[bjesson]

Those acetal clamps should work just fine. I've had the one on my table for a Bosch Colt for some time now, and I cut aluminum with it without tooling marks just fine.

This particular one in the photo is off a Probotix, who sells them for a variety of different sized routers.

Nice build, btw bjesson.

It's got me wondering about running two tables - how much trouble would it be to switch stepper and signal cables into the G540 from my current table into one of these tables. The SuperPID kind of complicates it. I guess there is an easy way to load different versions of Mach for each machine? May be more trouble than its worth.

Thanks for the compliment! I'm lovin having a CNC in the garage now. I spend hours on it almost everyday. One issue I am having with the design is the 1/4-20 bolts for the main carriage. If I try to remove too much material from a part it shifts the carriage. Tightening the four bolts works for a bit but eventually the studs (cap screws in my case) snap. I just cant torque them down enough because they are too small. So, I have bought 5/16-18 cap heads and once I finish the bosch clamps I am taking the carriage off the machine and modding it. Hope this will stiffen it up a bit more. Will post pics when done.

Billj

[momus_cnc]

One issue I am having with the design is the 1/4-20 bolts for the main carriage. If I try to remove too much material from a part it shifts the carriage. Tightening the four bolts works for a bit but eventually the studs (cap screws in my case) snap. I just cant torque them down enough because they are too small. So, I have bought 5/16-18 cap heads and once I finish the bosch clamps I am taking the carriage off the machine and modding it. Hope this will stiffen it up a bit more.

Bill, can you explain this one again, I'm not sure I'm understanding exactly what is happening. Are you saying there is movement at the four studs (your bolts) that hold the front vertically oriented carriage parts (parts #22, 23) to the rear horizontal ones (parts #16)? So are these parts moving so that they are no longer exactly perpendicular to each other? Or are they moving so that they spread apart (like the two part #16, for instance) and are no longer parallel? I've pushed my machine pretty hard, to the point of having the belt skip, without running into any problems with anything shifting anywhere on the carriage.

-Bob

[bjesson]

Bob, the four bolts that sandwitch #16,#22,#23. If I plunge too deep or move too fast on hard materials #22 and #22 rotate on the four bolts so they are no longer perpendicular. I dont have this problem in wood just when cutting hard plastics plunging anything more then 1/4 inch into the material and aluminum I can only go about 1/16th on a pass, Both around 6 IPM. above 6 IPM and it tends to happen. But not an issue anymore. I just spent several hours machining clamps for the Bosch router, then removed the carriage, drilled and countersunk for the 5/16 bolts, remounted carriage and re-aligned all axis' and mounted new clamps and bosch router. Right now I am much more comfortable with the bolts. I was able to clamp them down pretty hard without anything snapping. the only issue I had was with the new clamps, I had to add shims because the router head hit the flange mount bolts. I will throw some pics up of the whole thing tomorrow. Nappy time now!

Billj

[bjesson]

Ok here are the pics as promised. I used the Ridgid router to cut the clamps for the Bosch router. I have not tested cutting anything yet since I tore the carriage down to modify it. Enjoy!

billj

[bjesson]

in this pic you can see the 5/16-18 cap head screws where the 1/4-20 studs were originally to sandwitch the carriage together. You can just make out the spacer I used on the new clamps as well.

billj

[bjesson]

OK, so I loaded up some aluminum to test out the performance of the Bosch router, the modified carriage bolts, and the delrin router clamps. It is an easy 10 out of 10 now. I have this machine performing about as perfect as can be. I am getting damn near mirror finishes on aluminum and I am able to cut easily twice the depth and twice the speed as before without a hickup. I accidentally had the feedrate at 138 IPM but it did not hurt the machine in any way and easily cut the aluminum. The edge finish at that speed wasn't great but it still cut without issue. Lowering IPM to 20 made a clean edge for my rough cuts and lowering to about 12 IPM for finish cutting produced a near perfect finish. I am extremely happy at this point with this machine and will load up some 3/4" aluminum tonight to see if it can handle cutting clamps out of metal this time. Last thing, I wasn't going to bother with the Bosch router before since I put the Ridgid in but now I am happy I spent the time making the clamps for the Bosch and mounting it all up. It outperforms the Ridgid mostly I think because the Bosch has a metal casing as opposed to the 2401 which has a completely plastic shell. I would recommend the Bosch if you dont mind modding your setup.

Billj

[groswald]

Billj,

I would really like any details you can provide on the Bosch mod's. I haven't purchased a router yet and would prefer the Bosch for the reasons you mention. Maybe start another thread specific to the mod?

Regards,

Randy

[groswald]

I picked up a DB25 M-M cable at a local place that sells manufacturers overstock and used parts. I got it for a whopping six bucks.

Then I got home and discovered the computer I plan to use is too new - no parallel port. So now I have a PCI parallel port card on order. Sigh...

