Compound X-Y table

[esmiller]

I have been reading the posts, and notice that most everything is based on the gantry design, and all home-made parts (framing items that is).

I recently purchased a compound X-Y table for $81 +S/H (109 total) to eliminate having to manufacture everything myself.

I *DO* intend to make a gantry type router after this one, but this one should give me enough precision to make the parts i need to make the gantry design.

My problem is that I don't have sufficient machine experience to drill the holes with the tolerances needed to ensure that the rails, rods, etc. are true and straight.

Am I missing an obvious problem with the course of a pre-manufactured compound table? it has 7.5" * 11" of travel (personally verified), so it will do much of what i need for starters, and if I build a bigger one, the electronics, motors, etc can be switched over.

Eddie

[Damachine]

Where did you get the table? Can you post a picture or a link?
Thanks,
Doug

[esmiller]

I got my table off of an E-bay store called DiscountMachineShop at:
http://stores.ebay.com/discountmachineshop

They still have some left, as well as a ton of other CNC usable items.

I would be willing to post a photo, if I can figure our how to do it.

[esmiller]

Here is my current CNC project as it stands... obviously this was taken while I was working, and the mess remains

[esmiller]

Here is a closer photo of the compound table
I placed a washer between the handles and the table to eliminate alot of the backlash, but it still needs work.

I ran a rubber band between the motor and the handles, just to see if the motors could turn them, and it works, but I will need to find something sturdier than a rubber band. Perhaps some sort of belt assembly or something.

Right now I am waiting on some programmed PIC chips that were designed to serve as stepper controllers, to see if they will work or not.

Eddie

[berin]

For that kind of a rig you need belt drive. There are 2 handles at ether end of the x and y axises. you can remove one of them to introduce a better cog setup. Though those motors are under powerd for what you wnat to do. Those motors your going to want to run at 16-30v, use at least 150 ohms dropping resister on the +v wires at 30v. I know I have the same motors. a 2"x2" stepper motor is more in line with what you need. Just incase you have access to them. the old MEGA dot matrix printers with the one and a half foot printing area oftem have those motors along with nice driver chips. the pu4146 or (sla7024(m) series) driver chip's are common. One is just a quad darlington transister array. the other is a stepper controller chip which requires direct phase control but has onboard chopping current control. I tore apart about 3 large random dot matrix printers and got a lot of good parts I needed for my stepper setup.
the other advice I can give is mount your stepper below the work bed to the side of the axis control handle. Thre should be a few screws which you could mount a peice of aluminum on out to the side with. I see the little black motor to the lower left, you got that out of a floppy drive didnt you I love those motors.

[esmiller]

Lets, see.. yes, the little black motor is from a floppy drive, got a bunch of them!

As for mounting the motor lower, I was just experimenting in this setup. I have no idea how i will end of mounting them in the long run, but lower than the bed may be a problem.

As for the belt drive, I *THINK* I have a simple enough solution. I am going to slice up an old inner tube, and make a custom belt that will have the right length, with sufficient tension to help avoid slippage. done right, it will be just as strong as if it was made to length.

As for different motors, i have nothing else available, other than 2 of these items for the x-y portion of the system. I am spending every penny i can earn to make this, so buying new motors is not an option at the present. i *DO* plane on eventually purchasing some NEAM 23, or NEMA 34 motors, but they are prohibitvely expensive right now.

perhaps when i build my next system, which I plan to be a
18" X 36" system, with a mobile gantry. At that point more powerful motors will be a neccessity, but I am hoping that these will do until then..

Eddie

[esmiller]

btw.. for mounting my motors, i drilled & tapped two holes myself to the side of the handle, and am looking at buying standoffs to mount the motors on, if I can make sure that the holes can be the exact right spacing, and the standoffs look like they will be rigid enough.

Sound like it might work ??

Eddie

[berin]

I have a BLEEP load of stepping motors, in all different types and formats. For VERY cheep! I have some motors which would do a much better job then those in the picture will EVER doo. I'm going out today to scavang for some more motors. But keep me in mind if you want the nice motors which more often then not go for about $15-$30 a peice on ebay.
In the picture, the silver motor is that a 2"x1" motor? if so the next size up motors that I have are are 1.75"x2.25" in demention. after that I have 2.25"x2.5" all uni polar. I've got a million smaller motors but for what you have setup, they are less then what you need. Also you may want to look into getting a toothed belt drive or cogs. All of which are very cheep. Even more so if you get the parts from poeple here on cnczone who could make what you need.
The big problem with using non toothed belt drive is that no matter how you set it up. IT WILL SLIP OVER TIME NO MATTER WHAT!!!

Just a suggestion, but if you know of a place which has a lot of junk electronics LIKE photo copyers or that sized paper appliences of any kind. They have the REALLY NICE expensive stepper motors. There is a place an electronics salvage place not 2 min from my house. So i get to get a lot of good parts. half the time they'll let me raid stuff cause I'm just doing them a favor by stripping out stuff at not cost to them. Though they do some times charge me a few bucks for parts because they make there money on redemption value.

[esmiller]

I WISH I had a place for scavenged electronics.. small town here, and *NO* Electronics repairs companies or anything.
How much would you want for the motors above what I have? preferably the 2.25"x2.5" ones, since I will probably wish i had them if I go with the smaller ones? If you want, you can e-mail me off-list at sogregory (AT) charter (dot) net.
Perhaps I will take a trip to a larger town sometime and see if I can't find a company that discards old electronic equipment..

Eddie