A Different Kind of CNC Workpiece Clamp

7

[Mike Douglas] joined the world DIY CNC machining recently with a FireBall X90 CNC router. Instead of buying an expensive aluminum T-slot bed, he decided to try something we haven’t seen before…

His local hardware store sells aluminum bar clamps designed for clamping wood together — the best part? Only $10 each. What he’s done is added the bar clamps along the two sides of his bed, by adding plywood braces attached to the outside frame of the machine. He is losing a few inches of his usable bed area, but the added convenience of a quick clamping system is well worth it.

With the clamps in place, all he has to do is add two wooden braces (the black bars in the image above) to hold his work piece in place. This wouldn’t work very well for cutting metal, but this CNC router isn’t designed for that anyway.

Too bad he didn’t finish it sooner — it would have been a great entry for our recent Hackaday Hackerspace Henchmen CNC contest!

Comments

  1. Moser Labs says:

    I was wondering why ya spanned the bed with the clamps, but now I see that is wood. It’s being compressed by the clamps on the sides, and clamping the material. I’m curious how “off plane?” it becomes if these clamp, ie would it pull off the base on one side becoming non-level?

    • Mike D says:

      I haven’t put it to use yet, but the clamps are independent of each other and provide pressure to the work area from the front and back via the black wooden bars. The amount of pressure is really up to you as they are tightened via the vise end at the front of the machine but really don’t take much to hold the material quite firmly. Also, for thinner material, I would suggest a slight under-cut on the wooden bars to force the piece flush to the bed.

  2. pcf11 says:

    I have those exact clamps. I got them from Horrible Fright and I think I only paid about $4 a piece for them. So it sounds to me like Mom and Pop are marking things up too high again. Whoa, they have gone up in price since I got mine! I probably bought mine over 10 years ago now. I could swear when I got them they were dirt cheap, I mean I have 4.

    http://www.harborfreight.com/24-aluminum-bar-clamp-60541.html#.UyWRaqIbNpg

    On a good sale they’ll be half of that cost I bet. They’re OK clamps I suppose. Mine haven’t fallen apart yet.

    I was chatting on IRC with someone who has a V90 and his biggest beef was that the particle board table warps so badly he can’t mill circuit boards on his machine. You can say that V90s do not actually come with a table, they just have a sacrificial top when you get them that some people think is a table.

    • Phil says:

      Tell him to throw in a flycutter and skim the bed.

    • Smorges Borges says:

      Particle board is junk. MDF is the thing to use. But the dust is a really huge health concern, with all of the chemical binders and stuff. Also, it out-gasses after you cut it. If you do some searches you’ll find many folks seal the MDF, both sides, after they surface it. That helps improve the stability.

      Of course if you remove it you need to get it back in the same spot to be level.

      One strategy is to surface your MDF, seal it, and then mount thinner spoil boards on top of that. I use a variety of approaches depending on what I am doing.

      • Smorges Borges says:

        Forgot to mention, polyeurethane is a common sealant.

      • Mike D says:

        My experience with particle board (extreme junk) and MDF/HDF in CNC machines is “don’t do it”. I have used a home built one and talked to the guys that had theirs in Make Magazine when at a maker’s faire and the big issue is swelling from humidity. I would use 3/4 ply as it is extremely rigid and does not warp over time due to moisture.

    • JRDM says:

      If it’s not well-sealed, particle boards will warp with humidity. Cubicle work surfaces seem to work pretty well, because it’s well sealed. I think it might be made from a better grade of material too.

    • Mike D says:

      Exactly where I got them from (HF). There is only a few dollars difference between lengths, not the greatest clamps in the world for their intended purpose but perfect for this. The waste board is actually MDF and MDF in CNC builds is actually a pet peeve of mine, the waste board will likely be replaced with some 3/4 ply and I will be running it over with a fly cutter to plane it.

    • NKT says:

      How dare ‘Mom & Pop’ try to make a living! The swine. Saving you at least a day wait for shipping, and paying local taxes. How very dare they!

  3. zag says:

    That was a clever solution. Not having T slots must be a real pain when setting up work pieces. I laughed a little bit when he said other people were using screws to fasten material to the work surface. I understand that it would work well, but that would be a pain in the butt.

    • Mike D says:

      The screw systems I’ve seen…screws straight through the material into the waste board (yuck) and one where the waste board had a grid of holes already drilled that was used kind of like a poor man’s t-slot. Both were a PITA.

  4. zag says:

    On second thought, if he ran a few rows of woodworking T-nuts or threaded inserts on the MFD bed he could use some conventional style clamping solutions.

  5. Smorges Borges says:

    I like this idea, and can see where it could be very useful for edge clamping.

    My machine has a t-slot aluminum top. I use 1/4″ carriage bolts in many lengths, and pieces of scap plywood, as clamps. It just takes a few seconds with the bench grinder to create two flats on the head so they can slide into the t-slots. This is dirt cheap and it works really well.

  6. Jimf says:

    A full aluminum t-track table would be nice but for the size of my cnc, it would cost upwards of $400. Instead I just bought some aluminum t-track rails from rocker/woodcraft for about $75 total. Routed several grooves into a sheet of MDF and then bolted down the t-tracks. Simple and works great. I do a lot of engraving so t-track hold down clamps can flatten any slight warpage in the material. I have a full woodshop with jointer, planer and drum sander. I can quickly flatten and thickness a piece of wood pretty accurately. That piece of wood will come out of the drum sander nice and flat but let it sit for a few hours and I can guarantee it to be warped a little. That’s just the nature of wood and humidity. T track hold down clamps on each corner of the piece will flatten it down pretty good. I sometimes only vcarve engrave 50thou deep or less so any surface not flat will show up as uneven engraving. Plus it is much safer you won’t ever have the chance the material would pull up off the table due to cutting forces.

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