[DarkHorse]

Hey Guys,

This is kind of a rant but i thought my issues and frustrations would help people who are looking at a plasma table system. I bought a Torchmate 5x10 table a few months ago and I have been happy with the machine when it comes to cutting good objects however i cannot cut a good hole 9/16th or smaller to save my life. I have nothing bad to say about torchmate as a company and their tech support so far has been great. All the guys there are good at their jobs. I have talked with about all of them and i usually have my questions answered. Recently, I have been trying to cut tabs and gussets with the standard 1/2 inch hole and it is getting better but it still will not cut a hole that fits a 1/2" bolt unless i oversize it to .58".

Here is the shop setup:

Torch- Hypertherm Powermax 1250
Torchmate Height Control unit
Table- homemade w/Torchmate 3 gantry setup 5x10 w/ torchmate precision ground rails
Compressor-CP 7.5 QRS rotary Screw w/ Refrigerated Dryer- air system is copper tubing- air system drain valve 8" below tee for air compressor( never had an water in system)

I am cutting:
10 gauge
3/16"
1/4"
3/8"
1/2"
Even cut 3/4" (but the 1" hole was awful)

i have played with the 40 amp nozzles/ 60 amp nozzles/ and 80 amp nozzles and i have found that the 40 amp works the best on 10 gauge, not worth cutting 3/16". the 60 amp works great with 3/16" and some 1/4". the 80 is great with 1/4" and 3/8" and it cuts 1/2" as long as it isn't a small hole. I need to cut quality 1/2" holes on all material without having to go back over the hole with a drill or a die grinder.

The machine works great on everything except cutting holes. We ran the table for a week, went back checked square and level, checked all bolts, cleaned all parts, rechecked gear ratios, etc. All in all it has been up and running and cutting for about a month.

We built a water tray for the table with really helps keep smoke out of the shop and it keeps parts from warping. the Air pressure regulator built in to the hypertherm is always set at about 70psi

I cut some tabs out today and they were small in size( about 1.75x1.75 with a 5/16" hole. The outside of the tab came out great except the holes were bad, very bad, almost not even worth cutting because it would of just have been better if i had just drilled them( only about 1/2 the hole was cut out so when we went to drill the holes they were no longer centered).

Am i expected to much from my system?
Is my Plasma Torch to big for cutting 1/2" and smaller holes?

I am honestly at the point where i am going to buy a ironworker so that i can punch holes and then buy a torchmate plate marker attachment to give me a center so i can punch then more accurately. I know i need an iron worker anyways but i was hoping my $20k investment would of been a bit more versatile.

Rant over, constructive thoughts are much appreciated

Scott

[EBC]

what software are you using?


Gene Crain
www.plantasymaderas.com

[DarkHorse]

I am using the Torchmate cad software and their driver software.

I am going to post my line speeds and voltages when i get to work so i can see what you guys think.

Thanks,
Scott

[EBC]

I am using the Torchmate cad software and their driver software.

I am going to post my line speeds and voltages when i get to work so i can see what you guys think.

Thanks,
Scott

don't know much about their control software....have you looked at Cut2d?
www.vectric.com


Gene Crain
www.plantasymaderas.com

[Mike@Torchmate]

A few things, and I will copy the post on both here and pirate.

1: The General rule of thumb is no hole smaller than the thickness of material. The thicker the material the more this becomes true. A 1" hole in 3/4" material with an 80 amp plasma is going to have enough bevel that the cut may be off .080" top to bottom.

2: Have you tried cutting your inside circles at 60-70% of your program feedrate? This is always going to help improve the bevel and give you a straighter/nicer cut. There is probably going to be more low speed dross, but this is a trade off.

3: After personally cutting out 1/2" bolt hole tabs and some even smaller in 3/16" material and 1/8" material I can confirm that the machine and Plasma cutter are both capable of doing so. If you were to call me up and ask me on a brand new machine why the bolt holes are not coming out correctly, I am going to immediately point to a mechanical problem on the table. Why? Because after years of doing technical support on these machines it almost always ends up being a mechanical issue. I'm not saying it because I'm assuming you set it up wrong which is where most customers immediately jump to.

