First cutting test - Praha, Czech Rep.

[mrakoplas]

I started to build. These are the laser cut part that I got cut and bend for about 170 EU. The table is already in progress, I will post some pics soon.

[jhiggins7]

Looking good, Martin! Great price. Have you checked the specs on the parts? Would you recommend this supplier for other MechMate builders in your area?

Welcome to the Forum.

We're looking forward to your build and those "pictures" you promised. Good luck on your build.

[MetalHead]

Welcome to the forum !!!

[domino11]

Welcome Martin!

[mrakoplas]

I finished the table. Now I need to bring 5 friends to turn the table over. I am starting putting together the gantry. The laser cut parts seem to be cut and bent correctly. I ordered the wheels and bushings from superior bearings, fast delivery, the only problem is that they are still held in customs for last ten days. However, I started putting together the grinder and realized, that I did not buy bearings for it. Where do you buy those? Thanks

[Gerald D]

I am sure you will find bearings in the Praha yellow pages.

[mrakoplas]

Thanks Gerald. I thought I need some special ones. Found a shop close by that sells them. Best, Martin

[mrakoplas]

Here is the picture of the table. I already turned it over since and now I am in process of doing the rails. I initially wanted to bolt the table together. However, the two main big U beams were bended, and i found it very hard to straighten them with the bolts. Therefore, when I was half done with the bolts I got fed up and welded everything together. The welded frame now feels more rigid, beams are straight and if I want to move it I will put on a truck. probably better anyway then taking it apart and then going through all the aligning.

Now I want to buy the pinions and racks. I found a company http://opis.cz/cross-morse/pdf/Gears.pdf. The racks will be M1 - 15 x 15 mm, 20 degrees. But now I am not sure which pinions to get. I went through the forum and found people using different sizes. I will use Oriental Motor PK296AE-SG7.2, so what number of teeth should I use, 36? Thanks for any advice. Best, Martin

[Gerald D]

I suggest you use 30 teeth pinions and then see what type of work is important to you. The smallest you can go is 24 for hard material, slow cutting, fine resolution. The biggest is about 36 for soft material, fast cutting, slightly rougher resolution. the 30 will put you in the middle.

[smreish]

I have used both 20T, 24T and 30T.
I found that the 30T offered the best compromise of good jog speed, excellent slow speed - high resolution cutting.

[danilom]

30Tooth here too, with 3:1 belt, and it performs excellent.

[Gerald D]

To anyone reading/posting in this thread about pinion gear diameters, note that the posters are probably talking about 2 different pitch systems: metric module 1 versus inch diam. pitch 20.

Martin is clearly using metric module 1 (M1) and my reply to him is based on that.

[mrakoplas]

Thanks everybody for the replies. I will go for the 30 teeth pinions as Gerald suggests, and the pinion's bore should be 12 mm for the motors.

[smreish]

Thank you for the clarification Gerald, I was clearly assuming british units, not Metric.

[mrakoplas]

I have been away for last two weeks, so the built has been on hold. In the meantime I was outsourcing the PK296AE-SG7.2 motors and rack and pinions. One supplier gave me a quote for the motor 159 EU - http://en.kwapil.com/, while the other 120 EU - http://opis.cz/index.html. Quite a difference. However, I am now a bit confused about the backlash issue. I read all the discussions about it on the forum, and I hesitate now if I should not rather build belt drives. Can someone give me a quick opinion please, I don't want to open another long discussion about this.

[Gerald D]

If you have the time, build belt drives. If you are in a hurry, get the gearboxes on the motors. The difference in performance makes little difference.

[JasonC]

You got to name it "Old Yeller".

Jas

[danilom]

As I like to be able to repair everything myself, I choose to build. So the choice is to make belt drives. Its a personal preference.
Geared OM motors will be a quicker solution and I think that the statement they are flawed as some state (backlash) is not to be a very serious reason for not using them.

[mrakoplas]

Thanks for the replies, I will focus now on finishing the other parts of the build and then I will decide. I noticed I made a mistake about the prices about, they should be 220 and 259 EU.

[mrakoplas]

I realized today that I already bought the power supply for the geared motors, which is 39V, 13A - 363 VA. If I understand it correctly, that would not be sufficient to power the PK296-F4.5A or the PK299-F4.5A, would it? Thanks

[danilom]

As its stated on the OM site, PK296-F4.5A is 1.5mH and it would be maximum voltage 39V, for PK299-F4.5A its 2.5mH and max 50V.
with 39V you can run any motor with around 2mH. I run mine 86HS9802 2.4mH with 43V and get all the speed they can provide.

[mrakoplas]

Thank you. But I think that the problem is not in voltage, but in too small VA, because these motors would need more amps and my PS has only 363 VA. The four PK299-F4.5A should have 900 VA, so I assume that they will not get enough torque with my PS.

[danilom]

As the PSU is very cheap compared to other components (mine costed 30eur only) consider sizing it to the motors and drives once you choose on them.
I used EI core simple transformer and a friend made it for me. Also capacitors until 80V are pretty cheap.
But hey... use all the fancy stuff you want

[KenC]

There is nothing wrong to have dedicated PSU for each & every drivers.
My personal preference is running DC current lower than 4A. Seen what high current DC can do (welding sets) & don't like accidental self-concious loose wires run amok & weld anything that crosses its path... BUT of course others may enjoy watching the drama...

[MetalHead]

I have been testing 4 - 6.3 amp motors with a 400VA transformer and they are working fine. I would run the one you have and leave room in your control box for the larger one just in case you end up needing it. But I doubt you will. Many MechMates are running on 300VA transformers.

[mrakoplas]

Thanks for the comments. I will follow Mike's suggestions. I finally received the rail wheels today, and I will start grinding the rails. It was 5 weeks laying at the customs -(. I found out yesterday that I could actually buy them here off the shelf, but the ones from superiorbearing were still 1/4 cheaper, so I don't feel sorry waiting.

[mrakoplas]

I finished the rails. I had a Hitachi grinder for 125 mm discs, but I put in 115 mm and it worked. I had glazing problems with the grinding disc, so I put over it a sanding disc and it worked very well and much faster.

I am now trying to solve the making of the z-plate. I have a problem to have it done from tool steel. Two companies turned me down that the part is too big for their tools. I wonder how others dealt with it, since it cannot be done by normal tools and needs hardening.

[danilom]

Its just enhanced steel (I bought it cut to size from 100mm wide stripe) it can be drilled and machined with ordinary tools and drills nothing special, use the grinder on it for the sides and it will work.
its the same material from which tools are made, calipers etc thats the explanation I got from my friends at the workshop

[MetalHead]

Also keep in mind that if you absolutly can't get tool steel, you can use standard plate. You will eventually have to replace this part due to wear though. It will take a while before it will need replacing. Just make two if that is the case and stick one away for in the future. Also keep in mind the X and Y rails you just finished are only mild steel.

[mrakoplas]

I have been very busy with work for last two months, so not much of progress on the build.
I got the tool steel plate, apparently they come here only in thicker sizes, which I had milled to 6.5. Now I will grind the rails on it, drill the holes and have it hardened. I am only confused about mounting the spindle later. I don't have the spindle yet, but what I saw the spindle have four holes for mounting in its alu body, which would not fit the plate. Does it mean, that you actually drill new holes in the body to fit it the mechmate plate? One more thing I don't understand is, what are the dowel pins holes for? I search through the forum, but I did not find any explanation. Thank you