Detrick designs table

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moosefab
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Joined: Sat Jun 26, 2021 8:41 am

Detrick designs table

Post by moosefab » Sat Jun 26, 2021 8:35 pm

New guy here, I searched around a bit but can't find much info on the subject. Thinking of getting a 4x8 table and I'm looking a lot at Detrick Designs from Troy Ohio. Anybody have experience with them? I will be using a Powermax 45 (non XP) with it so I'll have to get a machine torch as well. My biggest concerns are accuracy of the steppers. I do need to be able to cut accurate holes on plate. My use will be mainly hobby related but I would like to do some custom work to help justify the cost of the machine.

tcaudle
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Re: Detrick designs table

Post by tcaudle » Sun Jun 27, 2021 6:27 pm

Accuracy (not resolution) is a function of a bunch of factors: Steppers are fixed resolution having 200 steps per rev.

1. Quality of the drivers and if they have microstepping
2. Final drive ratio between stepper and drive gear (i.e. belt reduction or gearhead)
3. Diameter of drive gear (pinion)
4.Rack & Pinion "mesh" (backlash)
5. Linearity of drive components (rack, gears, pulleys, etc)
6. Software : Trajectory Planner
7. Software Toolpath tracking tolerance

All of those are involved in the physical accuracy . It can be argued that servos have higher resolution (depends on the encoder line count) and because they are higher RPM motors the step gown gearing ratios are higher so that adds resolution and torque That may or may not contribute to actual higher accuracy since other factors contribute a lot more to inaccurate than raw resolution.

In a design you always trade speed (IPM) for Torque (acceleration) and increased resolution (one factor in accuracy) With steppers there is a "sweet Spot" where you get improved acceleration without giving up too much upper speeds. That ratio is roughly one inch of linear motion for one motor revolution. So with microstepping of 10:1 the steps per unit should be close to 2000.

Then there is the Plasma process itself: The cut kerf width varies with age of the consumables. Kerf width increases if you slow for curves and angles. The flame e is not rigid and bends as it cuts in different directions. Air plasma can hold about .015 of tolerate with new consumables and a constant cut height (arc gap) Consider the process . Its melting and vaporizing steel with an arc and blowing it out with air. If you require accurate holes (both dimensionally and round) you may be disappointed on ANY air plasma process.

Steppers can cut as accurate on plasma as servos on a well designed table with good software that optimizes for accuracy versus constant speed. So worry less about the type motors and more about the mechanics , software and plasma process. Fine cut consumables have a smaller kerf and can be more accurate BUT the older 45 torch does not support them for automated cutting.

in some circumstances if accurate holes or hole locations are required (especially smaller ones) a "peck plasma process" may be the best solution ' it leaves a conical peck mark at the hole centres and acts as a centre mark for mechanically drilling the holes the correct size. It does not penetrate all of the way though and leave a ragged hole with hardened sides. It takes special software and that custom feature .

I am not familiar with the brand of table. Its important you understand the variables I listed and what kind of controller and software is used. Ther are at least 40 manufacturers of tables that were not in business 5 years ago. The market is flooded with "hobby" grade tables. Things like support and reputation and system repairs are important. The end use of the table is important. While its not always true that you get what you pay for Its fair to say cheap tables have to cut corners some way.

Wehall
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Re: Detrick designs table

Post by Wehall » Sat Oct 02, 2021 9:56 am

I have one. I can't say enough good things about Gene. His table has worked flawlessly for 5 years.

adbuch
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Re: Detrick designs table

Post by adbuch » Sat Oct 02, 2021 6:23 pm

moosefab wrote:
Sat Jun 26, 2021 8:35 pm
New guy here, I searched around a bit but can't find much info on the subject. Thinking of getting a 4x8 table and I'm looking a lot at Detrick Designs from Troy Ohio. Anybody have experience with them? I will be using a Powermax 45 (non XP) with it so I'll have to get a machine torch as well. My biggest concerns are accuracy of the steppers. I do need to be able to cut accurate holes on plate. My use will be mainly hobby related but I would like to do some custom work to help justify the cost of the machine.
What sort of accuracy do you need? Assuming your table is tight (no worn belts/pulleys/etc.) with good anti-backlash - you can usually get your sizes dialed in by adjusting your kerf width in your program. So for example, say you have drawn a 1" circle and it is cutting at 0.990" diameter, then depending on if this is an inside hole or outer diameter, you can adjust your specified kerf width by 0 010" and this adjustment should get you pretty close to an actual 1" size. Your edge quality (cut quality) and taper will have a lot to do with how accurately you can actually measure your hole.

David

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tnbndr
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Re: Detrick designs table

Post by tnbndr » Sun Oct 03, 2021 1:46 pm

Thinking of getting a 4x8 table and I'm looking a lot at Detrick Designs from Troy Ohio. Anybody have experience with them? I will be using a Powermax 45 (non XP) with it so I'll have to get a machine torch as well.
Not sure if you made the move yet but I have been running an LDR Motion Systems 4x8 with scribe and a PM45 for 7 years. It will cut accurately. If you are still looking I would give them a call. They are located in New York State.
Also with the PM45 you can swap the machine and hand torch by simply unplugging one and plugging in the other. I use the hand torch to cut up my skeletons for scrap.

Good Luck
Dennis
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