Now a mechanical issue could be many things on the machine, from the obvious gear to gear rack mesh, to the cassette on the slide having too much play. Below I'll list the most common things.

Gear not fully meshed in gear rack, or intermittent meshing across the table.
Result: Small hole cut quality deteriorated, flat spots on the circles at 12,3,6,9 o clock positions.
Fix, mesh gear fully into rack and check in 6-12" increments across the table to see if the gear rack needs to be aligned with the rails.

Loose Set screws on Large or Small pulleys, or inside of gear box if applicable.
Result: Intermittent flat spots or axis pauses during cutting, resulting in flat spots, part coming out too small in one axis, jagged points in a diagonal cut. Small hole cut quality can be adversely affected if it slips during a hole cut.
Fix: Tighten set screws, a little loctite wouldn't be a bad idea.

Excessive play or "rocking" in the Cassette.
Result: At most direction changes the torch can "wonder" and result in deviations in corners and small cut quality.
Fix: Tighten set screw on cassette to decrease the backlash.

TM3 without Upgraded T-Section on the low side of the machine with worn brass bushings where the spur gear goes through the motor mount plate.
Result: "Scalloping" effect in the face of the cut during multi-axis motions, deteriorated small cut quality.
Fix: Replace bushings, build T-Section with two cam followers, or purchase upgraded aluminum extrusion T-Section.

In the end I would like you hear what you have done so far, and possibly some pictures of the cut's you're getting. These can help us visually identify any one of these problems.

-Mike

[DarkHorse]

Thanks for the reply's guys, and mike thanks for your help. I will post some pictures up of what we have.

i wanted to show you my results on what i found to be my best settings for my table:

40 Amp Nozzle:

1/8"- 50ipm 147v
1/4"- 30ipm 151v

60 amp nozzle:

1/8"- 70 ipm 140v
3/16"- 50 ipm 145v
1/4"- 30 ipm 153v - will not cut 1/2" holes, but will cut 9/16" holes

80 amp nozzle:

1/4"- 60 ipm 139v will not cut 9/16" hole
3/8"- 55 ipm 137v will not cut 9/16" hole

I am running on the slow side of feed rate because i am trying to cut holes, i can ramp it up a whole bunch to cut large shapes but i would rather have quality parts rather than more parts with bad holes.

i will get some pictures up online to show you what i am producing.

I want to make it clear that for every part that has larger holes or bigger shapes this machine has been flawless.

Scott

[pdjcutandfab]

do you have some pictures/diagrams of your water table that you could share, i'm looking to make one for my TM3 table that i have.

Thanks

Pat @ PDJ Cutting and Fabricating

[DarkHorse]

Here are some pictures of the table. the whole table is built out of 3"x3" 3/16 wall tubing at the exterior specs that torchmate provided. the tray is made of 3 4"x8" pieces of 10 gauge with 5" walls and it fits the interior dimensions of the table. The tray is removable if needed to rebuild it or clean it.

Right now we are drilling more holes in the torchmate provided rails becuase they are not perfectly flat.

We adjusted the play in the cassette today and we tightened the backlash on the x gears and it is doing better but we are going to make that rail perfectly flat.

[pdjcutandfab]

that's just what i was looking for, thanks

Pat

[jimcolt]

There are many different types of plasma on the market.....air plasma systems to industrial High definition plasma system. By themselves.....no plasma system can cut at all! Motion control in terms of x, y and z axis direction, following error and velocity are extremely critical to get good quality holes.

The keys to getting excellent hole quality with an air plasma system:

1. You must have a torch height control that finds the surface of the plate accurately before each cut, then retracts to the manufacturers specified pierce height. One pierce too close to the plate will damage the nozzle orifice with a microsopic nick......and cut quality in terms of edge angularity will suffer. THC acuracy is number one for cutting holes.