Randy

[kemper45]

Randy,

Bummer that this delay is happening when you are so close.

When I was planning my build I decided that I was going to have a dedicated computer for the CNC. I knew from Mach3 support that its specifications did not need to be cutting edge to say the least.

I ended buying through an online buy and sell site a P4, 2.0Ghz, at least 512 KB RAM, 40 GB HDD, 17" flat screen monitor, keyboard, mouse and printer/scanner/fax (for which I have no need) for $60. Almost near the specs I have for my other machine for next to nothing. Don't know how much your PCI Parallel port card is costing you but an option you may want to consider.

Looking forward to pics of the final machine and your first cuts.

Cheers, Dave

[groswald]

Dave,

It is indeed a PITA. I was hoping to put power to the motors this evening. The computer I am using was until recently my primary personal machine. I tend to hang on to replaced technology, "just in case." I have a box full of cables, keyboards, and mice; as well as a spare monitor or two, and the computer in question.

I still have lots of parts to fabricate though, so I will continue with that.

Randy

[bjesson]

I picked up a DB25 M-M cable at a local place that sells manufacturers overstock and used parts. I got it for a whopping six bucks.

Then I got home and discovered the computer I plan to use is too new - no parallel port. So now I have a PCI parallel port card on order. Sigh...

Randy

Don't worry too much, PCI parallel boards are around $10 ob ebay and maybe $20 at best buy. Not ahuge setback. You will have the board before you are done fabbing parts.

I'm looking at adding the same board so I can use a digitizing probe and all home/limit switches in the near future.

billj

[bjesson]

Billj,

I would really like any details you can provide on the Bosch mod's. I haven't purchased a router yet and would prefer the Bosch for the reasons you mention. Maybe start another thread specific to the mod?

Regards,

Randy

Good idea! will start one now.

billj

[Michael In Cali]

Bob, the four bolts that sandwitch #16,#22,#23. If I plunge too deep or move too fast on hard materials #22 and #22 rotate on the four bolts so they are no longer perpendicular. I dont have this problem in wood just when cutting hard plastics plunging anything more then 1/4 inch into the material and aluminum I can only go about 1/16th on a pass, Both around 6 IPM. above 6 IPM and it tends to happen. But not an issue anymore. I just spent several hours machining clamps for the Bosch router, then removed the carriage, drilled and countersunk for the 5/16 bolts, remounted carriage and re-aligned all axis' and mounted new clamps and bosch router. Right now I am much more comfortable with the bolts. I was able to clamp them down pretty hard without anything snapping. the only issue I had was with the new clamps, I had to add shims because the router head hit the flange mount bolts. I will throw some pics up of the whole thing tomorrow. Nappy time now!

Billj

Can we talk about these busted bolts a bit more?

You substituted 1/4" socket head cap screws for the all-thread to start with. Since you were getting some racking, you kept tightening them and eventually snapped the bolts. Did you snap the heads off or did you snap them at the threads?

Why do I care? A SHCS should have been stronger than hardware store all-thread by a goodly bit. Not only that, but they should be stronger than the aluminum threads you were intalling them into. I would think you should have been stripping threads. Your heads went down into the countersinks, yes? Were the countersinks flat bottomed? It is rather easy to snap off the head off a bolt if you put it in bending like bearing it up on a non-flat surface. (But you didn't say whether it popped the head or not, so I don't know this to be the failure mode.) Might you have been using an inferior strength SHCS? Most of the ones I find are grade 5 or better.

Just curious.

I'm also thinking a shear plate between parts 16 and the spacers (and using thinner spacers) would get rid of the racking but I haven't verified that there is no other interference. Of course, now that your machine is working, you could just hog out a fancy replacement.

[Michael In Cali]

I just checked and you don't have room for the shear tie I though could be added. Oh well...

[bjesson]

Can we talk about these busted bolts a bit more?

You substituted 1/4" socket head cap screws for the all-thread to start with. Since you were getting some racking, you kept tightening them and eventually snapped the bolts. Did you snap the heads off or did you snap them at the threads?

Why do I care? A SHCS should have been stronger than hardware store all-thread by a goodly bit. Not only that, but they should be stronger than the aluminum threads you were intalling them into. I would think you should have been stripping threads. Your heads went down into the countersinks, yes? Were the countersinks flat bottomed? It is rather easy to snap off the head off a bolt if you put it in bending like bearing it up on a non-flat surface. (But you didn't say whether it popped the head or not, so I don't know this to be the failure mode.) Might you have been using an inferior strength SHCS? Most of the ones I find are grade 5 or better.

Just curious.

I'm also thinking a shear plate between parts 16 and the spacers (and using thinner spacers) would get rid of the racking but I haven't verified that there is no other interference. Of course, now that your machine is working, you could just hog out a fancy replacement.

Ok, here is as detailed as I can get with this....

