[cncspear]

Hi guys! I just wanted to e-troduce myself and thank all of you for the great discussions on this forum. I have never posted before but I frequent this forum just to learn and get new ideas on machines. I find it to be very valuable information. I also want to share with you my new longbed router I designed and just finished building. This is my first self built router.

With what I've learned in the last year, I've been able to take the plunge into CNC which seemed quite intimidating to me at first. I started off by buying a little hobby grade stepper machine and did some hands-on learning and tinkering. However, I quickly outgrew it and found the need to either buy or build a larger and more sturdy machine for my small business. With my limited financial resources, buying a larger industrial machine was simply out of reach. So about six months ago I started laying out a servo powered machine of my own design on AutoCAD. I started buying parts and building as money became available. Wired the bugger up about a month ago, tested, tuned and still just getting used to it. I'm still climbing the learning curve and don't consider myself an expert at any of this. I only hope to become as skilled as I need to be to help me get ahead with my small business. All the while having great fun and satisfaction with the things I'll build.

I prefer to call it a heavy duty bench top router since many of the components are industrial grade stuff and I used steel wherever possible to provide vibration reducing mass and stiffness. The gantry uprights are welded pieces of 2x2 solid mild steel square bar. It's probably rigid enough to do light milling on steel. It rips through wood like butter!! It weighs in at roughly 400 pounds and it sits on a worktop in my garage. It has quite a long bed for a benchtop router, 80 inches to be exact. Why so long? It'll be used to make slender wooden spearguns up to 6 feet long. I'll be the first in the custom wooden speargun market to do this. Yes, you can call me crazy.

Here's the link to my CNC router page. It has quite a few pictures and some movies I think you'll enjoy. I list some of the machine's specs at the very bottom. Let me know what you think. Hope you like it… I'll gladly answer any questions.

http://www.spear-diver.com/temp/CNC_Router.htm



Gil

[JRoque]

Very nice, Gil! Mind if I ask you where you purchased the THK rails? I'm looking for 4, 60" HSR25.

Thanks!
Julio

[cncspear]

Thanks Julio.

The SR20 rails and blocks are slightly used and I found those on Ebay.

The SR30's I paid full price at http://www.thk.com/ You should be able to find your HSR25's here. Word of warning, THK's are the industry leaders in both quality and PRICE. You'll spend more than you'd like.

Gil

[samualt]

cncspear:
Thanks for the web page! I love looking at other peoples machines. Yours in particular looked very professional. And the videos were great also. It gave me lots of inspiration. Great job!

JRoque:
I found my THK's on Ebay also. Mine are 53.5" and cost about $250 total for 2 rails and 4 blocks.

:cheers:

[Mike F]

...... THK's are the industry leaders in both quality and PRICE. You'll spend more than you'd like.
Gil

I'll second that. I bought 2200mm, 700mm & 300mm ballscrews and linear guides from THK at a cost of £2,500 and that was supposed to be a special, educational price. These are for a school project to make a large CNC router. I have the frame made and now am trying to find a firm with a larger CNC to level the faces and drill and tap the 74 holes for the guides. Got one quote and it seems a bit high for our school budget.

Great looking machine - I hope mine turns out as good.

Mike

[Bloy2004]

Hey Gil!
You've put together a real nice machine!

[ger21]

Thanks Julio.

The SR20 rails and blocks are slightly used and I found those on Ebay.

The SR30's I paid full price at http://www.thk.com/ You should be able to find your HSR25's here. Word of warning, THK's are the industry leaders in both quality and PRICE. You'll spend more than you'd like.

Gil

I think everyone couyld save quite a bit of money by going with smaller size THK's, like the 15mm. We have a point to point machining center at work that has a cantilevered design with at least 1000 pounds hanging 4 ft beyond the rails, and they are only 25mm. Mcmaster Carr shows 15mm rails with 4 ball races have dynamic load capacities from 1500-2200 lbs. Rails with only 2 ball races still have over 900lbs capacity. Just a thought.

[buscht]

Gil, Great job! It's a wonderful example of sizing the machine for its intended purpose.

I personally would like to hear occasionally how well its really helping the business.

Thanks
Trent

[cncspear]

Hey thanks all for your thumbs up.