2. The x , y and z axis must remain in position unitl the pierce is complete.....most plasma manufacturers suggest pierce delay time....if not, ensure that the molten material is exiting the bottom of the plate before movement is allowed. If movement starts before the pierce is complete....the nozzle orifice and the shield orifice can be damaged.

3. As soon as the pierce is complete...the torch should index down rapidly to the manufacturers suggested cut height.....and the height control must be frozen at this height through the entire hole diameter.....do not use arc voltage height control on holes under 1-1/4" diameter is a good rule of thumb. The torch should achieve cut height before it is off the lead-in portion of the part program.....

4. Another rule of thumb: Holes under 1-1/4" should be cut at a much slower speed that the larger part contouring speed. A good place to start is to have a feedrate overide in your part program of 60% of the programmed cut speed for the rest of the part. This slowdown effectively straightens the lag angle of the arc to minimize taper in the hole. It will create low speed dross on the bottom of the hole....but will dramatically improve taper and roundness.

5. Holes should have as long of a lead in as possible....if your machine tight mechanically (no gear backlash) and has acceleration in excess of 40 miligees.....then a straight lead in works well. If your machine is sluggish...try a radial lead in that starts near the center of the hole.

6. No lead out. If your post processor software can do it....insert an "overburn".....go past the lead in kerf of the hole, staying on the hole radius for as much as .200". If your machine has the capability, shut of the plasma arc at the 360 degree point of the hole...and let the motion continue on the overburn. This allows the arc to extinguish while the torch is still moving.

7. If your parts are hole intensive...always use the lowest power set of consumables that will do the job. For 1/2" holes in 1/2" plate....I would use the 40 Amp shielded consumables on the Powermax1250......and follow all the above recomendations. the holes should have about .020" to .030" top to bottom taper, and should be very round.

If machine motion is jerky, accleration is below 40 miligees, or machine has flex or backlash....or the THC cannot accurately set pierce height and index quickly to cut height....expect poor quality holes! Attached is a picture of holes cut on a low cost cnc machine with a Powermax45 and a good THC. 3/8", 1'2" and 3/4" holes in 3/8" steel.....holes were drawn .010" over size, and bolts drop right through.

Jim Colt Hypertherm.

Hey Guys,

Recently, I have been trying to cut tabs and gussets with the standard 1/2 inch hole and it is getting better but it still will not cut a hole that fits a 1/2" bolt unless i oversize it to .58".


Scott

[DarkHorse]

Thanks for the posts on this issue, We went back to work in the shop on the table and figured out some more things and now it is working much better.

first thing we did was look at the backlash across the whole 10 feet of the x axis, I have the extruded alum gantry and the backlash is good up there, we found out that the x axis was way off. When i ordered the kit from TM i ordered the ground rails and we laid them on pieces on 3x3 3/16" wall tubing and then mounted the gear rack rails under the rails. It worked fine on long runs but when trying to cut holes it wasn't so pretty. we figured out that the backlash was not as tight as we had hoped and we drilled new holes in the rails every foot instead of every 3 feet like TM provided and then shimmed the rails as flat as we could. We then re-adjusted the gear racks to about .010" backlash. and we started to get rounder holes.

TM really needs to provide a good Backlash number in their instructions, When we called we got the answer of, " run some paper through it and if it cuts the paper its to tight", that is such a precise measurement. Anyways once the backlash was tightened and fairly straight across the 10 feet it really made a difference.

After watching the motors i realized that on a .5" hole the gear only uses about 2-3 teeth in the gear rail. If we have the backlash loose the motor may spin the pinion a half a turn and that might only equate to a half a tooth of engagement if the motors are reversing direction and taking up loose backlash.

We also started playing with the 40amp fine cut nozzle and it has made holes much better. I really think i can deal with the machine now. I am glad i asked the questions i did because it was you guys and the guys on cnczone that really helped the thought process. I know TM was helpful but i need to hear some real world thoughts on this. TM, dont take this the wrong way but learning from the teacher is not always as useful as learning from your peers.