I built the entire CNC as stated in the v1.0 plans. 1/4-20 threaded posts where stated. I wanted to build exactly to plans because I wanted to know this thing inside out since I knew it is my nature to modify things The very first cuts I did were in wood and it all ran fine but MDF is hardly a good test material unless it is just verifying gcode. That stuff cuts like knife through butter when using a new endmill bit. The moment I cut aluminum it racked. It was easy to see the issue was I didn't tighten the bolts to the studs enough, so a wrench and re-alignment and i was back in business. ran fine at slow feeds but at deeper plunges and faster speeds it racked again. So back at it with the wrence I broke the all-thread free from the threadlock so no damage to threads as the threadlock was the weakest link. This is where I switched to 1/4-20 stainless caphead screws which was easy because the post holes were all countersunk so I could do this all on the fly with out haveing to tear it all down, I also drilled out the threads. I overtightened all bolts to break them free from the threadlock. Got everything re-aligned and did a check on the SHCS to make sure they were torque down pretty good. I didn't crank them down extremely hard because they still felt kind of "soft" while tightening the first time but tighter then I was doing on the allthread posts. So, at this point it is a 1/4-20 SHCS, slightly widened hole, and bolt/washer. Everything worked fine until the deeper cuts again but this time it racked while cutting delrin which should be fairly easy for this machine compared to the forces required to cut aluminum. So squared up the carriage again and really torqued the bolts down and "SNAP". The SHCS broke at the thread where the washer meets part #16. Replaced the SHCS and tightened again, ran the machine, racked, tightened bolt...snap! So, this is where I ripped the carriage apart, went back to the NC mill, drilled out and countersunk parts #22 and #23 to take the 5/16-18 SHCS. It was a much bulkier bolt and when I tightened them down they would firmly stop to where I couldn't turn the wrench anymore without standing on it. Loaded up some aluminum, and accidentally ran it at 138IPM but it didnt rack where it would rack at 12IPM initially. Just to make sure there wasnt even the slightest bit of racking I checked squareness of the bit and it was still dead-on. This isn't a "must do" but for my machine and application I had to. And in all honesty it doesnt hurt to have the extra holding strength at this particular spot. the rest of my CNC router is using the 1/4-20 studs without issue.

Hope that clears it up...

Billj

[Michael In Cali]

Yes, that does.

Now I know part of the problem. Stainless Steel.

Stainless is about half the strength of a grade 8 bolt, can be even less.

I'll likely go with SHCS for many of the bolts as well and skip the all thread.

[groswald]

I'm thinking that I will simply thread parts 22 and 23 full-depth (no counterbores) and then make the studs from four 1/4-20 x 3" grade 8 bolts.

One could also thread the spacers (parts 24) and use them as nuts to pre-load the studs. This should increase the amount of torque that can later be applied to the stop-nuts without breaking the threadlock.

Thoughts?

Randy

[Michael In Cali]

When you get those grade 8 bolts cut, let me know. Not the easiest thing to cut. I'd recommend just building and see how it goes.

I'm leaning toward using studs as designed. McMaster has some "better than hardware store grade" medium strength all-thread for a good price. About $0.60 per foot. Item 98957A542.

[bjesson]

I ran into this while looking at what others are using for feedrates and RPMs when cutting aluminum...

http://www.cnczone.com/forums/genera...ling_feed.html

I remember on the original threads for Momus that the question of tapping and cutting fluids had come up. One person is using 90% isopropynol alcohol for threading/drilling/cutting and says it works perfect. Just food for thought. Unfortunately with the wood base and back door of the current momus design a litle work would be required to add a flood cooling system. When I do the build with an aluminum base Im going to add flood coolant. The other downside is the router motor is close to the work so flood systems could be a problem for the electronics in the router.

Billj

[bjesson]

I'm thinking that I will simply thread parts 22 and 23 full-depth (no counterbores) and then make the studs from four 1/4-20 x 3" grade 8 bolts.

One could also thread the spacers (parts 24) and use them as nuts to pre-load the studs. This should increase the amount of torque that can later be applied to the stop-nuts without breaking the threadlock.

Thoughts?

Randy

That's a good idea especially threading the spacers. Right now they are annoying with the 3/8ths hole because they move around when trying to align and tighten. Threading the entire width of the bar is a good idea also, more surface area for the threadlock to contact. I didn't have a problem with the studs breaking, my issue was the studs freeing themselves from the threadlock. The replacement capheads were the ones snapping which I rememdied with the bigger capheads. And grade 8 all-thread, hope you have a cutoff saw Hacksaw blades might dull out immediately.

What I have been considering is machining the entire carriage as one piece (#16,#22,#23, and spacers). This will take several hours to remove that amount of material from a 2.5 inch thick slab of aluminum but would be extremely rigid.

I'm gonna go price a slap of aluminum right now

Billj