Newbie- Table Size vs. Overall Cost

[RUN-A-MUCK]

All,

I am just getting into the planning stage of my CNC Plasma Table and I am trying to figure out exactly how big of a table I want/need to build. I have a Thermal Dynamics Plasma Tourch with both PCM-35 & PCH-35 torches.

I think the max length of material I will need to cut is around 5ft.

I have some questions that I could sure use some input on.

1) Is there any disadvantage (other than overall size) in building a 5x10 table over say a 4x6 table?
Going to a 5x10 table would allow for use of full 4x8 sheets of steel.

2) Will the drive motor requirements change with the larger table? I know the gantry could be heavier.


I really would like to build the largest cost effective table I can, and would spend the additional money for a larger table if it won't like double the cost. I don't think you ever complain about building things too big.

Thanks for any and all input

RUN-A-MUCK

[asuratman]

Good day, If you make 10X5 is no different from 8X4 if you DIY in case of motor and control size. I use GD and kelling 1125 oz in. Use rack pinion. Only more material to make table slightly bigger. So it is recommended to make 10X5 if you DIY.

[RUN-A-MUCK]

Thanks.

That is what I was thinking. I allways DYI. That is how I learn.

[RUN-A-MUCK]

Also. Why use rack & pinion? Wouldn't a link belt drive also work?

RUN-A-MUCK

[Dustin407]

Well, Table size depends on many things, which are personal decisions(cost, build time, shop space, what projects/material thickness u plan on cutting etc..) It depends more on what type of projects or jobs you will be doing also. Its nice to nest a full 4x8 sheet of parts and cut for an hour. Personally if I had to build my table over again I would make a 4' x 10' table. Then people would say if you make a 4' x 10' why not a 5' or 6' by 10'. Thats because the steel co. sells sheets around me very cheap for a 4' x 10'. If you go to wide(5' or 6') you will loose some accuracy in the table, and increase side chatter from vibrations. If you have a good design a large table shouldnt cost much more than a medium size table ( nothing fancy ). What did you have in your projected budget??? I would not recommend belt drive, only if u are trying to go super cheap. Belt drive will def. show up on your cut parts when the machine changes direction fastly. Hope this helps some...

[RUN-A-MUCK]

Originally Posted by Dustin407 Well, Table size depends on many things, which are personal decisions(cost, build time, shop space, what projects/material thickness u plan on cutting etc..) It depends more on what type of projects or jobs you will be doing also. Its nice to nest a full 4x8 sheet of parts and cut for an hour. Personally if I had to build my table over again I would make a 4' x 10' table. Then people would say if you make a 4' x 10' why not a 5' or 6' by 10'. Thats because the steel co. sells sheets around me very cheap for a 4' x 10'. If you go to wide(5' or 6') you will loose some accuracy in the table, and increase side chatter from vibrations. If you have a good design a large table shouldnt cost much more than a medium size table ( nothing fancy ). What did you have in your projected budget??? I would not recommend belt drive, only if u are trying to go super cheap. Belt drive will def. show up on your cut parts when the machine changes direction fastly. Hope this helps some...

My budget should be in the 2-3K range. I have yet to start on my shop, so there is no space issue at this time. I like to think things over, and look for great deals. Find scrap items. Cheap steel. Then start my builds. Drive parts are not easy to find used which is why I'm trying to figure out how I want things to move. I could get pieces over time to spread the cost out.
It may be 18mths before I can actualy get the table started. I'm thinking about making the table 1/2 length to start with then double it's size when I need to. I just don't want to under build the electronics. I'm not known for under building mechanicly.

[Torchhead]

From an electronics (cost) perspective it's all about the weight of the gantry. While a 5 ft gantry (probably over 6 ft overall) is heavier, the question arises how much more than a 4 ft? If you drive the gantry from both ends using a slaved motor approach the problems with racking and binding on the longer gantry go away and you have double the torque. Unless you plan on using the table for heavy contact cutting (routing, milling, etc) besides plasma, there is no reason to overbuild the gantry. It only carries the weigh of the torch (and maybe a scriber) and the motion components. The part that takes all the stress is the table below and you can build it as stout as you want. Using bigger motors and a heavy gantry may help with the "arr - arr" factor but adds nothing to the cut process. The analogy is needing a sports car for speed and maneuverability, and deciding to use a dump truck with a really big engine !

