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Here something I had though doing ,not to save money but be practical,in that case . I was doing some cuts for movie at some studios ,my idea was to build 2 concrete curbs and put some spare rails on it to ride the gantry. Screw the first ply to the concrete floor then glue the sacrificial board on it .
When not in use I could easily take the gantry home or some other place by myself in a small van . |
I would have saved a lot of money if I had read the plans carefully and made a list of all the fasteners (bolts and nuts) that I needed and placed one order from Enco or MSC rather than running down to Lowes or Ace Hardware and paying full retail price.
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I'll back you up on that one Doug!:)
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I think Doug makes one of the best cost savings suggestions so far.
If I was better at project planning, I would have saved numerous hours and cut costs substantially. Take your time men (only because no women are building so far), and document your plan to the end. Easier said than done. :) |
In the first post of this thread there is a link to homeshopcnc which has a motor RS23-570 which is a 420 in oz holding torque motor ( uni polar). I know this is a nema 23 motor and it is small, but I plan to use a 3:1 belt drive, so the torque will be over 1000 in oz. Might this motor work with the belt drive?
Dave |
Motor Mixing
Why would you need the PK296A2A-SG7.2 for the Z Axis?
Why not use a cheaper Motion King for the Z or one of the NEMA34 Motors? Or have I missed something that says they all need to be the same motor? All the threads I see say the Direct drives are working and for some savings you could use the MK for Z and SG7.2 to drive X and Y. |
Dave, the smaller motor with a belt reduction could work, but I don't see it making the system much cheaper. Plus there is the risk that it might not work. Can the small motor handle the belt load? How is that motor's torque at working speeds? (Small motor torques at working speeds are generally good compared to bigger motors - overlay some graphs for fun).
MetalHead, if you mix motors, you make fault-finding difficult. Out here, we stock a spare motor. It just makes our life easier if all the motors, drives and power supply voltages are the same. The other thing to consider is that the high detent torque of the gearbox helps to keep the z-slide from dropping when the power is switched off. |
Motors
Makes sense. Did not think about spares.
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Gerald I think the savings would be substantial IF these motors would work.
OM motors $250 each = $1000 BOB $100 Power supply $140 Drives $130 ea $520 Total $1760 MK motors With shipping $550 Drive G-540 $300 Power supply $140 Belt reducers $140 Total $1130 RS23-570 w/shipping $325 Drive G-540 $300 Power supply (less than) $140 Belt reducers $140 Total $905 True the motors might not take the side loading of the belt drive, but I’m working on that. I have a design that would only add about 50mm to the motor length, so there would be no side loading on the motor at all. So IF these motors would work, there would be quite a savings for me, I have a machine shop available to me to build the belt drive reducers and the coupling device (if needed). Is it worth the $350 or so gamble? On paper it would seem so. Will I try it? I’m not sure yet, the RS23-570 motors are pretty small. On the other hand, they are the same length as the MK motors, just the cross section is MUCH smaller. Dave |
Another cost savings would be using silicone to attach the racks to the rails instead of the VHB tape. $3 tube of caulk vs $45+ roll of tape
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Greg, that could work. Will need a good long curing time because of the 2 metal surfaces.
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MK motors and G540
Been lurking for a while now and considering the G540 as a driver largely because it's a bit more straight forward from the electronics side. Which MK motors are you considering for use with the G540, I haven't found one yet that appears to fit the requirements of the G540, keep ending up back at the OM PK296A2A-SG7.2 which I'd like to get away from as to purchase them here (Australia) your talking almost AUS$3500 or trying to import from US which I can't imagine being a lot cheaper.
