Pinion size affects:
Speeds - big=fast..........small=slow
Force/torque - big=low force/torque.........small = high force/torque
Resolution/chatter marks - big = poor resolution with marks.....small=fine resolution/less marks
Wear/life of pinion - big=longer life.......small = shorter life
PC's frequency output - small=high freq/fast PC.......big=slower PC

It is all a compromise between these factors.

Ed,
Did you use the aluminum channel for the Y with the hardened rails? From the pictures I see, it looks as though your rail holder is painted (steel?) Was there any problem with the Z and the slight offset with the hardened rails mounted that way? ( Normally, the V would be at the end of the plate, not offsett) If you have more pictures of the Y rail setup I would like to see them.

thanks

Heath.

Hi Heath,
I was going to grind my own rails and I got bad cutts on the y rails so I took the crooked cutt pieces to a friend that has a mill and had them milled down to 7/8". If I ever do another MechMate though I really feel it is better for me to go with the aluminum and premade hardened rails. If you look at the total cost of the MM (around 5-6K), and then look at the cost of grinding your own rails and include the cost of the brackets to hold the grinder and blades and grinding wheels and a grinder if you don't have a fairly heavy duty one already. Then compare that to the aluminum angle and premade rails and at most it's probably $150-$200 difference. It's my opinion that is is worth $200+ no to have the stress and time spent grinding and cutting wondering if it will work ect ect ect. So $200 on a 5-6K machine is pretty insignificant.

The offset didn't matter it just took less shim washers than it would take for a DYI ground rail. After installation they are about 3/16 narrower.
Here is a photo of how they bolt to the z slide plate.
If you use steel angle rather than the aluminum like I did you will have to also have the rail milled off for the radius of the steel angle, if you use the aluminum you don't have to do that it doesn't have a radius it is square on the inside corner.

Ed,
Thanks for the extra pics and explanation. I am still on the fence for the grinding or buying the pre made rails. I really like your Z slide idea, looks great. It looks like you did the 14 inch version of the slide? Did you use higher table sides to get more Z travel? Was just wondering how that worked out for you if you increased the Z clearance.

You speak of pinion life here, Gerald. Your machines have been running longer than anyone else's and from you descriptions, pretty much 40+ hours a week. Have you experienced an appreciable level of wear? Do we have a clue what the MTBF is on the pinions or the racks? I would think that the motors would wear out first.

This just kind of caught my attention, and is not really something that concerns me too much.

Roman

Can't see/feel any significant wear on our MechMate's pinions and racks (without stripping it down to inspect). Our ShopBot had narrow unhardened pinions which wore out after maybe 1000 hours of running. The MechMate must be over 3000 hours by now. The logic of longer life for bigger pinions is simply based on the fact that more teeth will be sharing the work.

I did the 14" slide but I am using the 6" channel rails. Since there is really no difference in cost in doing the longer slide, I did that just in case I may need to raise the rails someday. I probably should have used the 7" or 8" channel but then hind sight is 20/20.

I'd agree with you - I wish I had gone to 8" channel instead of the 7" I built with. It would have solved the problem with the X cable chain brackets being to short and it would have given me full use of the 250mm Z slide (with the support/spoil boards in place). I would also guess that it would be stiffer with the larger web of the 8" channel.

I am working on my dust collection now and I have a question. I see alot of you guys are building a sliding foot that attatches to the router mount. My router mount has only one hole for foot, that doesn't seem like it would work.

Do you have to have the sliding foot for the dust collector to work?

I was wondering if I built an adjustable pipe with an open bottom tapered intake that will be ajustable so that I can set it just above the work piece and it will sit about 4-5inches behind the router. I drew up a little picture of what I had in mind showing about where the router will be, but I don't know enough about what I need and what works yet. The dust cyclone I have is about 1100cfm, its pretty strong, I accidentally sucked the remote control for the dust collector off the table that was a few inches from the collector tube when I turned it on. That is why I was wondering if I actually needed a foot that totally encapsulated the router bit with the plastic or broom attatched to the foot.

ED -

Have you seen this post that I made about the fully adjustable dust foot that encloses the bit but can be opened up to allow a view of the material for setting Z and changing bits? My design is independent of the router mount, mounting to the existing mounting holes in the y-car. I has the ability to either ride a fixed level above the work surface or it can be fixed to the Z slide and thus go up and down with your bit. I have a 600 CFM system and pretty much nothing gets out. By the end of this coming week, I hope to have the design fully tested and I'll post the files for others to cut.

