turnaround do you need? If you need it "same day", or can it wait a couple of weeks?

4) Operators vs. jobbing it out - Who's going to run the machine? Is the Cad guy going to be running the CNC as well? Does anybody there have any experience with CNC?

5) Budget - How much do you have to spend? A CNC knee mill has a wide range of price, as well as capability - for instance, tool changers and rigid tapping are available as options on the Haas TM's. But these are machines that start at $20K and go up from there. From what you describe, a toolchanger would be better, but it's another 6K.

6) Company Expansion - do you see the CNC machine doing more than you currently are needing it for in the near future? IE, do you plan to start making custom rack enclousures, custom chassis parts to rebuild damaged ones, etc? The more likely this is, and the more complicated it's likely to be, the better the choice of a CNC mill makes sense.


HTRN

JCHannum
04-18-2006, 11:22 AM
The $30.00 figure is only a part of the actual cost, the cost of shipping back & forth and bookkeeping to order and process the transaction can often end up being more expensive than the bare dollar price.

Add to that the fact that doing it in house adds control and reduces turnaround time that can lead to more business from customer satisfaction rather than lost business because deadlines or special needs might not be met.

I know little of CNC equipment, but the MicroKinetic unit appears to be capable of handling your needs. The software is pretty much state of the art and well proven. For a dedicated operation such as yours, it would be easily mastered.

The max size limits are almost the same as your faceplate size, but if the actual area where the work is being done is less than that, it should be able to handle the job. A subtable can easily be made to hold workpieces that are larger than the mill table.

With aluminum, and the light cuts you will be taking, coolant use will be minimized, and control not a major problem.

I would suggest contacting the vendor and sending them a sample to prove what their equipment is capable of. I would be surprised if they could not accomodate you.

As previously mentioned, once this capability is added, you will find more uses for it than just a couple of holes now & then. I am sure that in a year or so, you will wonder how you managed so long with out it.

Don't be afraid to get a machine that is larger than needed at the moment, but avoid getting one that barely meets your needs. As time goes by, and new uses are found, the larger equipment will be appreciated, and you will end up not paying twice when you add capabilities not anticipated today.

Evan
04-18-2006, 12:10 PM
A Y axis requirement of 15 inches makes a huge difference in the cost of a CNC milling machine. If you can get by with 7" then the Microkinetics machine is reasonable. Keep in mind that it has an X axis travel of slightly less than 17" and that cannot be changed.

A gantry router/engraver would still be the best machine for your application and would give a lot more flexibility and work envelope. I assume the panels you are cutting are aluminum and probably no more than .10 thick. A system such as below would handle all the sizes you need.

http://www.larkencnc.com/cam24/index.shtml

[added]

Note that the above machine can also cut signs and vinyl graphics, something that might be handy.

Scishopguy
04-18-2006, 01:06 PM
If the engraving is the majority of the work you need on these panels why don't you look for a used Newhermes Engravograph. They make several models in sizes from a large four poster to a small table model that will do everything from name tags to large panels. I had one in my shop at the university, that we got used and we engraved panel rack instrument faces, large plexiglas chambers, and even round air sampler barrels with the help of an indexer. Most trophy shops have them and you might be able to find a used one, with fonts, for less than $2K. Go talk to someone in the trophy business and you might get a leed on one.

Jim (KB4IVH)

Wirecutter
04-18-2006, 01:38 PM
I was looking at the Microkinetics machine a bit, and I also have a question for anyone here with experience with it.

There is a motion controller, the MN400, listed as an "optional accessory" for this mill. (US$695) It sounds like the standard controller won't do some of the things that I would have expected of a modern CNC control, like coordinated movement and contouring. For tillman's application cutting panels, contouring is a moot issue, but it's closely related to coordinated movement. Isn't coordinated movement (or a rotary table, US$1295) needed if you want to mill a circle or a curve?

tillmann
04-18-2006, 04:50 PM
thank you all again for all the helpful replies!

JCHannum, you hit the nail on the head as to why we want an inhouse machine. Customer satisfaction will bring more sales back to us and will stop us from having to making useless apologies because the machine shop is a month overdue. If someone wants a custom job done in a matter of days and we have the facilities to do that, then we are a notch above the competition and that will no doubt be noted in our reputation. We have enough work doing the electronics, we can't have long delays with the rack cutting and engraving. Outsourcing each panel more or less one panel at a time is just not practical as far as time and money. That $30 I quoted was just for two rectangular holes, not including engraving nor the rear panel and that always took anywhere from 14-60 days for a more or less amateur looking result. I mean the cuts were great, but still, no engraving means an amateur looking rack for us. If we outsource it again, we have to deal with shipping each panel, one or two at a time and then wait for it to be done- just not practical at all. And all of you are machinists, you know that the people that are ordering mass quantities get the job done first and one-off's get put on the back-burner when things are busy. If we could find someone locally that could turn it around in 2-3 days, that would be great, but I doubt many machine shops would want to give us the priority that we need.

Thanks for the recommendation of the Gantry router. The thickest that we have to cut .18" thick aluminium alloy (5052-H32), but most of it is .125". Wait a minute, we may also have to cut some 16 gauge aluminium alloy. I'm not sure how thick that is in inches, nor what the exact alloy number is.

We will have to do the CNC work ourselves. My chief technician will be in charge of it. He will have several months to learn it and he's a bright fellow with that master's degree and all.;) We are basically cutting simple rectangles or circles. The engraving is the only rather "detailed" thing. But still, that should not vary too much after we get the hang of it. Perhaps a CNC router is more practical than a milling machine? Although I'm sure we will end up finding other uses for the machine, and may be able to do the same front panel work for other people in order to pay off the machine faster. We'll see how good we get with it.:cool: All that said, I think what we need out of the machine is probably pretty rudimentary in comparison to what the machine can do, especially since we would like to stick to cutting aluminium at the present.

Cheers!

tillmann
04-18-2006, 05:02 PM
as far as engraving, what would be the chances of being able to engrave the following logo on the rack with an engraver or a CNC machine:

http://users.adelphia.net/%7etiffmc/TGBLogos/TGBLogoGrey.jpg

Am I dreaming?

of course it will not be in color and will be much smaller.

mochinist
04-18-2006, 08:40 PM
as far as engraving, what would be the chances of being able to engrave the following logo on the rack with an engraver or a CNC machine:

http://users.adelphia.net/%7etiffmc/TGBLogos/TGBLogoGrey.jpg

Am I dreaming?

of course it will not be in color and will be much smaller.Do you have a vector image of that logo, or just a jpeg? If you have a vector image it could be imported into a cam system and programmed in about 10 to 30 minutes.

Another thing to think about, that I haven't seen mentioned yet is a cad/cam program. If all you will be cutting out is squares and circles, then a really basic cam system will do, oryou could hand code it, the engraving will need some sort of cam system though, for simple fonts their is a free program out there, I forget the name, but one of these guys will remember I am sure. For more complicated stuff like what you showed above, you will want to get something decent, I am partial to FeatureCam, but I can justify the cost of the program, I hear the guys over at the PM site rant and rave about OneCnc, and that is on the cheaper end of what would be considered a decent cam program. Whatever you do, don't contact bobcad, buy bobcad, or have anything to do with bobcad. They suck, their salesmen are blowhards, and the program is a piece of crap.