Jed |
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When I contacted Gecko Drives, they told me to add a 3.5K resistor for the current set resistor. They calculated that that would give about 87% of rated torque. If you decided to use this motor, or any nema 34 motor, you should contact them directly to verify the figures, before you buy a drive. Also you have to remember that with the G-540 drive, you don't get the option of an indexer. Which ever motor I use, I will use a 3:1 belt drive. We're working on a design that will allow me to change a broken belt in about 5 minutes. Even at 87% torque, I would have more than enough power to suit my needs. Dave |
Dave
thanks, will contact Gecko for more info, just on the face of it the 34HS9801 didn't appear to match the info in the 540 manual:(, but if they say it works I'll take their word for it:D. I don't need an indexer anyway I'm looking at building a heavily modified mechmate for cutting surfboards and occasionally some ply or mdf sheet. Was figuring that the G540 was a good place to start and relatively cheap if I wanted to get more complicated down the track then I can build new control box with G20x drivers. Not sure about the quality of the MK gearboxes but they tell me I can get 5:1 or 10:1 for $120 with the motor still asking questions about that. Thanks again Jed |
Jed
Here is a link to a very good thread on motors and power supplys ( I hope ) http://www.mechmate.com/forums/showthread.php?t=932 Also the math that I used for the 3HS9801. Dave |
sorry for bumping such an old thread....had a crazy idea while sitting in traffic today....
if you don't mind leaning over near the floor and have nice concrete slab, use concrete machine screw anchors, up to 5K lb pull out rating, more if using a better contrete http://www.confast.com/products/tech...ew-anchor.aspx reason I was looking into these was that I've been thinking about my lack of space, so if made a basic frame that I can bolt and unbolt to the floor, I can move the frame for the few times a month I see myself using it...when not in use, I can park my car in the garage where it belongs |
Hey, in this forum we don't have old threads, unless they are locked in the Archive, and it is much preferred to post in topical threads rather than start all over again. If a thread is not locked, that's an invitation to post - absolutely no need for apologising. :)
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some things I did to save $$
My control box was from Digi-key 377-1580-ND only 15.75X15.75X7.87" it is a little small but cost $86 and was ordering from them anyway. Found a great steel place in Reno NV (Proto- Fab) that would sell me any length at good prices. The 1.5" square by 9 inch long solid bar that I used for the ribs cut on 45's on both sides cost me $4 a piece. That allowed me to use a lot less steel under the table. I ordered most of the bolts from McMaster carr and Bolt depot. I used the G540 With the pk296a2a-sg7.2 motors. I will worrier about the indexer later, if ever. The G540 got me up and cutting fast and cheap. I used Cable chains with cheep foil shielded wire, 250ft for $80 off ebay. My thought is that it really did not need the braiding because it is not really rubbing on any thing. Anyway I have plenty extra. and we will see how long it lasts. I used Cold-rolled steel for the Z-slide plate instead of tool steel. 1/4"x4"x36" was $24 instead of $150. I used household light switches for E-stop buttons. and a $6 numerical pad for my bump remote, Works Great. I did not use a machine shop at all. Only tools i have there are a Hobart mini mig, A drill press, 14" abrasive cut off saw, 4" grinder, and a 3/8 Dewalt drill. I bought the router re-manufactured as well. And no paint. Yet. |
What does it cost to be up and cutting in the US? Any rough ideas on budget?
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Robb,
It depends on what you have already, what you buy new and what you get deals on, as well as the options you choose. I know several have built in the $4500 to $8000 range. here is one guy Quote:
http://www.mechmate.com/forums/showthread.php?t=460 |
Robb,
As I've said elsewhere, I built my 97" X 49" MM for about $4000. My major savings was in acquiring 3 USED Oriental Motors Vexta Stepper Motors for $125 including shipping. I had to buy one new OM Vexta Stepper at $257 plus shipping. Had I bought all new steppers, my cost would have been about $4700. As Heath said, your cost will depend on choices you make along the way. I did not "go cheap," but, I saved money where I could. |
I'm intrigued by this thread.
