Hi Guys, I have a bunch of questions and I'm hoping to get people's opinions.

I would like to start with the plans I downloaded from the shopbot website for the table. I was planning to build the Prt alpha 96 table and use the plans I found on the Mechmate.com website to make the gantry.

I've decided to use gear rack but I'm trying to find out what Pitch people are using for the gear rack. Also I would like to know what people are using or recommend for the pinion that would run in the rack. I've seen many of people use gear reduction using timing belt to get the resolution and torque. Which Sizes of belt and timing pulleys would be adequate? Also please let me know where you bought the parts. I would like to get a resolution of .001" I've attached a photo of the steppers that I was considering using. I have 6 of the Japan Servo steppers (kp86sm2-006) and 4 of the Superior electric. If anyone has the specs on the Japan stepper it would be appreciated I searched the web and emailed the manufacturer but haven’t had any luck yet.

I was planning to drive the gantry in the x with one motor coupled to a shaft that will drive in both racks at the same time so I wouldn't need to run 2 motors. Is this a good idea? I have the extra motors to drive each side but I don’t know much about the electronics that would be required to run both motors synchronous.

Next would be the electronics. I'm considering the Canadcnc.com SPECIAL #1 MP1000-THC Combo deal. I spoke to these guy on the phone and they were really friendly and answered all my questions with patience so my impression was that they would be good to deal with and their product looks like they have most bang for the buck. One thing that I like is they have a MPG for it. I've been running CNCs for 12 years and I really like using a MPG for setup. I would like to know anyone’s opinions with the pros and cons if any with using their product.

I was considering torchmate, but their quality is not up to my standard. I went and saw one of their machines in person at a local company but I really wasn’t impressed. Seems overpriced for what you get. I’ve attached a photo of the quote they sent me and a photo of the machine I saw.

Any comments will be greatly appreciated.

Thanks!

Dan

Dan
I don't know about the torchmate but the CandCnc parts are first rate. I have set a couple of these up and any time I had a question, It was answered in just a few minutes. they have a good support site and a great product.
mike

Hi Guys, still wondering what gear rack people have chosen to go with. I'm wondering what pitch mainly Please post what you have used and where you bought it. Also trying to decide between a cutmaster 101 or a hypertherm 1250 I would be going with machine torch. I've heard all the hype from both companies but I can't decide. The cutmaster is much cheaper. But on the other hand I heard the hypertherm is easier on the consumables.

I haven't used the cutmaster plasma, but the Hypertherm seems to be the weapon of choice for cnc applications. Thermacut also makes silver enhanced consumables available for the hypertherm MAX units, which pretty much tells the story: If there are aftermarket enhancements for the torch, its probably the system to choose. Hard to find a good deal on the machine equipped with the machine torch online- everyone seems to be selling the hand torch version, so I'm buying mine from the local boys. Better that way if it happens to break.

I used 12 pitch 20 degree rack for my main X gantry drive, and 16 pitch 20 degree for my Y. The Y is lighter for the fact its moving a far smaller load, and the 16 pitch saved me a bit of needed clearance on the gantry. I used 560 Oz. inch slo syn steppers for my X and Y, with a 3.75 :1 reduction running down to a 1 inch pinion for both the drives, 12 teeth on the X, 16 on the Y, and the X is a MASSIVE 1.25 inch wide cast iron timing belt system, coupled through a 1 inch diameter titanium hollow shaft to dual pinions tied directly on both sides to the gantry assembly. One of the racks is adjustable to allow for squaring. The whole gantry with motors weighs about 30 pounds.

The Y axis uses smaller timing pulleys- about 3/8 inch wide belt, but again steel pulleys and rack/pinion. The system should be able to run up to 600 IPM, but I wont know until I get a chance to test it.