If you can keep the total gantry weigh below 90 lbs you can use smaller motors (300 to 600 oz-in) 23 frame size, smaller motor drives (i.e Gecko 540) smaller less costly power supplies, etc. Then you have funds available to get the things important to good plasma cutting like a Torch Height Control. (:-)

Large size is only important if your jobs require you to be able to cut out BIG parts. It does not take a lot longer to cut two 4 x 4(5) sheets of nested parts versus one 4 X 8 or 4 X 10. The number of jobs you will have that will fill a full sheet will be limited. 90% of what you will cut will fit on a 4 X 4 or 5 x 5 cut area table. Half sheets of material are a lot easier to handle and most suppliers will shear them in half for you for free.

There is not a lot of difference between belt drive and rack & pinion With either drive your final speed to torque/resolution numbers (you can have one or the other but not both) is determined by the diameter of the final drive gear/pulley. You can get by with a 1" diameter pinion but that is too small for a drive pulley. A 1" diameter gives you a 3:1 speed increase but you give up a 3:1 torque LOSS and 3:1 resolution reduction. A 2" drive pulley changes those numbers to 6:1! Just hooking a stepper directly to a pinion or belt drive pulley may require you vastly oversize the motor to get sufficient torque for acceleration AND you won't be able to recover the lost resolution. Each step will be 3 to 6 times courser.

Your budget is pretty tight. Hopefully you have the plasma cutter already and access to a free machine shop.

TOM caudle
www.CandCNC.com

[RUN-A-MUCK]

Tom,

Yes, I allready have my plasma torch. I picked up a Thermal Dynamics PackMaster-50 with a PCH-35 torch at a swap meet for $250.00 In the Portland Oregon area. I know for some it may be a little small, but it works great on 1/4in plate. I got a PCM-35 torch off Ebay for $150.00. This was the first plasma cutter I ever used,and am hooked on how cool they are.

I wan to build custom bumpers and other parts for Jeeps, and will need to cut material in the 5-6ft long range. Thats the reason I think a table that could hold a 4x8 sheet would be great, but if I had to I could go smaller.

I have a lot to learn and lots of designs to look at that others have done. (This site is sooooooooo cool!!!!!!!!!!!)

I thought the first place to start is to define how big of a table I need/want to build, then work on figuring out the gantry and how heavy it will be. Then I can look at motor size, power supply, drive type, etc. This is how my brain thinks I should attack the design, but I'm open for input.

Is there any one thread that talks about drive type and the pro's and con's of each type? I am a real newbee on this part.

RUN-A-MUCK

[Dustin407]

Run A Muck,

Would you be interested in building the same machine I have designed and constructed (4x8)? I think the overall (table only mechanically ready) table was $2400. I have full 3-D AutoCad files, plus sections/details of the entire machine. I am willing to send you the files to reproduce. I have every part number of every single part( from v-wheels to bolts ) that I purchased, so there would be no questions or head scratching at all!!! Send me a PM if u would like to talk further about this conversation.... I have had several people come to me so far and ask me for the autocad files. I have not released any files yet, but I think I should. It would only help people in the long run from months of research/design/parts....

[tubesilly]

nice to see someone else from oregon i moved from portland to prineville. i am getting ready to start the assembly of my plasma table. on your size concerns i was going to build a 4x8 but when i talked to the only other guy in town with one and a few other people i decided to go 5x10 to have th ability to accept a larger job if it came around. i was also going to piece the machine together . to save alot of head ache and after a several emails to tom at candcnc the mans a genius by the way when it comes to cnc plasma. i called precision plasma llc and bought one of their gantry kits. then i bought the dragon cut system from tom at candcnc. saves alot of time and trying to figure out what works together. well enjoy your build and post photos. its well worth the time and extra steel to build it as a water table. DUST SUCKS!!!

[RUN-A-MUCK]

Originally Posted by tubesilly nice to see someone else from oregon i moved from portland to prineville. i am getting ready to start the assembly of my plasma table. on your size concerns i was going to build a 4x8 but when i talked to the only other guy in town with one and a few other people i decided to go 5x10 to have th ability to accept a larger job if it came around. i was also going to piece the machine together . to save alot of head ache and after a several emails to tom at candcnc the mans a genius by the way when it comes to cnc plasma. i called precision plasma llc and bought one of their gantry kits. then i bought the dragon cut system from tom at candcnc. saves alot of time and trying to figure out what works together. well enjoy your build and post photos. its well worth the time and extra steel to build it as a water table. DUST SUCKS!!!

I moved from Oregon to Illinois. That is where all the children and Grand Kids are. I miss the mountains, but not the rain. Hope your table design works great.

[jcc3inc]

Sir,

I understand your comments about kids and grandkids; I'm in a similar situation.

Just where are you in IL??? I'm in Arlington Heights, retired, and still interested in CNC controllers and the like.

Regards,
Jack C.