If you total up the numbers for a 48 x 96 machine built about as economically as possible using the ideas here, the total is significantly less than $4000. Code:
item qty cost ea total cost router 1 $200.00 $200.00 motors and drives 4 $230.00 $920.00 laser cut parts (with shipping) 1 $500.00 $500.00 pmdx-122 1 $100.00 $100.00 bolts, screws, bearings, racks, pinions 1 $800.00 $800.00 power supply 1 $150.00 $150.00 gantry steel 1 $300.00 $300.00 x-rails 2 $25.00 $50.00 x-rail table attachments 2 $25.00 $50.00 wire 1 $120.00 $120.00 panel goods for deck, braces and spoil boards 1 $150.00 $150.00 $3,340.00 The gantry could ride on a wooden table essentially made from four torsion boxes with large timbers supporting the x rails. Getting the rails perfectly parallel might be a challenge, but as Gerald has noted elsewhere, once the table is surfaced, panel goods will sit "flat" to that surface. |
Jeff,
Looks like you put some thought into this. :) What about a computer to drive the table? :) |
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This assumes a machine running ubuntu/emc which is pretty performance-tolerant. I have good 2d cadd software, and g-code compiler software isn't prohibitively expensive. When needs dictate 3d carving, one can upgrade. Unlike boards (the wood kind as well as the circuit kind); steel, welding talent and money are significantly constrained. :( |
Jeff,
Ok sounds like you are all set for the computer then. Take note that some users have had problems with multi core processors for machine control. |
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As soon as arcnet cards and 2400 baud modems become collector's items... I'm all set, baby. (My only multi-core computer is the least reliable machine I've ever had - for EVERY purpose. Especially for Ubuntu 64, but Vista isn't much better) |
Jeff, a quick scan of your list misses the cable chain and springs (gas+motor)...ie. the McMaster order
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Thanks, I should have elaborated, my intent was to try to quantify all the suggestions given including omitting cable chains, and instead "Hang the cables from the ceiling".
But I definitely forgot about springs. I'm strongly tempted to try this, to push the envelope. Within the constraints of safety and RF noise, how inexpensively can a a MechMate be built? Let's see where the points of possible economy lie, and which savings are penny wise and pound foolish. There's something about working with local resources and available materials which appeals to me too. I promise to lay bare all my stupid cheapskate mistakes for all the world to learn from. Momma always said I'd be a good role model... or a bad example. I also promise to not beg for a serial number until after I've upgraded beyond the bailing wire and duct tape and into a proper paint job ;) |
Jeff, I like your attitude, and you are obviously going into this with your eyes wide open. Will be watching with very keen interest.
Why use duct tape? Masking tape is cheaper! :D |
Reducing cost???
Gerald,
you basically said to me that an MM is an overkill for what I want to use it for (non production work or hobby like stuff) and you referred me here to this thread to see what could be done to reduce building cost. If I understand correctly, one of the biggest expense comes from the electric and electronic components requirements. If this is actually the case then I wonder if reducing the mass of the moving parts wouldn't be a practical approch. This of course should be done with minimal (if any) sacrifice to the structural integrity of the machine. Say one would build the grantry, Y car and Z axis from mostly aluminum. Since the Young's (elasticity) modulus of alu is about 3x less then that of steel one could more or less compensate for this by choosing a different cross section in order to increase the moment of inertia and get the same level of deflection. In simpler term, the formulas to compute stress, deflection and what have you, don't change but the properties of material do, so using aluminum would flex more then steel if both have the same cross-section but choosing a different cross-section for alum parts could reduce that to a minimum and still weight less. This weight reduction alone may not solve vibration problems (in fact it could increase), that's complicated stuff but it could allow one to use smaller motors and less costly electronics (drivers, power supplies, etc) and bring the overall build cost down. Vibration could be minimised by lowering the feed rate which may be a problem in a production environement but it may not be such a big deal in other situations. Just an idea, Yves |
The MM design is based on parts being DIY-weldable, small z, big x&y, 24/7 processing of softish boards/sheets. If you want to use lighter parts (non-weldable) and smaller motors, for processing tall parts in hardwoods then the MM is the wrong design for you.
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There would be minimal total difference in cost whether you buy size 23 motors (too small) or size 34 motors. The PK296A2A-SG7.2 motor costs about $260 each. The much smaller PK264A2A-SG7.2 motor costs about $160 each. So, you would save $400 dollars, but you would have a motor that puts out 17.7 lb*in of torque compared to 44 lb*in for the size 34 motor.
The same electronics could drive either motor with only a change necessary to limit the current to 2A for the 264 motor or 3A for the 296 motor. |
Another misconception is that the mass of the MM requires it to have big motors. . . . . The main reason for biggish motors is to power a 3HP router at full speed making loads of sawdust. Contrary to popular belief, the mass of the gantry has little effect on motor size.
