Open source CNC Plasma cutter, a general idea and a lot of info.

More
14 Mar 2019 16:25 #128595 by tommylight
Dust from plasma cutting is very fine and very sharp so it can do quite some damage to rails and bearings. Having a water table diminishes that problem a lot, but not totally, so daily cleaning of rails is a good practice.
Not seen any failed bearing on AC servo motors yet, same goes for DC motors and steppers.
Have seen what the dust from the brushes gathered at the motor commutator can do on DC brushed motors, from messing up the tuning during work to getting very hot with very little use and heating the drives to the point of shutting off.
The following user(s) said Thank You: jmr

Please Log in or Create an account to join the conversation.

More
15 Mar 2019 20:17 #128683 by tommylight
I do need some opinions here,
I am thinking of doing a small machine with simple bearings, since i used that over 10 years ago i really did not like them for linear movement at all. What do you guys think?
Usually up to 2 meters in length ( 80 inches ) i use round rails, 30 or 35 mm diameter with corresponding linear bearings, the problem with them is that with no support they do sag a bit and i can not find bearing holders here so i have to improvise.
If used with a THC, the sagging problem is non existent as the THC takes care of that difference easily. Without a THC they are usable only up to 1 meter in length.
The main issue right now is i am out of stock on long linear rails, got some THK 45mm left and some short 35mm and 30mm.

Please Log in or Create an account to join the conversation.

More
16 Mar 2019 08:49 #128719 by Grotius
Hi Tom,

I have made many machines with roller bearing's. They are all still working after 6-7 years.
It's a cost effective solution. The market for cheap machine's is bigger then for expensive machine's.
The following user(s) said Thank You: tommylight

Please Log in or Create an account to join the conversation.

More
16 Mar 2019 13:19 - 16 Mar 2019 13:20 #128734 by jmr
Hi,
Do you have any opinion on using pipes instead of full round bar? Those can be found in good precision, not always in size compatible with standard 20/25/30mm linear bearing size, like 1.5m long 22.5 (or is that 21.5?)mm diameter. There is one ball bearing based solution, I will take a photo. Not very easy to manufacture, however it could work out of 3d printer. I have a salvaged pair, its cast and machined aluminum - the machining is not very straight forward as it requires rotary indexed milling and drilling - not very possible for drill press only scenario. Could b e doable if one had a way to index the material for drilling and with crude angle grinder cutouts instead of milled slots. It also requires an eccentric element for play management.
Another idea to consider is round bar/tube which is preloaded - pulled on the ends. With pair of them and square tube or H-beam with brackets as structural beam between it could result in less sag than a rod/pipe just supported on ends. Anyone tried that?
Round bar has the advantage of easy solution for dirt scraper.
Last edit: 16 Mar 2019 13:20 by jmr.

Please Log in or Create an account to join the conversation.

More
19 Mar 2019 12:48 #128966 by andypugh

jmr wrote: There are claims of belt drive being a good way. I know it can be used as a rack, this way teeth can be facing the bottom and would not collect the dust deposit,


The Bell-Everman "Servobelt" arrangement is good this way, the belt teeth are protected by the "counterbelt"

community.carbide3d.com/t/bell-everman-s...belt-system/10923/11 has a nice diagram.
The following user(s) said Thank You: tommylight

Please Log in or Create an account to join the conversation.

More
19 Mar 2019 13:28 #128968 by tommylight
Seen that when they started, it is a very nice way of removing belt flexing on machines and with light loads it can do some very fast moves. Planning to do that for a long time now, but time is not on my side.

Please Log in or Create an account to join the conversation.

More
20 Mar 2019 19:16 - 20 Mar 2019 19:21 #129097 by Grotius
If a plasma machine runs 10 m/min it is not very fast. If a plasma machine run's 20 m/min it's very fast. I cancelled a order for a 20 m/min machine speed today. Because of future safety issue's.

Client want's a machine of 8000mm x 2000mm area. For aluminium cutting. Client has a machine working. His workman are walking on the machine cutting bed while machine is cutting.

I chancelled order because i don't want to be the killer company. :woohoo:
Client has no idea about safety issue's. So keep in mind the safety issue's.

Building a machine is one. Keep the safety plan in touch is two. Build a safe machine, if machine if very fast, make a fence and related safety option's.
Last edit: 20 Mar 2019 19:21 by Grotius.

Please Log in or Create an account to join the conversation.

More
20 Mar 2019 20:23 #129106 by tommylight
The thing with plasma CNC machines is, you have to know what you need from it. There is no "one size fits all" deal with plasma ( or any other cnc machine ).
The first and main question is: what do you want to cut with if ?
Now that is not addressed at the material you want to cut as plasma does not care much if it is cutting Alu, mild steel or extremely hard metals, that makes little difference.
Thickness makes a lot of difference as that is mainly dependant on speed, and speed is directly linked to profit i.e. less time to cut=more parts=more profit.
There are a lot of other things that will determine the speed of cut, but for us right now we are dealing with thickness.
Cutting from 1 to 3mm thick plates requires the machine to move fast, even with a 50A plasma source, so the machine needs to be light and agile and have very fast acceleration. At the other end of the spectrum, cutting 20mm thick plates goes slowly even with a 150A source, so the machine can move slowly, be heavy and have sluggish accelerations.
Then we to get to rapids. Rapids are not important for making one off's or doing large parts, say 2 to5 parts per plate. They are very important when you have to do 280 cuts in a single 2x1 meter plate and they are extremely important when doing 400 to 500 cuts on a 6x2 meter plate. This is very important for decorations and art.
Rapids greatly reduce the time it takes to do serial parts, and that in turn is good for profits.

Please Log in or Create an account to join the conversation.

More
20 Mar 2019 20:44 - 20 Mar 2019 20:48 #129111 by Grotius
Tommy,

People that walk around on top of the machine while the machine is cutting is very dangarous. When the rapid speed is 10 m/min
this can be triggered, but it's not the way to do certain things in life. But machine has no stop output when people are walking around on top. When machine speed up's to 20 meter a minute this can be deadly. So i chanceled the order.
I advised microstep to the customer. Maybe they want to take this risk.
Last edit: 20 Mar 2019 20:48 by Grotius.

Please Log in or Create an account to join the conversation.

More
20 Mar 2019 21:14 - 20 Mar 2019 21:15 #129114 by Grotius
About the general idea....

If you think simple. And after a few years you think about the fastest protocol ever...

You can be in the position to post a random picture. This machine is running on a parport. And today
the machine is still running.

So a general idea can be quite simple. It's just how you combine things in life.
If you want to end like Elon Musk. I don't say you are crazy.... bro....
Attachments:
Last edit: 20 Mar 2019 21:15 by Grotius.
The following user(s) said Thank You: tommylight

Please Log in or Create an account to join the conversation.

Time to create page: 0.142 seconds
Powered by Kunena Forum