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17Jan/10Off

Mendel build progress — day 7 (updated)

Today I cut to sizes all the sheets and also mounted the motors.

First I cut out the sheet, which goes under the y-carriages:

I printed the outline, and stick it to the 3mm PMMA sheet. I used a hammer and prick punch to mark all the holes, and guide the drill bit to properly center:

Here is a closeup photo of the prick punch:

Here is a photo of the drawings on the plastic sheet:

It was really difficult to cut this complicated sheet. I ended up using a dremel with a cutting disk.
The PMMA sheet is really brittle, three corners broke from which two broke off completely:

bottom right

top right:

bottom left:

Fortunately it does not really important, as there left enough bolt to level the carriages.
Beside the plastic sheet, finally the stepper motors has arrived too.
Here are some pictures:

The data of the motors:

  • partnumber: DPM42SH47-1AM.001
  • 400 steps/revolution (!!!)
  • 42.3mm (NEMA17)
  • single shafted, filed
  • torque: 3.17 Kg*cm or 0.317 Nm
  • Unipolar or bipolar wiring (6 wires coming out in total)
  • current/phase: 1.2A
  • rated voltage: 4V
  • resistance/phase: 3.3 Ohm
  • inductance/phase: 2.8mH
  • weight: 0.35 kg

Color specification

  • Phase A+: black
  • Phase A-: green
  • Phase Com Phase A: yellow
  • Phase B+: red
  • Phase B-: blue
  • Phase Com Phase B: white

Mounting the motors was surprisingly hard. The X motor brackets
needs a serious rethinking. The two 8mm bars are fixed to the
bracket using the motor's threads. It is easy to broke the threads of the motor.*
Here are a photo of Mendel, with all the scraps on his y-table (produced while cutting
the sheets).

* Update:
The x-motor-bracket part is really hard to print without warping. It is big x-y wise but has a small height:

As it is warped, the x-bar-clamp-nuts needs more force to counteract the warping.
Also the x-bar-clamp-nut is fixed to the stepper motor, so the threads of the stepper motor
needs to support this additional force. And also as it is warped, the holes (stepper motor, x-end-bracket, x-bar-clamp-nuts) dont really match, so it was really hard to screw the bolt into the stepper motor.

Next day is the belt day.

Comments (6) Trackbacks (0)
  1. Hi,
    Funky hammer!

    I don’t understand your comment about mounting the motors. They are fastened by four M3 bolts through a plate. How else could you mount a NEMA motor?

  2. Midge has a funky hammer like that too.

    Very nice step angle on your steppers, I see you have now made the old squashed frog plate too. The screw threads are very short on the steppers as the main screw holding steeper’s together is also using that hole.
    If your fixing screw is too long It is easy to strip the thread on the stepper mount, I have on one stepper done exactly that.
    I am inclined to agree re using the stepper mounting to hold other parts is not a good idea as the wrong size screw could be used inadvertantly thus enhancing the posibility of stripping the thread.

  3. nophead: I’ll update the post with some photos to explain you better the problem.

  4. nophead, the motor mount screws are also used to hold the bar clamps, a structural vitamin that requires significant force. this places undue stress on the motor’s mounting threads which are usually only 5mm long. Ideally, the motor mount screws hold /only/ the motor and structural members have separate mounts.

  5. Ah, I see now. No that is not very good design because the motor plate is only aluminium I think. If you do strip them you can remove the motor’s bolt, drill it out and put M4 studding right through the motor.

  6. for some reason i want to ask if you have any spare steppers..lol

    but it looks like you are making progress though

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