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My own research showed me that unless you go for something that holds a Dremel, the scale of the mechmate doesn't really affect the price as much as you would think.
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I know of several people within an hours drive from my house that have build the MDF type routers. I have seen them cut and they do work remarkably well. One I visited, the guy had build a Joes 2006 and spent around $4000.00 on it. That made my mind up to build a Mechmate for a little more. :)
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Would like to expend on Gerald's clarification on the mass.
1) Remember this? Force=Mass x Acceleration As long as the force is sufficient to provide enough or more acceleration, the mass is really no concern at all. 2) Also, with his beautiful sliding rail design, the static friction is negligible, so it won't add more work for the motor... 3) Leveling of MM is done with a spirit level, when done correctly, the static force acting on the car is purely vertical gravity... Heath, IMHO, these people has enough resources for self-indulgent. Perfectly fine to me. I'll do the same if I have the means. |
I've been sourcing around and scrounge hard for my 1st MM build. Here is my take
1) BOB + Driver + Motor from US$500 (Frugal direct drive + DIY BOB + direct chinese import of your choice) to US$2000 (PMDX + gecko drive + 7.2:1 Geared OM + all bells and whisle ) *DIY BOB is an option, but DIY driver is not for the light hearted... 2) Frugal Built, MM on concrete floor without table structure and work on your knee. *Faster and less work too... 3) Free/give away old PCs + CRT monitor + Linux + EMC2. 4) DIY V-tyre with any material in the junk box. since there are good result reported even with plastic. 5) No remote control, Zero Set, start, pause. No proximity switch. 6) Rack is surprisingly expensive... Look hard for better price... 7) size the work size for minimum left over 8) Chinese water cooled spindle + VFD isn't that much more expensive the high power router. I echo Gereld's concern on safety. It is admirable if one pursuing a goal till death, but it is plain idiotic to kill himself doing it. |
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in the case of moving mechanism such as the MM, one should use something like E = 1/2 mass * speed^2. As others have said, moving the gantry doesn't require much force or energy but if you add a working 3hp router and try to move it as fast as possible then you'll see why you need a more powerfull (step) motor then what would be suggested to just move the gantry. Yves |
Yves,
Yes, Kinetic Energy is another analytical approach. But I thought F=ma is more well known. As Gerald mentioned, the predominant force the stepper motors required to handle is actually the reaction force of the cutting action (dynamic load). When feeding the cutting tool into the job, it is like running it into a wall, the tool bit relied on the spindle + cutting edge geometry to "clear the way" by chewing away the "wall". So theoretically, if the spindle has enough power and the cutting bit is efficient enough to chew and clear the way, the reaction force will minimised and feed speed can be infinitely fast, like a hot knife cutting through butter ;). BUT, in reality, there is always a point of diminishing return... Steel is the cheapest metal known to mankind. Buying Aluminum with equal structural properties will only INCREASE the cost (3X more expensive is the general overall ballpark figure). I'd detailed my cost estimate, for now, $3380 is the best that I could do for 2440x1220... Frugal build, optimise steel usage, put a 2nd hand price tag on all the components from my junk box & salvage, c/w spindle + VFD, exclude all tools, consumable, workshop setup and my labour hours. Can't wait to start ;) |
Local Surplus Outlets
Another source for inexpensive/cheap material and supplies is your local surplus place. If you live near the NJ, PA or DE tri-state area, it will be worth the trip to Fazzio. This place has everything from all types of metals to surplus, going-out-of-business, bankruptcy items they buy at auctions and sell very inexpensive.
While there the other day I purchased for my build the following: (1) NEMA 12 Enclosure: 24"x20"x8" new w/scratches for $45. (2) Emergency Stops w/boxes new for $12 each. http://i585.photobucket.com/albums/s...a/DSC_4437.jpg http://i585.photobucket.com/albums/s...a/DSC_4440.jpg http://i585.photobucket.com/albums/s...a/DSC_4434.jpg Just be warned!!! This place is like a candy store for guys :D. I usually spend a minimum of two hours just looking around before buying anything. |
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