I just looked at your steppers as well, and judging by their appearance, they are a bit older style slo syn motors. I do not know exactly why this is, but the round body motors are said to be no good for microstepping. Not that I think it will matter, for we are looking at a plasma cutter here. I received my racks from Mcmaster-Carr today, and the 12 pitch is huge overkill for my machine. Go with the 16 if you haven't ordered up your material yet, or even 20. The 12 pitch doesn't run quite as smoothly, but I still think it will be adequate, so I'm going to go ahead and use it, but man, is it huge. It looks like it belongs on an arbor press...

The steeper motors in that picture are older, Torchmate does not sell those motors anymore.

I am currently running 20 pitch 20 degree PA gear and rack, and I am quite happy with that.
Hard to beat the service and product available at candcnc.
I would check on Ebay, Carrmcmaster, etc. for the gear boxes. I got my timing belts and pulleys from hubbardcnc on ebay. He has a good selection.

massajamesb,

Arn't the timing belts and pullys a replacement for gear boxes on the steppers? I.e. one or the other for your design?

Corvus corax,

I got some Pacific Science NEMA34's which are round body motors. They came with a micro stepping drive which seems to function fine but I've not put them in any machine as yet. Tell me there not like this older style slo syn motors your talking about?

If I understand your design correctly, why have you used a rack on both sides of your X and/or Y axis? Does it help to take up backlash?

Dan

[QUOTE=GalaticDan;226875]massajamesb,

Arn't the timing belts and pullys a replacement for gear boxes on the steppers? I.e. one or the other for your design?

yes, that is exactly right. It is a cheap alternative to gearboxes. For the price of one gearbox 1:3 ratio from most suppliers, I can get pulleys and belts to get the same result, on 12 different motors. I spent about 50 bucks US with shipping to get my belts and pulleys. No backlash that I can see, very smooth and quiet.:)

What size of pulleys are most people going with to get their reduction. 1 inch on motor to a 4"???

I don't go by the outer diameter, but by the number of teeth.
I would suggest a 1:3 ratio minimum.
say a 10 tooth pulley on the motor with a 30 tooth pulley on the output drive shaft.
Now, I will say that I am referring to toothed timing belts, not just regular v belts. Want to make sure and clear that up.

I just ordered 3 of the 500 oz/in steppers from homeshopcnc. 2 for the x axis and 1 for the y axis. I also have a tompson z axis coming. I have a 7' x 14' table. Gantry is all aluminum. Approx. weight 60lbs. Are 2 of the nema23 500's going to be ok? 95% of the time, the table will be run at speeds between 2 ipm up to 151 ipm. I'm told now that the torque on these motors drops off rapidly as speeds increase due to the "triple stack".

That will be more than fine. Just invest in some gear reduction boxes, timing belt and pulley, etc. to gain torque at higher speeds.
The low speed torque of those motors will amaze you, when driven by adequate (minimum 24 volts) voltage. Gear them down to at least 1:3 and good luck stopping them then!
With 2 motors on X, that will be a real bear of a gantry!
There are some premade cnc plasma machines available that only come with 130 ozin motors, and only one for X, and one for Y. They are geared down for adequate torque, and those gantrys, which are 80/20 aluminum, can do 200IPM.
Very good choice, IMO.

Where is the best place to pick up rack and pinion?

www.mcmaster.com is fair priced, they get it from standard steel specialty company. Search the threads for topic "cheap rack and pinion", someone had the number there. They are about 5 bucks cheaper per 4 foot length than McmasterCarr.
I paid 28 bucks for a 4' long section of 20 pitch 20 degree pressure angle.

I got my timing belts and pulleys from hubbardcnc on ebay. He has a good selection.

Is he still around? I looked for the ebay id hubbardcnc but couldn't find him.

Mike

Try this link, I was just on the site

http://stores.ebay.com/HUBBARD-CNC-COMPONENTS_POWER-TRANSMIION-PULLEYS-BELTS_W0QQcolZ4QQdirZ1QQfsubZ5QQftidZ2QQtZkm

You beat me to it.:)
Thanks grinder.