Scott

[DarkHorse]

Thanks for the posts on this issue, We went back to work in the shop on the table and figured out some more things and now it is working much better.

first thing we did was look at the backlash across the whole 10 feet of the x axis, I have the extruded alum gantry and the backlash is good up there, we found out that the x axis was way off. When i ordered the kit from TM i ordered the ground rails and we laid them on pieces on 3x3 3/16" wall tubing and then mounted the gear rack rails under the rails. It worked fine on long runs but when trying to cut holes it wasn't so pretty. we figured out that the backlash was not as tight as we had hoped and we drilled new holes in the rails every foot instead of every 3 feet like TM provided and then shimmed the rails as flat as we could. We then re-adjusted the gear racks to about .010" backlash. and we started to get rounder holes.

TM really needs to provide a good Backlash number in their instructions, When we called we got the answer of, " run some paper through it and if it cuts the paper its to tight", that is such a precise measurement. Anyways once the backlash was tightened and fairly straight across the 10 feet it really made a difference.

After watching the motors i realized that on a .5" hole the gear only uses about 2-3 teeth in the gear rail. If we have the backlash loose the motor may spin the pinion a half a turn and that might only equate to a half a tooth of engagement if the motors are reversing direction and taking up loose backlash.

We also started playing with the 40amp fine cut nozzle and it has made holes much better. I really think i can deal with the machine now. I am glad i asked the questions i did because it was you guys and the guys on cnczone that really helped the thought process. I know TM was helpful but i need to hear some real world thoughts on this. TM, dont take this the wrong way but learning from the teacher is not always as useful as learning from your peers.

Scott

[millman52]

Thanks for the posts on this issue, We went back to work in the shop on the table and figured out some more things and now it is working much better.

first thing we did was look at the backlash across the whole 10 feet of the x axis, I have the extruded alum gantry and the backlash is good up there, we found out that the x axis was way off. When i ordered the kit from TM i ordered the ground rails and we laid them on pieces on 3x3 3/16" wall tubing and then mounted the gear rack rails under the rails. It worked fine on long runs but when trying to cut holes it wasn't so pretty. we figured out that the backlash was not as tight as we had hoped and we drilled new holes in the rails every foot instead of every 3 feet like TM provided and then shimmed the rails as flat as we could. We then re-adjusted the gear racks to about .010" backlash. and we started to get rounder holes.

TM really needs to provide a good Backlash number in their instructions, When we called we got the answer of, " run some paper through it and if it cuts the paper its to tight", that is such a precise measurement. Anyways once the backlash was tightened and fairly straight across the 10 feet it really made a difference.

After watching the motors i realized that on a .5" hole the gear only uses about 2-3 teeth in the gear rail. If we have the backlash loose the motor may spin the pinion a half a turn and that might only equate to a half a tooth of engagement if the motors are reversing direction and taking up loose backlash.

We also started playing with the 40amp fine cut nozzle and it has made holes much better. I really think i can deal with the machine now. I am glad i asked the questions i did because it was you guys and the guys on cnczone that really helped the thought process. I know TM was helpful but i need to hear some real world thoughts on this. TM, dont take this the wrong way but learning from the teacher is not always as useful as learning from your peers.

Scott

Backlash is hard to get consistent any other way besides spring loading the drives into the rack gear. "0.00" backlash that way & most people do it that way. Mach software has backlash compensation in it to help eliminate the problem. But if you have .010 in most places but more & possibly less others The compensation could make things worse on those sections of the table.

[Mike@Torchmate]

I would recommend no backlash at all, as in the gear is fully sitting inside of the gear rack. Any backlash you have at the gears will reflect in your cut. Obviously it is difficult to get the alignment that precise across the whole table, but you don't need to. The Motor mount bracket itself acts as a sort of spring and will flex a small amount keeping the gear engaged.

Good to hear you were able to find and work out the issue!