David

My view is that the foot should be fixed to the y-car, and that it should not ride up and down with the z-axis. (Realise that I am biased to production board cutting). The optimum height of the skirt relative to the top surface of the board is in a fairly narrow range - if a thick board needs to be cut in 4 passes, inceasingly deeper, then the foot needs to stay at a steady height and not be squashed right down at the end.

We do often cut with the front of the dust foot removed and there is only a small loss in performance. Whether that leaves enough dust in the air to kill you......well, I don't know......yet! (Suspect though that the open foot still gets the "fines" while the coarser chips fling out)

Thanks guys that makes sense to me, and seems like it would be easier to build by attatching to the z car rather than the slide. I don't mind sweeping some of the larger stuff as long as it gets most of the fine powdery dust.

David, I will check out the thread, thanks.

finished cab fingerjointed with MM
 

The finger joints that I had cut in the earlier photo turned out way better than I could have imagined them to. It was also probably faster than using my dovetail jig also. I like the fit and the corners better than what I was getting with the dovetail jig. Just need more cabinet clamps though before I do any more, the glue was almost set before I finished clamping this one, because I was short on clamps.

This is a birch cab for a Marshall tube amp.

Very nice Ed, I like it. :)

Ed,

Very nice finger joint. I hope that when my MM is built, I get the same quality of work.

Umm Ed, I thought that you were a steelworker? Blokes like us are not supposed to do nice woodwork...or so I tell myself when I gouge some wood by mistake.

Good Stuff!

I noticed that all the wiring for the relays has been removed from the thread it was on guess things were cluttered and got cleaned up a little, I couldn't find anything in the archives either so I guess maybe it got deleted. For those interested in putting the j-box with the relays and bringing 12v to the gantry, I tried to clean up the drawing a little. I mounted the box on the opposite side from the 0,0 side of the table since I did not use three of the pushbutton stations, there was plenty of room there. There is plenty of room for a small 1-1/2" x 2" board, relays (common avaliable at Ratshack or Mouser or any place that sells electronic parts) terminal strips and lots of room for making the 7core wire connections. I added a small outlet on the top of the box for a 12vdc source on the gantry in case I need it later.

Ed,
Fantastic small package of limit switch/proximity relays. A little soldering and breadboard fun I see! Great, clean, compact solution.

Hi Ed,

I did not delete anything like that......are you talking of the posts in this thread. #'s 114 and 119?

Some very neat wiring! I can almost forgive the colour....:)

Hi Ed

Nice toy bet you have a lot of spare time to do good job.

Gerald,
I was thinking of the wiring layout that you had drawn to show the layout of the Proxies and the relays (it was a nice drawing). A schematic is good but sometimes a wiring layout like my drawing is also helpfull to understand how it works and making a plan on building the circut.

Since I have mine already built I found some very small (6-7mm round in size) simple to wire NO relays at Radio Shack. I think they were $2 each. With only 4 pins and the voltage pins are marked it would be pretty much impossible to not wire them correct. Might also be possible using those smaller relays to mount it all in one of the pushbutton stations???

Sean, Did you say that you do foam cutting?? I have a neigbor who wants to know if I can cutt some foam sheets into RC model airplanes. I guess the hot ticket with the RC planes now, is foam planes flying 3D stunts. He wants to see if it would be cheaper to purchase full sheets of foam and use a popular purchased plane profile to make duplicates. What kind of bits are best to use for cutting the foam if you want a small kerf that is good and square? The foam will be something called EPP foam?? Thickness is from .125 to .188 inch thick.

Ed, I would stay away from $2 relays for this application. The relays should be a little bit special - they should have gold on their contacts. We only have a puny 5V signal that we want to get through a lot of series wired contacts.

Ed,

Check out precisebits.com. They have speciality bits for cutting foam.

On a side note: Got my ClearVue operating and is it nice !!!!! I know Gerald likes to see dust, but, it's not going to happen with this system.

David that is problably a neater looking drawing of the layout and I remember that one but it is incorrect. I edited it to correct mistakes. Without the changes it looks to me like y and z could either or both have a crash and as long as x was okay you would still have a close loop. I edited it so that if any sensor has a capacitance change from not sensing a rail then the closed loop would open tripping the circut or stoping motion.

You can check for mistakes but I think the edited photo will work better.

In other words the relays need to break the loop or circut to stop motion. If you look close at the wiring circut and see that if the y sensor or the z sensor in the first photo stop seeing the rail and trip you would still have motion because there is still a closed loop with the x sensor relay being closed. Then look at the edited one, if any relay trips there is no way you will have a closed circut. Does the changes make sense?