I was wondering what anyone thought of the gas spring I attached to the z-axis end plate. This was a solution I came up with to counter a problem I only realized when I started testing the machine. The problem was that the entire z-axis assembly is heavy and that there is too little friction and mechanical resistance in the bearings and ball screw/nut. Under its own weight and no power applied, the z-axis would start to move and work its way down until it would slam to a stop. The servo has no problem driving it up and down despite the force of gravity working against it. But once power was cut, or if the gecko drive faulted, the servo would freespin and the axis would slide down again and come to a very hard stop. If the router is running while this happens, I could unintentionally drill a hole into my t-slot table, yikes!!

So I came up with the gas spring idea. I made a stop a the local auto store and picked one up and mounted it into the z-axis end plate. Turns out that this spring contained too high of a pressure and would drive the z-axis up! This wasn't what I wanted either. The final solution was a reduceable force gas spring I found in McMaster Carr. This allowed me to bleed off the pressure a little bit at a time to just the right amount of spring force to HOLD the z axis in its current position. It worked like a charm and I had to give myself a pat on the back.

Has anyone else encountered this problem and what was your solution?

Here's the picture: http://www.spear-diver.com/temp/images/dsc01633.jpg

Gil

[DSL PWR]

It looks like some people use a stepper on the z. They have great holding torque.

[ger21]

It looks like some people use a stepper on the z. They have great holding torque.

He said when no power is applied. Even steppers have no holding torque with the power turned off.

[Ol'Dusty]

Very impresive!

[3t3d]

Hey thanks all for your thumbs up.

I was wondering what anyone thought of the gas spring I attached to the z-axis end plate. This was a solution I came up with to counter a problem I only realized when I started testing the machine. The problem was that the entire z-axis assembly is heavy and that there is too little friction and mechanical resistance in the bearings and ball screw/nut. Under its own weight and no power applied, the z-axis would start to move and work its way down until it would slam to a stop. The servo has no problem driving it up and down despite the force of gravity working against it. But once power was cut, or if the gecko drive faulted, the servo would freespin and the axis would slide down again and come to a very hard stop. If the router is running while this happens, I could unintentionally drill a hole into my t-slot table, yikes!!

So I came up with the gas spring idea. I made a stop a the local auto store and picked one up and mounted it into the z-axis end plate. Turns out that this spring contained too high of a pressure and would drive the z-axis up! This wasn't what I wanted either. The final solution was a reduceable force gas spring I found in McMaster Carr. This allowed me to bleed off the pressure a little bit at a time to just the right amount of spring force to HOLD the z axis in its current position. It worked like a charm and I had to give myself a pat on the back.

Has anyone else encountered this problem and what was your solution?

Here's the picture: http://www.spear-diver.com/temp/images/dsc01633.jpg

Gil

The three common solutions on comercial products are:

Gas spring. Some with a resevoir, some with a pressure regulator, that
adds and subtracts air as the Z goes up and down.

Counterweight.

Elecric Brake. With energize to release. The control drops the Brake
release, before it powers off the servo. It also energizes the servo before
it releases the brake.

Pete

[cncspear]

Thanks Pete. Now I know my gas spring solution for the problem wasn't just a dirty fix. If they're doing this on larger, more sophisticated machines, its good enough for me...

Gil :banana:

[senor J.]

hey gil great machine. It says in your spec sheet that you used nema 34 servo motors what are the specs on them? You didnt by chance get them off of ebay? I just bought some nema 34 off of ebay and was wondering if they are the same? would like to know how they are working out for you. thanks
I like the speed of your cutting

[cncspear]

Senor J, yes I did buy them off Ebay from clangenf. So far so good. They run great with the geckos! The videos you saw was with my old 24V/12A supply. I was doing rapids there at about 70 IPM with my 10 mm pitch screws. But I just bought a 60V/12A supply from Dan Mauch (camtronics, also available thru ebay or his web site) and tested it out for the last few nights. I timed some rapids and its running at 260 IPM!! I could probably run even faster if I tweak the accelerations in my control software. More speed than I could ever need (for now at least). It's quite scary actually. But I'd rather have more speed available to me now than wanting more later. Seeyah...

Gil

[senor J.]

hey thanks a lot for the reply. Thats encouraging that they work well with the geckos even with the lower volts supplied. Take care.

Jacob