[BLOG] DIY hardware store CNC Router, Part 5b

KometeKomete Member
edited November -1 in Community
Hi all, I’ve made some progress in my design for the gantry that I’d like to share.

Like the rails on the bottom, the sides and upper rails will be made of steel too. As you can see in the sketch up picture, I’ll only be using 1-inch square steel. One great thing about working with square bars is they line themselves up. Everything is squared away pretty quickly. Mounting the legs to the table was a huge pain because the aluminum angle threw drilling off from center. All the holes for the gantry will be on the center line, making life oh so easy.

It is very important when designing a gantry that it resist any twisting or bowing forces. Any deflection here will be magnified by the time the router hits the table. It must be taught, strong, and square. Anything less and you will have the dreaded RACKING PROBLEM. Racking is basically one of your axis tripping over itself because there is too much slop in your machine. I’ve tried to incorporate the right amount of support throughout the structure. Some will say I went over the top, other will say you can do more, personally, I think I’m right on the money.

If you have Google Sketchup and download the file, you can scroll to the upper side of the gantry(the part is blue). I’m contemplating driving my X-axis screw right down the center. That would be the optimum place for it. I’m still working on the roller assembly, so it’s too early to tell if I will do it that way or not. But so far, I don’t see a reason not to.

Going down to the bottom of the gantry, between the two Y-axis roller assembly, you can see two cross sections in red. It’s best to drive each roller with its own lead screw, but that’ll add to the price and complexity of the machine. Plus, there is always the chance of one stepper motor being slightly off from the other. I plan on driving my Y-axis from right in the middle of those two beams. Which is the next best option. Many have done it with great success. Fingers crossed, I’ll pull it off too.

Last, but not least, is the Y-axis roller assembly (in yellow). I’ll be increasing the length of these by 1 inch for greater gantry stability. If the rollers are two close together you’ll have a crowbar effect in play, which can lead to the dreaded RACKING PROBLEM.

I don’t plan on building the gantry this upcoming weekend. But after seeing it sketched up, I don’t know if I’ll be able to resist.




On a side note, my machine needs a name. I’ve been calling it (hurts to say it), Little Brute, the wife calls it Morty. We shall see which name wins in the end. If anyone has a good name for it please hit me up. My children want to name it Wall-E, after the Disney robot.

PS, me and Brute had a long discussion and it will not have the dreaded RACKING PROBLEM.

Comments

  • BuddyJBuddyJ Dept. of Propaganda OKC Icrontian
    Wow, that design looks solid. I'd hate to try and move it with all that square tubing.
  • Thanks buddy J. I haven't check the weight yet, but I'm guessing by the time I'm done it'll weigh between 50 to 75lbs.

    You should have seen the gantry I had before this one. That thing looked barbaric.

    I'm still debating on whether I should try it out on aluminum first. I dunno. I need to hurry up because January 31st I'll be ordering some motors, electronics, and lead screws.
  • I just added up the lengths for the gantry. I need about 21 feet (factoring in extra metal lost with cuts)
Sign In or Register to comment.