BTW the last photo is showing everything in a non powered state. Once the MM is turned on and everything is active the relays shown in the photo will all go closed, creating the closed loop. I forget if that is called active low or active high but I remember that it is better to have it this way then having the relays NC and open when powered up.

Wiring it with NC relays would then require the wiring to be as the first picture to work and the picture would be shown in a powered up state. But I understand Gerald saying it is better not to wire with the NC relays.

ED, your series one is correct - dave had his switches shown in parallel. (will take his pic out now, to avoid confusion)

Can't figure what you, or I, are saying, or supposed to be saying, when you say the above?? :)

Use NO relays (spring Opens them, electricity Closes them) with very good contacts.

For the proximities, also use NO (metal rail Closes them, free space/holes/faults take them to Open)

Gerald, good point not to use cheap parts, I used the mouser Axicom brand:

http://www.mouser.com/Search/Product...Qs5mAEBg%3d%3d

These don't have gold pins but I have had no issues with them they have worked flawless so far.

Those are perfect - they do have the gold-plated contacts. Quote:

Gerald, I was cutting some small circles out of light ply today and when I finished and hit the ref home key, my z axis and y axis are moving about 3/4 to 1 inch away from the proximity sensor hole. The x axis is working correct, soon as it comes off the hole it stops.

Any ideas on what might of happened and how I should fix this?
:)

Ed, I have no personal experience of using limit/homing switches yet. Let's hope someone else drops a clue. Have you tried the Machsupport forum?

Hmmm..... maybe it was just a small glitch or something. I hit ref home again and now it is working correct and all axis are stoping soon as they come off the holes.

Does anyone know if you can cutt 1/16" rubber on the MM? I just had a customer that is building hydrogen generators and needs alot of rubber gaskets cutt. I told him I would try to find out.

Not sure how to hold it down either, the thought that came to mind was spray one side with super77 and attatch it to a thin ply, but that may be non removeable, I haven't used that stuff enough to know how well it bonds.
Maybe it depends on how much you spray on? Anyone have any experiance in this area?

Ed, the only way I have had any kind of decent luck "machining" rubber is when I sandwich it between two layers of somthing such as MDF. If I were going to try it, I would make a fixture involving a hinged lid held down tightly by the appropriate number of toggle clamps. I don't know how well it would work after the holes are in the lid following the first cut. If that doesn't work so well (and there is enough money in it), sacrifice a piece of 1/2" MDF with each cut and hold the lid and rubber down with toggle clamps all the way around.

That would be my approach. If the gasket is quite large, you might have to augment the edge clamps with some carefully placed screws (such as in the center of large cutouts).

My thoughts. Any other ideas? J.R.? Sean?

that sounds like it could work. I was concerned that cutting something so flimsy that the tool might try to grab it and pull the whole sheet of rubber to the router, but sandwiched like + the screws, it should keep that from happening. Too bad they don't make double sided tape in full sheet size.

...I have had "some" success by doing the sandwich cutting, but usually I use medium tack spray adhesive to keep the rubber (or in my case neoprene) down. When done cutting a little cleanup is required.
The other option is install a rotating cutter knife. You can source and get one that will cut well if you ask for the high angle cutter for Pen plotters that is made to cut sandblasting mask. The masking material, which is like rubber, is nominally 3/16" thick. SUMMA vinyl cutting website is a good source for the cutters. You will need to make a special holder if you have a router with collet. If you have a spindle, you can easily chuck it up if you have a nice selection of collet rings.
Good luck, Sean

When I glue up counter tops I use the red contact cement (spray grade). I use cardboard to catch the over spray, if you walk on the cardboard when it's just dry it will follow you around the shop and it's hard to pull off your shoes and I'm not talking about both surfaces glued, just one. I think this process would work for your application. I think the glue would stay on the surface you sprayed and not transfer to the rubber. You will need to play with it a little to see what works best. I know the faster you stick, cut and remove the rubber from the backer the better off you'll be. Good luck.

I don't know if you will make enough profit to justify a vacuum pump and table but it sounds perfect for this job.

Don't forget that J.R. experimented with a shop vac first, before the full blown vacuum system.

What's the size of the gaskets. Maybe a small vacuum "prototype" for this gasket project.

If you want to experiment with a spinning cutter, think of a very sharp down cut spiral cutter. The "Belin" cutter bits from France are very sharp, polished, cutters. Have heard there are some stockists in the US.